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Discussion Starter #1
I have an intermittent problem in my 1993 truck fuel injected engine. It may start and run normally for months and then decide it does not want to start. Sometimes it will sit overnight and not start in the morning and other times it will not start even though it was just shut off from a moderate distance run five or ten minutes ago.

What happens is that the cranking is normal but it acts like there is no or very little fuel getting to the cylinders. It may very briefly start but then die in one or two seconds. On occasion, when it does do the two second run if I can goose the throttle the engine will run fine for several minute if I keep the RPMs up around 2 or 3 thousand. Let it go back to around 1500 and it stumbles. L If it gets down to 1000, it will just die like it is out of gas.

If I wait an hour, or sometimes more, it will then start and run normally. I do not believe it is a vapor lock problem since it can occur with an overnight cold (30 Dg F temps) or on a just run 90 Dg day. The problem may come for a day or two and then, without anything being done to the engine, not appear again for four or five months. My garage guy even came to my house one time when the truck would not start. He tried starting it and it failed a few more tries and then, without him doing anything at all, it started up and ran normally for several months.

Other than this nagging problem, the truck runs fine. If it were a carbureted engine I would think a low speed jet blockage but since it is a fuel injected engine and there is only the one injector which runs fine if the the RPM is kept up even when the stall/no start problem happens it would seem the fuel pump and injector are working ok. It has the old style diagnostic connector, which hasn't been around for many years and neither he or I have a code reader capable of handling this old system so we can't even get a history code if one is actually set. There is not abnormal engine light when the this happens so I am not sure a code would even be set.

Any thoughts, anyone.
 

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Have you checked the fuel pump for pressure/volume? The in-tank fuel pump is likely culprit.
 

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Do a google search on the year, make, and model for your OBD I code reading procedure. Some use a test light while others require you to cycle the key from off position to on a few times to retrieve stored codes..
 

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Found this on the net. I was figuring it has something to do with fuel pump, and air flow sensors. Make sure your fuel pump is working when it does not start by doing what is said below. Pressure needs to be high enough to vaporize the fuel. Could be the fuel pump is not drawing correct amperage.

"Do the easy stuff first.

Use your Special Service Tool (paperclip) to jump FP and B+ inside the diagnostic connector. With key on, engine off you should be able to hear the fuel pump running. If you can't hear the pump, a bad pump is a likely diagnosis. If you can hear the pump, and it will start and run, you have a problem in the VAFM-COR circuit (which shuts off the pump when the computer doesn't sense airflow through the VAFM). If you can hear the pump, but it won't start, you need to check for fuel pressure (bad pump, clogged fuel filter, etc.)

Notice that you need airflow to keep the truck running. If you disconnect the air filter to spray starting fluid, the VAFM can't sense air flow and it will shut off the fuel pump.

Last, if it runs with the paperclip, don't be tempted to drive around that way. If you have an accident that breaks a fuel line, do want the pump to keep running? Find the problem and fix it.

Good luck!"
 

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I have a 2004 Ford Expedition - about the only thing to go wrong with it was this type of problem - turns out there is a relay in the power supply to the fuel pump. Ford's answer was replace the entire fuse panel (the relay dwells within) - $325 for the part & $300 labor. I opted for finding the relay on-line ($10) and replacing just that...

It is a known issue with the fuel pump power supply in Ford trucks. Tiny little relay carries the power to the pump - I could see right where it burned when replacing the old one.

Do you know someone with a 'Code Reader?' Chances are it will show up there - it did on my truck (DTC - P0231).
 

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Discussion Starter #8
Thanks to all. I will be talking with my garage man today and see if he can locate an OBD 1 reader. I will also mention the fuel pump relay (if it has one) and the Idle Air control. From what the IAC does, it sounds like it could be and I did not even know such a thing existed. I will have to find out where it is at, if it is on this old engine, to be able to give it a rap or two when the problem occurs next time.
 

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How many miles on it?

Flashmax is probably on it,

Can you "inline" a temporary gauge to see what the pressure is next time this happens?

DGH
 

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Start with a simple test, next time you have the issue, turn the key to the off Position then turn the ignition one click to the on and let it sit for a moment then try starting the car. It may be a bad check valve in the fuel pump. If there is no difference then you need to have the system checked for intermittent power to the pump, poor pressure and low volume. Some special test equipment and time is needed you could be chasing an intermittent short
 

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22-re's are great motors. Sounds like either a fuel pump or air flow sensor.

Not uncommon for the fuel pump or air flow sensor to fail after several hundred thousand miles.. Good luck
 

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Replace the lines from the tank to the frame rail. I went thru this for months on mine, more so during the heat of summer. It was the last ditch effort, took the tank off to check for debris and noticed that the hoses were super soft.
 

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I had a cracked air intake pipe on my 93 cruiser that caused the same types of problems. I noticed the crack while removing the pipe to check to airflow sensor so I duct taped it and the problem went away. I ordered a new pipe and installed it and no problems since - that was about 5 years ago.
 

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Discussion Starter #16
I took all the suggestions and thoughts, except for wolfram's, to my garage man. (he had already closed for the day). I will be seeing him tomorrow. I will report back here after he has had a chance to check out the assorted things suggested. Only problem with such a highly intermittent problem is you are never sure if you actually found THE problem or if it just decided to hide it for a year or two. I know that I absolutely hated intermittent problems in the electronic and/or computer equipment I had to repair. You could never be absolutly sure that you did actually fix the problem since it might show up months later.
 

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If you are not getting a check engine light there will be no codes and the old ones have no easy way to get data, I fixed one years ago that had the same symptoms every time there was a hard rain. There is a fuel pump relay in the right kick panel, truck had a windshield leak and very time it rained the relay would get wet.
Some of the other trucks had a relay called a circuit opening relay which also feeds the fuel pump, these would also have intermittent problems at times.
 

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Discussion Starter #18
My question about the fuel pump and/or fuel pump relay issue is if I can get it started and hold the high RPMs (3,000 or higher) without load,it would seem to my non-engine service trained mind, that the fuel pump would be sending fuel to the injector at a higher rate than when the RPMs drop down. Isn't the fuel pump just a single output pressure pump regardless of low or high RPMs? Does the pump pressure or volume change at the pump output? I thought that it was the injector pulse on duration that controlled the amount of fuel actually getting to the engine.

Now I can see where a higher RPM creating a higher fuel flow might push past a fuel line obstruction like a pinched fuel line but does the actual pump pressure or volume get modified by the engine computer?

Sorry for what might be a dumb question but my training on engines went out of date when breaker points and capacitors and vacuum spark advance timing system were replaced by transistorized ignition.
 

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Toyota salesman up the road has the wammy on you & your truck from his little radio box as he drives by. He'll offer you a great deal on a new one. Just pulling your chain, Joe
 

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If it starts and runs for a couple seconds and then dies, that is the symptom of the circuit opening relay. The truck is designed to have direct power to fuel pump while cranking and then switch over thru the relay once it gets a signal that it is running.
Pump pressure is constant with fuel delivery changed by injector pulse width. One item overlooked on the old ones is the fuel filter mounted along the frame rail or above the starter, that can cause all sorts of intermittent running issues before it plugs up totally.
 
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