Was driving my 94 ford 150, 4.9 dual tanks down the road the other day and it started acting up. Would lose power and engine light would come on. Then engine light would go off and would be back to normal, done this many times before I finally made it home. Turned truck off and tried to start again. Would not start, then noticed as soon a I turned the key to the on postion the fuel pumps would run all the time. Would never shut off. So checked pumps and fuel line to motor all looked good. But when I got up front noticed that when the pump was running it would by pass injectors and run threw fuel rail straight back to the pump. At this point I was lost. So these are the things I have done so far and none of these have helped. Changed regulator, Switched all relays around, Checked for bad fuses, Changed tp sensor, Changed fuel filter, Changed egr sensor, Checked pumps, Changed air/idler control, Checked fuel pressure, Changed map sensor, Checked computer since engine light was on (No Codes where brought up) Changed computer. Not many idea's left from me but really hoping somone has had same problem before and can help me out. Pretty sure it is a electric problem somewhere but where I have no idea. What ever tells those pumps to kick off is the problem I believe but think I have changed most things that mess with that.

need help please

Jabster

 

drop the tank and check the wires going to the fuel pump.

 

ECM tells fuel pumps to shut off if engine is not sensed rotating at 150 rpm.

Try reset ECM by disconnecting battery for 1/2 hour.

 

Fuel pumps not shutting off sounds like a bad computer(which he replaced already), only othre thing to suggest is that there is something grounding the fuel pump relay. Sounds logical since the same method is used ot test fuel pressure with KEY ON/ENGINE OFF.

If you disconnect the battery, this may be a good time to check for a short or ground between the fuel pump and relay located in the Power Distrubution Box.

Hopefully my logic doesn't sound too far-fetched.

 

Thanx for the help so far but not out of the woods yet.


Tried this here really thinking it would do nothing.

(ECM tells fuel pumps to shut off if engine is not sensed rotating at 150 rpm.

Try reset ECM by disconnecting battery for 1/2 hour.)


Was great when it worked though. But was short lived. Anyways here is what happened. Disconnected battery like g_50 said. Waited around for a while went back turned the key on pumps primed like they should. Started it up ran fine everything was working great. About 5 minutes later Check engine light come on and started to act up again. Was running really rough finally died. Turned key off and back on and pumps where on running once again. Never would change intill I tried this method again.

So tried this method 2 more times it all worked the same each time. So now I'm back to believing it is a bad computer once again. Now I did say I changed this but buddy of mine has a truck just like this and we just swapped them and nothing changed on either truck. We did not let them sit with battery cables off and reset. Not sure if that would make a difference or not. But thats why I said this had already been checked.

Too me this would not be a short or any type of grounding. Seems it would not act the same each time if this was the case. So now this is why I think computer again. Ok where do I go from here. Should I get my buddies computer again and change them but let them both sit so they can reset then try. Or is there some other way of testing this. Do you guys agree this still sounds like computer issue or not?

One other thing to clear up we are talking about the main computer on the passenger side behind glove box right?

 

Still looking for more info if anyone can help.