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2.9l Fuel Fouling Number 3 Cylinder


88 XLT Ranger

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Spark Plug fouling issue

I got my problem area figured out number 3 cylinder keeps getting fuel fouled. Its due to non evaporated fuel "rich mixture" it does it most when engine is under a load. I have changed the fuel injector for that cylinder I have also changed the MAP sensor, O2 sensor, TPS sensor, checked fuel pressure many of times in the driveway its good

Its an on and off deal run like crap popping than once the fuel evaporates off the plug it runs perfect. Its a pain in the Azzzz when it does it now I get out change the plug where good to go until the next hill to climb
 


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2.9l computer used Batch fire fuel injection.
On a V6 that means 3 fuel injectors open at the same time, it just alternated between each set of 3, so it would not be a computer problem or you would have 3 cylinders with over rich issue.

#3 is at the back of the engine and engine is angle down at the back, so maybe your Fuel Pressure Regulator(FPR) is leaking fuel in to it's vacuum hose, and that fuel is running down into #3 area.

FPR is front passengers side of engine, fuel return line is connected there, it's vacuum line runs back to upper intake, check vacuum line for fuel or fuel smell
 

Mark_88

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2.9l computer used Batch fire fuel injection.
On a V6 that means 3 fuel injectors open at the same time, it just alternated between each set of 3, so it would not be a computer problem or you would have 3 cylinders with over rich issue.

#3 is at the back of the engine and engine is angle down at the back, so maybe your Fuel Pressure Regulator(FPR) is leaking fuel in to it's vacuum hose, and that fuel is running down into #3 area.

FPR is front passengers side of engine, fuel return line is connected there, it's vacuum line runs back to upper intake, check vacuum line for fuel or fuel smell
This actually makes more sense than anything else suggested...and we did suggest the FPR quite a while ago but it was ruled out...and this particular aspect was not brought up at all...

Worth another look...does putting the engine under load increase vacuum? Would it increase it enough to override something and allow fuel to drip excessively?

I've never worked on these engines and have no idea about the physical layout of them (I did have one originally but tossed it due to oiling issues before I even got to work on things)...
 

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Ron & Mark

I checked the FPR the vaccum line has no fuel or fuel smell in it. I had a heck of time trying to get to start this morning. It would turn over slow try to kick over but woulden't fire up. I took and hooked up another battery to it turned over quicker. It still would kick over a few times I pulled number 3 plug wet I cleaned it. I tried to start it would kick over a few times the next time I got in as it tryed to kick over I gave it some throttle it fired up but was loaded took a few min to clear out. It seams like its getting to much fuel on cold start up when its hot no issues starting turns over quick
 

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All Fuel injection computers have a "Clear Flooded Engine Routine"

Turn on the key
Press gas pedal to the floor and hold it down all the way
(TPS, throttle sensor, will send 5volts to computer and with 0 RPMs showing computer will shut off fuel injectors, this is Clear Flooded engine routine)

Crank engine a few times, it shouldn't start or even fire, no fuel

Now check #1, #2, and #3 spark plugs for fuel

There are only a few ways for fuel to get into the intake and into a cylinder.
Fuel injector

Leaking FPR, vacuum hose to intake.

Leaking Fuel rail, while I have never seen it happen myself, the fuel rail is sandwiched in between upper and lower intake and it could leak fuel into the intake.

Pull upper intake and cycle key on and off a few times to build up pressure in the fuel system.
Look for fuel leaking in, I assume at rear by #3
 

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All Fuel injection computers have a "Clear Flooded Engine Routine"

Turn on the key
Press gas pedal to the floor and hold it down all the way
(TPS, throttle sensor, will send 5volts to computer and with 0 RPMs showing computer will shut off fuel injectors, this is Clear Flooded engine routine)

Crank engine a few times, it shouldn't start or even fire, no fuel

Now check #1, #2, and #3 spark plugs for fuel

There are only a few ways for fuel to get into the intake and into a cylinder.
Fuel injector

Leaking FPR, vacuum hose to intake.

Leaking Fuel rail, while I have never seen it happen myself, the fuel rail is sandwiched in between upper and lower intake and it could leak fuel into the intake.

Pull upper intake and cycle key on and off a few times to build up pressure in the fuel system.
Look for fuel leaking in, I assume at rear by #3

Ron

I had no idea of "Clear Flooded Engine Routine" as it kicked over a few times I gave it a little throttle it would fire up. When I had the upper intake off changing the injector I pressured up the fuel system to check for leaks. I have a powerful probe light there was no leaks inside or out. The FPR vacuum hose plastic with runner ends I sucked on it and it held vacuum. It might be the IAC not going to high idle thus hard to fire up. I did clean it a while back the idle came down before it was up and down. The fouling of the plug under a load a strain on the engine going up the highway grades as it goes from 65mph to 45 before it fouls the plug out I cant figure out. Maybe the FPR under a load its pushing to much fuel in the engine?
 

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FPR is a pretty simply device, it just has a spring and valve in it
Spring will allow valve to be pushed open at about 42psi of fuel pressure.
Vacuum pulls against the spring pressure so you get about 30-35psi fuel pressure while idling, high vacuum.

If you pull/block FPR vacuum at idle you will see FPR's max pressure with spring only, should be under 45psi.

25 to 45 psi pressure and engine would still run fine, no lean and no rich.

If you pull off the IAC valve and then hook up it's wires, turn on the key and you will see it's valve open all the way for starting, then unplug the wires and it will close all the way, repeat a few times to make sure it is opening all the way each time.


If you do the Clear Flooded Engine test is the #3 plug still wet with fuel?
 
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Mark_88

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LOL...I had to research the FPR and possible answers...only to find you posted an answer while I was researching...

So I deleted my answer...:)
 

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FPR is a pretty simply device, it just has a spring and valve in it
Spring will allow valve to be pushed open at about 42psi of fuel pressure.
Vacuum pulls against the spring pressure so you get about 30-35psi fuel pressure while idling, high vacuum.

If you pull/block FPR vacuum at idle you will see FPR's max pressure with spring only, should be under 45psi.

25 to 45 psi pressure and engine would still run fine, no lean and no rich.

If you pull off the IAC valve and then hook up it's wires, turn on the key and you will see it's valve open all the way for starting, then unplug the wires and it will close all the way, repeat a few times to make sure it is opening all the way each time.


If you do the Clear Flooded Engine test is the #3 plug still wet with fuel?
Thanks Ron

knowing more of how the FPR works I will check the IAC valve. When I cleaned it I did the test with it off to see if it was opening all the way it was but I only did it once. I got it running good now will do the Clear Flooded Engine test when it fouls the plug out again pull it see if its still wet with fuel
 

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Clear Flooded engine routine only works if throttle cable hasn't stretched, if it has then you no longer get WOT(wide open throttle)

Google: Ranger throttle cable mod

Simple fix to get full throttle back
 

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Clear Flooded engine routine only works if throttle cable hasn't stretched, if it has then you no longer get WOT(wide open throttle)

Google: Ranger throttle cable mod

Simple fix to get full throttle back

Ron

I fired it up I got it figured out on first start up as soon as it tries to kick over I give it a little throttle it fires right up. It seams a little loaded up If I let it start on its own it wont fire it tries to kick over. I drove to town today ran perfect up the 6 mile grade I pulled over to make sure its out of 4X4 its snowing here. I got back on the highway ran perfect for 1 mile once I took the off ramp and stopped as soon as I started moving popping. I stopped pulled number 3 plug perfect burning good it seams. This might be number 6 plug issue I replace the injector on that one as well. I remember last time I pulled it the plug seamed black carbon looking. The darn plug wire boot was stuck new wires I couldn't check it and it was raining/snowing to hard

The second time I stopped for 15min fired it up its running perfect again all the way home
 

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"I am sick of this pile of shit" :annoyed:

Can't anyone figure this out? I drove home popping like hell. I checked all plugs all burning perfect even number 3 dry. I fired it up pulled number 3 wire from cap I can see the arch but not change in engine. I took changed the plug 3 times still no change pulling the wire from the cap. I took and switched number 3 and Number I on the cap. I got a lot differaint popping noise and misfire I pulled number 1 plug looks good and dry. I put number 3 and 1 back fired it up running perfect. I pulled number 3 plug wire I herd the change in the motor. I also tried disconnecting the FPR vacuum line and plugging the plenum off. It ran no change in anything. I did run it disconnected with 1 and 3 switched and smelled a lot of fuel. I don't know changing the plug don't seam to help

Would it hurt the motor to run it with number 1 and 3 switched? I was thinking maybe less chance of number 3 fouling. When I pull number 3 wire from Dist cap the arch seams weak number 1 arch is much more powerful it seams. I did notice the old cap number 3 pole in side the cap was corroded real bad. I think number 3 has issues on spark maybe being so weak fouls the plug?
 
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Mark_88

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Without ever working on one of these engines I don't know the routing of the plug wires nd what they may be passing over or around.

Are you using those plastic wire separators, does the wire come in contact or close to any metal anywhere on the motor or did you try to isolate it from all metal contact.

It is otherwise impossible for the rotor/cap combination to limit spark to one particular plug so something is affecting the way the spark is getting to the plug...the excess corrosion tells me that it is shorting out somewhere...somehow...so that could be all that is causing the problem...sheild that number 3 wire...even put that plastic coated corrugated stuff on it if nothing else is available...to stop it from arching out.
 

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Are you sure it is gasoline that is fouling #3?

Could it be water/coolant?
 

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Without ever working on one of these engines I don't know the routing of the plug wires nd what they may be passing over or around.

Are you using those plastic wire separators, does the wire come in contact or close to any metal anywhere on the motor or did you try to isolate it from all metal contact.

It is otherwise impossible for the rotor/cap combination to limit spark to one particular plug so something is affecting the way the spark is getting to the plug...the excess corrosion tells me that it is shorting out somewhere...somehow...so that could be all that is causing the problem...sheild that number 3 wire...even put that plastic coated corrugated stuff on it if nothing else is available...to stop it from arching out.
Mark

I will make sure its not close to and metal see if I can get a covering for that wire. It has the stock wire separator on the valve cover
 

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