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I've looked thru my Bentley and I can't seem to find any mention of a crank position sensor. I am dealing with a 3.0 sc engine and not a 3.2.

Are you guys sure that there are crank sensors on the 3.0L engine?, and if so, where are they located?
Thanks
hughc
Old 10-11-2017, 03:59 PM
  Pelican Parts Technical Article Directory    Reply With Quote #41 (permalink)
Hey, nice marmot.
 
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Quote:
Originally Posted by RLJett View Post
You might want to jump to the end of that thread I provided above. His issue ended up being 1 or both crank sensors going bad once heat soaked. I believe there was a procedure where you could check the resistance cold and then hot to see it the sensors are failing once hot. Seems easy enough to try before sending your CDI anywhere.
There are no crank position sensors on a 3.0. Itís CIS, not Motronic EFI.
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'83 911 SC 3.0 coupe (NA)

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Old 10-11-2017, 07:11 PM
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Thank you Tim. It's unfortunate that there are dullards out there that feel they should respond to every posts even when their suggestions are way off base. As much as we like to learn it's a huge waste of time following up on recommendations that will get us absolutely nowhere. Rant over.
hughc
Old 10-12-2017, 10:33 AM
  Pelican Parts Technical Article Directory    Reply With Quote #43 (permalink)
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Quote:
Originally Posted by hughc View Post
Thank you Tim. It's unfortunate that there are dullards out there that feel they should respond to every posts even when their suggestions are way off base. As much as we like to learn it's a huge waste of time following up on recommendations that will get us absolutely nowhere. Rant over.
hughc
Lighten up Francis. He's trying to help you. Most of us don't fix porsches for a living so we rely on the community for helpful suggestions. Each suggestion has to be taken
With a grain of salt.
Old 10-12-2017, 11:50 AM
  Pelican Parts Technical Article Directory    Reply With Quote #44 (permalink)
Hey, nice marmot.
 
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Quote:
Originally Posted by hughc View Post
Thank you Tim. It's unfortunate that there are dullards out there that feel they should respond to every posts even when their suggestions are way off base. As much as we like to learn it's a huge waste of time following up on recommendations that will get us absolutely nowhere. Rant over.
hughc
I feel your pain but Iím not going to throw stones. Iíve been wrong before when I had good intentions.
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'83 911 SC 3.0 coupe (NA)

You can't buy happiness, but you can buy car parts which is kind of the same thing.
Old 10-12-2017, 06:01 PM
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Would be nice if this forum had a Like/Thank feature which would allow people to see the "Knows-His-*****" factor of any poster.
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82 911 SC targa
Old 10-13-2017, 06:55 AM
  Pelican Parts Technical Article Directory    Reply With Quote #46 (permalink)
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All right guys, I'll admit I was a bit harsh in my last post, and my apologies to anyone that may have been offended.
As you all know, it sometimes gets to be more than just a little frustrating when chasing a problem; and being sent on a wild goose chase doesn't make it any more pleasurable.

BTW who's Francis?

hughc
Old 10-13-2017, 10:50 AM
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No prob. Frustrating can be putting it mildly.

https://www.youtube.com/watch?v=0OnpkDWbeJs
Old 10-13-2017, 05:16 PM
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I knew I shouldn't have asked.
Old 10-13-2017, 09:39 PM
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Originally Posted by hughc View Post
Very, very, very frustrating. Things just seem to be going from bad to worst.

I removed the alternator from the vehicle and had both it and the VR checked by a professional shop and they both checked out OK, although I was told the brushes on the VR were wearing quite badly. The alternator was replaced app 20K mi ago, according to work records but I was also told the slip rings were noticeably worn.
So with the alternator and VR checking out OK that system can probably be eliminated as the cause to the fluctuating tach, but I do have a new VR on the way and will install it as I receive it.

What's even more frustrating now is that the engine is shutting of as I drive it. I went for a drive today and the engine quit at least 8 times. In every case I just had to turn the key off and restart the engine, no problem. Twice I pulled over and came to a stop, did not touch the key, just left everything as is, then with a voltmeter I verified that there was 12v to the FP relay and that was good. What I neglected to notice was whether or not the fuel pump was running (before I removed the relay). As it turned out I replaced the relay and the car started immediately.

So there appears to be an occasional electrical glitch that is causing the engine to quit, but where to look.
As mentioned earlier in my post the CDI unit was recently rebuilt by Bob Aschroft so I don't suspect that unit but I suppose any related wiring might at fault.
Any and all suggestions will be appreciated.
Thx
hugh
The problem you describe is typical of a CDI component failure as the CDI heats-up causing the
main CDI internal switching device to 'latch-up' (doesn't turn-off), requiring the ignition switch
to be cycled (turned off then on). The problem will continue until the CDI fully cools down.
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Old 10-17-2017, 09:12 PM
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Thx Dave. Other posters are of the same opinion and I may eventually send the CDI unit out to be checked but I have a few checks that I'd like to do before hand. I was out with the car today to run a few errands and it ran flawlessly ie no quitting.
I'll drive it some more until it quits then I'll be able to verify (confirm) there is voltage at the FP relay.

I suppose there is a remote possibility the ignition switch is at fault and by confirming there is voltage at fuse 16 would eliminate the switch.
Old 10-18-2017, 09:53 AM
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A little update. I've been out with the sc a few times this week (daily, actually) and it quit several times. The temperatures have been somewhat cooler here and the engine temp. didn't get up to normal and it still quit leaving me to wonder if the problem is actually temperature related.

But here is a real puzzler. Twice the engine quit. I knew it quit as there was no reaction to pushing on the accelerator. I immediately pushed the clutch in and started coasting to where I might stop to do a voltage check at the FP relay. I hadn't turned the key off and before I came to a stop the engine started on its own. I just pumped the accelerator a few times, downshifted and carried on.

I'm sure some of you guys will think I'm full of poop but that's the way it happened.
How can that be possible?

hughc
Old 10-21-2017, 02:07 AM
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Not sure what just happened here but I had almost finished my latest posting then lost it.
In any event I did send the CDI box away for verification and it checked out OK. Rather than send my unit back to me, Mr. Ashlock sent a replacement unit that he knew to be good.
I installed it today and after two try's, the engine fired right up but the idle was lumpy and backfired quite a bit, The idle was not as healthy as it had been and eventually died.
This was odd of course and I'm sure not at all related to the CDI.
It feels like the problem might be caused by an air leak of some sort.
While I was back there I also replaced a heat blower fan unit and I may have disturbed a vacuum line, so that will have to be followed up on.
Another possibility might be air leaking past the pop- off valve which I installed earlier this summer. I'll have another look at that as well.
I have read on the forum that if the CIS system is perfectly set, there should be no need for a pop- off valve, but I guess since I now have it Ill have to live with it and try to be sure that it isn't leaking.
Anyway, our snow season is just around the corner and I'd really like to get "Eva" sorted out before she's put away for the winter.
I'll keep you updated as to what I find.
Thx
Old 11-23-2017, 03:52 PM
  Pelican Parts Technical Article Directory    Reply With Quote #53 (permalink)
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Quote:
Originally Posted by hughc View Post
I have read on the forum that if the CIS system is perfectly set, there should be no need for a pop- off valve, but I guess since I now have it Ill have to live with it and try to be sure that it isn't leaking.
In theory, based on guys that know more than us. If you are a DIY guy like me, are we that good?

It ain't an air leak. If you have an air leak it ain't killing your car.

I am guessing but if your box is good, wiggle the shiet out of the green wire.

Ignition switch electrical component?

This sounds like CDI failure. My Permatunes would not start for 15 mins though. Not sure if Bosch is the same with heat soak. Send to Dave? He is probably able to stress it to induce failure. I would get a second opinion.
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Old 11-23-2017, 04:49 PM
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I decided to start from scratch and verify fuel pressure as per "CSI for Dummies" by Tim. Thank you Tim
Here's what I have.
1983 SC US model
WUR model 090
Ambient temp: 13 C
WUR resistance:25 C
System pressure: 76lbs
Cold control pressure :13 lbs
Warm control pressure: 45lbs after 5 min
Residual pressure: After 5min 35lbs
After 10 min, missed it
After 15 min, 28lbs
After 30 min, 24lbs
After 60 min, 21 lbs

I don't think anything here was way off so I decided to fire it up once again.

First attempt; it died immediately after starting.
Second attempt; a loud back fire.
Third attempt; it fired up and stayed at a reasonable idle. It continued to idle reasonably well and after 2or3 min I attempted to give it a bit of throttle at which point there was a loud back fire and it quit. Go figure.

That's where it stands. Sure is puzzling as it wasn't doing that before I sent the CDI box away to be checked.

Unless somebody comes up with something else to check I'll seriously have to consider sending the CDI box back for another look-see.
Thx
Old 11-27-2017, 02:50 PM
  Pelican Parts Technical Article Directory    Reply With Quote #55 (permalink)
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I've yet to receive my original CDI box to try on my engine but to be truthful I'm not holding out much hope that it will correct the current problems.

I was hoping someone with more experience would pick up on this thread and offer suggestions that I hadn't thought of. Is there anything else more obvious that I should be checking?. Really at a lost at this point.
Thx
Old 12-02-2017, 02:27 AM
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Quote:
Originally Posted by hughc View Post
A little update. I've been out with the sc a few times this week (daily, actually) and it quit several times. The temperatures have been somewhat cooler here and the engine temp. didn't get up to normal and it still quit leaving me to wonder if the problem is actually temperature related.

But here is a real puzzler. Twice the engine quit. I knew it quit as there was no reaction to pushing on the accelerator. I immediately pushed the clutch in and started coasting to where I might stop to do a voltage check at the FP relay. I hadn't turned the key off and before I came to a stop the engine started on its own. I just pumped the accelerator a few times, downshifted and carried on.

I'm sure some of you guys will think I'm full of poop but that's the way it happened.
How can that be possible?

hughc
Don't think you made it up but it's only possible if;

A. Your clutch wasn't fully disengaged and it was turning the motor over
or
B. Your starter engaged by itself
or
C. Gremlins
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Old 12-02-2017, 02:44 AM
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Thank you Gary, The darn gremlins worry me and I wonder if I'll ever be completely rid of them.

What's concerning me the most at the moment is the way the engine is behaving when I start it up and it's refusal to keep running.
I would like to think it's something quite simple but I'm not experienced enough to figure it out.

I do have someone with more engine experience that will come to have a look at it (when he has time) but until then I'll wait for my new CDI box and hope for the best after I install it.
Cheers
Old 12-02-2017, 07:22 AM
  Pelican Parts Technical Article Directory    Reply With Quote #58 (permalink)
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