Help No Power Going To Coil

[DaveSmed]

For Dave: Main is SPST, but 2 N.O. contacts.

Look at 1362-2 on the ETM. That is the ETA spec, but all are the same.

Ah, just a normal boring double 87. Checking for power at the injectors will tell you a fair bit then.

On the topic of the jumper... Does the main relay use the same cracked out pin arrangement the stuff in the fuse box uses, with (IIRC) 86 and 30 swapped?

[StereoInstaller1]

No, it does not. Normal Bosch spec... and the 20 year old relays have been dropping like flies! I could source a bunch and sell them, I mean my cost has to be under $2, I could sell them for $10 and be half the price of the dealer...but I just don't fucking care.

Funny thing is the coil still works on most of these...and typical retard shadetree dude says "whelp, it clicks, so it has to be good" when in fact the contacts are fried....

Good to see you back around these parts my man!

[DaveSmed]

Ah ok, thats good then. Any decent automotive electronics place will have the right stuff, or go buy the second cheapest blue fog light kit at Walmart for the china version of your main relay.

It's interesting, looking at the diagram, the main relay is the first to break in a normal non-stall engine shutdown, meaning it gets the brunt of the arcing, pitting, and metal transfer. At least they made it the cheap relay even if somewhat uncommon.


*Note* If you are reading this and need a main relay, look where I said somewhat uncommon. You need a "double 87" Bosch style relay, not the standard Bosch style with an 87 and an 87A terminal. If you use the wrong one, your car will NOT start.


And yea, good to be back. I finally drug my turd over to my new house, so the guilt of walking around it every day is making me want to fix it. I have an absolutely awesome E30, its just in lots of little boxes. :???:

[StereoInstaller1]

Dave, if it makes you feel any better, my M20 is 320,000 miles, 15,000 past due on the timing belt. I have all the parts sitting in my garage to do a timing belt...but I just scored an S50, so that is sitting in my garage too.

I feel your joy, man!

[DaveSmed]

320k! Nice! My friend's eta managed to just break 300k before he accidentally fed it a screw.

What kind of S50 didja get?

Oh yea, OP, sorry for the threadjack, post up your findings and we'll shut up.

[bimmer206]

No problem guys, power is going to the coil. I listened for the injectors clicking and there was no clicking sound. I tried to test for voltage with my multimeter but i didn't want to strip the wire and couldnt find my voltage gauge that punctures the wire so i just stuck the probe into the conector on the side of the red/white wire and got 12.5 volts when key was on the run position and when cranking it dropped to 8.3 so I'm assuming i did that wrong. I'm going to find my voltage tester that punctures the wire and try again but there was no clicking at the injectors.

If anyone who goes to the holman road dicks meet every Wednesday wants to come buy and look at my car ill buy you as many burgers, fries, and shakes as you can eat.

[DaveSmed]

No problem guys, power is going to the coil. I listened for the injectors clicking and there was no clicking sound. I tried to test for voltage with my multimeter but i didn't want to strip the wire and couldnt find my voltage gauge that punctures the wire so i just stuck the probe into the conector on the side of the red/white wire and got 12.5 volts when key was on the run position and when cranking it dropped to 8.3 so I'm assuming i did that wrong. I'm going to find my voltage tester that punctures the wire and try again but there was no clicking at the injectors.

If anyone who goes to the holman road dicks meet every Wednesday wants to come buy and look at my car ill buy you as many burgers, fries, and shakes as you can eat.

Don't look for that insulation piercer too hard, how you checked it is exactly how I would have checked that particular circuit. Those things cause bad things to happen down the road in stuff exposed to the environment.

Anyway... 8.3v kind of sucks. Make the jumper Luke described and check again with that in place of the main relay.

[bimmer206]

Here is how to bypass the main relay: make a 3 pronged jumper using 3) 1/4" male spade lugs and a couple of feet of wire. Jumper the 3 big red wires on the main relay: that is the one at the front of the 3 relays on your left front fender.

Also, make sure that pin 30 has power going to it.

IF you do this really simple test and your car runs, it is likely the main relay. Your car will not shut off with that jumper in place BTW, you must pull it before you shut it down.

Luke could you show me a picture if you have one.

I don't know what spade lugs are. Radioshack?

[bimmer206]

So i'm connecting the three red wires or am i giving all three power?

[DaveSmed]

So i'm connecting the three red wires or am i giving all three power?

Connect the three center wires together, should correspond to terminals 30 and 87 (x2) on the relay.

These are what Luke was referring to http://www.maplin.co.uk/Module.aspx?...T=41513_495297

They work well in the relay socket.

[Adrian_Visser]

If you are in fact getting 12v at the positive side of the injector connector then the main relay is functioning properly. Just to be absolutely sure check for pulsating ground on the other injector connector pin when cranking.

A lack of a pulsating ground points directly a problem with the reference and/or rpm sender or the flywheel pin.

Just like for the ignition coil the DME switches the ground to the injectors to make them fire.

[bimmer206]

Connect the three center wires together, should correspond to terminals 30 and 87 (x2) on the relay.

These are what Luke was referring to http://www.maplin.co.uk/Module.aspx?...T=41513_495297

They work well in the relay socket.

Okay this makes sense.

If you are in fact getting 12v at the positive side of the injector connector then the main relay is functioning properly. Just to be absolutely sure check for pulsating ground on the other injector connector pin when cranking.

A lack of a pulsating ground points directly a problem with the reference and/or rpm sender or the flywheel pin.

Just like for the ignition coil the DME switches the ground to the injectors to make them fire.

What is the proper resistance for the flywheel reference senders?
I know it's page 34 of the ETM but I don't know how to correctly read the wiring diagram. I searched and got 1.004

So your saying the DME is not getting the data and is therefore not squirting or sparking. Should I still test the relay?

[Adrian_Visser]

If you are in fact getting 12v at the positive side of the injector connector then the main relay is functioning properly

Self quoting ftw.

[DaveSmed]

12.5 volts when key was on the run position and when cranking it dropped to 8.3

8.3v is at/below the threshold that Motronic needs to function. He has 12v with the fuel pump off. Definitely easy enough to eliminate the main relay for just about free.

It may be fine, but i'd rule it out just the same. (and start carrying a spare main relay)

[bimmer206]

Thanks again everyone for your help, turned out the timing pin on the flywheel was ground off so the computer was getting no timing information.