CRBennington

Made a post about 3 months ago about intermittent starting with my 1987 951. Somewhat overnight, my starting went from being extremely consistent to being about 1 in 5 or so...And eventually no start, although it would turn over and push starting always worked. Replaced the DME Relay and the battery, but the problem continued. Fellow Rennlisters suggested that I replace the starter. The weather turned to crap, my time has been non-existent, and the 951 fund was empty. Basically, the car has sat for 3 months.

As of late, I've got a bit more time and money. However, it seems that the weather has been the deal breaker. Here in central Texas, we've been over 100 for basically 3 straight months. Now that the weather has cooled down, so does has my car's foul mood. Over the last 3 days, starting is 11 for 11. Any ideas what would cause the car to not start specifically during hot weather?

Black51

When the car doesn't start, is there any tach bounce? My bet is speed/ref sensors.

CRBennington

I'm trying to remember. I think possibly there was, but now that it is starting consistently, I can't say for certain. Any easy test for this?

This guy? http://www.pelicanparts.com/cgi-bin/...r%29%2C%20Each

Black51

Yes. Easy test is when you turn the engine over, watch for tach bounce while the starter cranks and before the engine fires. If the car fires, you'll get tach bounce. If the car doesn't fire, you might still get tach bounce, and you might not. If there is no tach bounce, then I would suspect the speed/ref sensors. If there is tach bounce, then the problem lies elsewhere.

gregeast

Speed/ref sensors is a good place to start, if it's not that then take a look at this thread of mine about repairing a solder break on the DME board.

I had similar, random no start (and even died while driving) issues. Don't know that ambient temp would have much of an affect with this issue but it's something for you to investigate at least.

JJK78

yeah like they said - reference sensors. Next time you have the no start an easy way to check is to have someone turn the car over while you tighten/jiggle the reference sensors connectors at the back of the motor, that will usually get em to fire right up.

Ronin-951

+1 on the Ref sensor eyeball test first, Second, I would try a new or known good DME relay, thats the only spare part I carry in the car at ALL times. Third, since your not driving the car - Pull the DME computer out and send it to 944online [a sponsor and Good Guys] for a resolder - and Yes, the DME board problem is all about heating and cooling causing expansion and contraction of a 'cold' solder joint.

zerMATT951

IIRC, the original no-start issue was more of a "starter won't turn the motor over" issue. Has it migrated to a different problem? Not sure why the battery would need to be replaced if the battery & starter are turning the motor over?

So... if it's just cranking and cranking (motor turning), definitely look at tack "bounce" first to make sure the sensors are working.

Black51

He said that it turns over.

EDIT: By the way to the OP, if your car has a cat, you'll ruin it by push starting the car. If it doesn't have one, then disregard that.

spanky

How timely. I am going through this also . The 1st indication of a problem was the engine shutting down as I was going down Hwy 17 last sunday 9/4 @ 65/70 mph. As I was going down hill for awhile coasting I restarted the engine while coasting, finished the drive home with no futher problems, parked the car. 2 hrs later I wemt to move the car in the driveway and it would not start. The starter rotates the engine as it should but a none start was the end results. I forgot to look for tach twitch while doing this. The next morning I attempted to start it and it starts as if last nite never occured. Every day I would test it by starting it up and each time it started. This past Sunday I did a short drive to the store. Car would not restart in the store parking lot. Changed out the DME relay to a brand new unit, still will not start. Rolled back the carpet covering the DME's , grabbed both the KLR & DME wire harnesses and moved them ever so slightly. Presto Start up occurs. I think I will start there at both harnesses ( possible bad conn/ wire/ ) and also change out the 2 referance sensors. Will post an update as soon as i find the problem.

Tom M'Guinn

I think we should change our collective terminology to tach "twitch" rather than "bounce." It's a pretty meager little bounce, at least in my car. Anyway, if push starting the car works every time, then all things equal that would point to something other than the ref sensors. Easy enough to check for the twitch to know for sure.

CRBennington

Didn't know about the cat, thanks for that tidbit.

Sounds virtually identical. I'll probably go through and check harnesses tonight. It really blows when you start up fine, drive 45 minutes away, and then listen to it turn over endlessly and not start on the return trip.

I checked this morning and am definitely getting a nice little twitch just prior to starting.

Didn't know when the previous owner had last replaced the battery, just one less thing to be unsure of.

Missed the multi-quote, but I did put a brand new DME relay in.

JJK78

I am a bit confused here, but how exactly can push starting a car ruin a cat?

Unless you are talking about a real cat under a wheel or something, I could see that...

CRBennington

If that cat is under there chewing on wires and hoses, it deserves to die. Like we all need more mystery problems to track down...

Black51

Unburnt fuel is not good for a cat(alytic converter).