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99 suburban fuel pressure


turkey28
11-12-2005, 06:43 PM
I have been thinking my fuel pump might be going out, loud whine, hesitation when taking off, etc. I got a gauge and checked the pressure, specs are 60 to 65 pounds. What I found was when the pump is priming it has 61 pounds, when it shuts off it drops to 50, engine off.
At idle the gauge fluctuates between 50 and 55, at higher rpm it holds steady at 50. I put injector cleaner in a week ago and it is running much better. I guess my question is, are my pressures normal? I don't want to replace the pump if it is good, it whines pretty loud but it has done that since I bought it 2 years ago.

GMMerlin
11-13-2005, 07:57 AM
Fuel pressure is too low

mobil_12
11-13-2005, 10:09 AM
key on engine off pressure should be 60 to 66 psi. Youre on the low end there but still within specs. engine running with vacuum applied to the regulator you should be 5 to 10 less than key up. sounds like youre ok there too. volume could be a problem. I believe that volume should be 1 pint every 30 seconds. maybe check into that, I could be wrong.

turkey28
11-13-2005, 12:11 PM
GMMerlin, could you elaborate on your opinion? Seems to me it is within the 60 to 66 range and 10 pounds less with the engine running....

GMMerlin
11-13-2005, 04:16 PM
GMMerlin, could you elaborate on your opinion? Seems to me it is within the 60 to 66 range and 10 pounds less with the engine running....

Even though the spec is 60-65 psi, you must take in account the condition of the injector poppets.
My guess is they are probally sticking a little bit and the lower fuel pressure won't overcome spring pressure.
Take that and the fact that the fuel pressure drops to 50 this is indicating to me that the fuel pump is not doing its job (spec is the pressure should hold above 55 psi)
this is not an opinion but experiance :icon16:

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