Fuel issues?

[sgmsavannah]

I've got an 86 325e sedan and since I bought it about 6 months ago it's always had a bit of a surging issue between 1500 & 3000 rpms and the fuel pumps are loud so I knew something may need replacing soon. Additionally both the odometer & gas gauge (and speedometer...) don't read accurately/at all so tracking fuel usage is a bit tricky. About two weeks ago I went to start the car and it's couldn't hold a consistent idle, jumping all around. When I gave it gas and tried to drive it still couldn't even out, jerking all over the place.

Cranked it up the next day to do some trouble shooting and it could idle this time, but couldn't sustain fuel pressure and bogged out when given any load. Went ahead & replaced the fuel pump (inline). Drove it around and still it couldn't handle load/keep fuel pressure up but was running.

Then I replaced the fuel filter as I knew it was quite old (from 1990 in fact). It wouldn't start after the replacement of the fuel filter, and then I found out I was out of fuel from tapping on the tank. I just put in about 4 gallons of fuel and it still won't start.

I'm planning on checking on relays and other basic things tomorrow, but thought someone may have had a similar situation and a possible solution to share. I've seen some people posting about their pumps being destroyed from running out of fuel - hoping that's not what's going on here since the pump is new. Has anyone had a similar issue? Ideas on what are likely culprits?

[tomstin]

Idle issues are typically vacuum leaks which these engines are very sensitive to. Also make sure the throttle position switch is working correctly. Check the fuel pressure as the fuel pressure regulator will cause surging / bucking issues. After those, I would look for a known good Air Flow Meter (AFM) to test or have it rebuilt.