M20 nightmares! Updated!

[brennon]

Having a nightmare with the car!

M20 with monotronoic injection

Not getting fuel to start.

Turns over fine, getting spark.

Wasn't getting power to the fuel pump so put a live on it.

Getting fuel to the fuel rail but no further, plugs are dry.

How do I find the fault, clearly electrical as injectors are not opening but where should I check?

Possible causes are the oil pressure sensor is not connected and the ecu is not bolted to the car (should it earth through the housing?!)

Having a nightmare with it so any help is apriciated!!

[nas80]

Did the car run ok previous to fault? have you been doing stuff and now it wont work?

It looks like the ECU isn't happy, so that is why it is not turning the fuel pump on. Id guess that its the crank angle sensor or the ecu itself. Perhaps it could even be something silly like the engine loom ground isn't connected etc.

[drjim]

Are you just trying the motronic for first time?

Two pitfalls I discovered...

1 Crank sensor connector is interchangable with the TPS one, both on top of engine. BMW kindly used same connectors. Try swapping them.

2 Depending where you spliced into the loom, you may need an extra power feed to a pin on the ECU. The green wire in the E21 loom appears to just need to connect to the green on the engine loom, but there's a second small green that connects to it in the C101. Goes to pin 24 or something and turns the ECU on! Make sure you have a big and little green in the engine side connected to power.

Jim

[Jeroen]

Two more:

The early Motronic versions produced roughly 9/85 to 9/86 use separate speed and position sensors on the bell housing. If you swap connectors, don't fit them at all or if one is broken, the car won't have its fuel system operated. This is said to be a possible issue on the later type as well (combined speed and reference sensor fitted to the front of the engine) but I've never encountered this myself.

Another option is a broken Motronic ecu due to humidity or welding for example. It may not be switching several options anymore. Wiring ok? Sure you have the right ecu?

[brennon]

Are you just trying the motronic for first time?

Two pitfalls I discovered...

1 Crank sensor connector is interchangable with the TPS one, both on top of engine. BMW kindly used same connectors. Try swapping them.

2 Depending where you spliced into the loom, you may need an extra power feed to a pin on the ECU. The green wire in the E21 loom appears to just need to connect to the green on the engine loom, but there's a second small green that connects to it in the C101. Goes to pin 24 or something and turns the ECU on! Make sure you have a big and little green in the engine side connected to power.

Jim

Number 2, green live, although this isn't my exact loom it's close enough for reference



Is that the magical green wire?
Should it be constant live or ignition live?

[nas80]

ignition live

[brennon]

So that is definatly the power to the ecu?
If so I could well be on to a winner

[nas80]

whats that plug go into? the little green will be a terminate as a signal wire to one of your relays, just check before you stick +12 lol

[brennon]

Completely unsure, at the moment nothing.
I had to remove loom from the car and refit I can't remember it being plugged into anything so it is unconnected at the moment

[drjim]

My green wire was in the loom. On my car I cut the C101 plug off and wired the engine loom to the e21 fusebox plug. I looked at the cut off end and found there should have been another green wire within the engine loom connected to ignition live.

I don't recognise the plug in your picture, is it on the car side of the e30 loom?

[brennon]

Just underneath the plug I assume to be the c101 is the big ecu plug, not seen a white one before :S

[drjim]

Ah I see what it is now. The big white thing is the ecu plug. That extra thing goes to something in an e30 you do not need. Pretty sure I still have that connector attached/unused but not near car to check.

The wire I am talking about is in the other end of the loom where it plugs into the car at the fusebox end. C101 is the round plug. If you are sticking motronic in that is the end where you splice the wires. Our former colleague Murran had a thread on howto do a motronic conversion which I used as reference (plus he helped me do the work/did a lot of it!). Murrans thread had wire colours from the body side of c101, I was at the engine side where there are two wires.

[luke]

The White ECU connector is missing its black cover. Not sure whether this would affect its operation or not via any kind of electrical interference?

Another problem could be the crank angle sensor plug & the no. 1 spark sensor plug if you are using the late motronic - these also have identical black plugs on them & can't be reversed.

[brennon]

I've found the problem!

It's not motronic, it's l-jet. There is a relay in the loom, bridged the live out to the red/ white wire that powers everything. With that bridged it runs.
So either the relay is dead or the ignition feed to the relay is not working. I'm rubbish at wiring diagrams, can anyone tell me what colour the ignition love wire is so I can test if it's getting power?

[Jeroen]

Had to say without knowing what relay, but in most cases pins have the same numbers. Remove the relay and connect pins 30 and 87 with a decent piece of wire, then check again. Make sure not to mix up pin numbers top avoid short circuits. Pin numbers are marked both on the relay and on the socket.