countryboy

92 4.9 6 still having problems starting no local guys can come up with an answer.Heres a new twist that i noticed if i just turn the key to on and the fuel pump runs a few secs and then shuts down it fires right up .But if it runs continuously then maybe 40 tries later it will start.(fuel press. at rail was good on earlier test no smoke when it does start ,,after it cranks the first time starts every time till you let her sit several hours,,Is there afuel press. sensor that tells pump to cut off that maybe causing my problems.I used apiece of tubing and listenedtoeach of the iject. and the press.regulator.they seem to be cycling just fine

Good old Bill

Led to believe the pump runs on a timer in the PCM. Works when key is turn to on, just 2-3 seconds and turns off. Lets see what the pros say.

countryboy

Since no one else seems to know looks like you may have it .Last time truck would not crank i tapped on computer box and it has fired off every time since then .
thanks again

countryboy

Need to know if PCM has timer for fuel pumps .Thought i had it fixed worked fine for a couple of weeks.Started same **** all over again.Tap on PCM did not work this time but after several tries truck finally started.Please if any body can help dont want to buy a new PCM if i dont have to .
THANKS FOR YA'LLs help ROY

Fast Hampster

My guess is that a PCM just turns the pump on for a time of a self test when you turn the key (2-3 sec). But it's really hard to believe that it's a timer-related issue. I think of following things - fuel pump relay (it might be sticking or providing not enough current due to bad contacts or both), it might be a fuel tank switching valves problem if you have dual tanks. Have you checked the time while fuel pressure drops with key off?

Good old Bill

The PCM does have an internal circuit for the pump just to prime the fuel rail for starting. Its not a replaceable timer. Its solid state stuff. The fuel pump relays come onto line after the engine starts and keeps the pumps running untill engine is turned off. Try to get a replacement at a junk yard, wonder if Ford has them available as rebuilts and at a cheaper price.

Fast Hampster

Thank you, Bill, i've never mentioned that that "timer" can't be replaced separately in my post

Tmkiowa21

To add to this.When the key is turned to on the pump will prime for 2-3 seconds and then set off you can confirm this with a volt meter.This is only for preignition of the vehicle.when starting the fuel pump relay will pick up and then supply power feed to the pump agin confirm with volt meter and not test light because low volts will not pick up....hopw this help

TMM

generalmotor

replace the puter with a new one or a junkyard piece make sure it doesn't have a sim card or chip inside. If it does make sure you get the one out of yours to put in the new computer you get it is like the soul of the car it wont run right without it. I know that the fuel pumps on those are controlled by the computer and it is pressure sensitive. Just a bunch of chips that rattle around in there and occasionally they come loose. My father had the same intermittant problem with his but he spent around 650 to a mechanic to figure his out.

Maintenance 6

There is a safety feature that kills the fuel pump if oil pressure drops. There is an over ride in the system for start up when there is no oil pressure. Check the oil pressure sending unit and the circuit.