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Chevy Vortec Low fuel pressure but engine starts and runs

  • Kember319
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26 Mar 2020 11:21 #38659 by Kember319
Please help! 1997 Chevy k1500 with CPI injection. Can’t seem to figure this out. Truck is getting 28psi when running and about 30 with KOEO. I have done a leak down test and it tested good but replaced the fuel pressure regulated anyways. I’ve replaced the fuel pump and sending unit. Put a new fuel filter on. When I had the plenum off I had all injector nozzles out and pressurized the injector unit didn’t see any leakage. Doesn’t seem to bog down like you have shown in videos. What am I missing?? Why is it starting/running with only 28psi? Can there be an internal leak inside the injector unit. I have used two different fuel pressure gauges both read the same thing. Thank you and I hope to hear back from you.
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26 Mar 2020 13:11 #38660 by Cheryl
How does power and ground look to the pump? Voltage drop test it?? Also new doesn’t meN good. Have you checked for possibly pinched feed line? If the return line was pinched or linked you’d have higher pressure. I think you ruled out leaks and bleed issues

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26 Mar 2020 20:31 #38682 by Kember319
No lines are pinched or kinked. Getting about 11.5 volts to the pump while the pump is running. I cleaned the ground when I installed the new sending unit.

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26 Mar 2020 20:51 #38683 by Cheryl
Try pinching the return fuel line see what the pressure goes up to? Should increase

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26 Mar 2020 22:03 #38684 by Kember319
I have done that. Dead heading the pump I get about 80psi. Could the poppets inside the injectors be worn out causing it to run on such low pressures??

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26 Mar 2020 22:13 #38685 by Cheryl
Almost sounds like the new regulator you got isn’t functioning. I don’t think the poppets could be worn out. Ive seen them stuck closed cause a misfire on cylinders. I’d try and exchange that regulator. Or just buy a hole new spider assembly with regulator included

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26 Mar 2020 22:15 #38686 by Cheryl
But if there isn’t any running or driving problems I’d forget about the reading on a 23 year old truck. Only if there aren’t any symptoms

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27 Mar 2020 13:49 #38706 by Kember319
Tried something else. Took the schrader valve out of the fuel rail and hooked up the gauge again now it shows 60 psi. But the fuel pressure drops immediately. Guess it’s time to swap out the fuel pressure regulator one more time.

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27 Mar 2020 20:20 #38718 by Cheryl
id expect it to bleed off with the schrader valve out.let us know howit goes. by the way how do your fuel trims look?

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28 Mar 2020 15:41 #38731 by Tutti57
I'm with Cheryl. Is there a drivability issue? If fuel trims are good, I might suspect a gauge issue unless you have tried a known good.

Nissan Technician

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Yesterday 16:09 - Yesterday 17:43 #38813 by Potanist
I was getting a lot of misfires with my high mileage 2002 Avalanche till I changed the injectors. Plus your fuel pressure will cause misfires if not running the right pressure. Do you have a 5.3 in it? This matters because different 5.3 ran at different pressures. If your fuel trims are good that's half the battle. Another thing bad with these trucks is the fuel pressure. Fuel pumps either work or don't work. I replaced the one in my truck 3 times before getting something within range. When you pull the vacuum line off the fuel pressure regulator your pressure should max out... At WOT fuel pressure should max out to that same pressure.
Last edit: Yesterday 17:43 by Potanist.

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