Porsche928DT

Tomorrow afternoon I will hopefully have some results for you all since I work early in the morning. Work and rain stopped me today . I'm so excited to figure this out and get the 928 running again.

Porsche928DT

Sorry about the delay guys. I had a little bit of time today to try a few things. Heres some info on what I did:

I disconnected the O2 sensor, made sure its wiring was fine, removed the Kickdown Relay, and made sure there is no short for the pin 16 EZF to pin 1 LH. The car is still a no go for the pump and injectors so I sprayed some carb clean and started it and the tach did jump so then the RPM reading from the EZF now seems to be fine. When I stated that I have fuel pressure earlier it was because I jumpered the pump. I have since put the pump relay back since I know it is fine. I jumpered the LH Relay and when I turn the key to the on position before crank the fuel pump runs for 2 seconds as its supposed to (and didnt do before) but when I turn the key to crank it does not run (not sure if its supposed to or if it waits till the engine starts up). I checked the pins where the relay goes and they all are functioning as they are supposed to. For some strange reason with the relay installed the LH pin #9 receives the +12V as it should when the relay switches on yet the LH does not activate the fuel pump for the 2 seconds as it does when the relay is jumped. This is where I ran out of sunlight so I will do some more tests and follow suggestions from you guys tomorrow.

Loren I couldnt follow your steps as I have the 85' 25 Pin LH brain and not the newer 35 Pin. Did you have a list for the 25 Pin?

ZEUS+

If you have power to the pump when jumpered, there should be power at the injectors. If not, its time to find the open.

Porsche928DT

With the pump relay jumpered I do get the +12V at the injectors but the LH does not pulse the ground to activate them. I'm going to jumper the pump relay and ground the LH pin #13 (IIRC) to see if I get the injectors running tomorrow. I believe they should run since I checked the wiring already. It seems my issue now is the LH is not activating the pump relay (minus the 2 second run if the LH relay is jumped).

John Speake

Do not short LH 18 (injectors) to ground - you may damage the LH.

Inspect pin 1 on the disconnected LH ECU as this pin can sometimes be corroded if there has been any water ingress.

Sounds like your LH may be bad

ZEUS+

I agree with John. With no injector pulse, most likely faulty LH. Noid light.

H2

Ben,

That's a great chart. With the colored lines, even I can almost follow the logic.

H2

Lorenfb

"Loren I couldnt follow your steps as I have the 85' 25 Pin LH brain and not the newer 35 Pin."

You're in luck since it's an early LH engine with the 25 pin LH ECM:

1. These ECMs rarely if ever fail.
2. That system is even earier to troubleshoot:

A. Check for +12 at pins 9 & 18, pin 9 gets power once pin 21 sends a ground to pin 85 of XXV
B. Check for grounds at pins 5 & 25, pins 5, 6, & 11 are connected internally on the ECM.
Check these with an ohmmeter.
C. Use an LED test light to check for the EZF signal on pin 1.
D. Check for +12 on pin 13 (output to injectors).
E. Momentarily ground pin 13 (back of connector) while cranking the engine as this will check
the injector wiring from the ECM to the injectors. This won't damage anything

This is about a five minute effort.

Porsche928DT

Problem Solved!!! Heres what I did. I grabbed a 12V LED to use as a Noid Light and found no activity on the injectors and no activity on the Pin 1 of the LH. I then simulated an RPM reading to the Pin 1 (tach moved as well) and the injector LED/Fuel Pump came to life! I at that point rulled out the LH computer and now had the problem being either the EZF unit or the Flywheel sensor. I went straight for the problem I mentioned before and sure enough the bad connection at the Flywheel sensor was the problem. I matched the connection up right then turned the key and PRESTO! Next problem now would be the white smoke that came out of one of the exhaust pipes and from the bottom passenger side of the engine. I think the head gasket was not seated properly or was damaged with the starting fluid . In all honesty I would rather a hard task that I know I can do rather than some unknown electrical problem that takes forever.

Thanks (in order of appearance) to Zues+, macreel, Ben, Bill, Matt, John, Glenn, Roger, and Loren! You all rock

Bill Ball

I've heard about fires and explosions with starter fluid, but how do you think you damaged the head with it?

Porsche928DT

I mean the head gasket not the head (heaven forbid that). I started reading the other thread where some think AlQueda may use it for their next attack since it is so combustible lol(someone also had a picture of a destroyed tractor piston from starter fluid). I doubt it would damage the gasket but thought I would say it just to spare someone else from bringing it up.

JHowell37

I beg to differ. I've got three of them sitting in my car waiting to go to the UPS store. One is the "test unit" of the place that supposedly repaired mine a few weeks ago. That one doesn't work so it's going back. One is my "repaired" unit that didn't work. That's going to the person who sent me a fourth functional unit, so he can diagnosis it and maybe find the issue that the first guy couldn't correct. And then there's my third one which will also be going to the same person so he can rebuild it.

WICruiser

Glad to hear that it was an "easy" fix once you figured out the source of the problem.

Was the white smoke only on start up? If it disappeared once you got it warmed up you may have had a lot of condensation in the exhaust system from all of the non-running starting attempts. The passenger side exhaust header to exhaust pipe connection, or the CO monitoring connection, or the diverter valve air supply to the exhaust are places I would check before I starting into head gaskets.

Hope it turns out to be as easy a fix as the original problem.

Porsche928DT

Im glad im not Brain hunting right now. I do plan to do some tests before digging in. Ill drop the exhaust system, do a compression test, and a bunch of other stuff. The smoke came from the passenger side of the exhaust system and I cant tell you wether it goes away after warm up because the engine shut off on its own. While this can turn out to be difficult I can live with that. Its the unknown that has always irritated me in life. Thanks for the good wishes by the way!

Lorenfb

"I beg to differ. "

Really?

"I've got three of them sitting in my car waiting to go to the UPS store. One is the "test unit" of the place that supposedly repaired mine a few weeks ago. That one doesn't work so it's going back."

Sounds like a poor choice of a rebuilder!

"One is my "repaired" unit that didn't work. That's going to the person who sent me a fourth functional unit, so he can diagnosis it and maybe find the issue that the first guy couldn't correct. "

Some just don't learn from the 1st lesson.

"And then there's my third one which will also be going to the same person so he can rebuild it."

Don't hold your breath!!!!!!!!!!!!!!!!

As I said before, these units rarely if ever fail with the exception of BAD DIY troubleshooting
induced failures. There's NO high failure rate component in those ECMs as in the later LH ECM.
As with most of the REAL problems, it's WASN'T initially a bad LH ECM before the
troubleshooting began.

Bottom line: A call to 928 Int'l for a rebuilt unit would've avoided all the headaches!