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Guest Anonymous

M20 no start - am I missing something?

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Guest Anonymous

Working on 02/m20 swap....

The M20 will not start. It has fuel, starter works, but no spark.

I was missing the main relay & fuel pump relay. I don't need the fuel pump relay at this point because I am turning it on manually (I have a battery in the trunk). I got a vanilla automotive relay from Autozone and it fits in the socket, and the pins on the relay line up with the pins that are used in the socket. Is the BMW orange relay a super special part? Or is cheapo relay ok?

I have power to the green wire of the ECU, I have power to the coil, the hall effect sensor (crank pos sensor) is hooked up as is the inductive pickup from one of the spark wires. I am cranking the engine by manually connecting the lower terminal of the starter motor to +12v. The fuel injectors are plugged in and all that. What could I be missing? I know the ECU could be bad but I have no easy way to test that so I want to eliminate all of the other possibilities first.

The 1st spark plug is not screwed into the block and I am watching it. I smell no gas so the injectors don't seem to be going off either.

Thanks a bunch. -Ben

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Guest Anonymous

Check for battery voltage at fuel injector connectors and at terminal 15 of ign. coil while everything is powered up or while cranking. These items are normally hot in the "run" position. If you have voltage at these items there's a good chance the DME is asleep. This test should at leat help you isolate your problem somewhat. Post results for more detailed assistance.

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Guest Anonymous

My coil gets very hot. Maybe I have it hooked up wrong.

It's a bosch blue coil, it has two outside terminals and the big center plug. One outside terminal is labeled 1 and one labeled 15... I connected "1" to ground and 15 to +12, but I am thinking that was maybe wrong... I obvioulsy had the center connected to the wire from the dist. cap.

The coil gets very very hot. does that mean it's shot, or did I connect it up wrong?

Thanks again.

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Guest Anonymous

if you've got the coil neg. hard wired to ground that would explain why it's getting hot.

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Guest Anonymous

I checked one of the fuel injectors... it has +10.7 volts on on both wires (with respect to ground). So the voltage across the two fuel injector wires is 0. (Battery voltage is a little low, about 11.7, but it is enough for the starter to work).

I manually connected +12 to the 15 pin of the coil, so I know it has power... or is it supposed to be pulsed by the ECU or something? I don't really understand what the coil is doing, is it a transformer that creates a high voltage when there is a voltage spike (this explains the three terminals) or is it just an inductor that works with a capacitor somewhere? In that case, what's the third terminal for?

Thanks skip, appreciate the help.

-Ben

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Guest Anonymous

I don't have a diagram here so I'm not sure of the pin number or wire color but the wire shouldn't change colors from the coil to the computer as I recall.

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Guest Anonymous

connectors. The ground is provided by the DME. DISCLAIMER: As a general rule never get near the circuitry of a modern vehicle with an old school test light as you can easily induce current to fry transistorized components! BUT: if you have one handy you can connect the clip end of the test light to terminal 15 of the coil and probe terminal 1 while an assistant operates the starter. If the test light flashes that indicates that the problem is in the ignition secondary circuit, i.e. coil, coil wire, cap / rotor. If the light doesn't flash it indicates that the DME isn't functioning for one reason or another.

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Guest Anonymous

I'll figure out which wire goes to the '1', if that doesn't fix it then I'll start looking at the injectors. I have access to an oscilloscope so I'll look to see if it is pulsing the injectors low.

Thanks for the help!

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