engine and drivetrain M20 no start - electrical problem (no spark)

[Guest Anonymous]

Ok, so I've been stuck at this stage for about two years. I have a '76 02 with an M20 from a 1990 325i. The engine will not start - there is no spark. I have the first spark plug undone and grounded to the engine block. The starter cranks the engine just fine.

The connections I have made are listed below. I have made no other electrical connections. It is my policy to be fat dumb and happy, so it is entirely possible that I have forgotten something blindingly obvious. I've spent hours and hours on this, and I am truly stuck.

*Battery + is connected directly to the big center terminal on the starter via a jumper cable. Battery ground is connected to the block. I manually crank the starter motor by using an alligator clip between the lower starter terminal and the center starter terminal. This works great - the engine cranks.

*The ECU is plugged in to the harness, and the big 10-gauge green wire on the E30 harness is connected to Battery +.

*The green wire on the 2002's harness is connected to power. This makes relays click, and the interior lights work.

*The center coil terminal is connected to the distributor wire (can't mess that one up), the "1" terminal is going to pin 1 of the E30 diagnostic connector (which goes to pin 1 of the ECU), and the "15" terminal of the coil goes to Battery +.

*The fuel pump is connected directly to the battery, and I hear fuel whooshing around.

*I have the inductive pickup and the crankshaft position sensor plugged in to the E30 harness, and I have tried swapping them because I'm not sure which one goes where. No effect.

What is the next step? I suspect that all of these components are good and I am just missing a connection. I do have access to a running 1989 325is, so I can test components if they are bad. Should I test the crankshaft position sensor and ECU, or am I missing connections?

Thanks a whole lot! I am probably moving to Germany in May so I really need to get this working.

-Ben[/u]

[TJW]

Was trying to post a schematic of the wiring but it won't work, if the wiring is correct then you can go to fault finding.

I could email it

[Guest Anonymous]

My email is benmoss@gmail.com. Thanks man.

[canadamatt]

Have you swapped out the main relay? I'd try that, especially if you can just borrow it out of a buddies car for a bit... if it doesn't work, try posting on e30tech.com maybe.

Matt

[Guest Anonymous]

Matt, does it seem like I have all the right connections?

I'll give the relay & the other forum a shot.

[canadamatt]

Matt, does it seem like I have all the right connections?

I'll give the relay & the other forum a shot.

Seems like it. On the m20 engine harness, close to the firewall, about in the middle (or maybe a bit closer to the passenger side), coming OUT of the big 1inch diameter harness is a smaller wire, 12ga maybe, that has a little eyelet on it. Is that hooked up? It should be, or at least mine required it (engine from 1990). I used the e30 battery terminal block, and this is wired directly to it.

Matt

[Guest Anonymous]

Seems like it. On the m20 engine harness, close to the firewall, about in the middle (or maybe a bit closer to the passenger side), coming OUT of the big 1inch diameter harness is a smaller wire, 12ga maybe, that has a little eyelet on it. Is that hooked up? It should be, or at least mine required it (engine from 1990). I used the e30 battery terminal block, and this is wired directly to it.

I found the wire you are talking about. It is pretty thick though; much bigger than 12 gauge. It has black insulation on it, but it might be a different color underneath. It has an eyelet. Just for confirmation, I hook it to battery + ?

I can take a pic if that helps.

[canadamatt]

Yeah, thats the one. You're right, much thicker than 12ga, I don't know why I wrote that... Its thick, but not battery cable thick. 8ga maybe? 6ga?

But yes, mine is going to +battery.

[canadamatt]

Actually, let me clarify that. I am using the e30 battery cable and distribution block. Alongside the thick e30 cable is a thinner wire, maybe 8ga (the same size as the eyelet wire that I"m talking about).

The thinner wire actually runs from the battery in the back, to the distribution block in the engine bay, alongside, but *separately* from the main power, to a separate area on the distribution block. THAT is where the wire coming out of the engine harness goes to.

Whats my point? Well, the thinner wire also has a fusable link inline near the battery. So my point is that you may not want to permanantly hook this wire directly to the battery without a fuse of some type. I'm not sure what the rating of the fusable link is though..

Matt

[TJW]

Mail and schematic sent

[Guest Anonymous]

I pulled the ECU, main relays, coil, and reference sensor out of the 02 M20 and tested them all in a running 325i. They were all good.

When I plugged the ECU into the 325i, I noticed it made a slight buzzing sound. Also, the idle control valve on the 325i makes a buzzing sound. Neither of them make a buzzing sound on the 02 M20, so I suspect I have a bad/missing power connection.

Next step is to check the wiring really well. Thanks for the schematic Tom. I also have another schematic for the ECU that I will check carefully.

[canadamatt]

Yep, it should be buzzing away happily. maybe crossed up a switched vs direct power connection?

Matt