Home  |  Forums  |  914 Info  |  Blogs
 
914World.com - The fastest growing online 914 community!
 
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG. This site is not affiliated with Porsche in any way.
Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners.
 

Welcome Guest ( Log In | Register )

> Help with Carerra no start
914ltd
post Aug 1 2011, 02:09 PM
Post #1


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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
 
Reply to this topicStart new topic
Replies(1 - 8)
Ferg
post Aug 1 2011, 02:19 PM
Post #2


914 Guru
*****

Group: Members
Posts: 5,948
Joined: 8-January 03
From: Boulder CO
Member No.: 116
Region Association: None



DME Relay?

http://forums.pelicanparts.com/porsche-911...rt-problem.html
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
pcar916
post Aug 1 2011, 02:30 PM
Post #3


Is that a Lola?
***

Group: Members
Posts: 1,523
Joined: 2-June 05
From: Little Rock, AR
Member No.: 4,188
Region Association: None



QUOTE(Ferg @ Aug 1 2011, 12:19 PM) *

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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
ConeDodger
post Aug 1 2011, 02:51 PM
Post #4


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.
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
phatnine11
post Aug 1 2011, 02:57 PM
Post #5


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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
scotty b
post Aug 1 2011, 03:14 PM
Post #6


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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
Cap'n Krusty
post Aug 1 2011, 03:25 PM
Post #7


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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
r_towle
post Aug 1 2011, 03:33 PM
Post #8


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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post
914ltd
post Aug 1 2011, 08:32 PM
Post #9


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
User is offlineProfile CardPM
Go to the top of the page
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



- Lo-Fi Version Time is now: 31st October 2024 - 05:20 PM