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What happened to my 930?

I was driving my stock 87 930 home tonight on the freeway at about 40mph (Friday evening traffic) when the engine suddenly died. There was no warning and the car was running fine just before, as always. I managed to get over to the shoulder, turned the ignition off, and tried starting it. The car started right up, so I thought "hmmmm" and ventured back out into traffic, this time staying in the right hand lane, just in case. A quarter of a mile later it did the exact same thing.

When I pulled over this time, it restarted again and I let it run for a bit, lightly revving the engine to see if it would continue to run. It died in short order. So... I opened the engine compartment and checked the coil wire to see if it was firmly connected at both ends. It seemed to be. I also opened the trunk and reseated the fuel injection relays. I got back in and started the car and it ran fine. I let it run a while on the shoulder and it continued to run.

With some trepidation, I ventured out into traffic again, keeping to the right lane just in case. It took me about an hour to get home and the car ran excellent, as it always does, all the way home.

Does anybody have any ideas? Could it have been the relays? Something unrelated? I'm not really sure how to proceed, this car is much more complicated than my meager diagnostic abilities can handle!

Thanks,
Eric
Old 09-30-2011, 06:01 PM
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Fuel pump
Old 09-30-2011, 06:12 PM
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Sounds like you might have narrowed it to the relays, clean and spread the contacts so you know they're making good connections. Others will chime in with other ideas , but try to get it to happen in the driveway so you can look and listen without the stress of traffic.
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Old 09-30-2011, 06:13 PM
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Pulling relays and fuses (like "rolling" the old bullet fuses) seems to cure many intermittent problems in these cars. The contacts get oxidized from moisture, smog, and just plain old age (the spring contacts lose their grip over time). Your car is 25 years old, it will have bouts of stubbornly finickiness.

Mark
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Old 09-30-2011, 06:15 PM
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Quote:
Originally Posted by infraredcalvin View Post
but try to get it to happen in the driveway so you can look and listen without the stress of traffic.
Would that it were that simple. I once had a POS Jag that was giving me similar fits, just wishing that the damn thing would do it in the driveway instead of "doing it in the road" - as the Beatles would say. Finally, one day, it konked out in the drive where I had access to all my tools and meters and such. Found a $14 dollar sensor was doing the funky chicken.

So, back on topic. By removing and re-plugging your relays in the engine compartment - which apparently solved the problem at least temporarily - that points to where your issue may lie (may, I say). By all means, spread the contact pins as already mentioned, and clean the piss outa them while you're at it. Squirt some contact cleaner into the female sockets as well.

In your 87, there is one particular relay (the yellow one from hell) that can give you fits. It's tied in with the overboost sensor as well as the fuel pumps as well as the metering plate/arm switch at the back of the fuel distibutor...as well as the relay under the drivers seat. Any one of those can fail you, but the yellow relay is a good place to start.

Go down to the liquor store, buy a bottle, and sit down to read everything in our sticky Sticky for common answers to why "My car doesn't start...."
It will give you one hell of an education and will point you on where to look and what to do.
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Old 09-30-2011, 06:25 PM
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One more thing... check your positive battery cable connection. Mine came loose once and it gave me intermittent running issues. It was sparking like heck and hot as hell on the day I figured it out. It's a 13mm wrench. For some reason, the German guy who designed the electrical system thought it was a good idea to hang a few extra 10-12 gauge wires off the battery terminal.
(One day Porsche will admit that it was the English ba$tard, Lucas the prince of darkness, that designed our electrical system... same guy who did MG and Triumph)
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Old 09-30-2011, 06:43 PM
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Thanks guys. I think I will start off with cleaning the contacts on the relays and check the battery connections. Hopefully that will fix it.

Thank you for all the quick responses. I read the won't start sticky when I got my car in April, but I think I should give it a quick review. I've got a nice Belgian/IPA hybrid in the fridge and a computer in the garage... perfect for quality relaxing.

Cheers,
Eric
Old 10-01-2011, 07:15 AM
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Aso, check under the driver's seat and make sure the cable connection to the speed relay, etc. is good.
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Old 10-01-2011, 08:36 AM
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Unlikely culprit, but I had it happen to me and it's a quick check: One of the plastic fuse blocks in the front trunk had split longitudinally, so that the metal tabs holding onto the fuses weren't generating much tension. So the fuses looked like they were in place, but they'd go out intermittently. I had a couple instances like you describe, where the motor would just die suddenly...and then start right back up.

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Old 10-01-2011, 10:40 AM
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Quote:
Originally Posted by DSPTurtle View Post
One more thing... check your positive battery cable connection. Mine came loose once and it gave me intermittent running issues. It was sparking like heck and hot as hell on the day I figured it out. It's a 13mm wrench. For some reason, the German guy who designed the electrical system thought it was a good idea to hang a few extra 10-12 gauge wires off the battery terminal.
(One day Porsche will admit that it was the English ba$tard, Lucas the prince of darkness, that designed our electrical system... same guy who did MG and Triumph)
My very early automible life was centered on MG's for more years than I care to admit. Lucas became a swear word akin to hocking up some deep lung phlem. If Porsche ever admitted to an affiliation with Lucas, I would be filing for divorce.
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Old 10-01-2011, 02:05 PM
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After doing all that today, I took the car out on a test drive, where it promptly died about 10 blocks from home. It took a while before it started this time but just before it did, I noticed I could hear the fuel pump running, I hadn't noticed it before. So... it is the pump or the relay/circuitry controlling it. At least that what it seems to be.

Eric
Old 10-01-2011, 02:45 PM
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Could it be something that keeps pluging the fuel filter?
Old 10-01-2011, 02:57 PM
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look up the thread on why my car won't start. The yellow relay and the speed relay are all part of the fantastic network of mystery that run your fuel pumps.
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Emery

1988 930 coupe - Silver Metallic
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Old 10-02-2011, 03:27 AM
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I just found a post about permatune cd causing this... it turns out my car has a permatune. The recommendation was to go with MSI.
Old 10-02-2011, 04:17 PM
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There is a subtle difference how a car quits running and this may help you. In one case the engine quits suddenly (zip, nothing) like you turned off the key and this points to an electrical issue. In the other case there is a bit of a hesitation, bucking, or slight lowering of the RPMs before it dies and this points to a fuel starvation issue. A smart mechanic told me about this and it can save you lots of troubleshooting time if you can eliminate one issue or the other. In other words it is rarely both issues at the same time.

Good Luck,
Mark
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Old 10-02-2011, 04:45 PM
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Mine did the same thing intermittently...It got worse and worse..I chked all fuses and connectins -electric tester/volt meter..(went kookoo..for awhile.) My readings would show my coil was good, then not good..etc..My distributor coil did the same thing..Changed both..And started on the 1st turn...

Walt
Old 10-03-2011, 04:53 AM
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Mark,
Thanks. Although I really already knew this, I was assuming that the fuel pump issue could act this way. After reading your comment though, I realize that I was wrong. The car dies like someone flipped a switch. I think the PermaTune may be the culprit. I found a local repair shop that the Pelicans seem to like and I will let him do the final diagnosis.

Thanks to you all for sharing your wisdom.
Eric
Old 10-03-2011, 10:17 AM
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Quote:
Originally Posted by Sandsini View Post
Mark,
Thanks. Although I really already knew this, I was assuming that the fuel pump issue could act this way. After reading your comment though, I realize that I was wrong. The car dies like someone flipped a switch. I think the PermaTune may be the culprit. I found a local repair shop that the Pelicans seem to like and I will let him do the final diagnosis.

Thanks to you all for sharing your wisdom.
Eric

I went through 3 PermaTune boxes with the same problems/symptoms as you. Switched back to the pricey Bosche box and all has been well for two plus years now...
Old 10-03-2011, 02:37 PM
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I had 2 issues like this.
1.) Car died as if you turned off a switch, but never came back to life=dead coil.
2.) Car died as if you turned off a switch, then started after a few minutes, then died a few more miles down the road, then after a few minutes started again, etc. etc. After 5 of these fit sessions it never came back to life= bad permatune CDI box, went to bosch unit, problem free for 3 years now of daily driving.

Mark

Last edited by full quack; 10-05-2011 at 08:17 AM..
Old 10-04-2011, 11:12 AM
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The problem was the PermaTune CDI box. I went back to the stock Bosch unit and am back on the road, just in time for a beautiful weekend here in SoCal.

Cheers,
Eric
Old 10-07-2011, 09:57 AM
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