1986 e24 635csi - fuel pump

I've got a no-start situation where I've got spark but no fuel.

So it looks like there's a fuel pump in the engine compartment as well as an in-tank fuel pump.

Is the fuel pump actually in the tank? Or just near it on this model?

Also, is it accessible through the trunk, or do you actually need to drop the tank?

I switched out the main relay and the fuel pump relay's with new ones from bmw.

I'm guessing its down to one of the fuel pumps being dead...

Thanks! Dru

thanks. will check this now. I've heard that the pumps will only engage when the ignition is set to "start" and that they won't even prime at "on".

Is this correct?

Also, lets say just the in-tank pump went (for whatever reason), will the bosch pump still be enough to deliver gas to the engine? Even if not enough to run smoothly?

Is this correct? Thanks. Dru

Blake Dods>Your car has two pumps- a transfer pump in the tank, and a bosch pump

The intank pump wont keep the car from running, it just helps to quickly prime the high pressure pump. Intake pump symtoms are hesitation on acceleration or in turns with low fuel.

The pump runs when cranking and running. To test your pump circuit take a volt meter and have someone crank the car over. Switching relays in the fuel pump circuit is cheap and can solve many running qwirks.

I have a diagram for your year and model.

Blake

Hmm. My mechanic just did the work. About to pick it up. He says he replaced both pumps...

From this it sounds like maybe only the main pump was damaged.

Too late now, but any ideas on what the process of swapping out the in-tank pump is like? How do you get access to it? i.e. drop the tank or go in through the trunk? Also, how long should it take to swap out.

Well. Thanks list...at least you helped me get to the point that I was sure it was a faulty pump...though it sounds like the in-tank pump may have been fine.

Also, what's the chances of both pumps going at exactly the same time? Car was running perfectly one day, then after 5 weeks storage wouldn't deliver fuel at all...

Thanks! Dru

Blake Dods>The intank pump wont keep the car from running, it just helps to

Hi,

To access the in-tank transfer pump you have you pull up the trunk carpet on the passenger side. There you will have easy access to the assembly; this job that takes me about 5 minutes to remove. Some people will only replace the pump, which I think is stupid. I replace the whole assembly; only $75. Re-assembly takes a little more time. Enitire job should take 30min. Replacing hoses ? Add more time.

The main pump can be had for $120ish (BOSCH), but replacement time can vary due to dirt and corroded hardware. I'd say an hour; includes filter change.

Both pump going at the same time? Not likely unless you ran the car out of gas and cranked the car until they sieze. Most likely a bad pump relay ($15). In-tank pump is cheaply made and will fail long before the Main pump will. If the main pump loses its prime, it can be damaged quickly. So having the transfer pump working is in your favor.

Blake