Car cranking, but not starting(Now with spark!)

[ST1G]

Hmm.

Unplugged the ABS control under the dash, Here are results.

With abs unplugged.
37 12v


With ABS unplugged and 36 grounded

37 0V

Edit: realized I undid c131 not c101. I will see about undoing socket 20 at c101.

[spdracrm3]

ok without reading thru the last ten pages it seems to me you swapped in a main relay at some point ,just to check things pull the relay and look at the numbers on the bottom are there terminals labeled 87 and 87a ? also are there corresponding wires in each female portion of the relay socket? if yes ohm test between 87a and 87 it should be open if its a standard 5 pin relay .

find your original main relay and compare the pin numbers and orientation compared to the one you installed to see if there is a difference . looking at the diagram there are two pin 87's which if they are not wire into the same socket means the relay that needs to be used for the main is not a standard 5 pin and should have two pin 87 (no pin 87a) and that they are both powered when relay is engaged ,if you have the wrong relay in there it could be causing the readings your getting on pin 37...

[ST1G]

ok without reading thru the last ten pages it seems to me you swapped in a main relay at some point ,just to check things pull the relay and look at the numbers on the bottom are there terminals labeled 87 and 87a ? also are there corresponding wires in each female portion of the relay socket? if yes ohm test between 87a and 87 it should be open if its a standard 5 pin relay .

find your original main relay and compare the pin numbers and orientation compared to the one you installed to see if there is a difference . looking at the diagram there are two pin 87's which if they are not wire into the same socket means the relay that needs to be used for the main is not a standard 5 pin and should have two pin 87 (no pin 87a) and that they are both powered when relay is engaged ,if you have the wrong relay in there it could be causing the readings your getting on pin 37...

I swapped the relay out to test it, but after a different working relay didn't work I swapped the original relay back in. It is a 5 pin relay. Relays can only be put in one directional, and are standardized. Keep in mind I jumped pin 87 and 30 on the socket. Yesterday I pulled the socket off the clip and the Red/Yellow and Red/blue both come from the same socket on the relay, meaning that pin 87 is supplying both. When I jumped the relay I verified that I was getting 12v from pin 30, to 87.

[ST1G]

Spoke to the old man and went through wire diagrams. He gave me a few ideas. There is a current drop when 36 is grounded. So he suggested checking 1.) The resistance of the wire at the socket for the relay, and the pin on the harness. 2.) The power at the socket/wire when 36 is grounded. This should help us discover the current draw, or extra resistance.

[ST1G]

I HAVE SPARK!!!!!!!!!!!





Resistance was good through the red/yellow and blue/red wires that go to the ECU and to the ABS.

So, I was kinda stumped. I then remembered that power to the ABS goes through C101. So I popped C101 off and measured at pin 20. I was only getting 10.6v. I double checked it was the correct pin and that pin 36 on the harness was grounded. It was. I then remeasured pin 20 on c101 and got.... 12v.

I then measured pin 37. I was getting 12v, with 36 grounded! I was jazzed. I reconnected c101, expecting that I would lose the 12v from pin 37. I didn't....

I reconnected the ECU and tested for spark.

I got it. Beautiful blue spark.


So, I get spark with ECU in, relays in, C101 connected, and ABS unit Disconnected. I'm not sure if reconnecting the unit will make me lose spark or not. I'm going to test that. But it appears as though the c101 was shorted and pulling current flow.

[itskingsteelo]

so is it running now??
im having the same problem, car wont fuckin start and i feel like setting it on fire

[ST1G]

so is it running now??
im having the same problem, car wont fuckin start and i feel like setting it on fire

Yep. Drove it tonight.


Well, start a thread and I can help you out. I did a lot of troubleshooting on this and understand it a lot better now.

[ThatOneEuroE30]

Great to hear you got it started.

[2002jm]

good work

Glad to hear it is running again!!
nice work,
jm

[spdracrm3]

congrats on getting it started ,have you looked closely at the pin in the C101 for any issues ? have you connected the ABS yet? youve found where the problem was just not what it was ,be nice to be very sure what the issue is before it randomly raises it ugly head again!

I HAVE SPARK!!!!!!!!!!!





Resistance was good through the red/yellow and blue/red wires that go to the ECU and to the ABS. resistance tests on circuits can be so misleading as the smallest amount of current is used in an ohm test and so a wire can be attached by one strand and still test good(this is why voltage drop testing on a loaded circuit is the only reliable test)

So, I was kinda stumped. I then remembered that power to the ABS goes through C101. So I popped C101 off and measured at pin 20. I was only getting 10.6v. I double checked it was the correct pin and that pin 36 on the harness was grounded. It was. I then remeasured pin 20 on c101 and got.... 12v. interesting ,which side of the connector 101 were you checking?(ABS pump side or the main relay side?) the 10.6 v combined with 12v (an approx 1v voltage drop)out of the main relay would give the 1v you were seeing at the 37 pin .

I then measured pin 37. I was getting 12v, with 36 grounded! I was jazzed. I reconnected c101, expecting that I would lose the 12v from pin 37. I didn't....

I reconnected the ECU and tested for spark.

I got it. Beautiful blue spark.


So, I get spark with ECU in, relays in, C101 connected, and ABS unit Disconnected. I'm not sure if reconnecting the unit will make me lose spark or not.did you do this yet ,i still suspect an issue with the ABS unit or wiring I'm going to test that. But it appears as though the c101 was shorted and pulling current flow.

[ST1G]

congrats on getting it started ,have you looked closely at the pin in the C101 for any issues ? have you connected the ABS yet? youve found where the problem was just not what it was ,be nice to be very sure what the issue is before it randomly raises it ugly head again!

I've reconnected it all back up and it's worked great all night. I've started and stopped it about 10 times with no issues. I think that the pin was shorted and pulling current. I was testing the engine bay pin on c101 (female end)

Abs is back in with no problems.

I really appreciate all your help. You were pivotal to figuring it out.

[HennaE30]

Car cranking, but not starting(Now with spark!)

Congrats on getting her back running.. Now you can play with some more wiring and swap 24v ;)

Edit: lol 23v.. That's when you drop an exhaust valve into cylinder 6.

[itskingsteelo]

i have spark!!
Turns out it was my fuel pump, i sent some videos to a few buddies on here and they were able to help me with the solution. S/O to Iron-E and Terry!!

[ST1G]

i have spark!!
Turns out it was my fuel pump, i sent some videos to a few buddies on here and they were able to help me with the solution. S/O to Iron-E and Terry!!

Yeah, this test would have giving you that answer fairly quickly.

[HennaE30]

It seems like everyone with an M20 E30 has this battle atleast once lol