Fuel pressure

Tiny
DOZER1401
  • MEMBER
  • 2004 CHEVROLET
  • V8
  • 4WD
  • AUTOMATIC
  • 120,000 MILES
I have a 2004 Dura Max 6.5 deisel with the Allison trans. I can not get it to hold its fuel prime, Ive changed out the fuel filter with new O rings on the filter, and used the onborad manual fuel prime pump, but still cant get it to hold its prime, once its started, it only runs a few minutes and its back to primeing again. Any ideas?
Sunday, June 20th, 2010 AT 8:59 PM

6 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Hopefully you filled the fuel filter before you installed it. You aer supposed to pump the hand pump 30 times then let it sit for a couple of minutes. Then Pump 30 more times and let sit. See if truck will start and let idle for 10 minutes it will take that long for the air to work out of the system. If it won't idle that long then you have air leaking in the system or a vacuum leak and should be checked by a pro.
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Saturday, July 10th, 2010 AT 7:03 PM
Tiny
JUSTJIM20B
  • MEMBER
  • 1 POST
  • 1995 CHEVROLET
  • V8
  • 4WD
  • MANUAL
  • 148,000 MILES
Replaced in tank fuel pump twice. Parts from napa both pump have only 8psi. Pump spec are 12-15psi. Checked ground, volted, replaced relay, pressure regulator.&Fuel lines. Also ran fuel pump out tank with out filter 8-9psi. Changed pressure guage 3 times to varify. Truck has very little power. Will the lack of pressure affected the power of the truck? PS TBI Help upset
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Tuesday, August 20th, 2019 AT 7:22 PM (Merged)
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
TBI system-the fuel pressure specification should be 9-13psi

These had what was called a "pulse dampener" on top of the fuel pump. It is a black plastic piece a few inches long between the pump and the tank unit that was supposed to create a steady fuel flow. They go bad internally and by-pass pressure. You should install your new pump with the piece of fuel injection hose supplied with the pump instead of the pulse dampener
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+2
Tuesday, August 20th, 2019 AT 7:22 PM (Merged)
Tiny
JOSHUAESP
  • MEMBER
  • 1 POST
Dropped the tank and did what you said. Runs perfect. Thanks so much I was going nuts
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Tuesday, August 20th, 2019 AT 7:22 PM (Merged)
Tiny
PILOTMOSS
  • MEMBER
  • 1 POST
  • 1988 CHEVROLET
  • V8
  • 2WD
  • AUTOMATIC
  • 37,000 MILES
1988 28 foot Bounder Motor Home, 454 carb. Engine, electric fuel pump in rear gas tank, regulator near tank.
What fuel pressure would be a good setting?
The original regulator was a Holly 12-804 (1 to 4 psi) or a 12-803 (4.5 to 9 psi) adjustable regulator, not sure which one (because last number unreadable).

Thanks, Bob
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Tuesday, August 20th, 2019 AT 7:22 PM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,761 POSTS
Electric fuel pumps are rarely used with carburetors because they require such low pressure and too much will cause it to flood. 3 to 4 PSI should be plenty.
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Tuesday, August 20th, 2019 AT 7:22 PM (Merged)

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