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Priming but not pumping fuel pump

Tiny
TILLDOWN
  • MEMBER
  • 1989 CHEVROLET S-10
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
Bought a 89 chevy s10, changed the fuel pump, then drove it 25 miles. Truck would not start after being turned off. Fuel pump sounded like it was priming (can still hear it working on auxiliary) but wasn't pumping. Replaced pump again this time with brand new one, and truck started one time then did the same thing. Changed fuel filter and there are no blown fuses. Any ideas? Thanks.
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Saturday, February 28th, 2009 AT 12:26 PM

13 Replies

Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Hello, did you check for codes? Did you check pressure with a gage? If you have TBI can you see the injectors spray, even a good spray pattern doesn't mean the pressure is good.

It shows you have an oil pressure switch in the fuel pump circuit, a redundant power supply to the pump, once you crank enough to bring up oil pressure, the pump should run, even without the rpm signal, but the injector/s won't pulse, without the rpm signal.

With the fuel pump prime connector, you can run the pump without cranking and check pressure.
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Saturday, February 28th, 2009 AT 12:54 PM
Tiny
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Thanks for the reply. I actually decided to dump out the old gas, and try new gas since it was sitting for a year before I drove it home. With that, the pump started pumping, through the filter, but it still won't start.

I haven't checking the pressure anywhere, but I think it must have been the old gas that was messing up the new pump. I was planning on cleaning the injectors to see if that's the problem.

New starter, and it's cranking but still not firing.
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Thursday, March 5th, 2009 AT 4:23 PM
Tiny
JDL
  • MECHANIC
  • 16,098 POSTS
Did you ever check for spark at the plugs, with engine cranking?
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Friday, March 6th, 2009 AT 7:54 AM
Tiny
TILLDOWN
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Went out to check the spark, and tried starting it first. It started, but no guages worked (fuel, speedometer, temp). I shut it off and restarted, and it was ok, but temp guage was maxed out. Let it sit for about an hour, and now it won't start at all again, but it's still cranking.

Sound like something simple?
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Sunday, March 8th, 2009 AT 2:03 PM
Tiny
JDL
  • MECHANIC
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Maybe I misunderstood your post, you don't need spark to crank it, but, you do need spark as well as other things, to start it, get it to run. Check for spark when it refuses to run.
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Monday, March 9th, 2009 AT 9:09 AM
Tiny
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No, it has spark. When I dump fuel into the injectors, it starts, and stays running. But if I turn it off and restart it, the injectors aren't spraying and the pump continues to prime and won't shut off. I took the top part of the injector casing off and cleaned it, but it still isn't working. So, it's either the injectors or there is this valve in the cover that's spring loaded that I guess could be it.
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Monday, March 9th, 2009 AT 7:06 PM
Tiny
JDL
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If your saying the pump runs with the key off, check the oil pressure switch.

Use a noid lite on the injector plug, see if there is a pulse with the engine cranking? The lite should pulse.
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Tuesday, March 10th, 2009 AT 9:02 AM
Tiny
TILLDOWN
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The injectors will spray if I pour fuel into the throttle housing to start the truck. But if I turn it off and try to restart it, they won't spray and the pump just continues to wind, but won't shut off. Have to pour gas back in to get it to idle.

Went to the junkyard and replaced the whole injector housing with a used one, and still nothing. Pump still just continues to prime and won't shut off, and it won't start.

New injectors are expensive so i'm trying to avoid buying them until I have to.

Where is the oil pressure switch?
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Saturday, March 14th, 2009 AT 1:03 PM
Tiny
JDL
  • MECHANIC
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https://www.2carpros.com/forum/automotive_pictures/170934_89_s10_1.jpg



This info is for an 89 s10 4.3.
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Saturday, March 14th, 2009 AT 3:36 PM
Tiny
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Ok thanks. I'm pretty much down to that, the fuel pressure regulator (which i'm also not sure of the location) or the injectors. Oil pressure regulator is the cheapest, so I guess i'll start there.

Either way, it'll have to wait til next week.
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Saturday, March 14th, 2009 AT 6:35 PM
Tiny
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Thanks. Any idea where the fuel pressure regulator is, or whether one that isn't working would cause a problem like the fuel not getting to the injectors when i'm starting the truck?
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Wednesday, March 18th, 2009 AT 6:07 PM
Tiny
CHARLES KERR2
  • MEMBER
  • 2 POSTS
Have the same problem did you everget your problem solved
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Thursday, April 4th, 2019 AT 10:44 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,513 POSTS
Did you replace the fuel pump relay? Here is a guide to help you test it:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Please run down this guide and report back.
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Thursday, April 4th, 2019 AT 11:26 AM

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