No Spark

[mysocal911]

Originally Posted by ant7

Hi All,
Well, took out the ECU again Yesterday, looked at the main solder joints that I know from what a few of you have stated are the first port of call, when you get the no spark issue.
Although they looked to be fine, I decided to re-do many of the joints, including the large transistor, and what I deem as its drivers too, I removed the old solder first, and re-soldered using original lead and tin solder I use for repairs and re-work on older Audio Equipment, as it is much more forgiving as far as flex and vibration than modern Non-leaded etc.
Anyway after completing the task, I decided to leave all the covers off [just encase] and plug the unit back in the car naked, and see if it would now start, sure enough, it started right up, and ran fine as it always has, so let it run for a while, switched off, re-started it a few times, no issues. I then removed the ECU and re-fitted all the case work, and tried it again, sure enough it started fine again.
I am going to wait until tomorrow now and see if it will start from cold before I re-fit it permanently to the floor, but for now I am quietly confident, lets see, I will update you all soon.
Thanks to everyone who contributed so far.
Ant.

Good progress! Before installing it, use your hand and tap the bottom of the ECM a few times, and wiggle the connector.

[ant7]

Cheers, yes, I did that, and wiggled as much as I could while the covers were off, and car running, fingers crossed!
I would post some picks, but can't remember how to upload picks directly from my computer to the site

Originally Posted by mysocal911

Good progress! Before installing it, use your hand and tap the bottom of the ECM a few times, and wiggle the connector.

[wazzz]

While posting, click "Go Advanced" and then you can browse to your pics on computer and upload. Code will be inserted in your post.

[ant7]

Cheers Wazzz.

Originally Posted by wazzz

While posting, click "Go Advanced" and then you can browse to your pics on computer and upload. Code will be inserted in your post.

[ant7]

Well, tried the car today after being left over night and...............................................
No start, again!

The check list I have completed so far;

Checked resistance on both reference sender and speed sender, all good new parts.
Checked wiring continuity back to reference sender from ECU multi-plug
Checked Wiring continuity back from speed sender from ECU multi-plug
Checked resistance on Temp sender [Stone cold] which turned out to be low at 2.8k

With ignition on; DME Relay in place;
Checked for voltage between pin 35 and pin 5, also between pin 5 and pin 18,
All good.

Checked earth on Fuel filter frame at rear and on engine intake manifolds,
All good.

Each and every time I have removed and opened up the ECU, afterwards refitted it to the car, it starts, and it will start every time, until the next day, and no start again.
It has to be a fault somewhere in the ECU, but where ?

[mysocal911]

Originally Posted by ant7

Well, tried the car today after being left over night and...............................................
No start, again!

The check list I have completed so far;

Checked resistance on both reference sender and speed sender, all good new parts.
Checked wiring continuity back to reference sender from ECU multi-plug
Checked Wiring continuity back from speed sender from ECU multi-plug
Checked resistance on Temp sender [Stone cold] which turned out to be low at 2.8k

With ignition on; DME Relay in place;
Checked for voltage between pin 35 and pin 5, also between pin 5 and pin 18,
All good.

Checked earth on Fuel filter frame at rear and on engine intake manifolds,
All good.

Each and every time I have removed and opened up the ECU, afterwards refitted it to the car, it starts, and it will start every time, until the next day, and no start again.
It has to be a fault somewhere in the ECU, but where ?

Yes! You still haven't checked for an injector pulse when in the no-start mode, right?
This will help you locate where in the DME ECM the problem is. Just checking injector voltage is inadequate.
Get and use a node light. You can disconnect the temp sensor to enhance the brightness of the node light while cranking.

This test will eliminate the sensors and proper input voltages as sources of your problems, which is a waste of time now!
If you get injector pulses, then the problem is most likely on the analog board. "Shotgun" re-soldering won't get it now!

Don't worry, you're learning and at the level of most so-called DME "rebuilders/experts"!

[ant7]

Scrap the original post, the reading I was getting was because of the positive lead still attached to the coil, its something in the power supply that's measuring around 9 ohm, not sure what though.
So with both leads disconnected from the coil, there is no measurement reading between either positive or negative terminal to the can of the coil.
Also, when the car is cranking and not starting, I don't smell petrol from the exhaust, so I am assuming that there are no injectors firing either.

Originally Posted by mysocal911

Yes! You still haven't checked for an injector pulse when in the no-start mode, right?
This will help you locate where in the DME ECM the problem is. Just checking injector voltage is inadequate.
Get and use a node light. You can disconnect the temp sensor to enhance the brightness of the node light while cranking.

This test will eliminate the sensors and proper input voltages as sources of your problems, which is a waste of time now!
If you get injector pulses, then the problem is most likely on the analog board. "Shotgun" re-soldering won't get it now!

Don't worry, you're learning and at the level of most so-called DME "rebuilders/experts"!

[mysocal911]

Originally Posted by ant7

Scrap the original post, the reading I was getting was because of the positive lead still attached to the coil, its something in the power supply that's measuring around 9 ohm, not sure what though.
So with both leads disconnected from the coil, there is no measurement reading between either positive or negative terminal to the can of the coil.
Also, when the car is cranking and not starting, I don't smell petrol from the exhaust, so I am assuming that there are no injectors firing either.

The coil shouldn't have measurements between either post and the "can", the coil body.
The measurement is between the posts, and between the center HV lead and either post.

Another test is whether the tach needle moves while cranking, which highly relates to the analogy spark circuitry in the ECM.

[ant7]

Hi Dave,
Yes, my thoughts exactly.
When the car wont start I have noticed the tack needle bounce up and down, Just put the ECU back in the car after being sat on my bench for most of the day, its not been apart, its just sat on my bench, I wanted to try the injector node light as described, anyway, turned the key, and the car started right up and ran normal. I usually have patience by the bucket load, due to my job, but I am starting to waiver now.
Ant.

Originally Posted by mysocal911

The coil shouldn't have measurements between either post and the "can", the coil body.
The measurement is between the posts, and between the center HV lead and either post.

Another test is whether the tach needle moves while cranking, which highly relates to the analogy spark circuitry in the ECM.

[mysocal911]

Originally Posted by ant7

Hi Dave,
Yes, my thoughts exactly.
When the car wont start I have noticed the tack needle bounce up and down, Just put the ECU back in the car after being sat on my bench for most of the day, its not been apart, its just sat on my bench, I wanted to try the injector node light as described, anyway, turned the key, and the car started right up and ran normal. I usually have patience by the bucket load, due to my job, but I am starting to waiver now.
Ant.

Then the problem is on the analog board. When it's running and you have the boards separated and opened,
you need to tap various areas on the analog board for intermittency.

[ant7]

Ok,
I presume your referring to the board with the large metal transistor fitted ?
By the way, if you disconnect the cylinder head temp switch the car will not start, can you explain how it affects the ECU, I ask as I am wondering if that may have something to do with it, anyway, just another thing to rule out.

Originally Posted by mysocal911

Then the problem is on the analog board. When it's running and you have the boards separated and opened,
you need to tap various areas on the analog board for intermittency.

[mysocal911]

Originally Posted by ant7

Ok,
I presume your referring to the board with the large metal transistor fitted ?

Yes.

Originally Posted by ant7

By the way, if you disconnect the cylinder head temp switch the car will not start, can you explain how it affects the ECU, I ask as I am wondering if that may have something to do with it, anyway, just another thing to rule out.

It causes the fuel mixture to be extremely rich, i.e. it floods the engine. Once that happens, it's not easy to start the engine.

[ant7]

Understood,
I just realised, I asked the question concerning the temp switch in another thread!
Anyway, that's enough for me for today, I will come back to it when I have a bit more time.

Originally Posted by mysocal911

Yes.



It causes the fuel mixture to be extremely rich, i.e. it floods the engine. Once that happens, it's not easy to start the engine.

[Schulisco]

Ant,
don't panic!
You already wiggled the cables towards to the ECU plug? There might by a cable broken.
If you don't smell any fuel but seeing the tach jumping I suspect the DME relay. It's got two relays in a single housing:
https://www.swchips.com/dmerelay.html
I have reports on even new relays also have issues. Today you cannot be sure that every new part will work perfectly! To rule this out use a three wire cable bridge:



https://dorkiphus.net/porsche/showthread.php?t=16859

Regards, Thomas

[mysocal911]

Originally Posted by Schulisco

Ant,
don't panic!
You already wiggled the cables towards to the ECU plug? There might by a cable broken.
If you don't smell any fuel but seeing the tach jumping I suspect the DME relay. It's got two relays in a single housing:
https://www.swchips.com/dmerelay.html
I have reports on even new relays also have issues. Today you cannot be sure that every new part will work perfectly! To rule this out use a three wire cable bridge:



https://dorkiphus.net/porsche/showthread.php?t=16859

Regards, Thomas

And the problem with the #30 wire's female pin being loose & needing to be soldered & not just crimped.

[ant7]

Hi Thomas,
Cheers, however, I ruled out the DME relays early on in this debacle, I have two, and re-soldered everything in both, and when the car runs, you can put either one in, and it will start fine. Ant.

Originally Posted by Schulisco

Ant,
don't panic!
You already wiggled the cables towards to the ECU plug? There might by a cable broken.
If you don't smell any fuel but seeing the tach jumping I suspect the DME relay. It's got two relays in a single housing:
https://www.swchips.com/dmerelay.html
I have reports on even new relays also have issues. Today you cannot be sure that every new part will work perfectly! To rule this out use a three wire cable bridge:



https://dorkiphus.net/porsche/showthread.php?t=16859

Regards, Thomas

[ant7]

Old Solder

New solder

Large pins soldered on Transistor.

The black felt pen on the last pick is so that I know I have done them!

[ant7]

Inside my DME before any re-soldering.

[wazzz]

[ant7]

Hi Wazzz,
All three had their solder removed, and re-soldered as in the "New Solder" pick.
However, although that pin looks to be bad in the pick, its just a trick of the light, because with the naked eye, it looked fine!

Originally Posted by wazzz