Chevy/GMC 6.2L and 6.5L Discussion of Chevy and GMC Trucks with 6.2L and 6.5L Diesel Engines

Is my LP shot?

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Old 06-30-2019, 08:29 PM
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Default Is my LP shot?

New member here. I've had 4 Duramaxes before selling my last one and stumbling upon a rusty 1997 single cab Sierra for $1800. I'm a fan of this truck already, even though it's going to be a major project to restore it.

Today I was changing the oil, as well as doing the fuel filter. Everything went fine, except I couldn't bleed the fuel system. No fuel would come out of the little bleeder opening on top of the filter, and I could not hear the lift pump working. I put the old filter back it (it's disgusting!), still no luck... jumped the relay with a wire, still nothing. Finally after several hours of messing around with it, it finally sputtered to life and now runs as it did before. In those 2 hours of jumping the relay, swapping filters, and cranking it over a lot, I did hear the pump kick on only once. It's pretty rusty... I'm guessing it's shot? But if so, how is the truck running without it functioning? I crawled under the frame with the truck running, and it doesn't seem to be making any sounds.
 
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Old 06-30-2019, 08:34 PM
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The IP can pull fuel through a non working LP but it puts alot of stress on it.
 
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Old 06-30-2019, 08:39 PM
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Thanks for the reply. Does my truck wire it through the oil pressure switch, or is it through the ECU? Just trying to see if I should replace the lift pump as well as that oil pressure sensor.
 
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Old 07-01-2019, 02:37 AM
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I'm not an expert, maybe someone who is will jump in here, but I think 97 should provide ecu backup power if the ops fails.

With the motor running , open the t valve wide open. Motor stays running =good lift pump. Motor dies=lift pump not working, then diagnose further to see if it's getting power or not.
 
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Old 07-02-2019, 08:28 AM
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If in doubt, throw it out! Id' replace the LP before it leaves you stranded....
 

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