Should both wires be hot at injector plug?

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Nova Shark
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Joined: Wed Mar 17, 2021 1:53 pm
Location: FL

Should both wires be hot at injector plug?

Post by Nova Shark »

I am still having issues with no spark to the sparkplugs and fuel injector's. Both main relay & fuel pump relay's work, ing. switch works, idle control valve powers up, both reference & speed sensors have power. I have two ECU. I have power to coil. It ran a couple weeks ago for a couple of minutes when I first got it going. I only had my headers bolted on and it was very loud as I wanted to hear the engine. So I shut it down until I got my Billy Boat exhaust system installed. Brought it back from the exhaust shop and now I don't have spark to the plugs or fuel injector's ( I have a noid light) I have reread the no spark procedure from this forum many times and as far as I know everything checks out but no spark now but I did have it 2 weeks ago????
My question is this: Does anyone know if I should have 12v of power to both wires of the fuel injector's? (rd/wht) & (brn/yel) I Have power from both sensors on flywheel. I do not have a resistor on the coolant temp sensor. I Have power to coil but spark plugs and injector's will not fire.
I am Stumped ???? Could someone verify that I should have power to both wires. I have a feeling that it is something really, really small but I cannot find it. Any Suggestions would be very much appreciated.
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hornhospital
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Re: Should both wires be hot at injector plug?

Post by hornhospital »

One wire should have continuous 12v with the key on, but not both. The injectors are fired by grounding through the DME (BMWese for ECU). If you have 12v on both, you have a shorted/failed DME.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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RossDinan6
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Location: SW FL, USA

Re: Should both wires be hot at injector plug?

Post by RossDinan6 »

I have to disagree Ken. 12 volts comes to the injectors and is obviously present on the RD/WT wires. It is on the BR/WT and BR/YL wires because the meter measures through the injector coil when referencing ground with the meter. There will be a very slight voltage drop on the ECU side, likely not measurable.

I'm curious if one of the known good components isn't.
Ross
'84 633 Dinan turbo
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