tank lift pump and fuel pressure

[JHZR2]

Hi,

What connection does an in tank fuel pump have with respect to fuel pressure?

y fuel pump has always been a bit noisy. Works fine, no hesitation or funny business at high or low speeds, no problems... but I have to wonder if it is putting out low pressure, resulting in an inherent lean condition that causes my NOx.

So, for a typical car, shat is the relationship between fuel pump and fuel pressure for the injectors? I assume there is no dedicated injection pump like on a diesel, correct? Gasoline injection is a low pressure system I would assume.

Thanks!

JMH

 

[andyd]

the 2nd hand lift pump in my 88 528e is very loud, the main is very quiet.. I ran the 88 for many yrs without a functioning lift pump. No issues. In cars with M 30, "big 6"engines, its reported that top end accelleration with less than 1/4 tank of gas will starve out if the lift pump is bad.

RE fuel pressure, the lift pump has no affect on it. Generally speaking, when the FPR fails, it leads to over pressure and richness results , not a lean condition.

NOx forms at temps over 2600f. What causes that is incresed compression from carbon build up and a lean A/F mixture. Cheap to fix culprits are vacuum leaks, fuel filter, O2 sensor. Ultimate fix may be a new cat.

 

[JHZR2]

but the later E30 cars had just one pump, in the tank...

As I mentioned - no signs of it being bad, except that it is slightly loud... not in any way horrble, I just hear it buzz.

Good to know about the FPR, I have no reason to think that it is bad...

Thanks!

JMH