# Fuel pump works a little while cranking, but otherwise not at all



## chandler48 (Jun 5, 2017)

If the system never pressurizes, the pump won't know when to stop pumping and should pump a solid stream with the key on. It could run intermittently from the suction on the engine pulling the fuel into the injectors. I'd almost say your pump is fried. The water didn't help.


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## Brainbucket (Mar 30, 2015)

Key on, fuel pump only run for a couple of seconds, then shuts off. Cranking it should run continuously.


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## HotRodx10 (Aug 24, 2017)

Brainbucket said:


> Key on, fuel pump only run for a couple of seconds, then shuts off. Cranking it should run continuously.


That's good to know. Maybe I'll try turning the key off and then on several times while I have the line off, and see if I get anything.


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## chandler48 (Jun 5, 2017)

Brainbucket said:


> Key on, fuel pump only run for a couple of seconds,


Not always. Only if the ECM tells it to stop. Older models relied on pressure to stop the pump and it started running when cranked as well. Of course this may not be an "older" model.


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## Domo (Nov 9, 2018)

The first problem is the water - drain your tank and lines and refill with known GOOD + Fresh gas.

After that - move to the next problem and let us know...


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## HotRodx10 (Aug 24, 2017)

Domo said:


> The first problem is the water - drain your tank and lines and refill with known GOOD + Fresh gas.
> 
> After that - move to the next problem and let us know...


I would, but I don't know a way to accomplish that without dropping the tank. That's that I was trying to avoid if it's not necessary. Since it died before there was water in the tank, that's obviously not the original problem. If I have to go to the trouble of dropping the tank, I'll probably replace the fuel pump assembly, anyway. I had a GMC where the fuel pump conked out at about this point in its life, so if it's not the problem now, it might be soon, anyway.


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## Nealtw (Jun 22, 2017)

HotRodx10 said:


> I would, but I don't know a way to accomplish that without dropping the tank. That's that I was trying to avoid if it's not necessary. Since it died before there was water in the tank, that's obviously not the original problem. If I have to go to the trouble of dropping the tank, I'll probably replace the fuel pump assembly, anyway. I had a GMC where the fuel pump conked out at about this point in its life, so if it's not the problem now, it might be soon, anyway.


That's your answer. Did GM ever have an access hole, they didn't in the 70s.


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## HotRodx10 (Aug 24, 2017)

Nealtw said:


> That's your answer. Did GM ever have an access hole, they didn't in the 70s.


They apparently did in the Impala at least from 2000 until 2005. I don't know about earlier models. 

My 2002 Sedona has an access panel in the floor for the fuel pump assembly. My #$%@% GMC Safari did not, and of course, the pump died while we were on vacation. I hate having other people work on my vehicle, and really hate paying through the nose for it.


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## HotRodx10 (Aug 24, 2017)

I suppose the most obvious culprit is the pump, but it spitting gas during cranking the engine made me wonder if there could be something else going on.


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## raylo32 (Nov 25, 2006)

Interesting, no GM I ever owned had an access hole. That was one thing I dreaded in my 1994 Z28, failing fuel pump. But it never happened and I sold it as a "historic" car, so it was over 20 years old. Got lucky, I guess. IIRC many people with these 4th gen Camaros would cut their own access hole rather than deal with dropping the tank.

Th other thing you need to do is check fuel pressure whilst cranking and again while running, if you can get it to run. That will tell you a lot. Some of those older GMs with the spider injector run higher than typical fuel pressure and it has to be in spec to start. Just subjectively "pumping fuel" is not good enough.



HotRodx10 said:


> They apparently did in the Impala at least from 2000 until 2005. I don't know about earlier models.
> 
> My 2002 Sedona has an access panel in the floor for the fuel pump assembly. My #$%@% GMC Safari did not, and of course, the pump died while we were on vacation. I hate having other people work on my vehicle, and really hate paying through the nose for it.


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## SPS-1 (Oct 21, 2008)

Let me mention this:

Back in the day (1980's) GM would put an oil pressure switch in parallel with the fuel pump relay, as a redundant circuit. The thought was, if the fuel pump relay failed, when you start cranking, the oil pressure would build up after a few seconds, and then the fuel pump would turn on.

This does not really sound like your issue, since your dies after 20 seconds.
(I had the opposite problem, oil pressure switch failed and the fuel pump would not turn off. Back in the days before the internet, I don't know how I figured out it was an oil pressure switch)

I think the engine computer runs open loop while starting, so maybe an engine sensor is bad and as soon as it starts up, engine computer decides to turn off the fuel pump. A scan might show this. Although, if this were the issue, I would expect the engine to die quicker than 20 seconds.


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## HotRodx10 (Aug 24, 2017)

Let me clarify, SPS-1. After I towed it home, I tried to start it and it ran (barely and badly) for about 20 seconds and died. It would not run at all after that. 

I did try swapping in an identical relay for the fuel pump; didn't help.


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## chandler48 (Jun 5, 2017)

Is the pump "sputtering" gas or water/gas when it does come on? Luckily a diesel has a water separator in the fuel filter where the heavier water falls down and sets off an alarm, "water in fuel"


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## HotRodx10 (Aug 24, 2017)

chandler48 said:


> Is the pump "sputtering" gas or water/gas when it does come on?


Kinda hard to tell. I assume it's a mixture.


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## RanK2 (Feb 19, 2020)

Just a 'shade tree' here with a question: Don't the pumps usually pull off the bottom of the tank where the water settles to?


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## Mike Milam (Mar 3, 2017)

RanK2 said:


> Just a 'shade tree' here with a question: Don't the pumps usually pull off the bottom of the tank where the water settles to?


Bingo


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## Randy Bush (Dec 9, 2020)

If you have mechanic skills you check and see if the pump is get power at the fuse block under the back seat. I have a 2009 Buick Lucerne that the fuse block went out on and acted this way.


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## a&b home (5 mo ago)

Hello new guy here . 
Gm fuel pumps for about 2 seconds when key is turned on . that will start the car.
oil pressure switch then takes over to run fuel pump.
Pump will not run with just key on after the first 2 seconds
There should be (somewhere under the hood) there should be an extra wire( that goes to the fuel pump .hook that wire to power and your pump will run to drain the water out


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## a&b home (5 mo ago)

I need to edit this fuel pump runs for about 2 seconds


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## HotRodx10 (Aug 24, 2017)

Well, I have dropped the tank, emptied it, cleaned it, and replaced the the entire pump assembly ($75 on Amazon). I'm going to try to get back in tomorrow.

I realize the pump only runs for a couple seconds when the key is turned on, but in that couple of seconds I would have expected to get more than a tablespoon of gas out of the line. That's all I was getting from the line off the tank after I disconnected it. The line was still pressurized when disconnected it, but the pressure seemed low, also (maybe 5-10psi).


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## Randy Bush (Dec 9, 2020)

HotRodx10 said:


> Well, I have dropped the tank, emptied it, cleaned it, and replaced the the entire pump assembly ($75 on Amazon). I'm going to try to get back in tomorrow.
> 
> I realize the pump only runs for a couple seconds when the key is turned on, but in that couple of seconds I would have expected to get more than a tablespoon of gas out of the line. That's all I was getting from the line off the tank after I disconnected it. The line was still pressurized when disconnected it, but the pressure seemed low, also (maybe 5-10psi).


Normal pressure should be 35-65 PSI depending on car.


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## HotRodx10 (Aug 24, 2017)

Randy Bush said:


> Normal pressure should be 35-65 PSI depending on car.


Yeah, I believe mine's supposed to be between 40 and 45.


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## raylo32 (Nov 25, 2006)

Is there some reason you haven't actually checked the fuel pressure during all this?


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## HotRodx10 (Aug 24, 2017)

raylo32 said:


> Is there some reason you haven't actually checked the fuel pressure during all this?


Just laziness, I suppose...and it just kind of snowballed on me. There wasn't any accessible place I could find attach a pressure gauge, and I needed to get the water out of the gas tank, anyway. I couldn't figure out how to do that without dropping the tank. Considering the mileage the car has on it, to go through the work to drop the tank, and not replace the fuel pump while I had it out, seemed like something I might kick myself later for not doing. 

It turned out it's a good thing I did get a new one. I had to disassemble the old fuel pump assembly to get it out of the tank. Either the OE pump was made to be forced through the hole into the tank, or it's grown since it was put in. In any case, I had to get the outer shell off of it to get it out, and I doubt I would have been successful at reassembling it so it was functional. The new one was a good 1/4" smaller and slipped right in. The $75 was easily worth it, even if the problem wasn't there.

My immediate problem is finding the clips to reattach the heat shield, or finding another way to attach it. As per usual, I broke them to get them off, and then I could see how they're supposed to come off.


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## Old Thomas (Nov 28, 2019)

The computer powers the fuel pump in two ways. One is a 3 second prime when the key is turned on. The other is energized when the engine is running. You are getting the prime but not the run cycle.


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## HotRodx10 (Aug 24, 2017)

Old Thomas said:


> The computer powers the fuel pump in two ways. One is a 3 second prime when the key is turned on. The other is energized when the engine is running. You are getting the prime but not the run cycle.


That's possible. It's hard to tell, since I haven't actually gotten it running since I got it home. 

I don't think that was the original problem, though. My daughter was in the parking lot at school, started it, and it ran very poorly and then died before she got out of the parking lot. She thought it was out of gas, but it based on what I got out of it when I drained the tank, it had 3-4 gallons in it. They put 1 gallon of water in it, and she was able to start it and drive it a little over a mile before it died again. 

I towed it home, and got it to start and run (just barely) for about 20-30 seconds. When I went to get more gas out of the barrel, I figured out the first gallon was water. I took the fuel line apart at a connection on top of the engine, expecting to be able to pump the watered gas out, but only got a few drops after cycling the key on and off several times. I tried cranking it probably about 4 minutes (in 30 second intervals, because it apparently has a cutoff where it only cranks that long at one time) and got maybe a quart of fuel out into the pan. At that point I decided I'd have to drop the tank, so I ordered the fuel pump, and got to work on that.


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## HotRodx10 (Aug 24, 2017)

Update: Got the fuel tank back in; got the fuel line bled out. Conveniently there's a valve at the end of the fuel rail that is the same as the A/C high side valve, so I was able to hook up the red hose from my A/C manifold gauge set. Definitely a lot more pressure than it had before. 

Btw, when bleeding from the valve with the key on, it doesn't stop pumping after 2 seconds. I think under normal circumstances, 2 seconds is about all it takes for the pump to pressurize the system, so maybe that's what caused the confusion there.

Anyway, I got it started, and after sputtering and dying a few times, it will stay running if I keep it above 2000 rpm, but stumbles and eventually dies if I let off the accelerator. I'm thinking it's possible it adjusted the air/fuel mixture for the seriously low fuel pressure, and now the mixture is way rich. I took the battery cable off, and I'll leave it off for 30 minutes or so, which supposedly will reset the computer. If it still runs as poorly after that, I'll have to look for other causes. 

The symptoms are similar to when the MAF sensor went bad on our van, but I'll probably pull a few spark plugs to see what they look like, before swapping any parts. That is, of course, if I don't get any more helpful from the code scanner than the "random misfire" code it's given me so far.


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## HotRodx10 (Aug 24, 2017)

Well, after 40 minutes, I reconnected the battery, started it up, and it still ran like crap.

Then as I was staring at the engine, wondering what to do next, slapped myself in the forehead and said "Doh!", plugged the vacuum line from the PCV valve back into the intake (I disconnected it to get to the fuel line connection), started it up, and it purrs like a kitten again (well, it more growls than purrs, but it sounds ggggreat, anyway).

Note to self: Always reconnect everything you disconnected.


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## SolomonMan (Feb 17, 2013)

All,
Isn't there a wire under the hood...I believe GMs are usually purple that is just a wire and connector at the end?

From memory, I would look it up(Chiltons/Haynes), if you power it (battery 12V) it will energize the pump. You can pressure test the system (typical GMs I have worked on (mostly late 90's and early 2000's) the pressure is just around 40psi but will run fine in mid upper 30s. Likewise, then you can test when its running and under different conditions (idle, under load etc) with a gauge. 

Buy the gauge if you do not have it. Usually less than $20 (Harbor Freight one will do).

I assume you changed the Strainer (In tank) and also the filter (if equipped)? Water affects filters.

Has the oil been compromised by the water in the tank? 

I doubt this could be a issue but then again I had a old Corsica 2.8 that the original owner got "watered" and they filled their fuel tank with water to top. The tank was bled dry, fuel water remover added to tank (full tank worth),,filter was changed (found to have screwed up paper element), I found the oil grey (almost like cracked head), I changed that as well. I also gave it a tune up (new plugs). Once started it took a 50 mile drive at 65 mph to get the missing to fully stop and smooth out. Once that was done I drove the car another 80K before getting rid of it.

What it taught me once water gets in the line its not a easy get it out.

Do not ask about my 1990 Ford Mark III Van. It has 2 tanks, 3 pumps, and mechanical selector valve. The vehicle sat for 10+ years with low fuel in each tank. The engine was only at 76K. The tank bottoms were black sludge. It took me a couple weekends to get it all working again. but everything was basically toast in the fuel system. I had never seen anything like it.

Thanks
Chris


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## HotRodx10 (Aug 24, 2017)

SolomonMan said:


> You can pressure test the system...you can test when its running and under different conditions (idle, under load etc) with a gauge.


Once I found the valve/port at the end of the fuel rail, I could have done that, but it was a moot point by then.


SolomonMan said:


> I assume you changed the Strainer (In tank) and also the filter (if equipped)? Water affects filters.


Yes. Changed out the whole assembly - pump, filter, pressure sensor, fuel level gauge/sending unit.


SolomonMan said:


> Has the oil been compromised by the water in the tank?


The piston rings aren't bad, so there's no reason the fuel should be mixing with the oil, but if any got in there, it should have evaporated by now.


SolomonMan said:


> I found the oil grey (almost like cracked head), I changed that as well.


Whatever was wrong with the oil, I doubt that was from water in the fuel system.


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## Old Thomas (Nov 28, 2019)

What does a scan tool say? Low fuel pressure or something else?


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## HotRodx10 (Aug 24, 2017)

Old Thomas said:


> What does a scan tool say? Low fuel pressure or something else?


It did say "random misfire" until I reconnected the line from the PCV valve to the intake. Now it doesn't say anything; no codes and it's running fine.


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