random no power to ecu with MSII??????

[der affe]

a month ago i started having a problem with this........ turn on the key, dash lights up, no fuel pump priming noise, crank the starter, no fire.

at first i tried to blame the MSII, but it turns out that it was not getting power to turn on the ecu so it could turn on the fuel pump relay.

i took a shot and replaced the ignition switch, because
A. it was the orginal one in the car with close to 300,000 KM on it.
B. it had an after market alarm at one time in it's life, i had removed all the left over relay and scotch taps, but it looked pretty bad after all the scotch taps were gone.

well the new ignition switch solved the problem for about a month, until last night, without warning, BAM, same issue again.

the fuel pump randomly clicks like it is trying to prime (with the key in the ON position), but i am getting no light on the MSII at the box meaning i am not getting power to it.

i checked the wiring and grounds under the dash and steering colum, they all seem to be fine. i was thinking that there was maybe a wire or ground issue in there that i "fixed" by moving the wires around to install the new ign switch and it has "unfixed" itself.

i have a handfull of fuel pump and o2 relays that i have swapped in as well as an extra known good main relay that is almost new. still nothing.

the bently was not too great for the wiring on this so i has a friend pull up diagrams from mitchell on line. much better!

from the looks of it, power goes through the ignition switch, then to the main relay, to the ecu, then the ecu triggers the fuel pump relay and it primes.

i think it is a grounding issue because of the way the fuel pump relay is clicking away, but i can't find a bad ground. is there another ground just for the ECU itself? if so where is it hidden?

any other ideas for this issue????????

[der affe]

i can trigger the fuel pump relay with my power probe, but the main (white relay keeps randomly clicking and no power to the ecu.

Can anyone tell me what the pins are supposed to be with the key on and off for the main relay?
unless I am missing it somewhere in the bentley, I can't seem to find it.

[der affe]

With the ignition switch on, #30 & #88 are +, #85 is - & #87 in the center is also - BUT I will not set off the chime on my power probe, it just lights up the neg light.

[e30leigh]

sounds like you have a short to ground. i wouldnt be looking for a bad earth id be looking for shorts.

if you try get wds wiring diagrams. im not too sure if they can be down loaded. but anything is possible. its extremely indepth and very accurate. alittle hard to use as there is just so much to navigate. but once you get your head around it, its the best wiring diagram system available for bmw's

[der affe]

I hope it isn't a short! The engine harness is new since the MSII install and was in super nice shape.

My next thing is to do a continuity test on the engine harness tomarrow.

I wish I could find out the deal on the main relay though, it would save me some extra work or at least point me in a direction.

[jlevie]

In the stock configuration, the main relay is controlled by the DME. When the START signal from the ignition switch is present at the DME the main relay will be activated. I don't know if and MS works the same. Another possible problem would be a bad fusible link.

[whodwho]

i can trigger the fuel pump relay with my power probe, but the main (white relay keeps randomly clicking and no power to the ecu.

Can anyone tell me what the pins are supposed to be with the key on and off for the main relay?
unless I am missing it somewhere in the bentley, I can't seem to find it.

At the ECU

3 - ground to fuel pump
18 - steady power
19 - DME ground
27 - power from ignition switch
36 - ground to main relay from DME
37 - power in from main relay

[der affe]

In the stock configuration, the main relay is controlled by the DME. When the START signal from the ignition switch is present at the DME the main relay will be activated. I don't know if and MS works the same. Another possible problem would be a bad fusible link.

So I would be looking for + power at the "dme" (MSII) from the ignition switch to the main power at the dme, correct?

Where are/ is the fusable links in the car?

[der affe]

At the ECU

3 - ground to fuel pump
18 - steady power
19 - DME ground
27 - power from ignition switch
36 - ground to main relay from DME
37 - power in from main relay

This is with the key on or off? Just making sure.

[e30leigh]

could be a fusable link. i think they are in the Ebox? not sure though. i know on e34's they are located in the main power coming from the battery under the rear seat. obvious that this cant be the same in an e30.

[whodwho]

This is with the key on or off? Just making sure.

That would be with the key on but there would only be ground for the FP on prime and cranking/run

[der affe]

At the ECU

3 - ground to fuel pump
18 - steady power
19 - DME ground
27 - power from ignition switch
36 - ground to main relay from DME
37 - power in from main relay

everything checks out except for:
#3 turns on the ground light on the power probe, but does not make the buzzer work

#36 is showing (+) and it should neg. that should be my problem

#37 shows (-) with the light, but does not sound the buzzer


so it looks like #36 and #37 are where i am going to start hunting.

just to check, the power goes from the DME to the main relaythen back to the DME. if the ground is bad to the main relay from the DME #36, it should be an open circuit and read as positive. because #37 is and open circuit, the relay can not open causing it to stay neg. (bear with me, these last few surgeries have kind of fucked with my thinking processes)

any idea where the ground for the DME is located in the car?

[der affe]

Does anyone know where the dme gets it's ground from? I have checked all the factory groumds and each of them seem to be in order.

[deutschman]

Also check the wires at the c101 port. If there is a short in the green wire then you could be having these problems. That should be power to your ECU.

[der affe]

Ok at the main relay key off:
#86 pos.
#87 (outside) ground
#87 (inside) weak ground
#30 pos
#85 nothing

With the key on
#86 pos
#87 (outside) nothing
#87 (inside) weak ground
#30 pos
#85 neg