Only getting spark when i let off the ignition

[bmwracing_6]

first off i had the hardest time to get a spark and have checked the cas and ignition module, and it has a new ignition coil and new ecu and this is what happens... i will turn the key and i do not get a spark and when i let off the ignition it will throw a spark.. i am lost and so confused to why this would happen.... somebody please help me thanks!

 

[toybreaker]

Wow, that's a mess!

I think it's time to disconnect the battery, and use the ohmeter function of your multimeter to trace where the ends of those wires go. You cannot use an ohmeter on a live (connected to the battery) circuit.

Your multimeter may require you to rotate the selector dial and switch the test leads into a different set of holes on the multimeter face to check ohms (continuity). You know you've got it right when you touch the two leads together and it reads 0, (or .2ish)

I'll go get the factory service manual, and be back in a bit.

I'm going to strongly recommend that you go back through what your friend "repaired" and solder and heatshrink every connection. Twisted together/taped connections have a way of coming apart at the worst possible time, leaving you stranded, or even on fire.

By the time you're done with this, you're going to have learned a lot, that's for sure. I bought a basket case z-car waaaay back in the day, and after trying to just get it running, ( and burning up a few pieces, )... I broke down and traced every single wire to both ends, spliced in some new wire sections, and then soldered and heatshrinked every single one of them. It was a major undertaking, but it taught me much of what I know now.

I drove that car for five years, and never had another electrical issue related to the harness

 

[bmwracing_6]

yeah I know... it is a big mess but I think that it could be a wiring issue with 3 wires unconnected it seems to me this must have something to do with my problem. However what I have gone through everything I think that it might be an issue came out to be nothing.

 

[toybreaker]

It looks like green/yellow and black/green are used together at the ecu coolant temp sender.

Those colors are also used individually in a few other places in the engine compartment, so you're going to have to track them down and verify that you're connecting them correctly.

Disconnect the vehicles battery.

Set your meter up to check resistance. (ohms)

Stick one end of the green/yellow wire into one of the alligator clips on the test lead of your meter. Pull the ecu temp sender connector off at the t-stat housing. It's the two prong plug. Place the tip of the other test lead into the connector and check the meter for a reading. Continuity (low resistance) means you've got the right wire.

Now, to check the other end. Find the other green/yellow wire end, the one that heads towards the firewall. It should be in the vicinity somewhere's. That end will go to the ecu at terminal #20.

Do the same with the green/black wire. One end goes to the ect, and the other end will go to the ecu at terminal #24.

If you don't get a reading on the meter, you've got the wrong wire.

And, so it begins. Wire by wire, you'll have to track these orphans down.

 

[bmwracing_6]

what about the black wire? This one is the main one I was looking at because I hear a click from the MFI relay when I tested it

 

[toybreaker]

I do have a few questions.

How did the harness get cut up?

That looks like a jdm (vr4 ?) motor. Are you using the harness or pieces of the harness that came with it?

Does your motor have the cyclone manifold, with the two stage plenum? There may be some extra wires related to that system, and I have no idea what color they would be.

Thanks,

John

 

[bmwracing_6]

well the engine does not have the cyclone minifold... the engine harness that came with the car was cut and the same with the engine. I dont have extra wire coming from the engine but there are more coming from the car.

 

[toybreaker]

what about the black wire? This one is the main one I was looking at because I hear a click from the MFI relay when I tested it

Was the key on?

According to my diagram, the mfi relay gets it's ground at grounding point 7, which is located inside the car, on the dash brace. (where my meter was grounded in my picture.)

 

[bmwracing_6]

yes the key was on

also my friend just match color to color on each wire but for some wire there was more than one of the same color would this make a electrical short? or would it not have any affect?

 

[toybreaker]

yes the key was on

also my friend just match color to color on each wire but for some wire there was more than one of the same color would this make a electrical short? or would it not have any affect?

OH, SNAP

It's quite likely that what's happened is one of the wires has been wired onto another wire of the same color that was not the right one.

If that's the case, the possibilities are endless. You could have a five volt circuit wired into a 12 volt circuit.

The best way to fix this is going to be matching the beginning and end of each wire one at at a time.

Just reference the wiring diagram for the wire colors, and then go to the ecu terminals, and then the components and ohm the wires out to figure out what goes where.

The good news is that it'll give you a chance to make a nice, secure, soldered connection that won't give you problems further down the road.

Good luck, and please feel free to pm me with any questions you might have.

 

[steve]

The best way to fix this is going to be matching the beginning and end of each wire one at at a time.

Just reference the wiring diagram for the wire colors, and then go to the ecu terminals, and then the components and ohm the wires out to figure out what goes where.

The good news is that it'll give you a chance to make a nice, secure, soldered connection that won't give you problems further down the road.

I agree with John. Now it's clear why your frying ECU's.

You will have to pull all this apart and identify where each wire comes from / goes to.
By the time your done you will be an expert on debugging electrical wiring.

The wire colors are a hint as to what the wires are for but the colors do get reused from time to time.

Steve

 

[bmwracing_6]

Well it looks like i have the work cut out for me. It will probably take me all day to do this however like you guys said it will help me learn the wiring of these cars. Anyway thanks for the help and Steve I blew one ECU man.

I'll be back for an update!

 

[freshlane]

If it's ## relay hit me up and i'll send you one for $2 (shipping) ... wire tracing time. good luck

 

[bmwracing_6]

I am having trouble with the pin numbers and letters. For example pin 109 A... What does "A" mean also there is a B, C and D. Now I counted all the pins and there are not even 109 pins. So my question is how do I located the each pin?

 

[steve]

So how do I locate each pin?

http://www.vfaq.com/mods/ecu-harness-1G.html
http://www.dsmtuners.com/forums/showthread.php?t=246467

Steve

 

[bmwracing_6]

I wired everything up however I still have extra wires (3) coming from the car. A green with black stripe wire and 2 yellow with green stirpe. Also one coming from the thermostat which is a green with red stripe. I looked at the wiring diagram and a dont see these extra wire and also tried to trace then to the ecu and I did not get a reading with the ohm meter from them. This just can not be right and something must have happened either my friend butchered the harness or they go the a nonconnected plug.

 

[toybreaker]

You checked and verified all the wires already? You must really want to drive this thing.

Are all the wires on the motor accounted for except the green/red at the t-stat.?

And the yellow/greens are from the car side of the harness?

The yellow/greens from the car have several choices.

The coolant temp sensor for the gauge, (the single wire connector on the t-stat)

The brake fluid level sensor.

The coil/transistor/engine speed connector aduster circuit. My money is on this as one of the yellow/green floaters. Just check it back at the coil/transistor. This wire never gets back to the ecu, it just kind of hangs out over on the firewall. tease: patiently waiting for some one to set their idle the correct way )

I'll see if I can get a better diagram, and look it over some more for you.

Could you be a little more specific about the location, and lengths of what you working with. It would be very helpfull to know exactly where these orphan wires are cut, and where they originated. (pics?)

Glad to see you making progress!

 

[bmwracing_6]

Its alive!!! Thanks for all the help guys.

First I want to thank toybreaker for the help for checking the mfi relay and how to check and trace the wires, Steve for the help with my ecu questions and for the help with the ecu pin diagrams, defiant for not locking down my forum during my bump-a-thon, and wret for sending me warning for my spelling grammer and punctuation.... I appreciate all of your help to get this car running. However, I have got it running I am sure I will be back when I break it! But now that I got it running I will be modding it up!!! Thanks to all and to all a good night!!! HAPPY NEW YEAR!!!

(I guess this will be my last bump)