Help!!! No start issue
 

Hello,

I need help with a NO START issue on my 1987 Porsche 911 Carrera

Background on issue:

I took the car out on it first drive after winter slumber. I drove it about 80 miles total when about 10 miles from my home I started smelling a sulfur type smell. I deduced that my battery was boiling (verified it). I assume at this point that the VOLTAGE REGULATOR is probably going bad. I decided to remove negative battery terminal and drive it home to solve the issue. 1 mile from the place I disconnected the negative terminal the car would intermittently stutter. It did this 3 times. At the last stutter the car went dead completely and would not restart even after I got out and reconnected negative terminal. I had it towed home. (Should have done this to begin with but felt confident that it would travel 10 more miles)

CURRENT STATUS
I verified the following;

Fuel pump is working and supplying fuel to the filter

There is a spark at the plug

The injectors are NOT ACTIVE

I sprayed starter fluid in to see if it would run briefly but it only tried to hit then nothing.

Could it be the brain is fried? DME relay? Injector Relay?


This where I am currently. Any advice on where to go from here would be really appreciated!

Thank you
J

Sorry to read your troubles. Welcome Aboard!

Let's finish reading...

Do you have a spare DME relay? If so try that.

But before that, you really should check the battery's condition. What is the voltage at?

Thank you so much. Battery is still good 13.87. I thought about DME relay but wouldn't the fuel pump not work if it were faulty?

Hmm, I stared at the INJECTOR comment while I was typing. I don't recall the injectors having a relay. I think it is controlled by the DME (ECU).

Can you test to see if you get a signal from the Injector connectors?

Sorry this is a new one for me. Never read anyone push their 3.2 like you did. I have AAA towing on speed dial.

Per Bentley, you can test the Injector signal at the DME pins 14 & 15 and ground.

��. No worries I welcome ALL suggestions.

Their is no pulse at the injector harness end. I used a noid light to see if the injector was receiving a signal.

I believe this is the injector relay

http://www.*********.com/gbproducts/WC/64-01049693.html?utm_content=YN&utm_term=1980-1989+Porsche+911+Relay+Bosch+W0133-1638497+80-89+Porsche+Relay+1986+1982&fp=pp&gbm=a&utm_source= google&utm_medium=ff&utm_campaign=*********+Google +Base&gclid=CPmUsuzD9csCFRJbhgodFtMCOg&ad=47433965 052

Hope you didn't fry the $$$ parts with the voltage spikes.

Have you checked the fuses ?

The only "regular" fuse that was fried was the one for the interior lights and radio. Now if I replace that fuse and connect the battery it immediately fries it.....

By $$$ parts are you referring to the "brain" the engine management unit under the driver seat ?

I checked the injector harness using a NOID kit.

Sorry for your troubles. Here are some pointers:

If the injectors are really not firing chances are there is damage to the DME or to one of the injectors: All injectors are wired in parallel. If one is short it'll prevent all of them from working, Here is what you want to try:

1. Disconnect all injectors and check with an LED test light or NOID light for pulses when cranking. If yes, the DME is good and it's one of the injectors. If no check for solid +12V on one side of the one of the injector connectors.

2. If you get pulses with all injectors off, connect them one at a time while leaving the NOID light in place and try to single out which one causes the short.

You are correct in that the DME relay and the sensors are fine. Else there would be no spark. Unfortunately, the elevated system voltage (not having the battery connected and having a failing regular) might really have caused damage to the DME (the brain under the seat). The injector driver is driving six low-impedance injectors via a sophisticated peak & hold scheme. And this driver might have suffered depending on how high the system voltage went. Do the tests above and get back with results.

Further, let us know where you're located. Maybe someone is close to you to check your DME in another car to confirm the diagnosis if your tests point towards it as culprit.


Ingo

All I can say at this point is do WHATEVER Ingo says...he is a freaking genius when it come so DME issues. He's very good at diagnosing issues on these systems.
Saved me a time of time and fixed my DME when it failed.

Ok so let me make sure I understand.

Unplug all the injectors and start at one end and plug the Noid attachment into each one testing to see if they fire?

Yes, and it doesn't matter into which of the 6 connectors you plug the NOID light. They are all wired in parallel.

I am located in Birmingham Alabama. If it is the DME I see that I can send mine to you correct?

Yes, if you think you got it down to the DME I am happy to help. But first, let's make sure it's not one of the injectors.

Sure thing, want to fix this then find out what's make the radio circuit blow. It all happened at the same time.

If I understand the system correctly...... Timing would NOT have jumped and does NOT need to be checked correct? As I understood it the position sensors dictate to the " brain" to adjust timing?

DME / Fuel Injector issue aside, I don't think you should run the ALT with the battery disconnected - I hope I misread that.

Thank you so much for lending your expertise!

Correct. The timing on these engines is done with the two flywheel sensors. One is to determine engine speed and the other determines TDC.

In your case I am afraid you might have damaged your radio. Some electronic have a Zener diode that limits momentary spikes. When exposed to continuous overvoltage they fail dead short. And that might be why your radio/interior fuse now blows instantly.

Unfortunately you did read that correctly. At the moment I misunderstood the role the battery played and made that mistake trying to drive it on home the last 10 miles. :confused:

If it us the radio I can handle it as it is not original to the car. The PO installed a Volvo radio??? He took a sharpie pen and colored in the logo and put a Porsche emblem on it. Lol

that's funny. Just disconnect it and replace the fuse to verify.

For the other stuff make sure to get the alternator checked out. The regulator is integrated and can be replaced.

At this point you don't want to do much beyond testing. And yes unfortunately, disconnecting the battery might have aggravated the situation. It acts as load and somewhat tames the alternator output. Once it's out of the circuit the alternator can drive even more voltage into the +12V bus and for the most part electronics suffer.

Email me to pcarsba (at) gmail once you have completed your diagnosis and if you need help fixing the DME.

Good luck,
Ingo

Could it also be the Relay for Injection Pump..?

no, the relay is a two-stage relay. The first stage comes on when you turn the key to ON or START. it then powers the second stage input, the DME and the coils and injectors.

The second stage is controlled by the DME. It gets turned on when either the flywheel moves with more than 200RPM or when the starter is energized. It powers the O2 sensor heater and the fuel pump. If you are certain that the fuel pump is running during cranking the DME relay is fine.

any updates on this?

Sorry for not updating. I am traveling at the moment and it will be the weekend before I can resume working on it. Will update ASAP.

Ok, I had my friend whom has been helping me go over to my house and unplug all the injectors and plug in the Noid attachment. He performed a crank test and NO LIGHT ON THE NOID INSTRUMENT!

Could the voltage regulator issue play a part from this being successful ?

Not likely. Check permanent +12V on one side

Also verified that there WAS spark still at the spark plug. If not the voltage regulator we can assume it is the "brain" ?

Once you have confirmed +12V at one side of the injector connector and ohmed out the other side to the 35pin connector at the DME (pin 14 or pin 15 depending on which bank)

If both check out it's almost certainly the DME itself.

Ingo

Can you elaborate a bit on the ohming out the 35 pin connector ?

The injector signal is carried from the DME via the DME harness to the individual injector connectors. On each injector plug one pin is +12V (when ignition is on) and the other pin goes to the DME. One bank goes to pin 14 and the other bank to pin 15. Inside the DME pin 14 and pin 15 are connected to each other and driven by the single injector stage output driver. See here:

http://forums.pelicanparts.com/uploa...1460125465.jpg


With the DME connected and all injectors unplugged check for +12V on each connector while ignition is ON.

Then turn the ignition off, unplug the DME, and measure from the other pin in the injector connector to it's two neighbors with and Ohm meter. It should be close to zero. Same one the other side.

Then pick one of the injector connectors and measure from that same pin to pin 14 or pin 15 on the DME connector. One reading again needs to be close to zero.