Fuel pump keeps running and truck wont start
 

My 92 f150 with a 4.9 had been running rough and dying over the last week. I thought I had the problem fixed when it died and I found a loose battery cable. Replaced the cable ends and the truck started fine but when I shut it off it would not restart. I cant get it to start for anything now and I need it to get to work.

I noticed that the fuel pump continued to run anytime the key was on. Im pretty sure it would always run for a couple seconds before and then shut off, but now it just keeps running until I shut the key off.

I replaced the fuel pressure regulator today, but that did not help. Also, now when I try to get computer codes it will not let me. I dont know if that is due to the pumop running or not.

Please help.

Anytime the fuel pump stays running with the key on it's either a stuck fuel pump relay or most likely a bad engine computer (PCM). Combined with the other issues you stated, it's most likely the PCM. Remove the connector, the retainer screws, then pull it out and open it. Look for signs of moisture, burn marks or leaking capacitors.

The PCM is located under the brake master cylinder/vacuum booster. It is removed from the engine side of the firewall.

I pulled the PCM out and opened it and dont see anything that appears burnt, or wet or "Abnormal" (not that I really know what normal is in this thing). I also swaped out the fuel pmp relay with another and it does the same thing. I do notice that the relay is clicking wildly as if it is getting power and then not getting it.

I dont really want to replace the PCM unless I am pretty sure that it is the problem. Is there any way to test this?

Just curious, if the fuel pump is running all of the time, shouldnt it still start since there would be pressure?

It will not start because the computer is not grounding the fuel injectors.
If the fuel pump does not run with the computer unplugged and the key on then you have a bad computer.

The fuel pressure regulator (FPR) or the fuel pressure has nothing to do with the fuel pumps running or not running.

Ok. So I turned the key on with the computer out and the pump did not run. So it is safe to say the computer is bad.

I had the EXACT same problem a few months back on my 91 4.9 turn on key fuel pump stays running and clicking relay and no start.... Replaced the PCM did the trick a few bucks but that was it!!! Thanks to FTE for solving my problem and im sure it will solve yours!! Good luck!
Donnie

Anyone know if the computer has to be an exact matc or will any of them from a truck with the 4.9 and standard Tranny work. There are a bunch of different options.

It will at least run with any 92 4.9 M/T module. The rest has to do with CA vs. Federal emissions, minor changes to sensors throughout production runs, etc. I used to sell computers and with Ford, Nissan, and Benz it's very rare that the numbers on the nameplate will match exactly even though it's the same computer. A computer for a 92 commercial truck shouldn't run you much $$, that's the good news.

Thanks for your help. I finally got the new computer today and the guy said to make sure to check all relays and switches before installing it or it will void the warranty. How do I go about doing that?

I guess what I am saying is can the components that need to be tested be tested at the computer plug?

Well you'd really have to check every circuit to the computer to say 100% there is not a problem that would kill the computer.

A computer just isn't that expensive so rather then go through all that I'd just take my chances.

You did enough testing as far as I'd be concern, the PCM and fuel pump circuits tested good without it connected so I plug it in and go for the "run". Just make sure the battery is disconnected when doing so, apply very light coat of dielectric grease to harness side connector before plugging it in.

I know I am bringing up an old thread but I have to ask because I just replace the PCM two years ago and I'd like to have to do it again. Here's my symptom. Hope it's not the PCM.

Turn the key to the on position and I hear what sounds like to fuel pump, but higher pitch than normal and just keeps running. Try to start and it cranks and cranks but no start. If I leave the key on for a few to 5 minutes, eventually the fuel pump changes pitch and pump shuts off. Try to start and she fires up and runs pretty well. I don't drive far but I've only one instance when it did an intermittent run then die thing, but I made it home.

Also, when its in the "no start" mode, if I spray some carb cleaner down the throat of the intake, she sparks and starts up and keeps going.

I guess I should note that the truck isn't used much these days as my father in law is doing chemo (i gave hime the truck to use around the ranch some years back) so it probably only runs once every 6 weeks or so, or when I'm visiting him (and I live 16 hours away so that's only 5-6 times a year), and it sits out in the Oregon rain the rest of time. It's only go about 70000 miles on it and we'd really like to keep her going, but also hope it's not another PCM. Thanks for your help.

I had the same problem with my 94 ford F-150. It would run sometimes and sometimes it wouldnt. I would be driving it and it would start running real rough and then try to die. One day when i went out to start it, it wouldnt start but just crank all the time. I replaced the alternator and it quit having the problem. Im not saying that this might be yours but have the alternator check out. Just trying to help out. Let me know what you find out.

I would say for what ever reasion the clock is not running in the computer.
This could be a bad computer, poor ground to the computer or voltage.

I cannot answer why it start on starting fluid and then run OK unless the clock started running the same as if you left the key on for that time span. I would guess bad caps in the computer.
As you know with the pump running and not timing out the fuel injector will not fire either without the clock running.

I think the battery voltage is good since the truck cranks for a long time off of the battery. Any ideas where I might check for bad ground or poor voltage connection. All of the accessories in the truck work just fine. I see no indication of a bad ground. Are there any checks that you can suggest so that I might be able to isolate. If I have to get yet another ECM, I have two weeks to get it and install it before I have to get back to work.

dezertdirt:

I do not know what year the truck is so I can not give you any ground locations. Pins 6, 40 & 60 are the ground pins at the computer plug.

But you can check the plug at the computer as a lot of the posters have fixed such problems by just unplugging the computer and plugging it back in. Make sure no pins are pushed in.

Did you use a lot of dielectric grease on the plug when you replaced the computer?
If not that alone causes a lot of computers to go bad around wet conditions and engine washing as the old grease dries up.

Also check the red wire going to the injectors from the power relay for voltage while cranking as it is the same red wire that powers the computers pins 37 & 57.
Pin #1 gets it its power from another location.

A little follow up on the ole F250. Although the battery was brand new (3months old) the voltage on it was just under 12 volts. i charged it with a trickle charger and the next morning the fuel pump behaved properly (it shut off after a second or so). I got it running and went out and ran it daily and that seemed to help. I did notice that when running the voltage from the alternator is a bit high, running at about 15 volts (although it will got down to 14 after an hour or so of running) where most vehicles I've worked on run about 14 volts. I'm not sure what that's all about. The power is pretty good although I think I have a miss on one of the cylinders. I don't think it's spark as all cylinders light a timing light. I guess it could be a fuel injector or a vacuum leak as some of the small vac tubing for heater controller is all cracked fromm sitting. It almost sounds like an exhaust leak at the manifold but I checked for that and couldn't find a leak.

Anyway, the next round of diagnostics is set for April when I go back up to check in on father in law. cleaning fuel injector, fixing vacuum leaks and whatever else needs fixing is in the plan. I suspect the truck won't get many miles between now and then but I'm feelin pretty good about myself as when I went up there he had an unusable vehicle and now its running ok. Starts fine, plenty of power for what he needs. Thanks for all the help. This is really a terrific helpful forum. I have another non-ford truck and their forums are not nearly as clear, supportive or helpful.

Oh, and subford, I did use dielectric grease when I put the new ECM in last Christmas. Thank you for all your help

I realize this is an older thread and the OP never came back with a resolution, but the one additional thing to consider here is a marginal PCM relay - the one that sits right next to the fuel pump relay.

I believe the resolution was either a slightly too low battery voltage for no use and or a marginal fuel pump relay from the same combined with sitting out in the winter weather. When I left at New Years she was running ok with the exception of this miss (that has the sound of an exhaust leak when it's under load. This issue has existed for at least 10 years and no one has been able to diagnose it. However, now that I own another properly running six, I know the ford just isn't right. Like I said earlier, I have my work cut out for the next round of diagnostics...it's either spark, a fuel injector not getting grounded or a bad fuel injector...or the exhaust leak I've never been able to find. Thanks to all

Well, i know I'm bringing up an old thread but i talked with my father-in-law today about the truck. He says that its taking about a minute for the fuel pump to bring the system up to pressure and then the truck starts fine. Until that time, the truck won't start. I guess I'll check the grounds next time I'm there, regrease the computer plug, change the fuel filter and maybe have the alternator checked. i was also thinking about taking a look at the fuel injectors to try to address the miss that the engine has had. I had hoped it tough starting from lack of use but i guess that wasn't it.

Did anyone think to spray a little starting fluid into the eng. intake to see if it would run even just for a moment. This would tell you if the computer is able to start your eng. It might be a great idea to make sure there is fuel in the tank, stranger things have happened before. Good luck, that's my two cents, if you want more you'll have to ask.

If the fuel pump runs for a minute and then it starts it is the computer that is keeping it from starting in that minute.
More than likely a bad computer but read on.
It is taking a minute for the clock to start running in the computer.

It may also be low voltage or a bad crystal in the oscillator circuit of the computer. This is taking for granted that the replacement computer has the right spec replacement caps in it that they changed out when they worked on it.
At any rate the oscillator circuit in the computer is not starting up for a minute or so.

Note Bill's comments above. We really need to know, very specifically, what you mean by your statement above. There are several ways to interpret what you wrote.

I didn't read the entire thread as I left for work but from now on I will. Excellent observation on your part. You keep talking and I'll keep listening.

Normally, when you start the truck, you would go out turn the key to the "on" position. You could hear the fuel pump fire up and humm for a couple of seconds and then shut off. Turn the key to "Start" and she fires right up. Recently, at Christmas, I went up with my family to visit my wife's mom and dad so that I could fix up whatever needed fixin and to share the holiday. This time, the truck when the key was turned to "on", you could hear the fuel pump humm but instead of shutting of after a couple of seconds it would continue humming. When I tried to start the truck, it would just continue to turn over but not start. When i sprayed carb cleaner in the tb, it started and continued to run, a little rough at first but then normal. When I drove down the road (country highway) a few miles, it ran fine mostly but did cut out a couple of times for a second but then continued to run. It did this for about a 10mile round trip. When I got back, I charged the battery good as I noted the battery voltage was a little low (about 11.5 volts) on a battery that was 4 months old (I bought it in August. After that I ran the truck nearly daily during the visit, including one off road expedition on the sand dunes, and it ran ok the whole time.

It's now been a few weeks and my father-in-law says its starting to do the same thing again, although he seems to be able to start it after about a minute. The computer is only a couple of years old (at most) and it was the same part number as the one it replaced (a California-based 4.9L with a manual transmission. It worked good for a couple of years.

So now we're plannig a visit at spring break and am hoping to get the truck running reliably again (I'm actually considering new fuel injectors as I think I have one bad one). Anyway that's my story. I looked for another computer from parts geek and the one model that it is out of stock is the one I need ("Y" in the engine code in the VIN, California based 4.9 with a manual). Thanks

Normally, when you start the truck, you would go out turn the key to the "on" position. You could hear the fuel pump fire up and humm for a couple of seconds and then shut off. Turn the key to "Start" and she fires right up. Recently, at Christmas, I went up with my family to visit my wife's mom and dad so that I could fix up whatever needed fixin and to share the holiday. This time, the truck when the key was turned to "on", you could hear the fuel pump humm but instead of shutting of after a couple of seconds it would continue humming. When I tried to start the truck, it would just continue to turn over but not start. When i sprayed carb cleaner in the tb, it started and continued to run, a little rough at first but then normal. When I drove down the road (country highway) a few miles, it ran fine mostly but did cut out a couple of times for a second but then continued to run. It did this for about a 10mile round trip. When I got back, I charged the battery good as I noted the battery voltage was a little low (about 11.5 volts) on a battery that was 4 months old (I bought it in August. After that I ran the truck nearly daily during the visit, including one off road expedition on the sand dunes, and it ran ok the whole time.

It's now been a few weeks and my father-in-law says its starting to do the same thing again, although he seems to be able to start it after about a minute. The computer is only a couple of years old (at most) and it was the same part number as the one it replaced (a California-based 4.9L with a manual transmission. It worked good for a couple of years.

So now we're plannig a visit at spring break and am hoping to get the truck running reliably again (I'm actually considering new fuel injectors as I think I have one bad one). Anyway that's my story. I looked for another computer from parts geek and the one model that it is out of stock is the one I need ("Y" in the engine code in the VIN, California based 4.9 with a manual). Thanks

It would probably be worth a shot to pull out the existing PCM (computer) then inspect the circuit board for signs of burning or pitting from leaking capacitors. Leaking caps are a VERY common problem and can be repaired for a few dollars in parts.

All I can say is re-read my post #23 above.

The other thing you can test is the ignition coil check the power going in and out. Do the same thing to a couple injectors.. If you got the same voltage on both wires, can't pull any codes, and the fuel pump keeps running it's safe to say it's the PCM or these trucks it's called the EEC. And the injectors and ignition coil ground through the computer so if they don't have a ground it's safe to say the computer is at fault. I just went through the same thing with my truck and finally diagnosis is a bad PCM. I got one coming Monday but I'm pretty confident it's the problem. I got a no start got fuel pressure and spark. Fuel pump won't stop running when key is on and I had no communication with a scan tool.

I am having a similar Problem. I have a 94 f250 5.8 It sat for a couple months that resulted in a dead battery. I tried to boost it off with my S10. It almost started one time but I felt the S10 just didn't have enough juice to turn it over quick enough. Next tried to boost it with my diesel jetta. Never did start again. Eventually, I determined that my pcm was bad after some diagnostic help from another thread. Not sure if I fried the pcm trying to boost it off or if it was just coincidence. Got the new cardone pcm in and plugged in. The truck starts now but runs very rough and the fuel pump runs continuously with KOEO. Not able to read the codes either. A side note is my engine compartment got soaked during a heavy rain after I failed to shut the hood (After diagnosing bad PCM and before installing new PCM) . Could moisture cause these symptoms? Im gonna try some of the advice listed above tomorrow.
Thanks

Sounds like another bad PCM with its clock not running. Take it back and try to get a good one.
Make sure the PCM has all three of its grounds and all three power sources verified.

Installed a second computer today and having the same problem. No you know where I can find more information on checking the power sources and grounds? Im not having much luck on searching. Thanks

The main body & PCM Computer grounds:
http://i54.photobucket.com/albums/g9...Bodyground.jpg

Computer case ground:
http://i54.photobucket.com/albums/g9...s/1995G104.jpg

http://i54.photobucket.com/albums/g9...pscgxodb9r.jpg

http://i54.photobucket.com/albums/g9...lwithkey-1.jpg

http://i54.photobucket.com/albums/g9...e-Relaybox.jpg

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Thanks, I feel pretty good about the grounds. Looking into the power sources now. My Battery is showing 64%. Had it tested today and per the advance store its good just needs charged. Prior to today I had been using a trickle charger... never got above 11.5 volts in 2 days on charge. I have it on a better charger now. Not sure if that could be related or not. Did try the jump start feature of the new charger without success.

Fuel pump
 

I have an 86 swb f150 5.0 v8 4x4 with a granny low 4spd. I put a brand new battery in it 2 days ago. I put negative cable on first. Then positive cable. The ignition was in off position and key on the seat. When I touched the positive cable to the positive post it sparked a little, then I heard a humming sound. The humming sound was fuel pump running while truck is off and key not in ignition. I removed positive cable and it stopped humming. Truck will still crank and run, but the battery is almost completely discharged in two days if I don't drive it. What causes the fuel pump to run like it does with truck off and key not in ignition? The fuel pump comes on and does what it's supposed to like normal when I crank the truck and it's running. The only time the fuel pump does that humming is when I first put a new battery in it. But it's still draining the battery in two days. Everything else that draws electrical power in the truck system is turned off. Why am I having this problem?

EEC relay is likely in need of replacement.

Is there a place on the internet that I can put the vin in a get the wiring diagram for the truck?

No there is not. Autozone has some diagrams available if you have an online account with them. Basic stuff, but there is some useful info. You can purchase Ford EVTMs from E-bay and other sources.

Bad computer simptoms i had on my 1990 f150
Bad idle, truck didn't want to move , rich exhaust some days truck would start some days wouldn't fuel pumps ran constant with key on engine off couldn't pull codes also check engine light on . i have another donor truck 1990 as well with a 302 aod i pulled the computer out of it and trucks runs fine. so a 351 and 302 comutor will interchange