I've been having a on going problem with my F150 5.0. It will stall out from time to time. Then it would run fin again. I was convinced it was a ignition problem, so I replace the pickup coil, cap, rotor, ICM, and coil. Plugs were also replaced. I was sure I had fixed it when I replaced the coil, it ran fine for about 2 months. Today it acted up again. I pulled in to a parking lot and it died. I cranked and no fire. The needle on the tach was jumping around with KOEO, I opened the hood and I could hear a arching sound coming from the area of the coil. I had heard this one other time along with the tach jumping. I figure it had to be the coil. This time I was able to jump up and get my hand in there. It seems like what I was hearing was either all, or one injector pulsing none stop. Still was not firing, so I checked for spark, I had spark. I pushed the shreader valve and gas came out, so I had fuel pressure. At this point I assumed the engine was flooded. So my son and I sat down for a while. It took a lot of cranking, but it started to fire, and fine started up. Ran rough most of the way home, then kind of smoothed out.

So, here's my question. What could cause an injector to fire none stop and make the tach jump? I know my way around a engine, but sorry to say I'm a GM guy, I'm a bit rusty on Fords and need a little guidance.

 

do you know the "pedal trick"? . . . if you hold the throttle to the floor while cranking, the injectors wont fire. if you are workin on it and suspect it to be flooded, this trick is useful cuz you can crank it without adding more fuel.

if youre getting juice to the injector then your ecm might be on its way out. check all grounds, and all the injector connections you can (of course the infamous ford tsunami intake manifold really gets in the way of that).

 

Thanks. yes, I know about floor it no gas. Still took a while, I could smell raw gas.

When I get a chance I'll have to go over all the connections at the injectors.

Hmm, never thought about the ECM. The engine seems to run fine, then it acts up, seems to have no rhyme or reason.

 

I had issues with random shift problems and decided to remove the connector at the ECM and clean the connectors with a pipe cleaner. It took care of the shift issue, rough idle, and my Keep Alive Memory failure code went away. You might wanna check that connector too!

 

I'll have to do that, any idea where the ECM is located so I'm not searching all over?

 

It's on the lower corner of the firewall, driver side. There should be a 10 MM bolt through the center of the connector that you loosen to remove it. You'll see the big wad of wires haha. It should be very easy, but if you wanna take the ECM out, that's kinda harder (You don't have to if you just wanna clean the connector). But on 1990 I think it comes out from the kick panel in the interior. My 92 comes out through the engine compartment and the fender well needs lowered.

 

ecm issues are often accompanied with "no rhyme or reason" conditions. in these trucks, its actually not the worst place to start if youre stumped (other sensors check out fine). theyre like 20 bucks at my local junkyard, cant imagine them bein much more where you are.

 

Sounds like a I have good area to try out. Worth a shot I guess. I'm totally stumped.