I have a 1990 F-350 EFI460, here is the story:

1.Key will not start truck, will turn power on, but have a trigger starter jumped directly on celonoid to start truck.

2. New Fuel Pressure Reg.
All Cyl firing properly
fuel pressure around 35-45psi
Full tune up


My truck fires right up(sometimes need to have foot on gas pedal), most of time will stall immediatly if not on the gas, and always popps and backfires out the exhaust. Will not idle just dies.

Cyl's seem to be flooding, plugs are constantly wet.
Fuel pump used to shut off a sec or 2 after turning key on. Now it does not stop.

ALL VACUUM LINES ARE IN GREAT SHAPE, and hooked up where they belong.

I was trying to pull the codes using the SDI and noticed two wires hangin around the fuel pump relay that appear to be cut.. One is Dark Green/yellow that the diagram says is supposed to be for the ignition module , and the other is tan and light green(diagram says should be connected to fuel pump relay).. they are both cut and do not appear to have a match(another same color wire to be connected too.)

Truck running like poo and I really need to figure this out.. any help would be appreciated. This truck sounds like a popcorn machine.

The kid I bought the truck from said that when truck started doing this he would slam the door and sometimes it would run great for like 20-30 min. Just figured I would throw that in here.

 

Check to see if the ignition switch to ignition coil power wires is keeping power after the key is turned. The ignition system gets some power from the "I" terminal on the solinoid while the starter is engaged.

 

replace MAP sensor,all the injectors should be clicking, youcan feel them click with your finger,sometimes they stick if truck sat for a long time,replace starter solenoid to fix starting problem,clean all terminals,check for melted wires ,fusible links,tripped ignition collision cutoff switch

 

Thanks, I will go through these things tomorrow and hopefully she will purr..... Will the MAP make it pop and backfire at idle? every few seconds it pops out exhaust right near bottom of collector.

 

your fuel pump should run for two seconds when you turn the key on then shut off until you crank,you can bypass all the fuel pump relay and run a 12vswitch direct to the pump if all else fails,,,did you check the ecm relay(usually brown colored),its good to know where it is often over looked,,a bad map sensor will flood the engine and the engine barely run ,it needs a good engine vaccum to it,,,,,my truck has two starter relays(f53 chassis) not sure if yours does,,,,also you might try replacing the ignition switch,,(not the ignition key switch) it usually has two tamper proof torx bolts, it sometimes mounted on the steering column, sometimes near the key switch

 

ok this is what I have discovered today.. The Fuel pump does not shut off. When I turn the key on the fuel pump(stock in tank) does not turn off. The injectors do not seem to be closing, hence it can not build pressure to turn the pump off. I am pretty sure that is why once started it is backfiring out headers. We know the injectors are ok because we changed one and it was still the same. What controlls the injectors? anyone have any ideas? The truck ran fine, then it sat for about 2 months.

 

I found a bad ground today, fixed it and still no good. Also discovered fuel in the oil. I am so lost with this thing. I may pull the injectors and fuel rail tomorrow and turn the key on and see if the injectors are leaking.

 

ecm might of gone in open loop mode, bad ecm ,rare but it happens,i would first find the hot wire to the fuel pump back in the tank disconnect from harness and run a hot wire direct from the battery with a switch to control it,i'v done it no biggie,i just used a house 110 switch to control the 12v,those switches never melt or burn out,makes a good anti-theft gizmo.the hot wire to the pump is usually pink with a black stripe,check with volmeter

 

ecm might of gone in open loop mode, bad ecm ,rare but it happens, MAP sensors not alway throw a code,i would first find the hot wire to the fuel pump back in the tank disconnect from harness and run a hot wire direct from the battery with a switch to control it,i'v done it no biggie,i just used a house 110 switch to control the 12v,those switches never melt or burn out,makes a good anti-theft gizmo.the hot wire to the pump is usually pink with a black stripe,check with volmeter,,, also replace all your spark plugs and ignition wires

 

ok so your saying, the ECM is why the injectors are not doing anything and are stuck open? How do I get the computer out of open loop?

 

Used a noid light today, computer sending signals to injectors fine, changed fuel pump relay. Pump still not turning off.