1987 325e Looong crank

[Gdayton31]

Hey guys. Thank you in advance for any help you can offer. I recently picked up a beautiful 87 325e. It runs absolutely great as my daily driver. ...but every morning its a good crankin before we're off to work. I've read quite a bit about a check valve in the fuel pump going bad, and have a heard a whine in the back right.. probably 2 or 3 times. Very inconsistent. I'm assuming fuel is seeping back down into the tank overnight and the long cranking is just my fuel pump priming the line again. If the car is relatively warm (3-4 hours since last drive) it starts right up, no hesitation, every time.

The car was well maintained and is in great condition. I have replaced some worn looking fuel lines, spark plugs, fuel filter.. might be forgetting something here. Recently I tried a check valve I purchased from Summit racing in my fuel line right above the fuel pump in the gas tank. The car would start with the check valve installed but would quickly starve out? Removed immediately didn't test overnight.

Anyways my questions here are how many fuel pumps are in this car? Which one do you think I have a problem with? Any way to test? I'd like to replace whichever one is faulty. Your thoughts?

[e30onBBSs]

Google is your friend man. It's almost definitely your check valve, you can install one in line, or just get a new pump.

[101]

There are two pumps in your car. An in-tank low pressure pump and an external high pressure pump.

The check valve function is built into the external pump.

The only way to properly diagnose is to run the fuel pressure and volume tests in the Bentley manual.

If the high pressure pump tests good (supplying adequate pressure, the check valve functioning so it holds pressure in the system overnight, etc.), then the low pressure pump may be suspect.

To check the low pressure pump remove the rear seat cushion and the access cover. Put a test light on the low pressure pump to see if it is getting power with the engine running. You should also be able to hear it run with the access cover off. If it's not running, the car can still theoretically start and run - it just makes the external pump work that much harder, and that usually manifests itself with more noise from that pump.

Others will have to chime in on how to diagnose the low pressure pump further. I haven't had to do that on one of mine yet.

Good luck!

[Seawolf]

Could also be your FPR going bad a bleeding pressure off via the vacuum line into the intake manifold.

If you pull the vacuum line, do you see any fuel there ?

[Gdayton31]

Hey guys, thanks for the replies.

After reading that the high pressure pump is where the check valve is that Im trying to imitate - I installed my check valve imediately after my high pressure pump/fuel filter. This has helped a lot with the cold starts, The car still cranks a little longer than usual - but nothing like before. It seems to me that the car might be fighting with the check valve? I blew through the device before installing it, and it did seem to take quite a bit of pressure to open up the correct way.

I still have yet to try and listen to the in-tank pump running with the car. I'll have a look at that tonight!

I pulled both lines off the FPR immediately after driving home from work yesterday and found no fuel in either side. The hose running to the throttle body was bone dry - so dry I replaced it, actually.. and the other hose smelled of fuel but none was immediately available. I tried pointing the line towards the ground in an attempt to dump some fuel out but didn't get any!

Yesterday I decided I would try a new high pressure pump. Bought the bosch model from Amazon (pretty good deal on there!! 100$) I'll have it tomorrow. I'm thinking it's something with one of the pumps! Hopefully the one I just ordered.. hah! if nothing else I am banking on Amazon's killer return policy to help me track down the problem :)

Thanks again for all the help guys, I'll report my findings w/ the new pump!

[Kershaw]

The fuel line running to the throttle body is going to be always dry. Every once in awhile it purges vapors, no liquids.

[Gdayton31]

Well guys, it's not the high pressure fuel pump. I replaced it Wednesday night (two days ago) the car still cranks a good 5 seconds or so in the morning. I removed the check valve I put in the line earlier - I think it was actually helping the starts in the morning. That being said overall the car runs much better now, it seems to be more full, smoother power. Not sure if the new pump is responsible or removing the check valve is.

I'm gonna get a fuel pressure gauge on it soon and get some measurements of what's going on with the FPR and low pressure pump.

I find it hard to believe cap/rotor/wires/plugs are to blame here just because it is so consistent.. cold - long crank.. even remotely warm - fires right up. Every time. Injectors possibly? Sorry for all the random questions.. computer nerd here tryin' to be a mechanic

Thanks for all the help.