Some serious help is needed.
#1
01-18-2019
Join Date: Jan 2019
Location: Savannah, Ga
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Some serious help is needed.
What’s going on everyone, I’m the new guy to this site which was referred to me by a friend who said everyone has been a serious help to him so I figured I give this a shot and see what everyone’s input and advice would be. I appreciate all input in advance and the time you’ve taken to read this(it might end up being a tad bit long)
I’ve had my truck since 2012, only had the tranny rebuilt and just had the engine replaced for the first time, I bought it with ~172k miles and has 302k miles on it now since I parked it tonight. It’s been a damn good truck I’d say.
Right at the 300k mile mark it started to run a little funny or a lotta funny. It runs as if it’s missing or the timing is off or something along those lines, I have a SCT X4 tuner running on it and the guages/datalog is something I constantly keep my eye on. The first thing I’ve noticed was a real strong gas smell like it’s running rich, I have the SCT programmed to read STFT and LTFT on both bank 1 & 2 and they both seem way off to me, short term reads right around 0.65-0.95 depending on the load and long term reads 1.08-1.25 which I believe it goes higher I just think that’s as high as the tuner can read it.
If I idle for around 5-10 minutes paying attention to fuel trims as well the truck will begin to bog down, idle like complete crap and sometimes stall out if I don’t give it gas. When this happens the fuel trims being read on the SCT go straight to 1.00, almost like the truck reset but then after running for a while they’ll eventually fall back in line to where they were like i said earlier.
Another big issue is when driving, the truck runs like a charm accelerating, sometimes it can seem like it’s lost A. LOT. of power. But my main concern is when it kicks into those lower gears like when I coast around 50 mph and when the truck goes into overdrive it shakes uncontrollably like a SERIOUS misfire and it won’t stop until I get it to go into a higher gear.
Ive tried many attempts on several occasions but to no dang avail, nothing works, I just had the fuel pump replaced along with the filter, a complete tune up, new plugs all gapped correctly, new plug wires and new coil pack. Replaced almost all vacuum lines and checked a few, I’ve got a leaky one that has something to do with the air system in the cab which is a line that runs right behind the glove box above the inertia switch, two lines running to one fitting. Also replaced the inertia switch and put a new camshaft synchronizer along with the sensor.
Im beyond lost with it and don’t have a clue as to which direction I should step in. If ANYONE has any type of advice whether this has happened to you as well or have a good idea as to where the problem may be I would love to discuss it and would greatly value and appreciate the inputs.
Thanks again guys for taking the time to read this and help solve this problem. I hope you guys have a great and one hell of a day.
I’ve had my truck since 2012, only had the tranny rebuilt and just had the engine replaced for the first time, I bought it with ~172k miles and has 302k miles on it now since I parked it tonight. It’s been a damn good truck I’d say.
Right at the 300k mile mark it started to run a little funny or a lotta funny. It runs as if it’s missing or the timing is off or something along those lines, I have a SCT X4 tuner running on it and the guages/datalog is something I constantly keep my eye on. The first thing I’ve noticed was a real strong gas smell like it’s running rich, I have the SCT programmed to read STFT and LTFT on both bank 1 & 2 and they both seem way off to me, short term reads right around 0.65-0.95 depending on the load and long term reads 1.08-1.25 which I believe it goes higher I just think that’s as high as the tuner can read it.
If I idle for around 5-10 minutes paying attention to fuel trims as well the truck will begin to bog down, idle like complete crap and sometimes stall out if I don’t give it gas. When this happens the fuel trims being read on the SCT go straight to 1.00, almost like the truck reset but then after running for a while they’ll eventually fall back in line to where they were like i said earlier.
Another big issue is when driving, the truck runs like a charm accelerating, sometimes it can seem like it’s lost A. LOT. of power. But my main concern is when it kicks into those lower gears like when I coast around 50 mph and when the truck goes into overdrive it shakes uncontrollably like a SERIOUS misfire and it won’t stop until I get it to go into a higher gear.
Ive tried many attempts on several occasions but to no dang avail, nothing works, I just had the fuel pump replaced along with the filter, a complete tune up, new plugs all gapped correctly, new plug wires and new coil pack. Replaced almost all vacuum lines and checked a few, I’ve got a leaky one that has something to do with the air system in the cab which is a line that runs right behind the glove box above the inertia switch, two lines running to one fitting. Also replaced the inertia switch and put a new camshaft synchronizer along with the sensor.
Im beyond lost with it and don’t have a clue as to which direction I should step in. If ANYONE has any type of advice whether this has happened to you as well or have a good idea as to where the problem may be I would love to discuss it and would greatly value and appreciate the inputs.
Thanks again guys for taking the time to read this and help solve this problem. I hope you guys have a great and one hell of a day.
#2
01-19-2019
Member
#3
01-19-2019
2002, 3 litre
Screamingeagle, check you fuel rail dampener, pull the vacuum line off of it, there should be no gas at that line, if there is, it has failed.
The vacuum line is a safety feature so if the dampener fails, fuel is sucked into the engine and not sprayed all over the engine bay.
Here's what it looks like.
https://www.rockauto.com/en/catalog/...re+damper,6120
Screamingeagle, check you fuel rail dampener, pull the vacuum line off of it, there should be no gas at that line, if there is, it has failed.
The vacuum line is a safety feature so if the dampener fails, fuel is sucked into the engine and not sprayed all over the engine bay.
Here's what it looks like.
https://www.rockauto.com/en/catalog/...re+damper,6120
Last edited by Jeff R 1; 01-19-2019 at 11:08 AM.
#4
01-19-2019
Welcome to the forum
3.0l OHV Vulcan engine, used in Ranger from 1991 to 2008, good reliable engine
First, I don't understand your STFT(short term fuel trim) numbers?
But they represent Fuel injector OPEN TIME in a % relationship to CALCULATED OPEN TIME
When you start a cold engine computer does no "on the fly" fuel calculations, so STFT means nothing, computer is using an air/fuel mix "table" it has in memory for a 3.0 liter engine.
To do "on the fly" calculations computer needs feed back from O2 sensors in regards to Oxygen level in the exhaust
O2 sensors need to be heated up above 600degF to work, this is why they are "heated O2 sensors" to get them up to temp faster than just the exhaust can do it, this usually takes 3 to 6 minutes depending on outside temperatures.
Once O2 sensors start to work computer switches to Closed Loop operation and "on the fly" air/fuel mix calaculations
Computer "knows" its running a 3 Liter engine, so it knows exactly how much air is being pulled into the engine at any given RPM and throttle position, its just math
What it doesn't know is the WEIGHT of the air, the TEMP of the air, and the LOAD on the engine, again this is just math but it must rely on Sensors for this data.
Gasoline has an air/fuel mix of 14.7:1 this is a WEIGHT RATIO not volume
14.7 Pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of fuel
A WEIGHT ratio
"Hot air rises", why?
Because its LIGHTER than cooler air, cooler air is HEAVIER
Air at 2,000ft elevation is "thinner/lighter" than air at sea level
MAF sensor reads the WEIGHT of the incoming air, it uses a heated wire, the faster the wire is cooled the HEAVIER the air, your reader should be able to test MAF by setting it to read gm/sec(grams per second), most engines draw in their displacement at warm idle, i.e. 3.0l would read 3gm/sec at idle, 4.0l/4gm/sec. 5.0l/5gm/sec, that at appox. 600rpm so if idle is 750 then it would be slightly higher
IAT(intake air temp) sensor reads the temp of the air coming in to engine
TPS(throttle position sensor) tells computer how far open the throttle plate is, from this the LOAD on engine can be calculated
So computer does its "on the fly" air/fuel mix calculations using its knowledge of 3 liter engine and the above sensors, and say it comes up with "open fuel injectors for 100 milliseconds(ms)", this is 0 STFT
After 0 STFT is burned the O2 sensors tell computer oxygen levels, Rich is low oxygen(.9v O2), Lean is high oxygen(.1v O2)
Say it was a Lean burn
In this case Computer would OPEN injectors 2ms longer adding 2% more fuel, STFT is now +2%
Then it looks for O2s to move to .4volts, sweet spot
If O2s stay at .1v then computer opens injectors longer, 4ms so STFT is now +4%
And this continues until O2 sensors are hovering around .4volts
And all this takes about 2 seconds, so engine is never actually running Lean or Rich
If STFT gets to -15% or +15% for any length of time then computer will notify the driver with a CEL(check engine light) and a Lean or Rich code
These codes mean there is a Calculation error, not that engine is running lean or rich
The rear O2 sensor, O2 bank 1 sensor 2, should stay at about .7-.8volts consistently, the Cats burn up most of the oxygen , so rear O2 shows "richer " voltage
Lean codes often indicate an air or vacuum leak, so not all the air is coming in via MAF sensor, so computer is getting incorrect data
Low fuel pressure can cause same Lean code, because computer is having to open injectors longer than 0 STFT to get the same amount of fuel when pressure was higher.
2002 Ranger runs 55-60psi fuel pressure
And you can get a "false Lean", if there is a leak in the exhaust manifold(or around O2 sensor) then that bank will suck in extra air so O2 is reporting Lean burn, too much oxygen, and computer will run that bank Richer than it should
Vacuum leak can be tested for using the IAC Valve
Warm up engine, over 5 minutes, let it idle and unplug the IAC Valves 2 wire connector
IAC Valve will close and RPMs should drop to 500 or so, barely running, or engine may even stall, either is GOOD, it means no vacuum leak
If RPMs do not drop then you have a leak
Air leaks occur in the air tube between MAF sensor and upper intake, it must be air tight
Rich STFT are rare, but can be cause by partially blocked exhaust, back pressure, or a leaking fuel injector
An exhaust blockage can come and go, as pieces shift around in rusted out Cat or muffler, so can be an intermittent issue
Vacuum gauge is still one of the best tools to diagnose any gasoline engine, $20, read here on testing: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine
Can test for exhaust blockage with vacuum gauge along with many other issue
Trouble shooting tip, O2 sensors are not used cold, but are also not used at warm idle OR at WOT(wide open throttle)
At idle the computer must run engine richer or it will over heat, and at WOT computer ignores "economy" and gives engine max fuel based on RPMs and LOAD
So if engine runs much better at idle and at WOT, thats "foot to the floor" not 3/4 or 7/8 throttle, lol, then there is an air/fuel mix calculation error happening
There was a TSB on the Ranger 3.0l but 2004-2006 3.0ls
Seems the exhaust valve seats could shift and cause slight losses of compression, generally you will get misfire codes, P030X or P0316(random misfire), which you don't mention
But I would still do a compression test
Remove all 6 spark plugs first
Hold gas pedal down to the floor when cranking engine, this turns OFF fuel injectors, also gives full air flow for test
Get 4 or 5 "hits" then write down results
Reason for compression test is that its either good, or it shows the problem, you can waste time and MONEY on non-fixes when there is a compression issue.
So take that off the table as soon as practical
3.0l Vulcan should be 165-175 psi in a static test, 9.3:1 ratio
3.0l OHV Vulcan engine, used in Ranger from 1991 to 2008, good reliable engine
First, I don't understand your STFT(short term fuel trim) numbers?
But they represent Fuel injector OPEN TIME in a % relationship to CALCULATED OPEN TIME
When you start a cold engine computer does no "on the fly" fuel calculations, so STFT means nothing, computer is using an air/fuel mix "table" it has in memory for a 3.0 liter engine.
To do "on the fly" calculations computer needs feed back from O2 sensors in regards to Oxygen level in the exhaust
O2 sensors need to be heated up above 600degF to work, this is why they are "heated O2 sensors" to get them up to temp faster than just the exhaust can do it, this usually takes 3 to 6 minutes depending on outside temperatures.
Once O2 sensors start to work computer switches to Closed Loop operation and "on the fly" air/fuel mix calaculations
Computer "knows" its running a 3 Liter engine, so it knows exactly how much air is being pulled into the engine at any given RPM and throttle position, its just math
What it doesn't know is the WEIGHT of the air, the TEMP of the air, and the LOAD on the engine, again this is just math but it must rely on Sensors for this data.
Gasoline has an air/fuel mix of 14.7:1 this is a WEIGHT RATIO not volume
14.7 Pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of fuel
A WEIGHT ratio
"Hot air rises", why?
Because its LIGHTER than cooler air, cooler air is HEAVIER
Air at 2,000ft elevation is "thinner/lighter" than air at sea level
MAF sensor reads the WEIGHT of the incoming air, it uses a heated wire, the faster the wire is cooled the HEAVIER the air, your reader should be able to test MAF by setting it to read gm/sec(grams per second), most engines draw in their displacement at warm idle, i.e. 3.0l would read 3gm/sec at idle, 4.0l/4gm/sec. 5.0l/5gm/sec, that at appox. 600rpm so if idle is 750 then it would be slightly higher
IAT(intake air temp) sensor reads the temp of the air coming in to engine
TPS(throttle position sensor) tells computer how far open the throttle plate is, from this the LOAD on engine can be calculated
So computer does its "on the fly" air/fuel mix calculations using its knowledge of 3 liter engine and the above sensors, and say it comes up with "open fuel injectors for 100 milliseconds(ms)", this is 0 STFT
After 0 STFT is burned the O2 sensors tell computer oxygen levels, Rich is low oxygen(.9v O2), Lean is high oxygen(.1v O2)
Say it was a Lean burn
In this case Computer would OPEN injectors 2ms longer adding 2% more fuel, STFT is now +2%
Then it looks for O2s to move to .4volts, sweet spot
If O2s stay at .1v then computer opens injectors longer, 4ms so STFT is now +4%
And this continues until O2 sensors are hovering around .4volts
And all this takes about 2 seconds, so engine is never actually running Lean or Rich
If STFT gets to -15% or +15% for any length of time then computer will notify the driver with a CEL(check engine light) and a Lean or Rich code
These codes mean there is a Calculation error, not that engine is running lean or rich
The rear O2 sensor, O2 bank 1 sensor 2, should stay at about .7-.8volts consistently, the Cats burn up most of the oxygen , so rear O2 shows "richer " voltage
Lean codes often indicate an air or vacuum leak, so not all the air is coming in via MAF sensor, so computer is getting incorrect data
Low fuel pressure can cause same Lean code, because computer is having to open injectors longer than 0 STFT to get the same amount of fuel when pressure was higher.
2002 Ranger runs 55-60psi fuel pressure
And you can get a "false Lean", if there is a leak in the exhaust manifold(or around O2 sensor) then that bank will suck in extra air so O2 is reporting Lean burn, too much oxygen, and computer will run that bank Richer than it should
Vacuum leak can be tested for using the IAC Valve
Warm up engine, over 5 minutes, let it idle and unplug the IAC Valves 2 wire connector
IAC Valve will close and RPMs should drop to 500 or so, barely running, or engine may even stall, either is GOOD, it means no vacuum leak
If RPMs do not drop then you have a leak
Air leaks occur in the air tube between MAF sensor and upper intake, it must be air tight
Rich STFT are rare, but can be cause by partially blocked exhaust, back pressure, or a leaking fuel injector
An exhaust blockage can come and go, as pieces shift around in rusted out Cat or muffler, so can be an intermittent issue
Vacuum gauge is still one of the best tools to diagnose any gasoline engine, $20, read here on testing: Technical Articles: Engine testing with a Vacuum Gauge - at Greg's Engine & Machine
Can test for exhaust blockage with vacuum gauge along with many other issue
Trouble shooting tip, O2 sensors are not used cold, but are also not used at warm idle OR at WOT(wide open throttle)
At idle the computer must run engine richer or it will over heat, and at WOT computer ignores "economy" and gives engine max fuel based on RPMs and LOAD
So if engine runs much better at idle and at WOT, thats "foot to the floor" not 3/4 or 7/8 throttle, lol, then there is an air/fuel mix calculation error happening
There was a TSB on the Ranger 3.0l but 2004-2006 3.0ls
Seems the exhaust valve seats could shift and cause slight losses of compression, generally you will get misfire codes, P030X or P0316(random misfire), which you don't mention
But I would still do a compression test
Remove all 6 spark plugs first
Hold gas pedal down to the floor when cranking engine, this turns OFF fuel injectors, also gives full air flow for test
Get 4 or 5 "hits" then write down results
Reason for compression test is that its either good, or it shows the problem, you can waste time and MONEY on non-fixes when there is a compression issue.
So take that off the table as soon as practical
3.0l Vulcan should be 165-175 psi in a static test, 9.3:1 ratio
Last edited by RonD; 01-19-2019 at 06:34 PM.
#5
01-19-2019
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Awesome man I appreciate the input. You sound like you know the engine from the inside out including the math that comes with it. You lo definitely have to swing by oreillys and pick up a compression gauge and get down to it and test each cylinder. I’ll get around to doing that within these next couple days (been pretty busy moving) and will share the results so a conclusion can be made.
Again i I appreciate the input! Joining this forum has already helped me more than I’ve helped myself because at this point I’m beyond lost with the problem and taking shots in the dark lol.
Ill keep ya posted!!
Again i I appreciate the input! Joining this forum has already helped me more than I’ve helped myself because at this point I’m beyond lost with the problem and taking shots in the dark lol.
Ill keep ya posted!!
#6
01-19-2019
#7
02-17-2019
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Okay so I know it’s been a while for an update but I’ve done a compression test on the first 3 cylinders on the truck. 1 is reading right at 100 psi, 2 is reading 150 and 3 is just straight weird. As I’m cranking the engine the gauge needle jumps as normal but as it hits the 90 psi mark it just stops and goes back down. Versus the other cylinders the needle would keep jumping until it has reached a max pressure point and stay there and would then go down as I stop cranking, just as normal. What would cause cylinder 3 to just stop building up pressure and then just relieve the air pressure?
#8
02-17-2019
#9
02-17-2019
Compression gauge should have a check valve on it, yours doesn't
Check valve lets pressure in but not back out, so as you crank the engine the highest pressure is shown on the gauge, and it stays there until you press the release pin on the check valve to test the next cylinder.
But yes what you are seeing seems like either a valve is out of sync or not opening or a blown head gasket between 2 cylinders, one cylinder is sucking out pressure from the other
But in any case the 100psi on cylinder #1 is low enough to pull the head and have a look
Check valve lets pressure in but not back out, so as you crank the engine the highest pressure is shown on the gauge, and it stays there until you press the release pin on the check valve to test the next cylinder.
But yes what you are seeing seems like either a valve is out of sync or not opening or a blown head gasket between 2 cylinders, one cylinder is sucking out pressure from the other
But in any case the 100psi on cylinder #1 is low enough to pull the head and have a look
#10
02-17-2019
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The gauge was hooked up correctly. It came with an adapter that would screw into the spark plug hole on the side of the block and you would continue to screw the hose onto the adapter and then connect the gauge to it. It’s one of those “evertough” rental tools from oreillys. Never had a problem with any of their tools personally.
But I will say this and this is why I get such a strong feeling the valves are what’s proposing a problem. The only time I really really have an issue with it is when the motor is cold, the morning it wouldn’t stay running it was a pretty cold one(low 50’s high 40’s), it would crank, turnover and run but only for a matter of seconds before I bogged down and died out, I changed the fuel pump, now reading about 45 psi off the fuel rail so that’s good, changed the fuel filter so I know that’s good, then I checked the inevitable. The compression. And there was my problem.
Also when pulling all the spark plugs, they were all black, either smelled like oil or just raw gas. Scratching my head I checked the codes for the hell of it but I’ve never had a check engine light and to my surprise I have lean codes for banks 1 & 2 and also some sort of o2 sensor something something indicates lean code as well.
I know compression is a huge huge problem contributing to why my truck won’t run but could anyone tell me as to what may be the underlying problem of this thing? I’ve had it since 2012 and I just wanna keep on pushing it.
Thanks guys I hope this helps.
But I will say this and this is why I get such a strong feeling the valves are what’s proposing a problem. The only time I really really have an issue with it is when the motor is cold, the morning it wouldn’t stay running it was a pretty cold one(low 50’s high 40’s), it would crank, turnover and run but only for a matter of seconds before I bogged down and died out, I changed the fuel pump, now reading about 45 psi off the fuel rail so that’s good, changed the fuel filter so I know that’s good, then I checked the inevitable. The compression. And there was my problem.
Also when pulling all the spark plugs, they were all black, either smelled like oil or just raw gas. Scratching my head I checked the codes for the hell of it but I’ve never had a check engine light and to my surprise I have lean codes for banks 1 & 2 and also some sort of o2 sensor something something indicates lean code as well.
I know compression is a huge huge problem contributing to why my truck won’t run but could anyone tell me as to what may be the underlying problem of this thing? I’ve had it since 2012 and I just wanna keep on pushing it.
Thanks guys I hope this helps.
#11
02-17-2019
Let the rental guys know the check valve is bad, see if they have another one with working check valve
CEL(check engine light) doesn't come on for every or any code, it only comes on if computer "thinks" the code requires immediate attention from driver.
Flashing CEL means engine damage may occur
Black spark plugs tips are carbon build up from misfires, same for the gasoline smell
Misfires do not burn the Oxygen that was sucked in with the fuel, because there was no ignition
O2 sensors "see" Oxygen only, not fuel
High levels of Oxygen in exhaust is Lean condition, Low Oxygen is Rich condition
So misfires dump all the unburned Oxygen into the exhaust manifold, which is Lean exhaust as far as O2 sensors are concerned
"Lean" or Rich" designation is when air:fuel mix is actually burned, which doesn't happen on a misfire
You are there, we are not, so only you can determine what may be wrong, and you can only fix one problem at a time and then see if that was the only problem.
But with low compression it doesn't matter what else you do, there is no fix for that except to pull the heads and find out why
You can do a WET compression test on #1 and see how much it comes up above 100psi, if it gets close to 140psi then rings are the problem, if it stays under 130psi then its valves or head gasket
CEL(check engine light) doesn't come on for every or any code, it only comes on if computer "thinks" the code requires immediate attention from driver.
Flashing CEL means engine damage may occur
Black spark plugs tips are carbon build up from misfires, same for the gasoline smell
Misfires do not burn the Oxygen that was sucked in with the fuel, because there was no ignition
O2 sensors "see" Oxygen only, not fuel
High levels of Oxygen in exhaust is Lean condition, Low Oxygen is Rich condition
So misfires dump all the unburned Oxygen into the exhaust manifold, which is Lean exhaust as far as O2 sensors are concerned
"Lean" or Rich" designation is when air:fuel mix is actually burned, which doesn't happen on a misfire
You are there, we are not, so only you can determine what may be wrong, and you can only fix one problem at a time and then see if that was the only problem.
But with low compression it doesn't matter what else you do, there is no fix for that except to pull the heads and find out why
You can do a WET compression test on #1 and see how much it comes up above 100psi, if it gets close to 140psi then rings are the problem, if it stays under 130psi then its valves or head gasket
#12
02-17-2019
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#13
02-18-2019
Nope
Compression allows any gasoline, or especially diesel, engine to run
Liquid gasoline can't be ignited by a spark, yes the movie guys take liberties with that fact, lol
Only gasoline Vapor can be ignited by a spark
Fuel injectors, or carbs, let in Liquid gasoline to the engine
When that liquid is in the cylinder the Compression is what heats it up and turns some of it to a Vapor, you need about 30% vapor in a cylinder for the spark plug to get a good ignition, which quickly vaporizes the other 70% of the gasoline.
Higher compression is higher heat generated in a cylinder, and lower compression is, well lower heat generated so lower vapor present
Once an engine is started, cylinders warm up quickly, so you can often keep a lower compression engine running once its started up
8.5:1 compression ratio is about as low as you can go with vehicle gasoline engines, and that's 150psi compression
Lawnmower or other small engines can go as low as 6:1 ratio which is 110psi compression, but can be very hard to start in cold weather
Your 3.0l is running 9.3:1 ratio so should show 170psi compression
Higher compression engines, 9.6:1 and higher, generate more power, rebound effect from the compression, but have a hard time running on Regular 87 octane fuel
So without proper compression you don't have an engine, its an air pump, not an engine
Setting up the crank, piston and cam valve timing and seals is the very first step in building any engine, and those are the parts that generate Compression
Compression allows any gasoline, or especially diesel, engine to run
Liquid gasoline can't be ignited by a spark, yes the movie guys take liberties with that fact, lol
Only gasoline Vapor can be ignited by a spark
Fuel injectors, or carbs, let in Liquid gasoline to the engine
When that liquid is in the cylinder the Compression is what heats it up and turns some of it to a Vapor, you need about 30% vapor in a cylinder for the spark plug to get a good ignition, which quickly vaporizes the other 70% of the gasoline.
Higher compression is higher heat generated in a cylinder, and lower compression is, well lower heat generated so lower vapor present
Once an engine is started, cylinders warm up quickly, so you can often keep a lower compression engine running once its started up
8.5:1 compression ratio is about as low as you can go with vehicle gasoline engines, and that's 150psi compression
Lawnmower or other small engines can go as low as 6:1 ratio which is 110psi compression, but can be very hard to start in cold weather
Your 3.0l is running 9.3:1 ratio so should show 170psi compression
Higher compression engines, 9.6:1 and higher, generate more power, rebound effect from the compression, but have a hard time running on Regular 87 octane fuel
So without proper compression you don't have an engine, its an air pump, not an engine
Setting up the crank, piston and cam valve timing and seals is the very first step in building any engine, and those are the parts that generate Compression
#14
02-18-2019
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Well I’m hoping and praying that’s not the case lol. I’ve only done a compression test on cylinders 1,2 & 3. I haven’t had the chance to test 4,5 & 6 due to work, class and the crappy weather. I will be taking a day off from everything to get down to the bone with it and take off the heads and intake to see where the problem may actually be and really hoping it’s fixable. All I’ve done is a compression test on the first three cylinders so as far as I can see right now is just the first 3 cylinders but I will be breaking it all down and taking a look at everything.
Now, if I wanted to check the piston rings is there any way I can do that without taking the pistons themself out? Or is that the impossible? Lol. I’ve done repairs in the past but never this technical and in depth. So if there are things that I should be looking for or should look for feel free to let me know by any means. I’m all ears at this point.
Now, if I wanted to check the piston rings is there any way I can do that without taking the pistons themself out? Or is that the impossible? Lol. I’ve done repairs in the past but never this technical and in depth. So if there are things that I should be looking for or should look for feel free to let me know by any means. I’m all ears at this point.
#15
02-18-2019
To do a compression test all 6 spark plugs need to be remove FIRST
Then you test one cylinder at a time writing down results
Test should be done with Throttle WIDE OPEN, maximum air into the engine, also shuts off fuel injectors
After testing all 6 you will see any low ones
Get a straw, like for drinking, dip the straw in a bottle of motor oil, so its about 1/2-3/4 full of oil then put your finger over the top of the straw and pull it out of the bottle
Put the end of the straw in the spark plug hole of a Low compression cylinder and remove your finger
The oil will flow down into that cylinder
This oil will temporarily seal the piston Rings
Now retest compression on this cylinder
It will go up, by how much will tell you if the rings are leaking or the valves are
i.e. if compression was 110 and goes up to 125 then rings are fine, valves are not, if it goes up to 145 then valves are OK rings are worn out
Then you test one cylinder at a time writing down results
Test should be done with Throttle WIDE OPEN, maximum air into the engine, also shuts off fuel injectors
After testing all 6 you will see any low ones
Get a straw, like for drinking, dip the straw in a bottle of motor oil, so its about 1/2-3/4 full of oil then put your finger over the top of the straw and pull it out of the bottle
Put the end of the straw in the spark plug hole of a Low compression cylinder and remove your finger
The oil will flow down into that cylinder
This oil will temporarily seal the piston Rings
Now retest compression on this cylinder
It will go up, by how much will tell you if the rings are leaking or the valves are
i.e. if compression was 110 and goes up to 125 then rings are fine, valves are not, if it goes up to 145 then valves are OK rings are worn out
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Zeddikus
2.3L & 2.5L I4 Tech
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02-22-2018 02:22 PM
