1985 911 - Crank, but no start.... - Dorkiphus.net
Navigation » Dorkiphus.net > Technical & Track Disussions > Porsche Technical Discussions » 1985 911 - Crank, but no start....

Porsche Technical Discussions Porsche related technical discussions and questions go here.

Reply
 
Thread Tools Display Modes
  #1  
Old 07-17-2018, 07:57 PM
Swoboda Swoboda is offline
 
Join Date: Feb 2012
Location: Baltimore
Posts: 68
Swoboda
Default 1985 911 - Crank, but no start....

Hello: I have a 1985 911 that was running great, then just stopped working.

Quick story: The car was running fine. I recently drove it to work, came home, and parked it in the garage. When I went to start it up a couple days later, it just cranked.

It doesn't start and it doesn't "catch" or "stumble".

I switched the DME relay with a new one. No change.

I switched the ECU with a known good one. No change.

I jumped the fuel pump at the fuse box and it runs.

I still have to check for spark--I'm running solo so I can't turn the key and be at the engine to check (but I will get some help soon).

Any thoughts on what it could be?

What I last had it out it was on one of those blazing hot days a couple weeks ago.

Thanks very much for any thoughts!
__________________
1985 Carrera Targa
Reply With Quote
  #2  
Old 07-17-2018, 08:46 PM
Jazzbass's Avatar
Jazzbass Jazzbass is offline
Site Admin
 
Join Date: Feb 2003
Location: Germantown, MD
Posts: 11,718
Jazzbass has eight HoF threadsJazzbass has eight HoF threadsJazzbass has eight HoF threadsJazzbass has eight HoF threadsJazzbass has eight HoF threadsJazzbass has eight HoF threadsJazzbass has eight HoF threads
Default

No start problems are usually flywheel sensors or DME relay. Try jumping the fuel pump so that you hear it running, then try to start. The fuel is a closed loop system so it’s fine to jump it for the tests.

If it starts and runs well, you probably have DME relay problem. If it tries to run but does so badly probably the flywheel sensors.
Reply With Quote
  #3  
Old 07-17-2018, 09:16 PM
Swoboda Swoboda is offline
 
Join Date: Feb 2012
Location: Baltimore
Posts: 68
Swoboda
Default

Thank you! I'll give that a shot.
__________________
1985 Carrera Targa
Reply With Quote
  #4  
Old 08-18-2018, 01:58 PM
Swoboda Swoboda is offline
 
Join Date: Feb 2012
Location: Baltimore
Posts: 68
Swoboda
Default

I tried jumping the fuel pump, and could hear it running. I tried starting the car, but still no start or even a “catch”.

I tried cranking for a good bit several times to ensure that the gas made it to the engine and I gave it a chance fire up.

Does this indicate the sensors?

Can I get access to the sensors with minimal jacking? The car’s in the garage with little space to maneuver?

Thanks for the advice!
__________________
1985 Carrera Targa
Reply With Quote
  #5  
Old 08-18-2018, 03:18 PM
VaSteve's Avatar
VaSteve VaSteve is offline
Essential Personnel
 
Join Date: Oct 2003
Location: Western Prince William County
Posts: 13,727
VaSteve has one HoF thread
Default

I always see the sensors tagged as a source of failure, but how often do they just fail? Did you swap in another DME relay?
__________________
1983 911 SC Targa - 1990 944 S2 - Past: 1986 944 n/a - "Doublemint"
"Every one drives to DE but few fly to flight school." - Vicegrip
"Sometimes arguing/reasoning w/Steve is like looking at a compass while having a 2lb magnet in your pocket." - }{arlequin
Reply With Quote
  #6  
Old 08-18-2018, 06:05 PM
Richard Curtis's Avatar
Richard Curtis Richard Curtis is online now
 
Join Date: May 2004
Location: Fairfax Station, Va.
Posts: 1,560
Richard Curtis
Default

old coils have been known to generate a weak spark over time, too weak to ignite the fuel mixture. Spark color should be blue. If any shade of yellow, orange or red, replace the coil.
__________________
Richard Curtis
Fairfax Station, Va. '93 911 C2
Reply With Quote
  #7  
Old 08-18-2018, 09:06 PM
86911TLCAB 86911TLCAB is offline
Tito
 
Join Date: Nov 2005
Location: Bristow VA
Posts: 2,025
86911TLCAB
Default

If you can get under the rear of the car you can get to the flywheel sensor.
__________________
Tito

82 911 SC with 3.2
73 RSR project
97 328is
99 328is
97 Lexus SC300 Manual

86 TL (gone)
993 (gone)
75 911S (gone)

Last edited by 86911TLCAB; 08-31-2018 at 02:07 PM.
Reply With Quote
  #8  
Old 08-19-2018, 08:06 AM
Swoboda Swoboda is offline
 
Join Date: Feb 2012
Location: Baltimore
Posts: 68
Swoboda
Default

I did swap the DME relay with a new one and, when that didn't work, I also swapped in a known good ECU.

I may have a spare coil to try.

I've have the car for 10 years and have been doing regular maintenance to it, but I've never looked at the sensors.

I'll see if I can play around with it more today.

I appreciate the suggestions and help!
__________________
1985 Carrera Targa
Reply With Quote
  #9  
Old 08-19-2018, 08:11 PM
Len 911's Avatar
Len 911 Len 911 is offline
 
Join Date: Aug 2013
Location: Baltimore MD
Posts: 305
Len 911
Default

I have an 85 also...had the same problem and it was the sensors on the flywheel..wasn't to bad of a job...I used the BMW sensors way cheaper and are the same..
Good luck
Reply With Quote
  #10  
Old 08-20-2018, 09:30 AM
86911TLCAB 86911TLCAB is offline
Tito
 
Join Date: Nov 2005
Location: Bristow VA
Posts: 2,025
86911TLCAB
Default

I recently swapped out the camshaft sensor in my e36...I decided to strip the wire to see what it looked like inside...and basically the covering on the individual wires was crumbling and wires were shorted in spots...so these things live in a hot environment and like anything else can eventually cease to function...
__________________
Tito

82 911 SC with 3.2
73 RSR project
97 328is
99 328is
97 Lexus SC300 Manual

86 TL (gone)
993 (gone)
75 911S (gone)
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump