Hard Start problem Pinpointed. I Think.

[Spartan]

I posted up a while ago that my 92 EX was having trouble starting. On the first turn of the key after sitting (warm or cold) it would crank forever, but not catch. On the second turn of the key, it would catch right away.

I bought a Fuel pressure tester the other day, and this is what I got:

Idling, FP was right where it should be, and it drops like it should when vac is reconnected to the FPR.

I noticed that the pressure WAS NOT holding after the priming cycle was done when you first turn the key. It went to around 40PSI, and bled back off to 0 within 5 or 6 seconds.

I replaced the FPR, just for giggles, and tested everything again. The truck actually starts better...... and now it responds to the "multiple key turns before trying to start" trick.


My Diagnosis? the anti-drainback valve in the tank. I never have a problem while driving, but every cold start is a pain. You could not hear the pressure leaking out of the injectors, and since there is no fuel leak anywhere, thats the only thing that it could be, right? Its a good thing.... i have to replace the pump/sending unit anyways because of a faulty float.


Does this sound right??

 

[Spartan]

WOW. 34 views, and nobody has any ideas? I just wanted to know if I was right, or if I'm overlooking something.

 

[mschewll]

i posted up a while ago that my 92 ex was having trouble starting. On the first turn of the key after sitting (warm or cold) it would crank forever, but not catch. On the second turn of the key, it would catch right away.

I bought a fuel pressure tester the other day, and this is what i got:

Idling, fp was right where it should be, and it drops like it should when vac is reconnected to the fpr.

I noticed that the pressure was not holding after the priming cycle was done when you first turn the key. It went to around 40psi, and bled back off to 0 within 5 or 6 seconds.

I replaced the fpr, just for giggles, and tested everything again. The truck actually starts better...... And now it responds to the "multiple key turns before trying to start" trick.


My diagnosis? The anti-drainback valve in the tank. I never have a problem while driving, but every cold start is a pain. You could not hear the pressure leaking out of the injectors, and since there is no fuel leak anywhere, thats the only thing that it could be, right? Its a good thing.... I have to replace the pump/sending unit anyways because of a faulty float.


Does this sound right??

i have the same problem a 1992 explorer,, it always starts perfect
on the 4th try,, and it is only when it is cold ,, i was told it was
the fuel pump relay.
Has anyone else had this problem

 

[Roadrunner777]

Is the pressure still dropping with the new FPR? If so, then it's going to be the fuel pump (there is no discrete valve, per se), or a really leaky fuel injector. If it were a leak, I guess you would smell the fuel. Actually, there is one more possibility. The fuel pump has a short rubber hose (like one inch) connecting it to the hard line. Clamps, etc... If there were a leak there, it would be quite hard to detect.

I have heard of people who never really resolved this past the multiple key turn procedure. A few have simply hotwired the pump to the ignition circuit. The ramification of this is that if the key is on, engine not running, and you develop a leaky injector, you could fill the intake with raw gas, which would be problematic.

 

[Anime]

There are times when the old relays (fuel pump relay and/or EEC relay) cause fuel pump issues. I've had several oddball ones, all of which were solved merely by replacing the relay. You might save yourself some hassle trying a new one, or even better, get a bunch from the salvage yard out of another Explorer/Ranger/etc. Always a good idea to keep a couple spares in the vehicle anyway in case a starting issue pops up so you don't get stranded because of a relay.

If different relays don't change anything and you're dropping the tank anyway, I'd agree on just going ahead and replacing the pump, especially if it's the original. Usually the original is mild steel and so is completely rusted away, and you'll need to use a magnet or other methods to get the rust out of the tank before installing the new one. If the old pump assembly is rusted that bad, it's best to just spring for the new assembly with the pump attached, often it's just a few bucks more than a solo pump. If the assembly is in good shape you can of course just swap pumps and throw on a new float.

If a new pump does nothing, maybe you're looking a blockage (fuel filter), leaky injectors, leaky o-rings on the injectors, or even something like a cracked/split fuel hose or fuel line somewhere. You'll need to inspect every inch with a flashlight from the pump to the injectors, all along the driver side framerail and around the engine.