Z3 M44 Crank no start

[caglar]

I have been working through this in my spare time and feel like I am getting to some kind of solution.


This started with a dead battery which had to be replaced. At the time I thought it might be an EWS-DME sync issue. But further tests proved that the engine does get spark and fuel pump DME does receive power.


Here is where I stand now;

• Fuel rail does not show any pressure (tested through schrader valve)
• Replaced Fuel pump relay and here is what I get on power
  
  • Ignition on Position 30-85-86 all show 12v and 87 no voltage
  • When attempting to start 30-86-87 all show 12v and 86 no voltage
  • Fuel pump fuse #18 shows 12v during starting. In my car model there is no fuse #13
  • Fuel pump power cable at back shows 12v during starting. However it only picks up 2v during key on

Based on these I get the feeling that I have either a bad. Fuel pump or blocked filter. The car is 80K miles and filter is likely factory and never changed.


Logic says that I start with filter an if that doesn’t solve move to fuel pump.


Could I be missing anything else that would prevent fuel from getting to rail?

[rf900rkw]

If you get 12V to the pump during crank, then the relay and fuses etc are working.

If you have a plugged up filter, one so stopped up that won't pass enough fuel for idle conditions, you have major major problems that will not be solved with a new filter. Contrary to the salesmen, fuel filters don't need regular changing until you get crap in the tank.

The one thing you haven't checked yet is the ground for the fuel pump.

[caglar]

How do you check ground for fuel pump?

[BladeRunner919]

Test for continuity between the pump's ground wire and a metal part of the car. But based on your previous thread this was always most likely to be a failed fuel pump.

[caglar]

Is there a way to test the pump without fully removing it?

[rf900rkw]

The best test would be an ammeter in series with the pump. The easiest way to do that is to pull the fuel pump fuse and hook your ammeter to the two terminals there.

[caglar]

Guessing that a 0 reading while key out is it’s fine?

[rf900rkw]

No no no uh-uh. You do not run an amp draw test with the key off and the meter set to ohms. You need an automotive meter with a 10 or 20A scale. Forget I mentioned this test. Do an ohm test across the pump instead.

[caglar]

Thanks ok well this one seems to have a 2/20A test should it try with that again with key ON

I’ll try testing the pump as well.

[rf900rkw]

No, because that is a house wiring meter. The Ammeter part is the clamp, not the leads. The leads are only for Volts, Ohms, Beep, and Diode tests, not Amp.

[sleeperz]

[caglar]

No, because that is a house wiring meter. The Ammeter part is the clamp, not the leads. The leads are only for Volts, Ohms, Beep, and Diode tests, not Amp.

Thanks. Yes this is definitely a subject I struggle with LoL

[z3forlife]

With the key on Set your meter to DC volts and see which side of the fuse holder shows 12 v. Then change meter to ohms and measure continuity at the other side (dead side) of the fuse holder to chassis ground. If you see O.L. Then you may have lost ground or the pump motor windings/brushes are open.

[rf900rkw]

Thanks. Yes this is definitely a subject I struggle with LoL

That's why I said to forget that test. When doing an amp draw test, you are effectively creating a short circuit through your ammeter. Let's not temp the gods of escaping smoke.

[caglar]

With the key on Set your meter to DC volts and see which side of the fuse holder shows 12 v. Then change meter to ohms and measure continuity at the other side (dead side) of the fuse holder to chassis ground. If you see O.L. Then you may have lost ground or the pump motor windings/brushes are open.

Found the one with 12v on ignition then tested the dead side (with key ON). It did return positive values as seen here. So sounds like ground is fine right?
IMG_6962.jpg

Do an ohm test across the pump instead..

Tested the posts in circle (that connect to large wires) and got back + value around 1.2 Ohm
IMG_6958.jpg

Where does this leave me?

[z3forlife]

Next I’d see if you have power at the pump plug. If so it would seem to be a bad pump. The winding are probably ok due to the ohm readings but the pump may have seized.

[caglar]

When car is cranking I see 12v at the plug guessing bad pump then.

If it’s the pump, is it better to replace the whole thing or just the motor? Not sure how long the plastic parts last.

[328 Power 04]

Wouldn't you be able to feel if the pump is working since you're right there at the pump now?
It's not easy to confirm via internet, but it does sound very likely that the pump itself is dead.

[caglar]

That’s the thing. When I turn on the ignition there is a brief sound from back there but can’t be sure.
Would it even make sense to remove the hoses connecting to tank to see what happens when it turns on? I could always get a longer hose and make sure it dumps whatever that comes out into a portable gas tank.

[BladeRunner919]

Yes, do that, but safety first!

[caglar]

Hate to leave a thread open so figured I would add the results. Removed the fuel pump assembly and found this rusted pump inside had some rust debris at the bottom of the tank which I cleaned to keep things safe.
Then replaced it with a new (cheap - https://a-premium.com/product/Fuel-P...variant=204985) unit.
The car immediately started... guessing it was the crapped out pump. The only issue with this cheap pump is that the fuel gauge shows tank empty even though its half full . Guessing something to do with how the unit measures. At this point I will not pull it out.

Here is a question to anyone that has changed the pump only. Would this old unit still be salvageable . Should I look at getting a OEM fuel pump and replacing it or is it better on the long run to get a new OEM pump assembly?
IMG_8182.jpg

[sleeperz]

Hate to leave a thread open so figured I would add the results. Removed the fuel pump assembly and found this rusted pump inside had some rust debris at the bottom of the tank which I cleaned to keep things safe.
Then replaced it with a new (cheap - https://a-premium.com/product/Fuel-P...variant=204985) unit.
The car immediately started... guessing it was the crapped out pump. The only issue with this cheap pump is that the fuel gauge shows tank empty even though its half full . Guessing something to do with how the unit measures. At this point I will not pull it out.

Here is a question to anyone that has changed the pump only. Would this old unit still be salvageable . Should I look at getting a OEM fuel pump and replacing it or is it better on the long run to get a new OEM pump assembly?
IMG_8182.jpg

I have done a pump-only replacement on several other cars, but not a BMW Z.
In my experience, if the fuel sender is working, then it is feasible to replace the strainer (very important), the pump, and any rubber hoses that are not pliable and have a good pump. Might not be cost effective though.
I did see where pump assemblies for the S54 cars seem to be no longer available. Not sure about other versions. There is a thread covering that rebuild. If you search, it might provide the info you are looking for.