Question about 1989 GMC Suburban

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My 1989 GMC Suburban (7.4L) has an oil pressure gauge that shows oil pressure after vehicle is turned off. The ignition switch must be partially turned to test and then off again to get this gauge to read zero. If the gauge does not read zero, the fuel pump continues to run even though the ignition is in off position and will continue to run until the battery dies. I've tried replacing the relay on the firewall but problem persists (possible that new relay was defective?). I believe problem began after replacing key cylinder but am uncertain. Fuel pump has since been replaced and problem persists.

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6ya6ya
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Posted on Jan 02, 2017

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  • 66 Answers

SOURCE: 1996 GMC K1500 Pickup Starting Problem

i would try a fuel filter first. the fuel gauge going crazy is most likely the sender they go bad and eventually stop working. the bummer is you have to replace the fuel module. these aftermarket are about 200 bucks. the module comes with the pump and sender which is the next part you want to look at. gm has some issues with the harness to the fuel pump externaly. it actualy will melt and start to lose conection. i would check this by visualy inspecting the plug on top of the tank. unplug it and take a look. if it is at all disscolored replace the pump (module). the new pump comes with a replacement harness (make sure its in the box)hope this helps and good luck

Posted on Feb 04, 2009

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SOURCE: where is fuel pump relay on 1989 chevy suburban 1500

passengers side firewall behind plastic cover thats about 12 inches long with a bump in the middle,where the battery cables hook together ,there should be 2 relays there and i think its the one closest to the drivers side

Posted on May 08, 2009

  • 1 Answer

SOURCE: 1999 gmc suburban fuel pump

I had the same problem with my 99 suburban. There was a memo sent out by GM to all of the service shops that tell them when you replace the fuel pump or just desconnect it you need to replace the pigtail wiring harness that connects to the pump or it will burn up the new pump. I went through 3 pumps before I found this out after I replace the pigtail it fixed the problem.

Posted on Jun 04, 2009

seans46
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SOURCE: 1997 Gmc yukon fuel relay switch continues to burn out

I would have to check the fuel pump with a scope to look at the pattern and check the amps it is drawing . the grounds need to be checked and the pcm checked and reflashed. on the fuel system that would affect the fuel pump and relay to where it would burn it out is grounds , pcm , fuel pump , fuel pump relay. so you should convince them to replace the fuel pump and fuel pump relay under warranty and replace the pcm . and get a diagram and check all grounds. If the pcm is damaged and the current has been affected and instead of say a 5 volt or 2 volt signal it now has a 13.5 volt signal or if a ground is out then the temp of the relay will keep rising non energized a relay is about 99 energized it is around 140 you can check to see how hot that relay is getting. and if i remember correctly you want the pcm drivers checked.

Posted on Jun 18, 2009

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SOURCE: 1999 GMC Suburban Wont Turn Over

It sounds like you have a security problem, I had the same thing it would fire and run for half of a second and then that was it if anything at all. Had the security system rebooted, now it starts and runs fine.

Posted on Jun 30, 2009

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