1985 e30 325e weird noise at the fuel pump

[zazexom]

I'm hearing a weird noise at around the fuel pump. The car hesitate under load in 1st and 2nd gear. Wonder if it's a fuel pressure issue ? New pressure regulator is installed in the engine bay.
Attached it a quick video I recorded while the engine is at idle.
Thanks in advance for your help.

[e30davie]

Bit hard to tell but it sounds like its cavitating. which sort of implies that its either sucking air or trying very hard to suck fuel and not getting any.

Does your car have an intake fuel pump as well? i can never remember which ones do or dont.

maybe the fuel pump is just stuffed, or the internal one is stuffed (if it has one)

[TobyB]

85 would have been dual pump-

so yeah, another vote for a stuffed low pressure in- tank pump.

Checking fuel pressure's important on these cars- they're not clever
enough not to murder themselves if it goes low.
Likewise, a plugged injector can be death...

I did the in- tank conversion to put the high pressure pump in there.
Far less hassle afterwards.

t

[McGyver]

85 would have been dual pump-

so yeah, another vote for a stuffed low pressure in- tank pump.

Checking fuel pressure's important on these cars- they're not clever
enough not to murder themselves if it goes low.
Likewise, a plugged injector can be death...

I did the in- tank conversion to put the high pressure pump in there.
Far less hassle afterwards.

t

What Toby says, hook up a fuel pressure gauge and see what happens. You'll want to know that the pump is able to maintain pressure at idle and WOT when you're flowing more fuel.

Converting to a single in-tank high pressure pump is easy and will be cheaper than replacing both of the dual pump setup. I made a DIY on this several years ago.

[zazexom]

Thank you all for the inputs!
Toby is your DIY in-tank conversion available somewhere ?

[zazexom]

is there a DIY to connect the fuel pressure gauge to the fuel line ?

[TobyB]

No, I just stuck an in- tank pump into the existing tank.

I think I had to braze a return line into it, maybe because the
HP setup returns to the driver's side to siphon fuel,
but the 'bottom crossover' tanks don't do that?

There are some really old threads that I followed.
I had the tank out when I did it, too, so it might be
harder to do if you leave the tank in place.

t
it was a long time ago, in the basement of a superfund site...

[McGyver]

is there a DIY to connect the fuel pressure gauge to the fuel line ?

For the fuel pressure gauge, dissconnect the fuel supply where it goes into the fuel rail. put a tee there. One leg is supply, one is the fuel rail, one is the pressure gauge.

my fuel pump DIY is here:

https://www.r3vlimited.com/board/forum/e30-technical-forums/e30-faq-and-diy/336596-diy-double-to-single-fuel-pump-conversion