fuel delivery question

joe_keefer · Post by **joe_keefer** » Wed Dec 29, 2010 12:52 pm

hi guys,

do both fuel pumps in a 79 528i get the signal to run at the same time?

i just replaced the in-line pump and i can hear it working away, but i`m unable to get fuel out of the tank. i took the tank pump out it seemed to be in order. the float moved nicely, the leads and connections are nice, the screen was clean, and the tank is quite clean! the tank isn`t quite full, it`s about 3" or so from the top.

should i fill the tank the rest of the way? i thought that i could get away with that pump not running. is that not the case?

thank in advance for your help! i really want to get her running! it`s driving me nuts looking at her in the driveway just sitting there staring at me saying please get me running and drive me. lol

grumpsjr · Post by **grumpsjr** » Wed Dec 29, 2010 12:59 pm

This may seem obvious, but have you verified that you don't have fuel coming out of the output end of the inline pump?

I had a similar problem and it turned out the fuel filter was really that clogged. I had fuel coming out of the pump, but it couldn't get past the very clogged filter - particularly if the car has been sitting a while (eight years in the case of my vehicle).

joe_keefer · Post by **joe_keefer** » Wed Dec 29, 2010 1:07 pm

yeah there isn`t any before the pump. the struts are shot so she rocks pretty good so i was thinking of rocking it back and forth while the pump was running. i just get worried the i`m gonna burn up the new pump trying to get the syphon started. yes i know it`s a brawn vs brain way to do it. lol but im 6'3 295lbs. so it`s usualy my first choice. lol hence why i tore the connector off the pump checking to see if it screwed off. lol

grumpsjr · Post by **grumpsjr** » Wed Dec 29, 2010 1:09 pm

You can always siphon it the old fashioned way - by sucking on the hose.

Mike W. · Post by **Mike W.** » Wed Dec 29, 2010 2:11 pm

They do both get signal at the same time, so if one works the other should too. If the main isn't working, whack it with the handle of a good sized screwdriver. Not a hammer, don't beat it up, but something to reseat the brushes. If that works you probably need a new pump. And I assume you know about propping the AFM flap open to turn on the pumps.

joe_keefer · Post by **joe_keefer** » Wed Dec 29, 2010 3:27 pm

yeah thats how i get the main running now. i think it was you that turned me on to that a few days ago. the main works great it`s brand new and is plenty noisey. do these cars have a disable mechinsm of some sort? my range rover has a fuel pump cutoff if i roll it over. although my main pump is running so i guess that wouldn`t be it anyway. i guess i`ll fill er` up and start sucken. lol

thanks again!

socalfiver · Post by **socalfiver** » Sun Jan 02, 2011 2:11 pm

It's possible that the hose between the pre-pump and main pump is shot. If so, the pump will run but no gas will reach it. That was the case with my '80 when I got it, and it had been driving just 2 months before.

I replaced the larger of the 2 hoses that you can reach through the trunk access hole. Kind of a pain to feed the new hose through, easier if you lower that corner of the tank.

Pull that hose at the tank, and if you can get any air through by blowing, it is shot. The smaller hose is a vent hose, and you will be able to blow air through that one.