I have a 93 F150 5.0 that won't start. The fuel pump comes on when cranking and i have spark at the spark plugs. I also have verified the fuel rail is pressurized at the pressure test port. When trying to start, it just cranks and won't fire. If you let it sit a couple of days, it will hit on a couple cylinders and then just be dead. Another strange thing is if you pump the gas pedal, it will fire a couple of times but not start. Otherwise it just cranks.

I changed the fuel filter thinking that was it and it fired for 3 second very roughly and then nothing. This is a farm truck that doesn't go on the road, so we don't want to just throw parts at it and spend big bucks. It has 360,000 miles on it, but it is a useful tool and we'd like to get it running again. Any advice on what to check? Thanks.

Dave

 

How did you confirm that the injectors were not firing?


Perhaps the engine is flooded, meaning to much fuel?
Try cranking the engine with the gas pedal floored.
This shuts off the injectors and will clear out a flooded engine.
Just lift your foot once of if it starts.

 

Does the fuel pump continue to prime with with the key in the run position(starter not engaged) or does it stop after about a second? If the pump continues to run there is a good possibility the PCM is bad and must be replaced but check that the fuel pump relay isn't stuck closed as well.

 

Well i thought they weren't firing, but they are. I sprayed starting fluid in the intake and it still didn't do anything, so I pulled the fuel pump relay and it started and ran for about 10 seconds. I pulled the dipstick and the oil that is only about 2 months old smelled strongly of gas. That made me think the fuel regulator was bad, so i replaced it. Now it starts cold, runs with a miss, and and runs worse and worse as it warms up. If you try to restart when its warm, its flooded and you have to floor the gas pedal. So I did the jumper wire thing on the computer and it said the ECT is bad. I think the regulator was bad but i also have other bad parts. I'll replace the ECT and see if it fixes it.

Thanks.

 

Exactly what codes did you get?

 

I got code 21 (Engine coolant temperature (ECT) sensorincorrect signal) in the engine off test. Once it gets warm it won't run long enough to do the engine on test. But I've seen some people say that code 21 is a normal code from cold operation, so I'm less ready to just replace the sensor.

I've borrowed a fuel pressure testor and i'm going to test the pressure and see if it leaks down (leaking injector). Then I'm going to attempt to test the ECT with an ohm meter before i replace it.

Any advice is appreciated.

Dave

 

I did a fuel pressure test this morning and here are the results:

Initial pressure after sitting 2 days: 0

Key on and fuel pump runs for 2-3 seconds: 10 #

Running: 33-35 #

Full throttle: 40 #

Key off immediately drops to 30#

10 minutes after key off 20#

15 minutes after key off 16#

28 minutes after key off 5#

My oil smells strongly of gas. Does this mean i have leaky injectors?

Thanks,

Dave

 

A bad regulator would bleed the fuel back to the tank, a bad injector will bleed the fuel into the intake and then into the cylinder and then past the rings into your oil. So I would have to say you have one or more leaky injectors. It may be only one. Now the question is, is how to determine which one?


Never had this problem so I can't help.

 

This is where you go old school and read the plugs. A single wet or really sooty plug is a dead giveaway.. that hole has a leaking injector. If all or many plugs are black then all those injectors could be dirty and leaking a bit.. this wouldn'e be surprising with a high milage, but the problem could also be a bad MAP sensor, or a leaking FPR(fuel is sucked into the intake through the vacuum line), O2 sensor dead or missing or the computer is fubar.

 

I determined i had multiple injectors that were leaking, so i installed rebuilt ones for all 8. The truck runs better but still will not start when hot unless you floor the gas. Also, it will start when warm/hot if you remove the vacuum line from the regulator. Anymore suggestions? BTW, the regulator is new.

Thanks,

Dave