81 528i, sat for 3 years now wont start

[paodom]

I burnt out the fuel pump inside the gas tank, which I just installed a new one. It has fresh gas. Both fuel pumps are working now. Its getting a spark, the battery is strong, the distributor rotor is good. It is not getting fuel though. I pulled the fuel lines from the motor and no fuel is present.
Any ideas?

[socalfiver]

it is probably the combo relay not turning the fuel pump on.

Remove the air intake and, with the ignition in the "on" position, open the door of the AFM with your hand. The combo relay should click, and the fuel pump should be running.

If there is no click, the relay needs repair or replacement. There's a FAQ on combo relay repair.

[socalfiver]

Another possibility is a clogged fuel filter since the car sat for 3 years. The fuel inside may have turned to varnish.

[Mike W.]

The intank pumps die young and the cars run fine without them, so that wasn't an issue. If you are getting spark, shoot some carb cleaner up the air filter to prime it. If you get a sputter off that it's a start. 3 years, well, that's not that long, I think my project car was sitting that long and it started with a fresh battery and a prime. But the filter could be plugged, injectors could be rusted shut, it's just a process of elimination.

[paodom]

Thank you everyone for your advice. You can hear the fuel pumps running so the combo relay is alos okay. I pulled the fuel line before the fuel filter and no fuel, so the filter is out.
Could fuel have turned to varnish in the steel fuel lines runnning the length of the underbody from the pump to the enhgine compartment?

[socalfiver]

The filter should be at the rear of the car.

It's possible that the hose that runs from the top of the fuel tank to the fuel pump is shot. If it is shot, the fuel pump cannot create vacuum to pull the fuel out of the tank. It's a bear to change.


It's possible but not likely that the steel lines are clogged with varnish. Disconnect at both ends and blow through them.

[paodom]

Im off weekends, and will pull the fuel line from the pump and see if fuel is coming from it, if it is Ill know its the steel lines running under the chasis, and get them cleared out.

[socalfiver]

And if there is no fuel coming from the pump, that will be an indicator that the rubber hose between the tank and pump has failed. I'd bet it's a failed rubber hose rather than clogged lines. The rubber is 30 years old and most likely hasn't ever been replaced.

[paodom]

I pulled the fuel line off of the filter, clamped it to a coffee can, turned the motor to on, heard the fuel pump and no fuel in the can. Next, I pulled the hose leading into the fuel pump from the tank, repeat, no fuel in the can. I then checked my connections on the gas tank fuel pump and they could be better. I put some serious effort into ensuring all connections are tight, tried to start the car and it still does not start. I replaced all of the fuel line so I the vacum is good, and Id driven it since then although that was a while ago not long enough to be the source of my problem.
I notice the exterior fuel pump, while running, sounds like something is loose inside when running. Can failure of the exterior fuel pump be an option even though I hear it running?

[socalfiver]

The in-tank pump is not enough to deliver fuel to the main fuel pump if the fuel line itself has deteriorated. You need to replace the line between the fuel tank and the fuel pump. It is only $3 of hose, but it can be difficult to fish into place between the body and tank. Do this before you attempt to replace your $170 fuel pump. If the pump is making noise, it will probably work.

[paodom]

The replacement of the fuel tank hose section will be next weekends project. By the way after reading the FAQ on how to do it, I figured out a method that I anticipate should be much easier than the duct tape method or the other method listed. I'll document it and if it is simpler submit it as an improved way to replace that hose.