3.2 No Start (I searched)
 

1985 3.2 with a no start issue. Drove it to work, no problems. Drove it home from work, no problems. 2hrs later go to take it out and no start. It'll turn over, but there's no spark. Here's what I've done so far:
1. Swapped DME Relay

a. Did this with 4 relays, just to be sure. Just to be EXTRA sure, I bought a new relay – no start. Then I bench tested all 5. One was bad, but not the one that was in the car at the time of the original no start.

2. Jumped the fuses to confirm fuel pump turns on – it does, no start
3. Jumped the pins on the DME Relay wiring harness – no start
4. Check the coil with the multimeter

a. 12v at the coil

b. Primary and secondary all within spec

c. Swapped in a spare coil (also within spec) – no start

d. “Borrowed” an MSD coil from Amazon – in spec and still no start

5. Checked Ohms on the Speed Sensor – all good, no start
6. Checked Ohms on the Reference Sensor – all good, no start
7. Checked Ohms on the Cylinder Head Sensor – all good, no start
8. Pulled out the factory manual and proceeded to:

a. Run all fuel delivery tests – all good, no start

i. Yes, fuel pressure too!

b. Run all ignition tests (including above tests already performed) – all good, no start

c. Did full pin-out testing on DME harness – all good, no start

9. Replaced Speed & Reference Sensors

a. Yes – gap set to 0.8mm

b. Double checked my work with the LED test – all good, no start

10. Pulled my DME

a. Checked every mm of the board for any cracked solder joint – all good

b. Checked every component for attempting to release the smoke – all good

c. Put DME back in – no start

d. Pulled DME out again, just in case I missed something – currently sitting on the bench

11. Somewhere in the above testing, I also bought a pocket oscilloscope to “up my testing” abilities on the sensors. I’m not exactly scope savvy, but the waves all looked good to me.
12. Only thing I haven’t done, that I’m considering is replace the fuel pump and one way valve, but that shouldn’t be spark related.
13. Ran out of things to test – jumped on Pelican to plead for help. I have pics or vids of just about every step above, including inspecting the DME boards. Let me know what you need to help diagnose. I'm sure there's other tests I've forgotten to include above (e.g. all fuses tested).

TIA

check the ground on no1 intake - just an idea..

Ivan

Thanks Ivan! I'll double check it, but I was using that as my grounding point for my test light early on in the process. I'll pull the wires off tonight and give the terminals a quick clean.

Have you actually checked for spark?

Check the AFM voltage signal maybe? Fuelling at start is probably not dependant on it, but it's an idea...

Is the tach bouncing and indicating cranking RPM while you're cranking? I think it should, and would be a sign that the DME is alive, at least.

Read this; http://forums.pelicanparts.com/porsche-911-technical-forum/621262-911-3-2-no-start-troubleshooting.html

Simple, isn't it!

A while back I had a funky similar situation (though the non-start would come and go randomly). My relay, and sensors were good, so I found the connection between the speed sensor and wire harness seemed to be an issue ("jiggling" there would sometimes result in a "fix). I changed out the the connector there (that mates to the sensor) and the problem disappeared. Just another item to check...good luck.

No spark is definitely the issue.

Yes - forgot to include those tests in my list. I put the multimeter to the IVC and the AFM. Both in spec.

I'll have to check the tach for bouncing tonight. Thanks for the tip!

Maybe someone can chime in and offer some advice on what you should be seeing during cranking from the DME, as it sends a tach signal to the tach. Maybe a clue as to whether or not the DME is conscious or not.

Hahaha - I wish it was simple! That's one of several threads here and on Rennlist I used in my troubleshooting.

I've done a full pinout test on the DME harness and everything seems to be sending a signal or has continuity. Once I put the DME back together, I'll try some jiggling and keep my fingers crossed!

Yes, we know you have no spark! So, where's the test for the injectors? You are aware that "no spark" & no injectors provides a different,
& more complicated failure mode to troubleshoot?

The AFM & ICV tests are useless for your failure mode!

Actually, it is that simple! If you fully did the test and understood the results (test step "B"), then you have a major failure in the DME ECM logic board.
Open the DME ECM and setup your bench test with a signal generator & a scope. You've done that before, right? Good luck!

I have a noid light and I'll test the injectors tonight. I didn't bother to test the injectors, since I had no spark coming off of the coil. Will rectify that oversight tonight.

Understood on the AFM & ICV, but that was a recommended test on a few of the other threads, so I figured I might as well rule them out.

Totally meaningless tests for your problem.

I appreciate the passive aggressive help, because it's still help. However, repeating yourself isn't helpful. I can read. If it's tongue and cheek, I can't read that tone through the forum, so my apologies.

Agreed, it's a totally meaningless test, given what you and I both know now. At the early stages, it seemed reasonable, since everything else was checking out per spec and several other no-start threads recommended testing them. I'm fairly certain my DME is shot, but before I shell out a bunch of cash for a new one, I'm trying to exhaust all other options.

No I don't have a signal generator and I'm a trained monkey with a scope. I can recreate what I saw on a YouTube vid and that's about it. I know reading is fun for mentals, I mean fundamental, but as you must already know, I did more than the pinout testing in test step "B" and everything came back within spec. Again this indicates it's likely my DME, but I'm exploring all options before I replace it. To that end, I'm taking your advice and will run a noid test on the injectors tonight.

I'll let you know what the results are and eagerly await your next recommendation.

The odds are in your favor, i.e. it's extremely rare that the digital circuit board fails. If it's the early beige color circuit board (early),
they can become intermittent. There's a 14 pin IC that fails on that board, resulting in no-spark/injectors.

Thanks Dave. Boards are green. There were a few darker solder joints so I resoldered those to be on the safe side. I'll put things back together shortly and then try a start. If it's still a no-go, jiggle and noid test will follow.

Jiggle didn't work and no flashy flashy with the noid.

For the triple (maybe quintuple at this point) check, I just checked pins 1/18/35 and all have full voltage. Pins 5/16/17 all tested positive for continuity to ground.

Dumb idea: double check all of the battery connections.
My positive terminal was tight but the little wires attached to the outside of the clamp
Bolt were slightly loose, leading to lower voltage to the DME. Cranked but wouldn’t fire up (993)


Sent from my iPhone using Tapatalk