Eta-to-M50: Build thread

[dager325]

Wild guess, fuseable link off the power from battery?

[shiboujin]

I'm too lazy to actually look at the wiring diagrams. The ECU prooobably isn't fried. I'm figuring something isn't tripping the ECU to give power to the relays. It's probably just something switched or something not hooked up. I await more info so we can figure ish out.

[Farbin Kaiber]

Also, a noid light, or just a test light will let you know if the injectors are getting signal. I'm thinking this is more of a signal to DME instead of power or ground to/from DME issue.

[cramer]

If the FP relay isn't getting power its either in the wiring or the DME isn't sending a signal to the relay. If you aren't getting spark either, I'd suspect the DME. Now it's down to tracing out which sensor isn't working right to tell the DME the engine is trying to start.

If you are unsure of how you tested the spark, you can leave the jumper for the FP relay on so the FP is pressurized, and see if it'll start.

Good luck!

[Jand3rson]

Honestly, I wouldn't be surprised if your harness is scabbed from another car.

Sigh... as much as I'm sure you'd like that to be true, I doubt it. The harness was in good shape, still attached to the engine, injector wiring and fuel rail in the stock fashion, the plastic cover on the injector wiring rail didn't even look like it had ever been removed.

The harness is hard-wired in, no adapter. Andrew wired my car's harness directly into the X20 connector. Pinouts for an '86 325es and the E34 525i were used.

It sounds to me like what Wh33lhop and Yoshi are saying, that the ECU isn't getting power and trying to start the car. If the fuel pump replay works when I jump it, but not with 2 other known good relays in place, the relay is not getting a signal from the ECU to fire the injectors and start the car.

Andrew is on his way over right now, and we are going to get to the bottom of this.

[ck_taft325is]

Honestly, I wouldn't be surprised if your harness is scabbed from another car.

[ShowStopper]

Sounds like what happened to me josh.. i had all the same symptoms. ended up being a bad harness.

U have a adapter for ur harness or it built into the e36 harness??

[Jand3rson]

Redhoodridah ok'd me and said that he was having the same issue, and his ECU wasn't getting any power. At this point, that seems like the most likely culprit.

[Wh33lhop]

look at them sometime - there are a few different relays that are triggered differently and that react differently. Some are normally closed and open when tripped, others are opposite. There are of course a lot of generic Bosch style relays but they are most definitely not all the same. They can even differ slightly between generations of BMW.

Basic relays like the FP, fan and headlights are typically normally open. Unless there is wildly different current handling (fan/lights/FP are all on the same order of magnitude), triggering voltage (no) or pin configuration there is not a whole lot left to differ, functionally at least.

[Van Westervelt]

Did you jump the FP at the tank or in the fusebox? If you only jumped it at the fuse box using its own signal, then its a bad relay.

[Farbin Kaiber]

As long as the unloader circuit is not suspect, I'm going to assume an issue in/at either harness ore the DME itself. More likely the former than the later, but it could be.

[nando]

I don't see how the FP relay would differ from the other simple normally-on relays.

look at them sometime - there are a few different relays that are triggered differently and that react differently. Some are normally closed and open when tripped, others are opposite. There are of course a lot of generic Bosch style relays but they are most definitely not all the same. They can even differ slightly between generations of BMW.

[Wh33lhop]

AFAIK the FP and O2 relays are different from say, a foglight relay. It's been a while since I looked at them closely.

I don't see how the FP relay would differ from the other simple normally-on relays.

Normally the FP turns on when the ECU sees an RPM signal from the crank sensor. If you hear the FP when you've jumped it, it means that the FP is working and there is power. It doesn't tell you if the ECU is seeing timing signal, but it could mean the relay is bad. What you could do next is check for spark. It can be a little difficult to hear the FP turning on while you're cranking it - but if there is spark, the ECU is definitely getting an RPM signal.

Since you can't just put a timing light on the spark plug wires, what I normally do is carefully ground a spark plug on the block somewhere and watch for it to fire. just make sure your heart isn't part of the circuit..

He is not getting spark dude, catch up! :p

But I think Yoshi is right, it does not seem like the DME is actually trying to start the car.

[shiboujin]

immpossible to have the crank and cam swithced. One is male and the other is female. You could have them plugged into one another but not wrong on the harness side.

good luck man...This is the frustrating part but also very rewarding when you figure it out. BTW did you use new sensors?

I'm pretty sure on a non vanos they are the same. I'm trying to find evidence but I'm actually busy today.

AFAIK the FP and O2 relays are different from say, a foglight relay. It's been a while since I looked at them closely.

Normally the FP turns on when the ECU sees an RPM signal from the crank sensor. If you hear the FP when you've jumped it, it means that the FP is working and there is power. It doesn't tell you if the ECU is seeing timing signal, but it could mean the relay is bad. What you could do next is check for spark. It can be a little difficult to hear the FP turning on while you're cranking it - but if there is spark, the ECU is definitely getting an RPM signal.

Since you can't just put a timing light on the spark plug wires, what I normally do is carefully ground a spark plug on the block somewhere and watch for it to fire. just make sure your heart isn't part of the circuit..

They do make magnetic pickups for spark. But they do make testers and such anyway. I think at this point it's safe to say that the ecu isn't sending out signals for anything. Meaning the problem is ECU or prior on the electrical food chain.

[nando]

AFAIK the FP and O2 relays are different from say, a foglight relay. It's been a while since I looked at them closely.

Normally the FP turns on when the ECU sees an RPM signal from the crank sensor. If you hear the FP when you've jumped it, it means that the FP is working and there is power. It doesn't tell you if the ECU is seeing timing signal, but it could mean the relay is bad. What you could do next is check for spark. It can be a little difficult to hear the FP turning on while you're cranking it - but if there is spark, the ECU is definitely getting an RPM signal.

Since you can't just put a timing light on the spark plug wires, what I normally do is carefully ground a spark plug on the block somewhere and watch for it to fire. just make sure your heart isn't part of the circuit..