bmwe21.net forums

Hi guys,
i have done some work on my E21 where i threw out the solex carbed engine and threw in a 2.0 motronic unit from an E30. thanks to all the threads and forum inputs from most of you guys i read , it is in and wired it up and it purrs nicely.
just finished my front caliper upgrade recently by throwing on a set of volvo 240 calipers.
now i am having an issue with fuel delivery. for now just to get things running, i have fitted an aftermarket fuel pump. i have mounted it in the engine bay below the left shock tower. the prob is, i have read that the engine bay is not the most ideal location for it to be as the heat would give it a short lifespan. i also read that these fuel pumps are best meant to push fuel up the fuel line instead of pulling it through the fuel line. are these true?
and as for the fuel pump it now whines like a dying cat whenever the engine runs. but the revs are strong and no probs with idling.is it possible that there is air in the system? this only happened after the fuel tank went dry once before..

well to cut a long story short, can i keep my pump where it is? if no, what fuel pump arrangements can i go for? would an in tank fuel pump off a 318i E30 be enough as i read that those models relied only on the in tank fuel pump and had no secondary pump...

any input would be valuable.. really need to get this lil babe on the road..

Cheers!

Well there must be good reasons why electrical fuel pumps are always closer to the pick up, and that may very well have to do with the fact that they should not waster energy on sucking in fuel and concentrate on generating a decent fuel pressure. Not sure if the E30 in tank pump fits or can be made to fit but it's worth the try.

Supposing you fueled the car up after running empty that should not be the cause of your current noisiness. Most likely is that it picked up some dirt from the bottom of the tank, did you check the fuel filter, if any? You may want one, or a new one haha! Still it could be picking up air due to a worn fuel line but chances are small if you don't have any leaks I guess.

BTW did you connect a fuel return line to get rid of excess fuel after the fuel pressure regulator?

Hi Jeroen,
nice to get a reply from the man himself.. haha.. read up on many of your write ups while working on my car. cheers to that!!
well i guess you have a point on the dirt getting in. all the excitement of getting her started meant i cut some corners here and there and i fitted the filter much later, just before the entry to the pump. there are a lot of bubbles of air in the filter when the engine runs so thats whats making me think that it might be air. will check the hoses. darn hoses...
and yea the return line is connected back to the fuel tank.
well i put the pump where it is now because in case it fails while i am on the road i wouldnt have to chuck out the rear seats to get access. hmm.. think i will place it somewhere more accessible closer to the tank.

thanks for the input Jeroen!

Hi manic, just to give you my experiences, most fuel pumps sound like a dying cat in an E21 I've found! Had mine replaced last year and even have a rubber housing to help, but you can still hear it. I'm not sure if you've connected it directly to the body of your car, but BMW sell a bracket to shield any noise and vibration from the rest of the body and that could help a little with the noise too.

Agreed, but you should not see any air bubbles. That means you have a leak or a bad connection somewhere. Perhaps the leak is minimal and the vacuum drawn by the pump more or less opens up the crack.