why wont my ranger start right up? - Ranger-Forums - The Ultimate Ford Ranger Resource


4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 04-14-2014
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why wont my ranger start right up?

I have a 2001 4.0 ranger with a 180,000 miles on it and it ran fine until about 9 months ago. when its cold it starts up just fine but when the weather gets into the 60's I have to pump the gas peddle and crank it over 2 or 3 times before it will start. some maintenance info, I bought it used in 2011 and have the oil changed every 3000 miles. I had the gas filter changed in 2012 and I was getting about 360 miles to the tank. when this problem started the first thing I did was to clean the Mass Air Flow Sensor, but the problem still was there, next I took it next door to have it tuned up and it still had the same problem but I was on my way south and had to leave the next day so I put it off till I returned a month later, I took it back to the same place and a new owner looked at it and replaced something on the top of the engine near the front, not sure what it was but it was small and expensive and I checked with ford and they confirmed the price (about $300), I have the paper work somewhere I just have to find it. make a long story short its been ringing fine all winter starting right up but now that the weather is warming up its having the same problem again and now I'm lucky to get 250 miles to the tank and I don't want to take it back to the people I've been taking it to because so far they've gotten me for about $1400 and I just don't trust them, I'm on a fixed income but I'll spend the money because I love the truck because it holds my tools and I just had all the bodywork done and painted after someone side swiped me while i was sleeping and had the police officer not left his card i would have never found out, the other driver was being chased by the police for driving drunk and luckily had insurance and the insurance company was more the happy to pay for any damage and then some so my truck looks brand new and has very little rust and in none at all so I'd like to fix this problem but I don't know what to do, I'm a carpenter not a mechanic so any suggestions would be great , thanks for reading
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Old 04-15-2014
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Just FYI, pumping the gas pedal doesn't do anything on fuel injected engine....no accelerator pump like a carb had.

Your engine is getting too much fuel, I know duh, lol, lower MPG says that.

A cold engine needs more fuel(i.e. choke), so no issues on cold starts, colder weather/air also needs more fuel so again you wouldn't notice it as much with the denser air(cold air).

Warmed up the engine needs less fuel in the fuel/air mix.

So what controls fuel air mix at start up?
MAF is the main sensor for fuel/air mix
IAT(intake air temp) sensor plays a part, it is part of the MAF sensor on your year.
ECT(engine coolant temp) sensor also plays a part in fuel/air mix, fuel injected engines have the ECT "sensor" which has TWO wires, and a Temp SENDER, for the dashboard temp gauge, this one has ONE wire.
These look the same.
O2 sensors are not used on startup

Since MAF was cleaned already and IAT is probably OK because it pays a small part, I would check the ECT sensor first.

ECT sensor is easy to check with OHM meter but hard to get to, it will be under the throttle body on the front of the lower intake just above thermostat housing, remember you want the TWO wire one.

For the ECT to effect warm start but not cause CEL(check engine light) to come on it would have to go to high resistance(ohms) when sitting and then jump to lower resistance(ohms) once engine starts.

Computer sends ECT sensor 5volts which passes thru the ECT's resistance and goes back to computer, high resistance(cold) would pass lower voltage to computer so it "thinks" engine is cold and sets "choke mode" for cold starting, so extra fuel is sent to engine.
As ECT warms up the resistance gets lower so computer gets a higher voltage and it reduces the extra fuel.
Computer has a timer that starts with the cold engine if ECT voltage is not changing within 5 minutes CEL will come on.
If ECT wire is disconnected, 0 volts at computer, CEL will come on.

When warmed up ECT will show about 2,000 OHMs, when cold about 20,000 OHMs, these are not meant to be exact, computer learns ECT values, so "about" is the key word.
If ECT resistance is changing(so no CEL) but is not going low enough then computer continues to run engine rich which lowers MPG.

New ECT sensor should cost about $35, so up to you if you think changing vs testing is better, these rarely fail, not never fail, just rarely.



Another test to do is for sticking/leaking injector, it could be causing a rich condition which effects warm starts and MPG.
All fuel injected engine have a "clear flooded engine mode"
To get computer into this mode do this:
Turn key ON, do not crank engine yet
Press gas pedal to the floor and hold it there(no pumping, lol)
Now crank the engine

Engine should NOT fire or start, this "mode" turns off fuel injectors but leaves spark on.

If engine fires a bit or starts then there is fuel in the intake, and there shouldn't be

Warmed up engine is best for this test.
If you release gas pedal while cranking engine should startup normally

Last edited by RonD; 04-15-2014 at 11:00 AM.
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Old 04-15-2014
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wow thanks Ron, that's the first detailed answer I've gotten. when the guy tuned it up he told me he cleaned the fuel injectors but I'm not sure he did anything.

I'll try the sticking/leaking injector first. so if it turns out I have fuel in the intake what should be done?

I'll just go ahead and change the ECT sensor after, if its only ~$35 to see if that clears it up. if that fails would you recommend I change the MAF?

thanks again
Jim
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Old 04-15-2014
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What might be a good investment and fun to have, is a OBD II reader.
If you have a smartphone then you can get a $30-$40 bluetooth interface that plugs into the data port on the vehicle and then get the FREE app(make sure the interface has a FREE app before buying it).
Then you can monitor sensors and fuel in REAL TIME, at idle and while driving.

You can then check MAF voltage to see if it is within spec, also other sensors like the ECT and O2s.

These work on any OBD II vehicles, so anything made after 1996
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Old 04-16-2014
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I tried starting the engin with the gas peddel to the floor and it wouldn't stary, took my foot off the gas and it started right up. My luck it was in the 60s yesterday and today its in the 40s so its starting right up anyways. I'm checking out OBDii righht now for my nook, easyer to reed the screen. Now if I'm not getting waarrning lights will the OBD still be able to ddetermin if there's a problem?


Again thanks Ron

Jim
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Old 04-16-2014
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Yes, looking at OBD II readings can point you in the direction of a problem.

The Codes that come up are helpful but most people misinterpret them and start replacing sensors when it was the sensor that detected the problem, lol.
"Shooting the messenger" is common for DIYers.........and some mechnics
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Old 04-16-2014
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my 99 did the same thing your truck is doin it was the coil pack that's what fixed mine
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