911Jetta

I have a no start issue with my car, a little background information (sorry if it's long-winded, but hope it's helpful in resolving the issue):

Actually, I experienced an occasional no-start issue ever since I got my car months ago, but it was so random that I thought it was related to the aftermarket security system that's was installed on the car. The alarm system (or whatever it is) has a couple green and red lights, on the small panel just to the left of the ignition key. I usually ignore the lights and the car starts as normal. In most cases the lights blink in some random combination and the car starts fine (regardless of red or green flashing lights). Every so often the car won't start (1 in 20 times), but usually starts the second try or soon afterwards. Annoying, but I always thought it was alarm related since is was so infrequent.

Lately the no start issue had been happening with greater frequency, but still randomly and with no warning. Everything's fine, then all of a sudden at a gas station hours away it wouldn't start again. Fortunately it did after a couple minutes, but the car felt different on the drive home. It seemed to hesitate on the highway, and felt jumpy. Power still felt good, but the engine only felt good above 3-4,000 RPM. Below that it didn't feel smooth. As soon as I parked it in the garage, I tried to restart it (as a test) and it wouldn't start at all.

After researching here a bit (thanks RL community), I concluded it must be the DME fuel relay. I put a new one in and the car started right away (actually the second try, maybe it took a second for fuel to get to the engine). I tried an old relay and it won't start. New relay again, started right away. As a test, over the next couple of days I started the car a couple times in the garage and it always jumped right to life. Even the aftermarket alarm was flashing green. I thought I was in the clear.

Yesterday I tested the car and almost ended up stranded again. The car drove great and started with no issues, but after 30 minutes of driving it started to feel jumpy again during smooth throttle, idle RPM was unsteady and the alarm system lights were flickering quite a bit. I parked the car in the garage, and now it won't start again. It's never died while driving, only fails to start.

I've included a short video showing the lights and sounds when you turn the ignition on: I took the DME relay out and it felt very hot. I let it cool down and retried it. No start.

So it's either a faulty DME fuel relay (even though I just installed a new one), an issue with the coils, plug wires or fuel pump. All over my head...
I'll keep trying to get it started, in hopes of getting it to the shop under its own power.

What do you guys think? Thanks in advance for your assistance!
Was hoping to take it back up the the mountains this weekend; that's out now...

Rocket Rob

Start with the basics. What is your battery voltage? In the video, I couldn't hear if the starter is engaging or not. Is it? Have you checked your grounds and battery connections? Are they clean and tight? Don't forget the ground strap at the starter.

911Jetta

Thanks Rob (as always).
Starter is not engaging.
I skipped right over the battery, because it always starts so well, when it starts. Also got side-tracked by all the other symptoms. I'll test the battery when I get home... if I can only be so lucky.

Rocket Rob

Also check the battery voltage with the engine running. Perhaps your alternator is weak. By the way a simple test on the battery is try jump starting the car.

fasterlaster

It may be best to start at the starter on Terminal 50 (Schematics says it's Yellow wire) and work your way back. Print up the schematics and just work your way back. With the cutting out and rough running I suspect the issue is much further forwards, such as Ignition switch area, but with a known issue (starter not engaging) you may be able to identify where the issue is easier. Also I had a similar occasional poor running a few years ago with what appeared to be a alternator going out with voltage on the low end. After replacing the alternator, I found out my problem was a very poor battery ground cable. Looked good, but when I pulled it off and slit the insulation there was a tremendous amount of corrosion inside. $10 later I was on the road with no issues

911Jetta

kkswow12

hey man ...i am in a similar boat here...(i should insert here there has been no check engine light and i understand there is one in here somewhere as there is an OBD port for the "hammer", so i am looking for an indie with said instrument as opposed to going to PZ for an €80 piece of paper, though i will save that many times over buy not just chasing the gremlins down randomly....have you checked the CEL?).......got stranded on the road few weeks ago, found the dist belt was kaput, had it rebuilt, bearings and all, not the problem...thinking fuel cuz the car sits mostly...maybe 100kms in 3 years, new filter, some octane booster in 1/2 tank of fuel...she likes that, but feels like running on less than 12 plugs for lack of a better description...so i am chasing in the direction of fuel problems and you are going down the electrics road...will we end up in the same place? and now i am thinking new plugs and wire set might be next, but before i let this spiral for parts i may not need i need the OBD readout ... theres the DME relay, a cat (don't even know if i have one), lambda sensors, what else are they called? idle sensors, if there are such things anon...so i look forward to your progress and will let you know what i get up to...and good luck...oh, and....totally worth all this...

911Jetta

kkswow12

on the no start, did the starter even engage? that sounds like your starter is jammed...and the second one, is that a blower motor before you start? if so and all other things being equal, sounds electrical, like bad ground cable? just grasping here...mine is different in that it always turns over and starts, it is in the running motor i am finding the issues...hmmm, gonna check the ground wire in my frunk

Rocket Rob

It definitely seems like an electrical fault. Perhaps your starter or ignition switch. Good luck in finding it and keep us posted.

urquattro20Vt

My half guess is ignition switch. They can be unpredictable before dying.

Brandon
'91 964 Turbo

kkswow12

maybe just a loose connection in the switch itself...?

Ralph3.

The electrical portion of the ignition switch can do some strange things.

nirich

My 2c worth:
If the battery is not even turning the starter motor over, then check the battery. You indicated that the battery registered at 12.5V..........not enough, a good battery will show closer to 14V. (Could be battery or alternator).
Some years a go i had a similar issue, some days it would start right up other days just dead. The earth lead wasn't healthy..........sometimes it would spark/arc and weld enough to the chassis to start. New earth lead fixed it as i figured that the old lead must have been corroded or semi-broken somewhere down its length.

A very easy and cheap thing to do to eliminate or confirm the issue.

911Jetta

I got one more start out of the 964 this morning and dropped the car off at my shop.

As I was describing the situ, they popped the hood and one of the techs immediately said my battery cable looked green. One battery terminal was warm and other cold. He pressed on the cable and it made a connection and the car started right up. He said you could see where the contact was cleaned before. So left the car for them to replace the cable and checkout the rest of the car while it's there. Sucks that I couldn't find the issue, but at the same time relieved that it might be that simple.

Regarding the battery cable turning green cable... I could barely tell until they educated me. It was subtle, and everything is so clean on the car I thought all the cables and contacts looked great.
Simple fix. Thanks for everyone's help and suggestions (It's not like you guys didn't try to point it out to me!), but I'm just glad I can plan a trip back to the mountains this weekend!