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New fuel pump issue?

Tiny
RUDY1
  • MEMBER
  • 1994 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 2WD
  • AUTOMATIC
  • 198,759 MILES
I put a new fuel tank in my truck at the same time I put in a new fuel pump. It started right up but I do have random issues that it won't start you can hear the pump start sometime the pump runs for a while (this is when it does start). Other times it runs for a shorter time (sounds like it builds up pressure then quits) but these are the times it doesn't start. Replaced that pump but still having the same issues with the new pump
I got the pumps from the same vendor. Should I replace it again but this time from a different vendor or what are your thoughts on my issues?
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Saturday, December 17th, 2022 AT 7:54 AM

12 Replies

Tiny
RUDY1
  • MEMBER
  • 14 POSTS
I forgot to mention I also replaced the fuel filter and fuel relay during the first pump issues.
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Sunday, December 18th, 2022 AT 4:52 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
When you turn the key on, the pump should prime for approximately 2 seconds and then turn off. Once the engine starts, it should turn back on. Is that what is happening?

Do me a favor. The fuel pump relay is under the hood mounted on the firewall. Disconnect it and inspect the connection. Make sure there is no corrosion or damage on the connectors. If there is a different relay on the truck with the same part number, switch them and see if that makes a difference if there isn't, here is a link that explains how to test one:

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

I attached a pic below showing the relay location.

Let me know what you find or if you have other questions.

Take care,

Joe

See pic below.

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Sunday, December 18th, 2022 AT 11:06 AM
Tiny
RUDY1
  • MEMBER
  • 14 POSTS
I replaced the relay during the first fuel pump issue. The fuel pump runs longer than 2 seconds and shuts after building up pressure but I can time it for you, both situations when it will run and when it won't (the pump kicks off sooner when it won't start. FYI. You can hear the difference when the pump runs. Both the pump does run in both situations, truck runs and when it doesn't, when the pump turns off in the shorter time. I have cracked the line loose at the fuel filter and there is no fuel there.
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Sunday, December 18th, 2022 AT 6:36 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Have you checked things like the connector at the pump and the ground? If you have a weak ground, this could be happening.

Let me know.

Joe
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Sunday, December 18th, 2022 AT 9:36 PM
Tiny
RUDY1
  • MEMBER
  • 14 POSTS
I sand blasted the ground screw and sanded the attachment area. The connections seem to be clean. FYI, I timed how long the fuel pump runs. When it starts the pump runs for about 10.5 seconds. When it doesn't start the pump only runs for about 6 seconds. It does sound like it's building up more pressure (or labors more) when it only runs the 6 seconds. You can crack the line by the online filter and there's no fuel there.
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Monday, December 26th, 2022 AT 5:59 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

When you had the original pump removed, did you confirm there wasn't a lot of dirt at the bottom of the tank? Also, there is a fuel pump strainer at the bottom of the pump. Was it replaced? See pic below.

If there is no fuel to the filter, something is plugging it before the filter.

Let me know.

Joe
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Monday, December 26th, 2022 AT 8:20 PM
Tiny
RUDY1
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  • 14 POSTS
My tank started to leak. So, I replaced the tank and put a new fuel pump in at that time trying to eliminate potential future pump replacement, but the old pump worked fine.
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Tuesday, December 27th, 2022 AT 5:11 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,755 POSTS
Hi,

We have to be missing something simple. If the original pump worked and both replacement ones do not, it doesn't make sense. Do you still have the original pump? I know you installed two new ones but if they are by the same manufacturer, they both may have been bad.

If you have the original one, I would reinstall it and see if the problem goes away.

Let me know your thoughts.

Joe
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Tuesday, December 27th, 2022 AT 5:22 PM
Tiny
RUDY1
  • MEMBER
  • 14 POSTS
Yes, I was thinking about doing that, at least it will or will not rule out the pump, not for sure when I will be able to get to that, an issue came up with my daily drive (another fuel related problem). Maybe you can help with that? 2000 Toyota RAV4 300,000 miles won't start. Turns over but doesn't run, I don't Have a manual so I'm not sure which relay maybe for the pump. (Looked on line but the fuse box and relay box are different than what I have seen). But anyway. I pulled the plug off the pump and checked the current the ground seems to be good (white wire). And supposedly check the power wire (blue) when the key is turned on, but my test light will not come on, so I'm thinking it could be the relay, but I don't know which one it is. I did move the like relays around in the relay box but no positive outcome.
Thanks again for your help!
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Wednesday, December 28th, 2022 AT 5:37 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I would be more than happy to help with the Toyota. However, I have a favor to ask. We try to keep the threads specific to one type of problem and vehicle to make it more helpful to others. I need you to copy the info on the Toyota and paste it into a new thread. Here is the link to start a new one:

https://www.2carpros.com/questions/new

I hope you understand. When you do it, make sure to include all the things you have already tried. Also, let me know if it starts for a couple of seconds using starting fluid. That will confirm if it is a fuel-related issue or ignition-related.

Take care,

Joe
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Wednesday, December 28th, 2022 AT 11:57 AM
Tiny
RUDY1
  • MEMBER
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It seems (at least so far) the fuel pump was the issue, After putting in my old pump back in it has started every time. So thanks for your help.
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Friday, January 20th, 2023 AT 6:20 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Thanks for the update. I'm glad to know it has been working properly. If I had a nickel for every faulty part, I've gotten over the past two years, I could retire. LOL

If anything changes, let me know. Also, please feel free to come back anytime in the future.

Take care,

Joe
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Friday, January 20th, 2023 AT 8:09 PM

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