Can I test the green wire?
Thread Starter
Instructor
Joined: Jun 2005
Posts: 194
Likes: 2
From: Lakewood, CO
Can I test the green wire?
is there a way to test the green wire on my '81? It looks fine but everything else checks out. I mention what I have done so far in my other thread "'81 revival" but wanted to start a new thread since this is a specific question. I have replaced the fuel pump and have 30psi at the rail. I checked the Injection relay and it is working, I can hear it and when I energize it the current flows properly. I have hooked up a noid light to one of the injectors and it flashes as I crank the engine but it looks weak. Basically I am at the point where I am starting at the beginning and re-checking everything but the one thing that I don't know how to test is the green wire.
Thanks.
Thanks.
Team Owner
Joined: May 2004
Posts: 31,333
Likes: 4,289
From: Philly PA
to test the green wire install a new green wire then turn the key.
If the engine starts then your old green wire was bad.
Otherwise if your green wire is faded tan, brown, black ,or the insulation is cracking ,
or the connector ends are crumbling its time to replace it
If the engine starts then your old green wire was bad.
Otherwise if your green wire is faded tan, brown, black ,or the insulation is cracking ,
or the connector ends are crumbling its time to replace it
Last edited by Mrmerlin; Aug 27, 2013 at 05:30 PM.
Team Owner
Joined: May 2004
Posts: 31,333
Likes: 4,289
From: Philly PA
It would be nice if the wire was less expensive,
BUT since its Bosch parts its also Bosch quality,
and thus it will last another 25 years without causing further running issues,
That should save a few towing bills,
pay now or pay later
BUT since its Bosch parts its also Bosch quality,
and thus it will last another 25 years without causing further running issues,
That should save a few towing bills,
pay now or pay later
Three Wheelin'
Joined: Nov 2003
Posts: 1,481
Likes: 1
From: Doylestown, PA
I despise replacement mechanics as I am a cheap SOB. I can't see why you can't check resistance while bending the wire and wiggling the terminals.
Rennlist Member
Joined: May 2003
Posts: 3,402
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From: Bristow, VA
I don't mind replacing a part I've tested, but really a wire is a wire, it is a conductor bundle that meets a set of specifications, it isn't magic. I play with RF generators and plasma systems for a living, this can't be harder.
Team Owner
Joined: May 2004
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From: Philly PA
FBIII I think your terms are conflicting.
What you should say is that you hate replacement technicians.
These guys just swap in new parts and could not fix any of the parts they remove.
A mechanic is capable of fixing subsystems and parts of them.
AND,
is also smart enough to know when fixing a broken wire without replacing it is only going to cause issues after the engine is running when it leaves his shop.
Like after a car wash or rain storm,
how many times have you read that thread,
I washed my car and now it wont start
It will only take one tow truck trip to pay for a fouled green wire, when its old and cracked and the ends are crumbling its time for a new part, plain and simple.
The damage to the wire is what you cant see on the inside of the insulation.
I am quite capable of fixing many things on the 928 instead of replacing many of the parts they contain..
HOWEVER I am also smart enough to KNOW that the green wire is best replaced with the new correct part , as there isnt any such wire thats been capable of a substitute that will perform flawlessly for another 25 years like the original Bosch part will do...
So please dont think that I am being smug with my answers,
I have spent more than a few times chasing ignition issues only to find that the cause is a bad signal being sent to the computer, and installing a fresh Bosch green wire makes the engine run perfectly, and for quite a few years to boot
What you should say is that you hate replacement technicians.
These guys just swap in new parts and could not fix any of the parts they remove.
A mechanic is capable of fixing subsystems and parts of them.
AND,
is also smart enough to know when fixing a broken wire without replacing it is only going to cause issues after the engine is running when it leaves his shop.
Like after a car wash or rain storm,
how many times have you read that thread,
I washed my car and now it wont start
It will only take one tow truck trip to pay for a fouled green wire, when its old and cracked and the ends are crumbling its time for a new part, plain and simple.
The damage to the wire is what you cant see on the inside of the insulation.
I am quite capable of fixing many things on the 928 instead of replacing many of the parts they contain..
HOWEVER I am also smart enough to KNOW that the green wire is best replaced with the new correct part , as there isnt any such wire thats been capable of a substitute that will perform flawlessly for another 25 years like the original Bosch part will do...
So please dont think that I am being smug with my answers,
I have spent more than a few times chasing ignition issues only to find that the cause is a bad signal being sent to the computer, and installing a fresh Bosch green wire makes the engine run perfectly, and for quite a few years to boot
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Three Wheelin'
Joined: Nov 2003
Posts: 1,481
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From: Doylestown, PA
I was referring to the process not the individual. As far as his wire is concerned we do not know it is damaged. All we know is what has been replaced. And until someone convinces me otherwise a green wire is a wire and can be tested for resistance. We all been dabbling with 928's for some time. It is quite possible I have been dabbling with them quite a bit longer than even you.
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Thread Starter
Instructor
Joined: Jun 2005
Posts: 194
Likes: 2
From: Lakewood, CO
ok, ordered a new green wire. With 2 cars one is bound to be ready for one either way. The one on the '81 is definitely more brown than green so I will swap it out and report back.
Rennlist Member
Joined: May 2003
Posts: 3,402
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From: Bristow, VA
No smugs or abrasives intended or taken, replacement of the green wire right now is a relatively easy option, but I'm thinking down the road Bosch will quit supplying the things. Similar wires exist on several vintage Porsches and I think it will be advantageous to end source a replacement someday.
Former Vendor
Joined: Feb 2005
Posts: 15,228
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From: Anaheim
There are some pieces that are cheaper to just replace, instead of sitting around trying to figure out what "could" be wrong. Labor/thinking/tracing problems is expensive.
Here's how I determine if I put in a new green wire:
If there is voltage at the coil and there is no spark....it gets a green wire.
That only fixes 99% of the cars....but it also only costs about $15 worth of my time to come to that conclusion....and another $15.00 worth of time to install a new green wire. Pretty cheap repair......for a 99% return. (I use 99% as just an estimate of the cars, which did not have spark, that the green wire repaired. I've never seen a bad C/D unit in an early car. I've only ever seen 1 bad "coil" inside the distributor, which generates the signal. The remainder that had voltage at the coil, yet no spark, were all green wire problems.)
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From: Double Oak, TX
The issue with replicating the Green wire is the connector at the distributor - John Speake had a replacement and I sold it for a while but continued production was dependent on receiving a useable core connector.
They were mostly none usable and the replacement wire died a natural death.
At $128 this is a part that should be replaced on all cars of that era if they have the original.
The same as replacing the CPS on the later cars.
They were mostly none usable and the replacement wire died a natural death.
At $128 this is a part that should be replaced on all cars of that era if they have the original.
The same as replacing the CPS on the later cars.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission?
George Layton March 2014928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
Nordschleife Master
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From: North Country
Banned
Joined: Apr 2013
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From: Humble, TX
I couldn't agree more. As I was doing an intake refresh, I discovered the green wire was held together with black tape and rotten at both ends. So Roger sent me a new old and I added new plugs, wires, cap and rotor and refurbed injectors from Witch Hunter. It runs great with no hesitation, but the engine seems to like 27 degrees advance much better than 23 degrees.
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From: Up Nort
I was referring to the process not the individual. As far as his wire is concerned we do not know it is damaged. All we know is what has been replaced. And until someone convinces me otherwise a green wire is a wire and can be tested for resistance. We all been dabbling with 928's for some time. It is quite possible I have been dabbling with them quite a bit longer than even you.
I gave the green wire off my 79 to a friend that is an EET with every known piece of testing equipment short of a NASA lab. He found nothing wrong with it yet replacing it fixed my WOT miss. Put the old wire back on.... the miss returned.
It's a wear item that lasts 25+ years that gives the source signal for your fuel and ignition.
My time is money, the effort that goes into testing one of these pales in comparison to the cost of the wire and the length of time to replace it. The ratio goes through the roof for most 928 owners that pay someone to work on their cars.