I have a 2000 Ranger V6 3.0L Flexfuel that is a tad bit rough at idle/stops, otherwise runs ok. Just picked up a compression test kit at Harbor Freight and will wait for sun light out tomorrow to test all the cylinders in accordance to these instructions.

So far, I have only Ω'ed out the coil pack. Connector-side and and plug wires-side both check out. I figure if I get bad compression, I am going to have to evaluate if I wish to go further with the investment in lower engine mechanical repair. If I get good compression, then I'll approach it as a tune-up. But if I start throwing parts at it right away (new sparks, wires, coil pack, fuel filter, etc.), I won't be approaching the job in the most economical way. I'll update this tomorrow.

Sound strategy?

EDITS w/Additional Details:

1. Mileage +165k
2. CEL doesn't come on
3. Scan shows P0301 & P0305 DTC's

 

Of course it's a sound strategy.
Provide mileage in posts.
Make sure the engine-to-frame ground wire is good.
Like they say: Check your compression dry (all 6) then wet with oil.
Awaiting results.
What a good new year's thing to do.

 

Sound strategy

Compression is mechanical so once ruled out you can look at spark and injectors, so yes it is economical choice

3.0l Vulcan engine runs 9.3:1 compression ratio, so expected dry test/cold engine would be 160-170psi, but depends on compression gauge calibration, which is why you need to test all cylinders first, that will give you calibration for the new gauge

Actual PSI number is dependent on battery voltage, starter motor speed, altitude above sea level, and gauge itself, so you are looking for stable average, not high numbers
Once you have the stable average then you can see if any cylinders deviate from that average

Also keep spark plugs in order after removal, their tips may show you a hint if a problem is found in one or two cylinders

 

I updated the OP with the mileage (+165K) and thanks for the encouraging words. A little FYI on this Ranger, I just picked it up on the cheap and will decide to keep it or let it go depending on if it passes or fails the compression testing. Passes, keep and fix misfire + tune-up. Fails, let it go. Previous owner tells me he didn't change the coil pack or wires. He said he did change the spark on cylinder 1.

So......no update. I got all the plugs out and they looked good (see below), new even. Anyhow, I could not get the compression kit's hose to thread into the engine block. Just couldn't get the proper angle on it to bite within the cramp space and on account that the hose is rather long. Spent 45mins-1hour trying to thread onto cylinder 1 and 6 (the easy to access ones) and could NOT pull it off. A combination of good ol' Ford engineering, making components hard to get to, Chinese HF tools, and having short big arms made it impossible. Went to different stores looking for a longer compression adapter or a M14 riser. No luck. Ended up renting a compression test kit at Autozone and will stack compression testing adapters so I can get better leverage to complete the job. Will report back tomorrow.

Anecdote with one of the sparks and visual inspection in the spoiler.

 

Question: Disabling spark. Is it sufficient to simply leave the connector disconnected from the coil while I perform the compression test? Or should I pull a fuse? If I should pull a fuse, which one do I pull?

 

There are no spark plugs so no need to disable spark

But yes you can just unplug the 4 wire connector on coil pack

What was the part number for the kit at harbour freight?

 

Thanks. The part number on the HF kit is 62638. I read another thread reply (might have been yours) that it is not good to use the adapters with the rubber grommets. So I didn't even try those. If it doesn't work out tomorrow, I might have to pick up this

extension

extension

. Though, not sure if I will run into another problem with clearance for the rear cylinders if I use the extension. Will check how much clearance I have tomorrow.

One more question: Given my stance that I will only test for engine mechanical failure and not do further repair if compression testing validates loss in cylinder compression, do you recommend in this instance to do both the dry and wet compression test? I mean, if I am testing dry on a cold engine and cylinder 1 and 5 end up being 10% decrease in comparison of the average to the middle 4 compression readings in the other cylinders, no point going further with the wet test, right? I've validated that it is a mechanical problem in the engine. The wet compression test is to isolate it to the either the piston rings or head (if increase in PSI, then piston rings. If no increase, then head). In either instance (piston rings or head), I don't really plan on investing further in the instance of engine mechanical failure. Given my stance, no value in going further with the wet compression test, is there?

Nevermind. If I get this compression tester threading thing solved or if the rubber adapters work out, it will be small effort to also perform a wet compression test. I'll just use a turkey baster to add in the oil for the wet test. Then I can make a more informed decision from there.

 

Oh also, If it is a 2-man job, is it ok to use the rubber stops? One guy cranks the engine. One guy holds the stops in place with force and reads the gauge? Maybe put a bit of oil on the rubber so it acts as a bit of a seal?

 

Yup, it's OK to give 'em a little coating.

 

Its odd that kit didn't work, are the inserts hitting head or exhaust manifold?

No, on the rubber plug, very hard to get accurate readings above 100psi holding the rubber plug against spark plug hole
You can certainly try it
Problem is the "hard to get at" ones will probably show lower compression numbers because of weak seal, so hard to diagnose
Compression test is about the consistency at the time of the test, outside temp, engine temp, battery voltage, starter motor crank speed and gauge

If you tested an engine and then tested it a month later it would show different numbers, depending on the above, but thats OK because its not about the exact number its about the comparison between the cylinders for that one test

 

There are always slight differences between the SKU's with products at HF. HF's site shows 4 different SKU's: 62638, 66216, 69885, 39224.

In the kit I got, the adapters are different than the picture in the link shown (see pic below). Firstly, the adapters I got are shorter and made of brass. Also, they don't have the hex head as show in the picture. Instead, they have knurling on all but the M18 adapter. If it had the hex head, I would have used a socket and small piece of paper towel to keep it from falling out of the socket to get it in. Box says it comes with the M10, M12, M14, M18 adapter. So the M14 adapter has to be the 3rd largest one. I lined up the threads on that adapter to one of the plugs and lines up in terms of size and threads. Incorrect angle/leverage, shoulder on the adapter being too wide, I don't know. Couldn't get a single thread to bite. Hopefully, stacking the adapter with the rented one from Autozone helps move things along (the chrome adapter in the picture). Or, I might have exchange this kit for another one with the other SKU's in this line-up.


Yeah, I figured as much. Didn't think I could get the same leverage force on this engine. Maybe a different car/engine where the cylinders are pointed up vertically to open air, the rubber plugs would work. Just don't see this happening on this engine. Will give it a whirl though before buying that extension.

 

Welp, it is not looking good. The cranking seemed to be very weak during the dry test; anything to make of this?

Here are the single-pass dry test results:

1. 60 PSI (P0301)
2. 92 PSI
3. 105 PSI
4. 120 PSI
5. 32 PSI (P0305)
6. 107 PSI

I ran out of light, so I couldn't do the wet test. Will dry test cylinders 1 & 5 again tomorrow. Then wet test just those two cylinders. I may consider giving fixing it if it is the head. Tranny is good. Body is good. Paint is good.

EDIT:
I wasn't able to get the compression tester to bite even in the slightest. I went to HF and swapped it out for the Quick Connect version where there are individual short hose adapters for each of the spark thread sizes. Even still, I couldn't get the proper angle/leverage to get it to work. Thankfully, I still had the rented compression tester from Autozone. The threads on the adapter with this kit are longer. So I coupled that adapter to the end of the HF adapter hose, then it went in easily. Quite possible the HF compression testers won't work on this engine as the threads are really short. I think you'll need an adapter in all cases no matter what HF compression tester you use.

 

Slow crank speed will lower the numbers, metal valves on metal seats and metal rings against metal cylinder walls are NOT good air tight seals, lol, nor do they need to be at 200rpm(cranking speed), or running RPM 700-5,000rpm

But if cranking speed drops so do the numbers, and pretty fast

But you got usable numbers, and the reason for the misfire codes, 60 and 32

You can do a WET test to confirm its not a ring issue, numbers will always go up on WET test just not up to 101psi, your average, on cylinders with bad valve seals

I see new heads in your future

 

Will do another dry compression test again tomorrow as a sanity check to see if I get different numbers at mid day. I don't expect the diagnosis to be any different. Just want to see if i get different PSI readings at mid day outdoor temperatures. Will do the "good" cylinders first (2, 3, 4, & 6), then do the two bad cylinders (1 & 5). Then quickly will wet test 1 & 5, finally will wet test the remaining cylinders for good measure. EDIT: That doesn't make any sense. Will just do each cylinder one at a time: dry test first, then wet test before moving to the next cylinder. That is, as long as it doesn't rain tomorrow.

The good news is that I think this proves that this is the most economical way to DIY diagnose a P030x DTC. I think others would have thrown dough away on these parts:

• Spark plugs: $5.00 each
• Spark wires: $40.00
• Ignition coil: $100

That would have been $200 in parts wasted. In this case, it cost me $30 for the compression tester which I will use at some point in the future I am sure. Or, I could return it and lose a 10% restocking fee (think I'll just keep it).

Yeah, LoLoL! I must be a bit twisted. I should dump this right now. But I am thinking of fixing it if it is just the heads. Keep your fingers crossed for me that it isn't the piston rings :{

 

Since the 1980s piston rings last 400k miles at least, so long shot to have these failing unless there where other issues like long term pinging/knocking, but that usually destroys exhaust valves before piston and rings

 

Well, I managed to only do cylinder 1 before realizing the turkey baster method wasn't a good idea. Oil got everywhere. Will get some tubing and a small funnel for the rest of the cylinders. But here is what I got:

• Cold/Dry = 60 PSI
• Cold/Wet = 75 PSI

So it went up a little like you said, but no where near my average of 101 PSI. Piston rings?

EDIT: Probably will have to get an average across all cylinders before making the determination of head vs. piston rings.

 

I use a drinking straw to add oil to spark plug hole, i.e. Burger King, McDonalds, ect.......
Drip straw in oil, put finger over top, lift straw out
Put straw in spark plug hole, remove finger

Use a teaspoon of oil, it isn't that much, you can see how much that is by dipping the straw and letting it drain into a teaspoon(regular spoon), then you will know the "dip depth", lol

 

I tried the straw too. But it fractured. Figured a more limber tubing will work better.

 

LOL, you have to take the straw back out of the cylinder after adding the oil

Install the compression gauge hose and put some oil down the hose, blow into the hose

 

Of course I took the straw out of the cylinder. I meant, the straw broke as I bent it to work it into the cylinder to deposit a little oil. I'll use refrigerator water supply tubing. Smaller diameter than a straw but flexible and won't break like a straw does. I have that laying around.

Nah, isn't that hard to get oil into a cylinder :). Just working with limited time and light now between meetings and such.