Im getting fuel but no spark

[JRH]

Have voltage but no spark help!

I have a bmw e30 325i 1987

I have been having this no spark problem for a while I have tested voltage to the coil and I get 12 volts on the positive and negative side I don’t know if that’s what im supposed to get. We have tested the spark with a test light directly from the coil through the coil wire and not through the distributor(we are getting a light when cranking) we also connected a spark plug and grounded it to the valve cover and noticed that we get a discharge spark every time we turn the key off we also get a single spark 1 out of 10 times of cranking the car and I’m stumped

We have replaced the coil, wires, rotor, distributor, cps, and spark plugs on the car

We have tested all of the relevant pins on the dme and they all check out, I have checked ohms on the cps all checks out I can also confirm the fuel pump works as we smell fuel but we haven’t confirmed that the injectors work but I don’t think it’s relevant if we don’t get a spark in the first place I also have not checked a ground wire I don’t know if that could be a problem or not

When testing the coil with the test light we do get a light but though I think it’s outputting a enough voltage to trigger the light it’s not enough to trigger a spark plug, other than when it is discharging when turning the the key in the off position. I’m completely lost and near hitting the end of options and potential solutions

Please help

[82eye]

Have voltage but no spark help!

I have a bmw e30 325i 1987

I have been having this no spark problem for a while I have tested voltage to the coil and I get 12 volts on the positive and negative side I don’t know if that’s what im supposed to get. We have tested the spark with a test light directly from the coil through the coil wire and not through the distributor(we are getting a light when cranking) we also connected a spark plug and grounded it to the valve cover and noticed that we get a discharge spark every time we turn the key off we also get a single spark 1 out of 10 times of cranking the car and I’m stumped

We have replaced the coil, wires, rotor, distributor, cps, and spark plugs on the car

We have tested all of the relevant pins on the dme and they all check out, I have checked ohms on the cps all checks out I can also confirm the fuel pump works as we smell fuel but we haven’t confirmed that the injectors work but I don’t think it’s relevant if we don’t get a spark in the first place I also have not checked a ground wire I don’t know if that could be a problem or not

When testing the coil with the test light we do get a light but though I think it’s outputting a enough voltage to trigger the light it’s not enough to trigger a spark plug, other than when it is discharging when turning the the key in the off position. I’m completely lost and near hitting the end of options and potential solutions

Please help

first i'd check to see if you are getting injector pulse. if you are missing both pulse and spark it would point to a bad cps.

what's the production date ? there were changes in 9/87.
the ecu gets the start signal either off the ignition switch pre 9/87, or through the c101 post 9/87. it's not common but there could be a break in the wiring or a bad connector somewhere. there is also an obc relay box the start signal travels through that could be suspect.

other possibilities would include a bad fusible link on the battery, poor ground on the ecu, or even a cooked ecu. to check ecu i think pin 27 on the ecu is power, it should get voltage in the start and run key positions at the ignition.

hopefully someone with more experience sees this and adds some insight.

edit : if you don't have it pull a copy of the bmw etm for your car from here : http://wedophones.com/Manuals/BMW/
you can use it to trace the start and fuel system electrical to troubleshoot. make sure to save a copy as the resource could disappear.

[JRH]

Hey thanks for the response so my car is a 1/87

And for the Ecu we get good voltage and continuity on both 36 and 37 of the dme but to get voltage on pin 37 we had to jump main relay pin 87 87a and 30

we have also bypassed the obc by splicing the wires together because we were afraid it could have been the theft system

We also looked at the engine ground and there’s little nicks in it but I didn’t think it would be enough to cause a no spark/weak spark

we checked pin 27 at dme and it checks out

i haven’t check the pulsing at the injectors but when we attach a test light to then end of the coil it pulses

we also manually grounded the dme via main relay pin 85
finally when we did ground the dme, when cranking only one time we got a good spark blue and consistent but after that we couldn’t get it to do that again


Hope this gives a little more insight on my situation thanks in advance

[82eye]

is the fuel pump priming at first key position ? you should be able to hear it.

[JRH]

No it was to my understanding that the fuel pump doesn’t prime but instead only sends fuel when there is a start signal that being said I did pull a fuel like and can confirms that is happening

I can also hear it when I jump the pump relay

[82eye]

it's kinda getting down to the fusible link, main relay, and ecu.

[JRH]

Yea that’s the point I’m at right now i don’t know how to test the fusible link or the dme

i have checked the main relay it seems pretty good I have also replaced it with the high beams relay (another 5 pin) and nothing happened

do you know how to test the other 2 though or have a forum to refer me to

[82eye]

Yea that’s the point I’m at right now i don’t know how to test the fusible link or the dme

i have checked the main relay it seems pretty good I have also replaced it with the high beams relay (another 5 pin) and nothing happened

do you know how to test the other 2 though or have a forum to refer me to

i don't think the main relay has an equivalent swap but you can jump it. the other tests are in the diagnostic link on the other forum.

[JRH]

Yea I did jump it 87 87a and 30 main relay and you should get power to dme pin 37 which did but still didn’t get spark

i also cleaned up the main engine ground that also didn’t do much

[JRH]

So I actually noticed when my dme is unplugged I get battery voltage to the coil but with it plugged in I do not anyone know the problem here

[82eye]

might be an idea to try a known good dme. i have a good spare from an ix i keep around for testing use just in case.

[JRH]

Will do thanks