Help with Carerra no start |
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Help with Carerra no start |
914ltd |
Aug 1 2011, 02:09 PM
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#1
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Member Group: Members Posts: 243 Joined: 18-April 03 From: Peoria, IL Member No.: 581 Region Association: None |
Hi guys, I have an 84 Carerra in my shop (OK, it's not a 914 but there's more talent here than some other forums) with an intermittent no start. The car has no spark then will start and run fine. I have checked the DME and coil connections but nothing else. It is getting fuel smell at the exhaust during no start. Anyone know of a condition that might cause this? Thanks, Brad Mayeur
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Ferg |
Aug 1 2011, 02:19 PM
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#2
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914 Guru Group: Members Posts: 5,948 Joined: 8-January 03 From: Boulder CO Member No.: 116 Region Association: None |
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pcar916 |
Aug 1 2011, 02:30 PM
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#3
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Is that a Lola? Group: Members Posts: 1,523 Joined: 2-June 05 From: Little Rock, AR Member No.: 4,188 Region Association: None |
DME Relay? That's always my first thought. I have both an '84 Carrera and a'95 DME engine in my 914 and I carry a spare DME relay in both cars. Other than that, the DME won't send spark out to the coil until specific sensors report in successfully... I looked at the factory electrical diagrams to see which devices are energized at each ignition switch position. |
ConeDodger |
Aug 1 2011, 02:51 PM
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#4
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Apex killer! Group: Members Posts: 23,799 Joined: 31-December 04 From: Tahoe Area Member No.: 3,380 Region Association: Northern California |
The DME relay would be my first guess. They usually just go, not intermittent but as they are only $40 or so and you should always carry a spare, I would start there.
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phatnine11 |
Aug 1 2011, 02:57 PM
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#5
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Member Group: Members Posts: 286 Joined: 22-March 05 From: Rancho Cucamonga, CA Member No.: 3,798 |
The CHT sensor! This sensor gives off very strange symptoms. Verify that the CHT is the updated 2 wire unit, this one adds a better ground.
Good luck, Phatnine11 |
scotty b |
Aug 1 2011, 03:14 PM
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#6
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rust free you say ? Group: Members Posts: 16,375 Joined: 7-January 05 From: richmond, Va. Member No.: 3,419 Region Association: None |
Order of most likely :
DME relay CDI If it has been converted over ( Had a similar issue on a Maserati Bora that turned out to be the CDI. Interestingly enough, the Bora uses the exact same CDI the 911 does (IMG:style_emoticons/default/smile.gif) ) Coil |
Cap'n Krusty |
Aug 1 2011, 03:25 PM
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#7
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Carreras with Motronic don't have CDI boxes.
The Cap'n |
r_towle |
Aug 1 2011, 03:33 PM
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#8
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Custom Member Group: Members Posts: 24,638 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States |
dme relay, cht, grounds grounds grounds.
Cap and rotor also...but I assume you checked that. Coil also. The DME relay was made when they were doing a crappy type of soldering....so was the DME itself. There are pics on Pelican of all the bad solder joints in both the relay and the DME that cause all sorts of weird conditions. If you look at the backside of many of the boards from that era of german cars you will see a discoloration and ring around the post of the resistor, capacitor etc. That ring is a break in the solder and when it gets hot, its stops contact...when cold its fine. Lovely thing to track down, but if you look at enough you can learn to see if with a magnifying glass pretty quickly. It takes ten seconds to fix them....just reheat. I did all the ones on the BMW Lights computer...took about 5 minutes...all problems gone. I just re-solders all of them (acutally had a friend do it who is really good at soldering) Its a common issue. The ignition is controlled by the DME so start there. There are a number of tests that you can do with an Ohm meter at the DME plug to help you diagnose the wiring, I suggest you may want to do that first. There are breakout boxes to test the car live while running to diagnose all the other bits, but the CHT is a simple one to do at the plug in the engine bay (provided the wiring tests out good) Those tests are in the factory manuals and in the Bentley manual also. There is a good flow chart in the bentley for "no ignition" Grounds seem to solve alot just by ensuring that certain circuits do not heat up. Steve Wong has alot of articles on the DME and Carrera FI system. I think its www.911chips.com. Rich |
914ltd |
Aug 1 2011, 08:32 PM
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#9
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Member Group: Members Posts: 243 Joined: 18-April 03 From: Peoria, IL Member No.: 581 Region Association: None |
Thanks guys, I thought the DME relay controlled the fuel pump??? since the problem seems to be spark, I passed it by. I ordered one with the hopes that cures the problem. I'll post yea's or nay's.
BTW, I cleaned all the grounds and replaced the CHT 6 months ago chasing an idle problem. Brad |
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