Sporatic No Start...with video! so Frustrating

[mray2686]

Newbie to the 911 world. Have an '84 targa that has a sportic no start.
In my non-technical words, it sometimes just doesn't turn over!

Battery has been tested. No problems there. DME relay has been replaced.
What's strange is that almost all the time it turns right over and fires up. then times, like today, it won't. i bet it will tomorrow...

I have a Bentley manual and 101 book, so with the right guideance i should be OK finding my way around this thing.

Let me know your thoughts.

'84 targa - no start - YouTube

[Tippy]

I'm a little confused. When it wont start, you are saying the starter won't turn over or does the starter turn over but the engine won't start?

[mray2686]

Originally Posted by Tippy

I'm a little confused. When it wont start, you are saying the starter won't turn over or does the starter turn over but the engine won't start?

The starter turns over...but the engine doesn't start.

I actually just got it started. Will post another video when my buddy emails it to me.

I've been cranking it all day...and then this last time it tried it, we started.

[Tippy]

Ah, I watched the video now.

I would get a multimeter, pull the main harness off the DME under the drivers seat, and test your sensors - mainly, the speed reference and TDC sensors.

[mray2686]

So yesterday afternoon, after countless attempts to start, we get lucky. My buddy happened to be filming.
Nothing different as far as changes since that morning, which makes this so difficult to comprehend or explain.

Here is his video. Apologize for his cheer!

And now she starts... - YouTube

I called a local porsche shop because I want to have a keen set of eyes look her over. Over the phone today he mentioned maybe a faulty DME, or even a fuel pump.
My concern, at $90/hr, is that I bring it in a everything is fine...because I took her to and from work today, no problem, not even hesitant to start.

Got home after dark, so could not troubleshoot. Will get a multimeter and test as recommended. Any other suggestions? I'd love to try to figure this out and learn.

[Tigerrat]

Spark? Pull a plug and check. Fuel? Try some starting spray in the intake. Then go from there.

[S ECU Repair]

My advice will be biased toward the DME of course, but I get DMEs from Porsche Targas at my office for intermittent no start all the time.

If the problem persists, tap on the DME, and see if the car shuts down while running, or if it starts while you are trying to crank it.

As Tippy said, also check those reference sensors at the DME harness with a multimeter (~1000 Omns). And physically look at them to make sure that they are clean, and in good condition.

[mray2686]

Thanks guys! I'll give these suggestions a shot and report back to you.

[ant7]

hi,
it could be ignition switch faulty, ie; when turning it to start position the ignition circuit is losing power hence the starter turns but no power to ignition or fuel circuit.
the DME relay holds two relay coils, when turning on ignition listen out for a faint click from under the drivers seat.
you can also bypass the DME relay by temporarily putting a bridging wire from the top of the 6th fuse in line [counting from left to right while looking at the fusebox under the bonnet/hood] to the 9th fuse from the left in line.
this will allow the fuel pump to run continous while the ignition is on.
hope this helps.
Anthony.

[kidrock]

Sorry guys, I'm with Tigerrat on this one. Best to start from the beginning and find out if we've got spark and fuel.

[mray2686]

Originally Posted by S ECU Repair

My advice will be biased toward the DME of course, but I get DMEs from Porsche Targas at my office for intermittent no start all the time.

If the problem persists, tap on the DME, and see if the car shuts down while running, or if it starts while you are trying to crank it.

As Tippy said, also check those reference sensors at the DME harness with a multimeter (~1000 Omns). And physically look at them to make sure that they are clean, and in good condition.

I took the targa to work this morning. took a half second longer to fire the engine on first attempt, and I thought to myself I would have an issue tonight.

Leaving the office, I cranked it, and the engine wouldn't turn over, just like in the first post video. After about 7 tries, same result, I was about to catch a ride with a co-worker.

I remembered this post, and knocked on the DME while turning the key. Lo and behold, she fired up.

Got me thinking it IS a DME problem. How fast is the turn around for diagnostics?

[Joe Bob]

As fast as the shipping company. Don't know anyone on the east coast, but Ingo can help.

3.6@cox.net

[S ECU Repair]

Originally Posted by mray2686

I took the targa to work this morning. took a half second longer to fire the engine on first attempt, and I thought to myself I would have an issue tonight.

Leaving the office, I cranked it, and the engine wouldn't turn over, just like in the first post video. After about 7 tries, same result, I was about to catch a ride with a co-worker.

I remembered this post, and knocked on the DME while turning the key. Lo and behold, she fired up.

Got me thinking it IS a DME problem. How fast is the turn around for diagnostics?

I cannot tell you how many times I see the same intermittent start problem with Targas every week...I can definitely help you out.

Send it over. I 'll test it for you, and let you know what I find.

[Lorenfb]

"it sometimes just doesn't turn over!"

And the DME ECM controls the starter on a 911 3.2, right?
Could also be the radio, as some Pelicans report a no-crank
situation when the radio was 'on'. Please!!!!!!!!!!!!!

"see the same intermittent start problem with Targas every week"

Right, it's always those Targas. Glad I never bought a Targa!

PLEASE!!!!!!!!!!!!!!!!!!!

"let you know what I find"

Right, and there's always some problem to be found.

And here's the typical result:1988 911 dme problem

[86 911 Targa]

Originally Posted by mray2686

I took the targa to work this morning. took a half second longer to fire the engine on first attempt, and I thought to myself I would have an issue tonight.

Leaving the office, I cranked it, and the engine wouldn't turn over, just like in the first post video. After about 7 tries, same result, I was about to catch a ride with a co-worker.

I remembered this post, and knocked on the DME while turning the key. Lo and behold, she fired up.

Got me thinking it IS a DME problem. How fast is the turn around for diagnostics?

Swap out your DME relay with another known working unit.

AND:

If your DME relay is a ÜRO brand, replace it with a Bosch.

Lots of members have had ongoing issues with ÜRO products.

Good luck,

Gerry

[mray2686]

Originally Posted by 86 911 Targa

Swap out your DME relay with another known working unit.

AND:

If your DME relay is a ÜRO brand, replace it with a Bosch.

Lots of members have had ongoing issues with ÜRO products.

Good luck,

Gerry

Where do you see a Bosch relay? Mine is a ÜRO and I will replace. All I see here is the ÜRO and the genuine porsche DME relay.

[mray2686]

OK - Been a few weeks, but I've done a few things to get to the bottom of this.

- Tune up. Replaced spark plugs, distributor cap, rotor. I have spark.
- Examined fuel filter. Was very dirty, replaced.
- Replaced DME relay, again.
- Had the ECM out, looked over by a pro. They reported back no issues with the ECM itself.

Put it all back together after tune up, and for the first few days we were running well without any "no starts."

Then, this week, it's back. Every time it has not started at first attempt, I've pushed back my seat, and with left hand turning key, right hand is knocking on ECM/wiggling ECM harness, and she will fire up...

I bought a multimeter today, have the Bentley manual out, and want to check if the harness is causing me these issues.

Problem is, I'm not really sure how to test this. Never used a multimeter. If anyone can talk me through this, I want to disconnect the harness in the morning and test to make sure it is all working well at the harness/ECM connection.

Am I looking in the right place? I find it so weird that if the car doesn't start right up, I've got to fiddle with the ECM, and then we are fine. SO Frustrating...

Thank you in advance for your help.

[Lorenfb]

"Had the ECM out, looked over by a pro"

Pro??? 'Looking over' doesn't always find the problem!

[mray2686]

Originally Posted by Lorenfb

"Had the ECM out, looked over by a pro"

Pro??? 'Looking over' doesn't always find the problem!

What would find the problem with an ECM?

Bench testing?
Swapping it out for a known good unit?

What do you recommend I do Loren?
Thanks!

[Lorenfb]

"What would find the problem with an ECM?"

"Bench testing?" - NO

"Swapping it out for a known good unit?" - YES, with a lengthy test,
which I do often when conditions like this occur.

"I've pushed back my seat, and with left hand turning key, right hand is knocking on ECM/wiggling ECM harness, and she will fire up..."

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