I have been messing with this problem for a few weeks. Here is the problem, on the 92 f150 300 w/e4od. When you go to start the truck, and turn truck to on, the fuel pump starts, but does not shut off. Go to start, and the truck just cranks and cranks, does not start. It does this almost all the time, sometimes, when it is warm outside, it will start up, but will run real rough(With CEL on) and after a few minutes something clicks, and the idle settles out and it runs smooth. Thereafter, when its warm it will start and stop like it should.

Things I have done/checked. Fuel pressure at rail@50PSI. Checked 1 fuel injecter with noid(Blinked on and off) Pulled codes(Got one for ground/constant running in fuel pump circuit) Checked/swapped around fuel pump & ECM relays. Checked fuel pump relay by itself with 12V(Coil pulled in contacts like it should). Checked ECT sensor, resistance got less as temp got more and referance voltage read 4.53V(On harness). I put new plugs, wires cap and button on. Battery is fully charged, and engine turns over really good. This has got me stumped. I wonder about the fuel pump being weak...or possibly the ECM being bad(As it is supposed to open a ground and therefor kill the fuel pump circuit during starting, until it sees a crank indication). I am getting a little tired of this thing, but dont want to start throwing parts at it. Any troubleshooting ideas?

 

I had same problem last fall with my 92 351.When cold out below 30 degrees

truck fuel pump would not shut off and no start issue would happen. When

temps went up above approx 30 degrees would turn key on and listen to fuel

pump and it would whirl for about 2 to 3 seconds and the truck would start.

I tried first pulling the IAC valve and cleaning it with throttle body cleaner and

still had problem on cold mornings.Then I changed the fuel fiter which was full

of crap and also allowed the line to drain.With fuel filter off had turned key on

to pump line clean from pump to filter area.Replaced fuel filter nad have not

had problem since.Good luck hope this helps.


PS. When getting replacement fuel filter pick up replacement fuel line snap

springs and fuel line tool (looks like a pair of scissors) if your line is same

style. I got filter ,line tool and line springs from local napa store.

 

Well, Swapped out the fuel filter. But it didnt help. I guess it needed done as dark colored fuel drained out of the dirty side of the filter. Any other suggestions?

 

well, does it have spark? does the tail pipe smell like gas when your cranking it? are the plugs fouling?

 

Well, I tinkered with it a little bit more today. However, I dont feel like I am any closer to a solution. I pulled a spark plug, and it was sparking(cant say how strong a spark it was). Then pulled the wire off one injector to stick a noid light on it, to see what it was doing, it was blinking(During cranking). Cranked, no start. So, I hit it with a shot of ether, it hesitantly started, but ran really rough...very rich(Black smoke@500RPM idle). Let it run for a while, but decided to pull the wire off the injector again. This time I noticed the light was blinking alot brighter(Not sure if thats what it is supposed to do or not) Do the injectors work off of a full 12v or what? Then after a while, something clicked, then the idle smoothed out and it wasnt running rich any more and the idle adjusted itself to about 750-800rpms(Where it normally is). Shrugg, I just cant seem to understand what it could be. I amleaning towards the computer...but they are so expensive to buy, I wish I had one to just pop in and try it. Open to suggestions!

 

I am fighting a similar problem with my 96 f250 460. Won't start right off in the morning but starts fine after initial start. I am going to replace the IAC valve tonight. I tried the Ignition Control Module, didn't help. I have done the obvious, Fuel Filter, plugs, wires, cap, rotor. Need help also.

 

Im about 95% sure my problem rests with the ECM. I checked the grounds and found one of the grounds going to the ECM wasnt right. SO I repaired it and it didnt do a thing. SO then I pulled the ECM, and opened it up. Theres a burn spot on it, which to me is good enough to warrant buying a new one.

 

Well, my procrastinating self, finally went and got a ECM, and it was indeed the problem. Truck is ok for now! Thankfully.

 

Looks like your patience paid off.You could have thrown a lot of parts at it for nothing. It's not very often the computers go bad.