Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Registered User
 
Join Date: Apr 2016
Posts: 15
Engine starts when releasing ignition (key)

Hi. I need some help. I recently had my engine out of the car to change clutch and some other work (cleaning, replacing some parts). It is a 911 SC from 1980.

After it wouldn't start and backfired a few times.
There was only a spark on random occasions. We started to troubleshoot the ignition system. The coil, distributor and wires looked good. We suspected that the CDI box was the problem.

But today the engine started easy, but the idle was quite high (2000rpm) at first but dropped and now she runs like before.

But there is one strange thing, the engine does not start till you release the ignition (key). On ignition is cranks over, and when you release it the engine starts.

Is this normal? What can be the problem, we didn't change anything related to the ignition. And I have double checked that all the wires are connected correctly. Have i missed anything?

//Wenta

Old 04-15-2016, 04:24 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
grateful user
 
don gilbert's Avatar
 
Join Date: Mar 2008
Location: collierville tn
Posts: 1,336
Garage
Did you hook the main ground from trans mount to body up?
__________________
fully disassembled, blasted, customized and restored 75 targa with factory hard top, 993 style turbo ft fenders, steel flares, C2 bumpers and rockers, 82 3.0 sc 9.5/1 engine with PMS flywheel, 964 cams, flowed heads, ssi's short geared 915 w/lsd, polybronze, bilstein,working lambda, modified and highly tuned cis, tensioners, pop valve, backdated exhaust and heater, 2300 lbs. no bolt left untouched. 1970 911E. Nice car but needs a re-do.
Old 04-15-2016, 10:23 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Apr 2016
Posts: 15
Yes, the transmission ground is connected
Old 04-15-2016, 12:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Registered
 
Join Date: Sep 2002
Location: Metro NY
Posts: 2,995
Garage
I'm actually having a related problem (but I haven't fixed it, so take that into account.:-) )

Pull your harness plug from the bottom of your CDI box and check for battery voltage at pin 15 when the key is on. That tells you that power is getting to the CDI when it should to run. Now have someone crank the engine and make sure you still battery voltage at the same pin. If you don't, it means somehow your car doesn't have spark while cranking. You may have a bad connection that, under the load of the starter, doesn't want to power your CDI pin. Since you had the engine out recently, it's reasonable to start second-guessing your battery to starter cable connection, the starter-to-alternator on the same post, or the alternator to relay panel wire. As the other poster suggested, the ground from tub to trans could be suspect too.

Start there and good luck.

Here's a great link: Coil fire check
__________________
Ken
1986 930 2016 R1200RS

Last edited by gsxrken; 04-15-2016 at 03:17 PM.. Reason: Added link
Old 04-15-2016, 02:32 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
Join Date: Apr 2016
Posts: 15
Thanks! I will test that next week (My car is at my fathers place)

Good luck with your car :-). And please post if you find the problem.
Old 04-16-2016, 01:07 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered
 
Join Date: Aug 2015
Posts: 2,752
Garage
Did you reverse the cold start injector/sensor plate wiring connectors on the back of the engine?
Old 04-16-2016, 04:51 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Registered User
 
Join Date: Apr 2016
Posts: 15
Which connector is that?
Old 04-16-2016, 06:09 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
non-whiner
 
mreid's Avatar
 
Join Date: Aug 2012
Location: Slightly right of center
Posts: 5,235
Sounds like a bad ignition switch to me.
__________________
"Too much is just enough."
Old 04-16-2016, 08:24 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered
 
Join Date: Aug 2015
Posts: 2,752
Garage
Quote:
Originally Posted by wenta View Post
Which connector is that?
There's two connectors one for the cold start valve and one for the sensor plate they can be easily confused because they're both blue plastic fuel injection plastic.

what is the blue connector on the sensor plate for

Last edited by gomezoneill; 04-16-2016 at 12:59 PM..
Old 04-16-2016, 12:56 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Author of "101 Projects"
 
Wayne 962's Avatar
Quote:
Originally Posted by gsxrken View Post
You may have a bad connection that, under the load of the starter, doesn't want to power your CDI pin. [/url]
I agree, that's the first place I would look, and it's an important clue. Check the operating voltage on that CD box, both with the car running and without, and also during starting. I suspect you have a grounding problem.

-Wayne
Old 04-16-2016, 09:10 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
Join Date: Apr 2016
Posts: 15
Update

Hi thanks for all the answers so far. But she still isn't starting. The CDI gets voltage when the ignition. But when I turn it to crank the voltage disappears. We checked and fixed the transmission ground, and the ground next to the cdi box, tried without starter motor just to see if the box gets voltage. Nothing have worked so far.

The cold start injector/sensor plate wiring connectors are correct, they does not fit eash over on my car.

I have studied the wiring diagram and it looks like wire number 50 is the one that goes out from the ignition when starting. But it only seams to go to the fuel relay. Where does the signal to the cdi come from?
Old 04-18-2016, 09:37 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered User
 
Join Date: Apr 2016
Posts: 15
Problem found!!

It was a problem from when we removed the old alarm. We put the ignition cable on the wrong fuse. That she started before we did the engine must have been luck.

Thank you all for the input. The summer is saved :-)

Old 04-21-2016, 09:24 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
 
Reply


 


All times are GMT -8. The time now is 05:09 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.