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Discussion Starter #1
I have a 96 Chevy 3500 2wd dually 6.5td
Started up like normal then died about 20 seconds later. Checked power at the lift pump and it is not getting power. Replaced my ops fuel pump relay and got a new pmd. Pmd is getting power. Just not sure where to check next down the line from pmd or another sensor that would kill power to the relay and lift pump. Any help would be greatly appreciated. I don’t have a code reader and since it doesn’t start I can’t get it to a mechanic to check for codes.
Thanks to anyone in advance
 

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Welcome to DieselPlace

Have you checked all of your fuses and gone through your grounds?
 

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Discussion Starter #3
Checked all the fuses but have not checked all the grounds. Checked the ground at the lift pump and a few under the hood that I could easily check
 

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Did you replace it with ACDelco OPS?
 

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Yes acdelco ops. Thanks for the read on grounds. Any grounds in particular that usually cause problems?
 

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There is also a relay in the relay box under the hood.

Relay hardly goes bad but it is still a possibility.
 

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Yes acdelco ops. Thanks for the read on grounds. Any grounds in particular that usually cause problems?
All of them..
One bad ground can cause a lot of issues in a 6.5L
 

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Have you checked each pin of the lift pump connector separately? The + is the switched one in this case and the ground is always there. Maybe its just the ground at the pump that is missing? That happened to me and at least on a 96 burb for some dumb reason that ground runs to the back of the truck. I never did find it so I just made a new one on the frame close to the pump.
 

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Discussion Starter #10
I used a test light and grounded to the frame and checked both pins for power and nothing came up. So that doesn’t mean that ground isn’t bad but it does tell me I still don’t have power to the pump. I’ll be checking all my grounds this week including that one though
 

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How about at the relay socket? If you pull it out they usually have a diagram on them showing the pin numbers and locations. The switch contracts are 87 and 30. I don't remember which is which but one of those should be +12 all the time and the other one is the one that leads down to the pump. IF you have power at one of them and then install a jumper between them that should send power down to the pump.
 

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Discussion Starter #12
I’ll test that when I get home. So one should have constant power and the other should have power with the key turned?
 

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Does the ORANGE wire at the OPS have 12v. all the time.
 

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your 30 pin should be power all time
 

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Discussion Starter #15
Thanks for the info. Hoping to try out some of this week or weekend at the latest and let everyone know what is going on
 

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I don't understand why people keep chasing this gremlin . Just run a ground from your lift pump to the frame and a fused hot wire from any wire that's hot with the key on . The way these things are wired from the factory with the OPS is just a safety so if you lose oil pressure it will shut down the engine to prevent further damage . A little heads up IT WILL RUN LONG ENOUGH TO DESTROY IT ANYWAY .
 

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The OPS is there to stop the lift pump in the event of an accident.
It is not foolproof, but if you were stuck in your upside down truck and the lift pump was pumping fuel all over the place....
Unlike gas engines, these diesels will run just fine with the lift pump not working.
Not recommended, but that is the way it is.
 
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