Author Topic: Fuel Pump and Main Relay issues... (Read 7921 times)

BenMcG · « **on:** March 26, 2008, 08:42:03 AM »

Well, I've been having trouble getting my newly acquired 318i started, so I thought I might what you guys think.

I just replaced the fuel pump, since the P.O. said the one in the car was bad. However, I couldn't get the fuel pump to turn on through the relay.

Jumped the Fuel pump relay at Connectors #30 and #87 and heard it turn on. Threw in a known good relay, and the pump will still not turn on.

This morning I pulled the main relay and fuel pump relay off, and tested them with a 12V test light w/ the ignition off. Apparently there is power going to #30 on the Fuel Pump Relay, and #30 and #86 on the Main Relay. WTF?

I don't want to start tearing the harness apart, but I noticed all of these power go to the Battery Junction Block (See page 1360-1 Injection Electronics on the Troubleshooting manual).

Anyone else have an issue like this? Thanks for any advice/input/suggestions.

Ben

ak96ss · « **Reply #1 on:** March 26, 2008, 05:25:44 PM »

Have a spare DME? If you have good power at 30 and 86 on the main relay, and good power at 30 at the fuel pump relay, I would hazard a guess that the DME is possibly at fault.

BenMcG · « **Reply #2 on:** March 26, 2008, 06:33:11 PM »

Quote from: ak96ss;45575

Have a spare DME? If you have good power at 30 and 86 on the main relay, and good power at 30 at the fuel pump relay, I would hazard a guess that the DME is possibly at fault.

I do have a spare 175, but I'm not sure if it is good or not. I'm assuming that power should not be flowing through those wires when the ignition is off.

Also, just checked the resistance of the Crank Position Sensor and I don't even get a reading. Cam Position Sensor reads 1250, so I know the multimeter isn't faulty. Could this be an issue as well?

Cobra Jet · « **Reply #3 on:** March 26, 2008, 08:09:43 PM »

So, putting everything aside - you do have the new fuel pump installed, correct? If so, when you turn the key "on", do you hear the fuel pump prime at all? Almost every EFI vehicle, as soon as the key is turned on (KOEO), the EFI fuel pump should immediately prime (you should hear a distinct short "whine"). Are you hearing the new fuel pump prime at all?

Prior to purchasing the vehicle, did you hear it start up and run - or did it not run or start when you purchased it? If it was running when purchased, what symptoms were you experiencing that pointed to a fuel pump replacement? Did you get or pull any codes from the DME prior to replacing the pump?

BenMcG · « **Reply #4 on:** March 26, 2008, 08:21:18 PM »

Quote from: Cobra Jet;45582

So, putting everything aside - you do have the new fuel pump installed, correct? If so, when you turn the key "on", do you hear the fuel pump prime at all? Almost every EFI vehicle, as soon as the key is turned on (KOEO), the EFI fuel pump should immediately prime (you should hear a distinct short "whine"). Are you hearing the fnew uel pump prime at all?

Prior to purchasing the vehicle, did you hear it start up and run - or did it not run or start when you purchased it? If it was running when purchased, what symptoms were you experiencing that pointed to a fuel pump replacement? Did you get or pull any codes from the DME prior to replacing the pump?

Yes, the new fuel pump is installed. No, when I turn the key to "on", i do not hear a whine, or prime. What I was saying earlier is that if I jump #30 and #87 on the fuel pump relay, it turns on no problem. Yet when I put in a known good relay, and check for power at the fuel pump, I don't have any.

No, I bought the vehicle non-running assuming it needed a fuel pump. P.O. did a few things like change the alternator, belts, and is actually a member of this site and others (Majikal). How do I pull codes from the DME? Diagnostic port in the engine compartment? And can I pull them even if the engine doesn't run?

Thanks for the detailed reply.

Cobra Jet · « **Reply #5 on:** March 27, 2008, 09:23:26 AM »

You can pull codes by turning the key to "on" (KOEO - key on engine off) and you will then need to press down the gas pedal 5 times consecutively within 5 seconds. If you depress the gas pedal too slow or too fast, you won't get the CEL (check engine light) to blink in the dash cluster... If you do it correctly, what will happen next is the CEL will start to blink any stored codes. You will need to count the CEL flashes and then once you have the codes, you can determine what may be causing any problems...

For instance, if there are no faults or stored codes, the CEL will produce:
blink -pause- blink, blink, blink, blink -pause- blink, blink, blink, blink -pause- blink, blink, blink, blink (this is the no fault code of "1444").

Get yourself a pen & paper to write down what the CEL does.

Here is a link to the Motronic codes: http://ee1394.com/bmw/docs/bmwDTCodes.pdf

Also, have you checked over any grounds & fuses - it's possible there is a ground fault or fuse problem.

Good luck!

D. Clay · « **Reply #6 on:** March 27, 2008, 10:57:08 AM »

Check also the layout of the relay pins. BMW changes the layout of the 30-87 and 86-85 pins. There are three or four options. You may have the wrong relay.
http://bmwfans.info/original/E30/2-T/318is-M42/USA/L/M/1990/04/mg-61/ill-61_0638/

ak96ss · « **Reply #7 on:** March 27, 2008, 04:02:13 PM »

Quote from: D. Clay;45628

Check also the layout of the relay pins. BMW changes the layout of the 30-87 and 86-85 pins. There are three or four options. You may have the wrong relay.
http://bmwfans.info/original/E30/2-T/318is-M42/USA/L/M/1990/04/mg-61/ill-61_0638/

Good call, I'd forgotten this somehow. Most BMW relays have the diagram posted, doublecheck it with the wiring diagram.

BenMcG · « **Reply #8 on:** March 27, 2008, 06:58:58 PM »

Well, I yanked some from my DD '89 325i, so I'm sure they are the same.

Also did the DME diagnostic thing. Got a 1444 Code, even though I'm almost positive the crank sensor is bad. Hopefully I can figure this out.

Thanks guys.

RED IS 91 · « **Reply #9 on:** March 28, 2008, 04:12:04 AM »

Put your meter on the pins of the crank sensor .You should have around 650 ohms.
If you don't get a reading then it is faulty and should be replaced.

BenMcG · « **Reply #10 on:** March 28, 2008, 06:12:20 AM »

Quote from: RED IS 91;45679

Put your meter on the pins of the crank sensor .You should have around 650 ohms.
If you don't get a reading then it is faulty and should be replaced.

Yeah, I didn't get a reading on the crank sensor at all, so I have one coming from the dealer today. But I think there is more to the problem.

Cobra Jet · « **Reply #11 on:** March 28, 2008, 08:20:50 AM »

A bad crank sensor will not allow the vehicle to start at all - you can turn the engine over, but it would never start, it will just keep "cranking". I had this happen on my prior E36 M3 - bad crank sensor. The car died when driving home from work one day, just turned off w/o any warning (that was fun). I got the codes by doing the gas pedal trick while waiting for the flat bed service and that's what it was, faulty crank positioning sensor... After ordering and installing the new, it started right up. If I remember though, the fuel pump will still turn on and prime when just turning on the key... So, I don't think a faulty crank sensor will prevent the fuel pump from priming...

?

Did the prior owner screw around with the wiring harnesses - meaning, did he cut any wires or can you visibly see any damages to any of the engine/dash/fuel pump harnesses? Do you have any blown fuses?

BenMcG · « **Reply #12 on:** March 28, 2008, 08:39:50 AM »

Quote from: Cobra Jet;45692

A bad crank sensor will not allow the vehicle to start at all - you can turn the engine over, but it would never start, it will just keep "cranking". I had this happen on my prior E36 M3 - bad crank sensor. The car died when driving home from work one day, just turned off w/o any warning (that was fun). I got the codes by doing the gas pedal trick while waiting for the flat bed service and that's what it was, faulty crank positioning sensor... After ordering and installing the new, it started right up. If I remember though, the fuel pump will still turn on and prime when just turning on the key... So, I don't think a faulty crank sensor will prevent the fuel pump from priming...

?

Did the prior owner screw around with the wiring harnesses - meaning, did he cut any wires or can you visibly see any damages to any of the engine/dash/fuel pump harnesses? Do you have any blown fuses?

Not that I can see, or know of. The engine wiring harness has been untouched as far as I can see, the only addition to the electronics is the Aftermarket Keyless Entry/Alarm, but that was when the car was in the early 90's.

Cobra Jet · « **Reply #13 on:** March 28, 2008, 09:05:33 AM »

hmmm.. alarm system - depending on what type of alarm system... are you sure it's not in active mode of which it *could be* preventing the vehicle from starting? Some alarm systems do have an ignition/fuel pump kill circuit. If the alarm is in active mode, it *could be* possible that if the alarm does have such a feature, it's killing the fuel pump circuit...

just a wild guess...

I wonder if you can bypass the alarm system to see if there are any differences after bypassing?

BenMcG · « **Reply #14 on:** March 28, 2008, 04:45:50 PM »

Well apparently I must be deaf (couldn't hear the fuel pump turn on), because I just replaced the Crank Position Sensor and the car fired right up.

Guess it was a good thing I didn't have to go chasing electrical gremlins.

Thanks again guys.