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91 318i low fuel pressure

 
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hi91-318i



Joined: 08 Apr 2005
Posts: 114
Location: Hawaii

PostPosted: Mon Oct 03, 2016 8:39 pm    Post subject: 91 318i low fuel pressure Reply with quote

I have been dealing with a hesitation and lack of power with my 91 318i M42 for a while. It starts easily hot or cold (slightly extra cranking from cold start) and idles perfectly. The lack of power and hesitation shows up with moderate to heavy acceleration, feels like it's starving for fuel and CEL will sometimes come on until I back of the gas pedal. Stomp test says 1222 (rich/lean reading).

Replaced the O2 sensor and fuel filter, old filter was not clogged and did not find rubbish in the old filter. Bought a fuel pressure gauge and got only 20psi with the fuel pump relay jumped. With motor running, 20psi and no change nor increase with the fuel pressure regulator vacuum hose disconnected.

In tank fuel pump needs to be replaced? Read that a Chevy Vega pump could be retrofit but I think the Vega pump is for dual fuel pump Bimmers? Also not sure if the Vega pump gives 45psi?

Anyone know about those 255LPH replacement pumps? Specs show higher than spec fuel pressure but a sells for less than Bimmer replacement pump...
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hi91-318i



Joined: 08 Apr 2005
Posts: 114
Location: Hawaii

PostPosted: Thu Oct 27, 2016 3:47 pm    Post subject: Reply with quote

Fuel pump arrived but didn't install it because the hesitation gone and e30 runs like normal. Just re-checked the fuel pressure and it's now 30# with the original pump.

Pressure does not change with pressure regulator vacuum hose pulled. Jumped fuel pump relay and still read 30#.

With the motor off I can hear the fuel pump but it's an erratic ticking sound but don't know what a properly functioning pump should sound like...

With everything running properly, I don't know if I should install the new pump.
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