92 XLT fuel pump runs open! Plz help fix!

[1exploder]

I am unable to start my vehicle due to the fuel pump not shutting off.
I replaced the fuel pump relay w/ a kragen's $10 relay and it worked
for a minute (i.e. after the install I turned the ignition to the on position
and I could hear the fuel pump click on & off. However the following day no such luck).
Had it towed to my mechanic and after his troubleshooting
proceedures it left him scratching his head. I suggested the thread
advising about the inertia switch wiring causing a shorts to the relay
but he is not buying it yet...Any suggestion?

 

[Blacksheep Josh]

Try a new relay... maybe the one you had was defective..

 

[MrShorty]

A short in the inertia switch would not cause the pump to be stuck on. Some other short to power in the fuel pump circuit between the relay and the pump might do it, though.

Check for a short to ground between the coil side of the relay and the PCM.

Does it seem like the relay is stuck closed causing the pump to run continuously, or something else?

 

[unclemeat]

Replace the fuel pump relay with a Motorcraft piece.

 

[BrianDye]

Replace the fuel pump relay with a Motorcraft piece.

x2

 

[Verno]

Ok, I'm missing something in this story: You cannot start the vehicle because the fuel pump will not SHUT OFF ??????????????????
So what you are saying is when you turn key on, pump primes and keeps running? I would then say it is either Fuel Pressure Regulator, or a defective relay not allowing pump to stop priming, but your fuel pump SHOULD be running while engine is! This should NOT inhibit engine from starting

 

[1exploder]

reply

Ok, I'm missing something in this story: You cannot start the vehicle because the fuel pump will not SHUT OFF ??????????????????
So what you are saying is when you turn key on, pump primes and keeps running? I would then say it is either Fuel Pressure Regulator, or a defective relay not allowing pump to stop priming, but your fuel pump SHOULD be running while engine is! This should NOT inhibit engine from starting

My understanding is a fuel pump relay takes control of the fuel pump during engine startup, but shuts itself off after the engine is running. An oil pressure mechanism resumes control of the fuel pump after the fuel pump relay shuts off and the vehicle's engine is running. 'Yes' in my sistuation the pump keeps on priming. The mechanic sez the relay checks out okay...Now he is so busy
with high dollar jobs he doesn't have time to deal with my Explorer...He will do further checks when he has time...Nice hunh?!...I am in no hurry..As long
as he is willing to keep the repair price down to a minimum. I will mention your
suggestion but like I said it's getting the gas.

 

[1exploder]

Replace the fuel pump relay with a Motorcraft piece.

The mechanic sez he replaced it w/ a Ford relay and still a no go...

 

[nmos]

My understanding is a fuel pump relay takes control of the fuel pump during engine startup, but shuts itself off after the engine is running.

I could be totally wrong but I don't think that's right. I believe the fuel pump relay is ON whenever the ignition is ON.

 

[1exploder]

A short in the inertia switch would not cause the pump to be stuck on. Some other short to power in the fuel pump circuit between the relay and the pump might do it, though.

Check for a short to ground between the coil side of the relay and the PCM.

Does it seem like the relay is stuck closed causing the pump to run continuously, or something else?

Thanks...I will see if my mechanic has done that check regarding short
between coil side of relay and pcm...

 

[1exploder]

Thanks...I will see if my mechanic has done that check regarding short
between coil side of relay and pcm...

 

[snkmug]

Im having the same issue.....when the pump cycles and does not shut off, the car will not start? Replaced the cps and it was fine for a week or so, now its back to doing the same thing. If the pump primes then shuts off, the engine will start and run fine....fuel pump and eec relay is working fine....Checked the pcm grounds too....look fine

 

[DryDog]

I replaced my original fuel pump at about 175K, only because the whine it made was getting scarey loud. I haven't driven it in a while (my son's truck now) but I would swear that pump runs until the engine is shut off.

 

[snkmug]

does no one know how to fix this thing....sometimes it will start and run fine like today, other times the fuel pump runs all the time with the key forward and it will not start......

 

[squireofgothos]

Same problem...

Hey folks,
I have been having the same issue. Fuel pump runs constantly with the key in the on position. When it would do this, I could not pull any OBD-I codes. When it would run OK, I would pull codes, but none that made any sense considering the issue. I took it to a shop to have detailed diagnostics done, and the tech could not pull the codes when the engine would not run properly. Once it stopped "acting up" the readings showed MAF sensor showing both over and under voltage, which made no sense. It was running fine (which is why he could pull codes) so he told me to take it home and if it did it again, repalce the computer. Well, it acted up the very next time I started it. I replaced the computer and it seemed to solve the problem, but I was skeptical due to this thread. My neighbor (a computer repairman) looked at the board and immediately found the problem. One of the primary capacitors had corosion on the solder lead, causing the point to overheat and melt the solder trace. This accounted for the intermittent problem (heat the spot and it would run fine, or it would solidify with good electrical contact).

To sum up, $140 engine control computer fixed the issue. Here's the catch.... This issue is DEFINITELY a computer problem, but the trick is to determine what caused the fault. If the computer is failing due to a short in the system, then replacing the computer will result in the new unit failing in the same manner. In my case, the failure was in the computer itself. I took pics, and will post them as soon as I figure out how.

 

[Turdle]

Hey folks,
I have been having the same issue. Fuel pump runs constantly with the key in the on position. When it would do this, I could not pull any OBD-I codes. When it would run OK, I would pull codes, but none that made any sense considering the issue. I took it to a shop to have detailed diagnostics done, and the tech could not pull the codes when the engine would not run properly. Once it stopped "acting up" the readings showed MAF sensor showing both over and under voltage, which made no sense. It was running fine (which is why he could pull codes) so he told me to take it home and if it did it again, repalce the computer. Well, it acted up the very next time I started it. I replaced the computer and it seemed to solve the problem, but I was skeptical due to this thread. My neighbor (a computer repairman) looked at the board and immediately found the problem. One of the primary capacitors had corosion on the solder lead, causing the point to overheat and melt the solder trace. This accounted for the intermittent problem (heat the spot and it would run fine, or it would solidify with good electrical contact).

To sum up, $140 engine control computer fixed the issue. Here's the catch.... This issue is DEFINITELY a computer problem, but the trick is to determine what caused the fault. If the computer is failing due to a short in the system, then replacing the computer will result in the new unit failing in the same manner. In my case, the failure was in the computer itself. I took pics, and will post them as soon as I figure out how.

Thanks!. That is very helpful!

 

[squireofgothos]

Update.... Have been running with the new ECC for 3 days. The truck runs better now than it has as long as I have owned it. The new unit smoothed out the engine timing issue I had been having, and feels more powerful than ever. Thanks again for all of the help everyone!!

 

[Anime]

Mine seems to be having the same problem now. Over the past few years, just replacing the fuel pump relay has fixed all issues of the fuel pump running/not running, then just recently I had to change out the EEC relay as well. Now changing out the relays doesn't change anything, the fuel pump won't stop running with the ignition key turned, and it won't start. Looks like it's new computer time.

This should be a recall issue, too. It's great that they last this long, but really a solid state part should never have this kind of failure at all.

 

[EastoutWest]

Funny, I wish I would have had that issue when I went to drain my fuel tank. I sat there cycling the key for a half hour with the fuel line in a gas can before I remembered that I'm scrapping the vehicle and punched a hole in the tank...

And by my observations, I would say that (at least on my X) the pump is not turned off (key on, engine off) by a pressure regulator, it's on a timer. About 2.5 seconds of pumping every time I turned it to "on."