fuel pump won't shut off - The 1947 - Present Chevrolet & GMC Truck Message Board Network

aggiedave98 · 12-24-2007, 12:02 PM

I've got a '98 burb with 94k miles on it and what I believe is the original fuel pump.

Just recently I noticed that after I turn off the engine the fuel pump used to stay on for 3-5 seconds but it started staying on longer. Today I shut off the car and it just stayed on. I popped the hood and took out the fuel pump relay, but it stayed on. I put the relay back in a while later the pump shut off.

I out of town and down have my manuals. So I have some questions:

1) Can somebody tell me what the wiring diagram is for the fuel pump?
2) Why would the fuel pump stay on when I remove the relay?
3) What would make the fuel pump stay on?? Does the computer control it staying on after you shut off the car?

thanks!

ChevyTech · 12-24-2007, 12:51 PM

I don’t have schematic to look at for your truck but I believe it a redundant circuit that supplies power to the fuel pump when it has oil pressure. This circuit goes through an oil pressure sensor/sender.

Try unplugging the oil sending unit.

aggiedave98 · 12-24-2007, 05:04 PM

Quote:

Originally Posted by ChevyTech

I don’t have schematic to look at for your truck but I believe it a redundant circuit that supplies power to the fuel pump when it has oil pressure. This circuit goes through an oil pressure sensor/sender.

Try unplugging the oil sending unit.

Ok, I found a diagram for it. You're right. The computer turns it on and then the oil pressure switch supplies it power. I'm going to replace the switch.

Any idea where that would be on my engine or what it looks like? I haven't ever replaced one and don't have my manuals here.

thanks!

ChevyTech · 12-25-2007, 02:26 PM

I think yours should be a three wire.
http://www.autozone.com/N,15700134//...eResultSet.htm

I don’t have a photo link saved for your truck, but this is the closest thing I have.
http://shbox.com/1/op_sensor.jpg

aggiedave98 · 12-26-2007, 05:17 AM

Thanks. Yeah, I just picked one up at Oreilly yesterday but the problem seems to now be intermittent and even when it stayed on recently it still shut off within about 20-30 seconds. So I think I'm going to wait until I get home just in case I mess something up (have an oil leak or something) since I need to drive home 200 miles. I'll let you know what happens.

ChevyTech · 12-26-2007, 06:12 AM

Quote:

Originally Posted by aggiedave98

I think I'm going to wait until I get home just in case I mess something up (have an oil leak or something) since I need to drive home 200 miles.

Good plan!

Quote:

Originally Posted by aggiedave98

I'll let you know what happens.

I will be watching this thread.

Merry Christmas

ChevLoRay · 12-29-2007, 08:31 AM

Quote:

Originally Posted by aggiedave98

Thanks. Yeah, I just picked one up at Oreilly yesterday but the problem seems to now be intermittent and even when it stayed on recently it still shut off within about 20-30 seconds. So I think I'm going to wait until I get home just in case I mess something up (have an oil leak or something) since I need to drive home 200 miles. I'll let you know what happens.

I noticed that mine will run for a few seconds after shutting off the truck....I'm guessing it is for a good reason.

drunkbus · 12-29-2007, 08:56 AM

I am having a similar problem on my 97 Tahoe, it has about 105,000 miles on it. At about 95,000 miles the fuel pump started making an annoying whining sound and it stays on for about 5-10 seconds after I shut it off. I assumed the pump was going out, but I have put 10,000 miles on it since with no trouble but I am affraid I am going to end up stuck on the side of the road one of these days.

**bwood** · 12-29-2007, 05:21 PM

I think it is normal for it to run for a few seconds after you shut it off. Mine has done it since I bought it (48,000 miles). Some don't hear it until the pump starts to make more noise as it runs. I believe it should run the same amount of time when you turn it off as it does when you turn it on without starting it. I don't know why it does it, but my 98 Sierra, Friends 98 Z71, Mom's 99 Tahoe and Grandpa's 00 3/4 ton Sierra all run for about 3-5 seconds after the key is turned off and 3-5 seconds after the key is turned on without starting. My only guess would be that it keeps pressure on the fuel system for easy starting??

drunkbus · 01-09-2008, 02:38 PM

Quote:

Originally Posted by drunkbus

I am having a similar problem on my 97 Tahoe, it has about 105,000 miles on it. At about 95,000 miles the fuel pump started making an annoying whining sound and it stays on for about 5-10 seconds after I shut it off. I assumed the pump was going out, but I have put 10,000 miles on it since with no trouble but I am affraid I am going to end up stuck on the side of the road one of these days.

UPDATE: My feelings were correct. I ended up stuck on the side of the road this morning on my way to work after the fuel pump quit on me. I knew in the back of my mind that this was going to happen sooner or later. I guess it just goes to show you that when the fuel pump starts howling get it replaced and save yourself a tow bill.

53GMC · 12-28-2011, 12:52 AM

I recently started having this same issue with my 96 chevy s10. It's never done it before today and I replaced the fuel pump about a year ago and have put very few miles on it since. Any ideas as to how this could be a problem? Would fuel pump relay be a fix perhaps?
Posted via Mobile Device

53GMC · 12-28-2011, 01:32 AM

Couldn't I just unplug the oil sending unit and if the fuel pump doesn't run after I shut the truck off, then I will know it's the sending unit that needs to be replaced correct?

Thanks for your help!!
Posted via Mobile Device

aggiedave98 · 12-28-2011, 12:20 PM

Chevytech, 4 years later, I'm finally giving an update! (Since I got the email when 53gmc posted). For me I got home and tried to replace the oil pressure sensor. Well, I could not get it off just because of the angles to get in there (if I remember right) and even had the special socket fall down where I couldn't get it. Since it was intermittent, I think it even may have gotten better completely. I can't quite remember. Eventually I sold it without it ever being a real issue (meaning it didn't affect anything else).

53GMC, look at the wiring diagrams in the links posted above to understand how it works.

>>Ok, I found a diagram for it. You're right. The computer turns it on and then the oil pressure switch supplies it power. I'm going to replace the switch.

How it works from what I remember and from what I posted if you turn the key and the computer turns on the pump for 3-5 sec. Then when you start the car, the oil pressure sensor "takes over' in the circuit.

For everybody on the thread, when you turn off the car, does the computer tell it to keep fuel pressure? I don't think so because if so we wouldn't have this problem of some people having more than 3-5 seconds, so it must always be the fuel pressure switch I believe.

I don't believe it's the relay. If it were the relay it wouldn't work at all. At least my opinion without looking at schematics again.

12-24-2007, 12:02 PM	#1
aggiedave98 Senior Member Join Date: Aug 2003 Location: Sugar Land, TX Posts: 1,007	fuel pump won't shut off I've got a '98 burb with 94k miles on it and what I believe is the original fuel pump. Just recently I noticed that after I turn off the engine the fuel pump used to stay on for 3-5 seconds but it started staying on longer. Today I shut off the car and it just stayed on. I popped the hood and took out the fuel pump relay, but it stayed on. I put the relay back in a while later the pump shut off. I out of town and down have my manuals. So I have some questions: 1) Can somebody tell me what the wiring diagram is for the fuel pump? 2) Why would the fuel pump stay on when I remove the relay? 3) What would make the fuel pump stay on?? Does the computer control it staying on after you shut off the car? thanks!

12-24-2007, 12:51 PM	#2
ChevyTech Registered User Join Date: May 2004 Location: Minnesota Posts: 4,621	Re: fuel pump won't shut off I don’t have schematic to look at for your truck but I believe it a redundant circuit that supplies power to the fuel pump when it has oil pressure. This circuit goes through an oil pressure sensor/sender. Try unplugging the oil sending unit. Last edited by ChevyTech; 12-24-2007 at 12:53 PM.

12-25-2007, 02:26 PM	#4
ChevyTech Registered User Join Date: May 2004 Location: Minnesota Posts: 4,621	Re: fuel pump won't shut off I think yours should be a three wire. http://www.autozone.com/N,15700134//...eResultSet.htm I don’t have a photo link saved for your truck, but this is the closest thing I have. http://shbox.com/1/op_sensor.jpg Last edited by ChevyTech; 12-26-2007 at 06:07 AM.

12-26-2007, 05:17 AM	#5
aggiedave98 Senior Member Join Date: Aug 2003 Location: Sugar Land, TX Posts: 1,007	Re: fuel pump won't shut off Thanks. Yeah, I just picked one up at Oreilly yesterday but the problem seems to now be intermittent and even when it stayed on recently it still shut off within about 20-30 seconds. So I think I'm going to wait until I get home just in case I mess something up (have an oil leak or something) since I need to drive home 200 miles. I'll let you know what happens.

12-29-2007, 08:56 AM	#8
drunkbus New Member Join Date: Jun 2007 Location: Coos Bay, OR Posts: 1,077	Re: fuel pump won't shut off I am having a similar problem on my 97 Tahoe, it has about 105,000 miles on it. At about 95,000 miles the fuel pump started making an annoying whining sound and it stays on for about 5-10 seconds after I shut it off. I assumed the pump was going out, but I have put 10,000 miles on it since with no trouble but I am affraid I am going to end up stuck on the side of the road one of these days.

12-29-2007, 05:21 PM	#9
bwood Registered User Join Date: Jan 2003 Location: Denison, Texas Posts: 1,920	Re: fuel pump won't shut off I think it is normal for it to run for a few seconds after you shut it off. Mine has done it since I bought it (48,000 miles). Some don't hear it until the pump starts to make more noise as it runs. I believe it should run the same amount of time when you turn it off as it does when you turn it on without starting it. I don't know why it does it, but my 98 Sierra, Friends 98 Z71, Mom's 99 Tahoe and Grandpa's 00 3/4 ton Sierra all run for about 3-5 seconds after the key is turned off and 3-5 seconds after the key is turned on without starting. My only guess would be that it keeps pressure on the fuel system for easy starting?? __________________ 2013 Ford F150 FX4 2006 Chevy Silverado 1500 1982 Chevy C1500 2020 Ford Explorer Limited 2008 Ford Escape

12-28-2011, 12:52 AM	#11
53GMC Registered User Join Date: Jul 2009 Location: Washington, GA Posts: 319	Re: fuel pump won't shut off I recently started having this same issue with my 96 chevy s10. It's never done it before today and I replaced the fuel pump about a year ago and have put very few miles on it since. Any ideas as to how this could be a problem? Would fuel pump relay be a fix perhaps? Posted via Mobile Device __________________ 1953 GMC/S 10 Swap http://67-72chevytrucks.com/vboard/s...d.php?t=357365

12-28-2011, 01:32 AM	#12
53GMC Registered User Join Date: Jul 2009 Location: Washington, GA Posts: 319	Re: fuel pump won't shut off Couldn't I just unplug the oil sending unit and if the fuel pump doesn't run after I shut the truck off, then I will know it's the sending unit that needs to be replaced correct? Thanks for your help!! Posted via Mobile Device __________________ 1953 GMC/S 10 Swap http://67-72chevytrucks.com/vboard/s...d.php?t=357365

12-28-2011, 12:20 PM	#13
aggiedave98 Senior Member Join Date: Aug 2003 Location: Sugar Land, TX Posts: 1,007	Re: fuel pump won't shut off Chevytech, 4 years later, I'm finally giving an update! (Since I got the email when 53gmc posted). For me I got home and tried to replace the oil pressure sensor. Well, I could not get it off just because of the angles to get in there (if I remember right) and even had the special socket fall down where I couldn't get it. Since it was intermittent, I think it even may have gotten better completely. I can't quite remember. Eventually I sold it without it ever being a real issue (meaning it didn't affect anything else). 53GMC, look at the wiring diagrams in the links posted above to understand how it works. >>Ok, I found a diagram for it. You're right. The computer turns it on and then the oil pressure switch supplies it power. I'm going to replace the switch. How it works from what I remember and from what I posted if you turn the key and the computer turns on the pump for 3-5 sec. Then when you start the car, the oil pressure sensor "takes over' in the circuit. For everybody on the thread, when you turn off the car, does the computer tell it to keep fuel pressure? I don't think so because if so we wouldn't have this problem of some people having more than 3-5 seconds, so it must always be the fuel pressure switch I believe. I don't believe it's the relay. If it were the relay it wouldn't work at all. At least my opinion without looking at schematics again.



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