And the saga continues!

[SithLord44]

Hello everyone,

Need some continued help. For some context, I have put together a '95 318 TI Club Sport that I basically bought in bins. Since putting the car back together, I have had a number of issues that with the help of you all I have been able to fix. As I fix one thing, another thing pops up. This time I have a crank no start symptom that I have traced to a bad fuel pump relay. In the process of diagnosing the condition, I removed the relay and jumped the fuel pump at the power distribution box and got the pump to work. I bought a new relay, which BTW, I couldn't find the actual 4 prong relay that came with the car. The one listed as being the one that superseded it is #61368373700. I put the relay in its place and when I turn the ignition to run or try to start the vehicle, nothing happens. Again, if I bypass it, the fuel pump works. Would love some additional input of what could cause the condition to persist. BTW, I did test the new relay and it works. Thanks.

Alex

[Eric93se]

The prong layout MUST be identical from the one that came out, unless the wrong one was in there (and this could be what's going on in your specific case). People do get the relay/fuse box diagram wrong, that happens a lot because the boxes are not the same across the years and models. There are electrical diagrams in the links at the top of the forum.

With the pump running what happens? What was the contact resistance on the bad relay?

[SithLord44]

Thanks for the reply. I will check with the diagram to make sure the prongs are correct. I did notice that the relay goes in one specific way into the fuse box. As for the pump, once I bypass it, its starts to work with no issues. I did try to started the car that way but I was not able to get it to run. I am going to remove the fuel hose after the fuel filter to see if when I bypass it, I have fuel coming out. I will keep you updated.

Alex

The prong layout MUST be identical from the one that came out, unless the wrong one was in there (and this could be what's going on in your specific case). People do get the relay/fuse box diagram wrong, that happens a lot because the boxes are not the same across the years and models. There are electrical diagrams in the links at the top of the forum.

With the pump running what happens? What was the contact resistance on the bad relay?

[pbonsalb]

Could be someone else used the wrong relay and fried some wires. Did that myself about 15 years ago. Check the wires in the cowl tray. A new used wiring harness solved my problem, but if you find fried wires you can try splicing in good wire.

[Eric93se]

Also, seeing fuel come out is not good enough you have to use a gauge.

[SithLord44]

Thanks and agreed but at least, in the meantime, it will tell me that fuel being pump toward the engine.

Also, seeing fuel come out is not good enough you have to use a gauge.

- - - Updated - - -


Thanks. Will do.

Could be someone else used the wrong relay and fried some wires. Did that myself about 15 years ago. Check the wires in the cowl tray. A new used wiring harness solved my problem, but if you find fried wires you can try splicing in good wire.

[SithLord44]

Update:

I was able to reaffirm that the fuel pump is working. I did pull the hose, jumped the relay box and fuel came out. I tested the old relay and the ones to make sure they are working and they are. I was also able to verify the on the relay box, 30 is being supplied with constant power from the battery, 86 when the ignition switch is turned to "on". I am not getting 12V at 87 when the relay is on because its not coming on. I did test 85 and this is where I am a bit stomped. With the ignition switch off, there appears to be power going to 85. If I understand correctly, when the ignition switch is turned on, the DME is supposed to ground 85, meaning no power should go it. When it does that, then 87 is supposed to have power and activate the fuel pump. Is this correct? if it is, the next logical questions would be, what would cause the DME not to ground 85 when the ignition switch is turned on. Can someone chime in? I would love suggestions. Thanks.

[Eric93se]

The dme will only supply ground to the relay for a second to prime the pump, if its not priming the pump then something else is wrong.

Open up your dme, get access to both sides, check for any white oxide. If you see any, get a can of Deoxit 5% and spray down everything and lightly scrub with an old toothbrush, repeat 3x. The dme has to be 100000% dry before plugging it back in.

[SithLord44]

Will do. Quick ?. Could the crankshaft sensor cause the DME not to ground the 85 on the relay if it is bad? The sensor is new but just wanted to ask.

The dme will only supply ground to the relay for a second to prime the pump, if its not priming the pump then something else is wrong.

Open up your dme, get access to both sides, check for any white oxide. If you see any, get a can of Deoxit 5% and spray down everything and lightly scrub with an old toothbrush, repeat 3x. The dme has to be 100000% dry before plugging it back in.

[Eric93se]

Yes bad crank sensor will prevent it from running. I've had a bad brand new one.

[pbonsalb]

Update:

I was able to reaffirm that the fuel pump is working. I did pull the hose, jumped the relay box and fuel came out. I tested the old relay and the ones to make sure they are working and they are. I was also able to verify the on the relay box, 30 is being supplied with constant power from the battery, 86 when the ignition switch is turned to "on". I am not getting 12V at 87 when the relay is on because its not coming on. I did test 85 and this is where I am a bit stomped. With the ignition switch off, there appears to be power going to 85. If I understand correctly, when the ignition switch is turned on, the DME is supposed to ground 85, meaning no power should go it. When it does that, then 87 is supposed to have power and activate the fuel pump. Is this correct? if it is, the next logical questions would be, what would cause the DME not to ground 85 when the ignition switch is turned on. Can someone chime in? I would love suggestions. Thanks.

I have not studied the BMW wiring diagram recently enough to comment on the E36, but a standard Bosch 4 or 5 pin rekay relay is turned on by either proving power to 85 or 86 or by providing ground to 85 or 86. The two prongs are interchangeable in that either can supply power or ground depending on how you wire the relay. You can also use either power or ground to turn on the relay. For example, 85 could supply power full time but the relay won’t turn on until ground is supplied to 86. Or vice versa. The electric cooling fan on at least the 6 cylinder E36, for example, is turned on when the ground circuit is completed.

[SithLord44]

Thanks. In this case, I was able to verify that in fact, the DMW does provide ground to 85 and that is what gets the fuel, pump going. At this point, that is not happening to my relay.

I have not studied the BMW wiring diagram recently enough to comment on the E36, but a standard Bosch 4 or 5 pin relay is turned on by either proving power to 85 or 86 or by providing ground to 85 or 86. The two prongs are interchangeable in that either can supply power or ground depending on how you wire the relay. You can also use either power or ground to turn on the relay. For example, 85 could supply power full time but the relay won’t turn on until ground is supplied to 86. Or vice versa. The electric cooling fan on at least the 6 cylinder E36, for example, is turned on when the ground circuit is completed.

[pbonsalb]

As Eric pointed out, the trigger is momentary to prime the pump and not full time until the engine is running. I have never tested all this myself so I don’t know how to tell you to test further. I like the idea of opening the ECU for a look, but don’t know much about the 4 cylinder ECU and never had any issues with my 6 cylinder ECUs.

Is there any anti theft device on the 94 318i that could be an issue? Whenever a car is assembled from boxes of parts, there is opportunity for many errors. Could be something indirect having an effect.

[SithLord44]

Crankshaft Sensor Connector.jpgHere is a thought and a ? I am wondering if I connected the crankshaft sensor incorrectly. Here is a pic of where the crank and cam sensor connect to. Both are 3 prong and the same wire color. I cannot find anywhere where it specifies where each connect to. I do not want to have to take apart the intake plenum again just to find out that it makes no difference. Could this make the crankshaft sensor not read and let the DFMW know to ground 85 for the fuel pump to prime?

[Eric93se]

I was going to ask because a lot of the connectors can be plugged in the wrong location. All those crusty connections should be cleaned with Deoxit 5% and scrubbed with a toothbrush.

[SithLord44]

LOL. This is just from another wiring harness that I have from another 318 TI with the same engine. Prior to putting the engine back together, I cleaned the entire wiring harness and connectors. None of the connectors in the wiring harness have any rust or dirt to include the connector to the DME. I will try to remove the plenum tomorrow and see but I still need to know where the crankshaft sensor connects to.

I was going to ask because a lot of the connectors can be plugged in the wrong location. All those crusty connections should be cleaned with Deoxit 5% and scrubbed with a toothbrush.

[pbonsalb]

I don’t know the obd1 cars well or the 4 cylinder cars but the crank sensor did change on the 96-on 6 cylinder cars and there was a wiring harness adapter to change from 5 to 12v. If you don’t plug the adapter harness in correctly, you can misconnect several sensors. Usually the plugs are designed to match only one sensor but not always.