I am new to the forum and hunting for some advice. I have a 1990 F-150 inline 6. I have recently replaced Coolant Temp Sensor, Thermostate, O2 Sensor, IAC, Plugs, Wires, Cap,and Rotor and whole bunch of other stuff. I have done my best to rule out any electrical issues, but the problem persists. First thing in the morning I start it and it immediately stalls. Once it warms up it runs great and usually does so for the entire day. I though for a while it might be a fuel pressure issue, i.e. loosing pressure over night, but I don't think so.

I have been reading alot about the EGR Valve possibly being stuck open. Have any of you run across this problem. What did you do to fix it. I am getting ready to drive across country and trying to get this things taken care of. It's driving me crazy.

 

Hello revchad....

I will tell you right now, I am not too smart when it comes to these new cars and trucks. But it sounds to me like you're getting eitherr too much fuel or not enough when the engine is cold. If you have an injector or 2 bleeding off, you could possibly get this problem.....at least thats 1 of the possibilties I have read about trying to learn how to work on these newer ones. I am trying to learn some things about my '96 and if I stumble upon some more ideas for you to think about I'll make sure to post it for you

 

Thanks for the input. I did an experiment the other day and tried to prime the fuel system by turning to ON and the OFF a couple of times before starting. Didn't start well but felt like it was flooded. In my mind that confirms what your were saying. The regulator should have prevented that from hapeening and should also act like a check valve keeping fuel from draining back into the tank while it is off. I think the regulator is shot. The problem now is that in turning my key back and forth, perhaps a little too fast, I messed up the ignition linkage. Driving down the road last night and the starter kicked on and the key isn't going back to ON after starting. I hate working under the column, kills my back, so I dropped it off at the mechanic's this morning. He can fix my igninition issues and perhaps the other problem while he's at it. I be sure to post the solution if we find one.

 

Are you sure you replaced the right coolant temp sensor. Unless I am wrong it has one for the guage and one for the computer. If you did the one for the guage the computer may think it is colder then it is and be flooding it.

 

Nope, you're not wrong, it does indeed have two. The one for the gauge has a single wire, and the one for the ECM is two wire. The single wire one (gauge) should be down on the intake manifold in the water jacket on V8's, but not sure where it is on the I6 (perhaps the side of the block?), and the ECT for the ECM is normally mounted in the tee where the lines for the heater split off. Dunno why Ford put 'em where they did, nor why they felt two were needed, but I'm sure some engineer had a reason. Technically or theoretically, one is measuring ENGINE temperature for indication, and the other is measuring COOLANT temperature for fuel control. To me, woulda made more sense to add an analog output to the ECM and drive the gauge with that. But, I work in the industrial world where we do things that make sense. (sometimes)

A quick test of the FPR/injectors is quite easy. Push the accelerator to the floor, turn the key to START, and the truck should NOT crank. If it does, leaky injector, or possibly a leaky FPR. Pull the vacuum line off the top of the FPR, cycle the key to ON a few times to let the pump build pressure, but don't start the engine, and see if fuel leaks from the nipple on the FPR. If so, replace the FPR. If you have a fuel pressure gauge, connect it to the Schrader valve on the fuel rail. Turn on the switch a couple times and the pressure should get up to around 55-60 PSI on the 300 6 banger. (45-50 on the V8's). It shouldn't leak down any more than 2 or 3 PSI in 5 minutes. Leaking down faster than that will probably mean the FPR is weak, or again, a leaky injector. The first two tests would have told you which, though.

Do these tests on a COLD engine. No point in risking fire and much bigger problems with the truck, and having your face burned off will ruin your day.