Monday 19 July 2021

Checking past work... is my new fuel pump bad or something else? 996 fuel pump low pressure and flow quantity

 On another cold rainy lockdown day, decided to run some basic tests to see if the work I've done so far is OK.

1) Vacuum test - unable to detect any leaks (will talk more about my homemade smoke machine later if I feel like it!)

2) Removed airbox, restart - no good

3) Removed airbox, removed drive belt, no good

4) Replaced everything except MAF, no good

5) Replaced everything and bypassed fuel pump relay with jumper wire - no good

6) Swapped MAF for a dodgy cheap yum cha china MAF bought from aliexpress - no good. Put back the Bosch unit

7) Swapped in two spare car batteries from my other cars - no good.

Then thought I might as well check the new fuel pump.

Porsche workshop manual specifies 850ml in 30 seconds output - this is well short!

Engine off, powered fuel pump on - only 2.2bar of pressure instead of the 3.8 it should have!

SO, is it a bad new fuel pump, or is there something else? Now need to check
  • Check fuel filter - just ordered a replacement part, only $35 delivered for a Mahle filter, but won't arrive for a week. Change it out, then recheck pressure and flow. Try starting car.
  • If still no good, check for low voltage to fuel pump (should be at least close to 12V). Perhaps a bad ground, loose connection, or bad wiring. Or maybe the voltage is fine.
  • Obstructed fuel lines - visually check as much as possible for any crimps, bends, folds etc that would obstruct flow.
Making progress? Wouldn't call it that, but need to get this fixed anyway. What a saga.

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