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08-23-2024, 08:10 AM
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#1 |
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Registered User
Join Date: Mar 2012
Location: Woodbury, Ct.
Posts: 1,687
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Fuel Pump Not Priming
My 6.0 swap (2005 DBW) has been running flawlessly for about 7 years. Recently it has on occasion failed to activate the fuel pump when turning the key on which would cause it to fail to start. I cycle the key back to off and on again, then I here the pump prime and it runs fine.
Could this be the relay going bad? The pump? |
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08-23-2024, 09:59 AM
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#2 |
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Registered User
Join Date: Oct 2013
Location: Alabama
Posts: 1,227
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Re: Fuel Pump Not Priming
check your grounds. I've found that most electrical gremlins that involve components working "erratically" involve a bad or loose ground.
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08-23-2024, 01:36 PM
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#3 |
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Senior Member
 
Join Date: Nov 2013
Location: East Tennessee
Posts: 2,182
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Re: Fuel Pump Not Priming
I agree with Willie M....check grounds first, then check for power to the fuse and to the relay with key in run position.
The PCM sends 12v to the fuel pump relay to trigger it. It could possibly be the relay is going bad and failing intermittently.
__________________
1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer ............. 
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08-23-2024, 01:47 PM
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#4 |
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Senior Member
Join Date: Mar 2015
Location: washington
Posts: 2,280
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Re: Fuel Pump Not Priming
I believe it is the other way around.
The PCM grounds the fuel pump relay to trigger it. |
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08-23-2024, 02:16 PM
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#5 |
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Senior Member
Join Date: Nov 2013
Location: East Tennessee
Posts: 2,182
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Re: Fuel Pump Not Priming
Maybe on some? but not on mine.
__________________
1967 C10 Step side 1968 C10 Step side 1970 Chevrolet K/5 Blazer 1972 Chevrolet K/5 Blazer .............
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08-23-2024, 04:38 PM
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#6 |
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Registered User
Join Date: Jun 2015
Location: Carlos MN
Posts: 2,091
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Re: Fuel Pump Not Priming
Either pos or neg supplied to the relay just get a new one and see if it helps. Relays are cheap but buy a "good" one.
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08-26-2024, 10:37 AM
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#7 |
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Registered User
Join Date: Mar 2012
Location: Woodbury, Ct.
Posts: 1,687
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Re: Fuel Pump Not Priming
So Saturday morning I turn the key with the relay in my hand. I feel it click but it does not prime. Tried it twice. I swapped in a new relay and it worked as it should. I drove the truck all weekend with no issues.
I tossed an extra relay in the glove box. |
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08-30-2024, 10:03 AM
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#8 |
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Registered User
Join Date: Jan 2016
Location: Kings Mountain, NC
Posts: 13
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Re: Fuel Pump Not Priming
If your problem returns it might be your fuel pump. I had this same issue on my 2001 Silverado 5.3. It would not start after the vehicle set for over a couple hours. I would cycle the switch on/off three or four times and it would start fine. I am not sure of the exact pressure, but the fuel system should retain some pressure when it sets. I checked my fuel pressure after the truck set for a few hours and it would drop down to nothing. It was the fuel pump; replaced it and no more issues.
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