87 f 150 4.9 troubles

[bigbadrat]

ok here is the problem,truck will sit and idle till it will run out of gas.but with in 2 minutes of driving it,it starts to bog down like it is out of fuel.then it will crank but not start.sometimes if i hold it to the floor it will start but then shut bad down.if i try a few more times,then it will start back up and run.but within a few minutes it does it all over again and will not start.

i have replaced the fuel pump on the frame.new fuel filter,cap rotor,plugs and wires.tried a ecm another distributor and even replaced the injectors.i do know that the fuel pumps in the other tanks are still working.i am just really puzzled about this.

is there anybody out there that has had the same problem.


please help me because i am going crazy

[mechhound]

The first thing you need to do is determine if it is a FUEL DELIVERY problem or an IGNITION problem. At the point where it will no longer start, you need to see if you still have spark at the plugs. My favorite way to test this is hook up my timing light and see if it flashes while cranking the engine. I realize not everyone has a timing light. If you are losing spark, I would say it may be the coil given what you already replaced. If you still have spark, get a guage to check the fuel pressure at the schrader valve.

[bigbadrat]

well i did check to make sure i have spark and i do everytime.i havent checked to see what kind of pressure was coming out of the valve on the fuel rail.i guess i better check that tomorrow.

thanks for the quick reply and for ur info.hopefully it is something so stupid i have overlooked.

[bigbadrat]

anybody else has idea of what it might be?i was told converters were clogged but that isnt the case.

[cujafish]

did u replace the coil ?
problem with coils is that they dont break - they weaken
under load ( while moving) the coil may not be putting out enough juice for the distributor

also check mapping sensor

the kind of problem u have is 80% issue of : fuel pressure (pump/regulator)
or not enough spark -coil

[bigbadrat]

well i was starting to think about the coil being it but was unsure of that.also the pressure regulator could be bad and not letting the right amount of fuel when it is under a load.i know all the pumps r fine.i guess i can try those 2 things out tomorrow to see what i get.

[Donut Dunker]

Mine did that - i put aftermarket locking gas caps on it, they did not vent right, you might try taking off gas cap, make sure system is venting properly, mine would run about 2-5 minutes then act like it was out of gas

[bigbadrat]

thing is they r the original ones on the truck.just the weird thing is that it will idle till it is blue in the face but once i get it under a load is when all hell breaks lose.