I have been reading and lurking for a few weeks now and learning a lot about my Ranger. It's a 1998 2.5L with 216,000 miles. I bought it about 3 months ago and have been fixing all the little issues. Now in the last few weeks it has been harder to start when cold. I have cleaned the IAC, MAF, IAT, Throttle body. Replaced the ECT Sensor. I checked fuel pressure and it's about 60 to 65 psi when running. It does however bleed off when the truck is not running. From reading here it first sounded like the check valve for the fuel pump. I did the key on for 3 seconds then off and back on (three times) and it still had a very hard time starting. When it did start it ran VERY VERY rough. What I have done now a few times is as soon as I shut the truck off I release the fuel rail pressure at the shrader valve. Now when I start it, it starts pretty fast. Runs slightly rough for 3-5 seconds then smooths right out. To me it now sounds like the fuel is bleeding off past the injectors causing a flooded symptom. Does this sound right?

 

Welcome to the forum

Possible but easy test for that

All fuel injection computers have "Clear Flooded Engine" routine

Turn key on, cycle it on and off a few times if you want
Press gas pedal to the floor and hold it down <<< at 0 RPMs, with throttle wide open(WOT) computer will turn OFF injectors but spark will be on

Crank engine over, it should NOT start, it should NOT fire, injectors are off

If you have a leaking injector engine will fire

When you release the gas pedal injectors will start

 

Thanks for the fast response!
I have done the "Clear Flooded Engine" test and it does not start or act like it wants to. But if only one or 2 injectors are leaking would it try to fire up? To me they may be leaking and if I do not release the fuel pressure from the fuel rail it takes several hours for the fuel to leak past and into the combustion chamber. Just kind of thinking out loud here. I have read many posts from you and tried everything you have suggested to others. Just not sure now how to accurately diagnose a leaking injector on these.

Not sure if this helps but my mileage has gone from almost 18 mpg down to about 16 1/2 mpg in the last few weeks. I have run some fuel injector cleaner through it twice (some stronger stuff. not the cheapo 99 cents a bottle stuff!)

 

The MPG dropping is troubling and could be leaking injector(s) but engine would fire in Clear Flooded engine, even with a little fuel, you can wait an hour and then do the clear flooded engine test, to be sure, that would allow more fuel to leak in, if it is leaking in

The computer calculates open time for the injectors based on engine size, air flow(MAF), throttle position and fuel pressure
If you have a leaking injector extra fuel would be coming in and the O2 sensor would "see" that as less oxygen in the exhaust, Rich running, so computers calculations would be off and it would shorten of open time for the injectors to compensate for the extra fuel, and if there was enough extra fuel it would set a RICH code and turn on the CEL(check engine light)

But the drop in MPG could mean time for a new upstream O2 sensor, they do wear out over 150k miles or so, and they do cause Rich running as they go bad, so drop in MPG without setting any codes

At one end of the fuel rail is the Pulse Damper, it will have a vacuum hose attached, check that hose for gasoline, although rare the Pulse Damper can leak, so fuel would be sucked into engine via that vacuum hose

 

That all makes perfect sense! I will wait a few hours and the clear flood engine test again. I have checked the Pulse Damper and no fuel there. I can try the O2 sensor also. I wasn't even thinking that! I used to repair cars for a living but that was quite a few years ago. I'm a little rusty! LOL

 

I am kind of back to square one. I let it sit for about 5 hours and did the "Clear Flooded Engine" test. It did NOT want to start so I'm guessing I do not have an injector(s) leaking. But if I do not release the pressure from the fuel rail it is still very hard to start when cold. It acts like it's flooded. Once it starts it runs extremely rough for about 20-30 seconds then finally clears up.
If I do release the fuel pressure it can sit over night and start right up in the morning.

Any other ideas or things to check or clean that I have not done yet?

Thanks!

 

A bit of how it works
Gasoline can't be ignited by a spark, yes the movie guys take liberties, lol

Only gasoline VAPOR can be ignited by a spark
Gasoline vapor comes at fairly low temps, if you can smell the gasoline you are smelling the vapor, if its cold enough no gasoline smell so no gasoline vapor

Vapor level is the reason for the Choke on gasoline engines, and the reason for compression on any engine, to change liquid fuel into a vapor fuel
Compression is heat, heat causes vaporization of liquid fuel

You need a minimum of 30% vapor in a cylinder for spark plug to ignite the fuel
If the liquid gasoline coming out of injectors(or Jets) is at 10% vapor because engine is cold, then you need at least 3 times "normal" amount of fuel, that's what the Choke is for, on carb's the choke plate caused more fuel to be sucked in from the Jets, with EFI the computer uses data from ECT sensor and adds 3 times as much fuel to get the higher vapor for cold start

This higher liquid fuel level can temporarily foul spark plugs because they get wet so weak spark and no ignition
After a few cranks cylinders heat up from the compression strokes so vapor level gets higher spark plugs get drier and engine starts up, but it can run rough until all the liquid fuel is used up.
This also causes carbon build up as the liquid fuel bonds to metal surfaces prior to vaporizing.

With EFI the ECT(engine coolant temp) sensor is key to make sure Choke level of fuel is not too high, flooding the engine, or too low so not enough vapor for start up, either would act the same way, no start and rough running after it does start for a few moments.

New ECT sensor means a NEVER TESTED sensor has been installed, new used to mean tested and working, not anymore, lol


Spark plug gap is also important, the 2.5l shows gap of 0.044, which is "average gap" set by Ford
A gap of 0.049(wider) will give a stronger spark which is better for cold start and low end power
Smaller gap, 0.039, would be better for high RPM ranges, i.e. racing, it gives coil more recovery time for constant RPMs above 5,000

First I would check to see if engine is being Choked too much, do not release fuel pressure
Crank cold engine and if a no start pull out 1 spark plug, check its tip for fuel, wet tip
Also check its gap

You have a Dual spark plug engine, this is for performance, this same engine was used from 1974 to 1988 with just 4 spark plugs and a distributor
So after engine is warmed up shut it off
Unplug one coil pack, pull off its 3 wire connector
Start engine
It should run smooth lower RPM but no misfires, if its missing then one of the spark plugs or its wire is bad

Now shut off engine and reverse this
Plug coil pack back in and unplug the other coil pack
Start engine
Check for misfires

You can drive with just the 4 spark plugs, just less performance, but should run fine

One of the benefits of dual spark plugs is if one spark plug fails no misfire, one of the drawbacks is for the same reason, lol, because you don't know there is a problem until BOTH spark plugs fail
So good to check each sides spark plugs every now and then

 

Ron
Thanks for the info and advice! I will try this now. I appreciate you taking the time to respond!!

 

OK... I did the "Clear Flooded Engine" test again twice and both times it DID want to start up but then stopped. It chugged a few times then nothing. I could smell raw fuel too when this happened. Is this a good sign of leaking injectors?

I also did the IAC test when it was at normal operating temp and the RPM did not drop at all. So it looks like I have 2 separate issues.

 

Yes, possible leaking injector, now the hard part, taking out 1 spark plug from each cylinder

You don't need to warm up engine for this test

Do Clear flooded engine again but YOU need to be watching which spark plug hole is spraying out fuel, that would be the one with leaking injector
Cycle key on and off a few times before the test to get extra fuel at that cylinders intake port
Engine will have no compression so will spin really fast.

Or you can just get a set of 4 injectors for $70-$90

Yes, separate issue on the RPM
If you add extra fuel to an engine you get a flooded engine, add extra air and you get higher RPMs

 

Thanks again for the response!
I think it will be easier and better to replace all 4 injectors. I figure all 4 have the same wear and mileage. No need to do this multiple times!

I ended up replacing the IAC and now it still does not drop RPM when unplugged but it does increase the idle RPM at start up then drops down to normal idle. I'll leave that as is for now so I can focus on the injectors.