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Talby
Joined: 05 Aug 2015 Posts: 8 Location: Montana
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Posted: Wed Aug 05, 2015 2:50 pm Post subject: Ignition troubleshooting--Need Advice |
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Okay, so for the past eight or nine months I have been trying to get my car back on the road after what seemed like her final day. During a late night drive the engine died after rolling up to a four way stop and would never start again. At first I thought it was a fuel pump issue, and so I replaced the relay and jumped the wires to see if the pump was functioning. It was. So I thought it might be an issue with the coil and promptly replaced it. Still nothing. I noticed the later models did not have ballast resistors on the side of the coil but resistor wire instead, but they both read the correct resistance give a tenth of an ohm. After sorting through several more possible issues and addressing them properly, as well as spending countless hours scratching my head over the electrics flow chart in a haynes manual, I believe I found the hay in the needlestack.
Tadaa
For some reason the previous owner spliced this connector into the old circut between the distributor and the ignition unit, and I found that one side no longer has continuity
My question is does anyone know where I could get a new one or am I going to have to strip it out of a salvage car. I am not even quite sure what it is called but the connector is molded directly onto the wires so I can't exactly strip them back and adjust the connections. Any alternatives would be helpful too--tempted to cut it open with a hacksaw at this point. _________________ "The phoenix asteroids..." |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Wed Aug 05, 2015 10:11 pm Post subject: |
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We replaced this in its entirety in our racecar.
We found some small (smaller than normal) spade terminals would fit onto the terminals on the distributor, once cut down (and properly insulated from eachother).
For the wire itself, ideal would be a shielded, twisted-pair wire. Probably have to source this from a real electronics store, such as Newark Electronics or Allied Electronics. I don't know that Radio Shack would have it. We scrounged ours from work.
Connectors at the ignition box are nothing special, just normal spade connectors.
Hope that helps. _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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fiat22turbo
Joined: 18 Jan 2006 Posts: 4040 Location: Portland, OR
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Posted: Thu Aug 06, 2015 4:19 am Post subject: |
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DIYAutone.com has the shielded wire, since its used in ignition solutions. _________________ Stefan
1979 924 Carrera GTS (clone-ish)
1988 944 Turbo S (Silver Rose) |
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RC
Joined: 25 Mar 2007 Posts: 2636 Location: Australia
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Posted: Thu Aug 06, 2015 12:14 pm Post subject: |
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That connector and infamous green wire are a commonly occurring problem on these and other similar vintage Porsches. Replacement connectors are AFAIK unavailable from Porsche or Bosch dealers.
The easiest & cheapest option involves fitting 2 of 1/8" female spade connectors to the existing green wire, if it is in good condition, and isolating & insulating with heat shrink tubing.
Another better solution is to solder wires directly to the male terminals on the distributor and use a weatherpac type sealed connector to join to the green wire. Note that the green wire is actually a shielded cable, earthed on the outer sheath, signal on inner. Substitute replacement cable, in varying quality grades will be easily available at any good electronics shop.
Pay attention to the polarity as the engine will still run either way but timing will vary and probably run like crap the wrong way around.
See these threads for more details & pics.
http://www.924board.org/viewtopic.php?t=24998
http://www.924board.org/viewtopic.php?t=28398 _________________ World`s quickest 924 2L slushbox
Allan @ DTA wrote: | I have no issue with superchargers, they are for guys who want to drive a car rather than talk about horsepower with their baseball cap on backwards |
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Talby
Joined: 05 Aug 2015 Posts: 8 Location: Montana
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Posted: Sat Aug 08, 2015 7:50 am Post subject: |
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Thankfully the green wire was still good up to the connector--that was the reason it took me so long to find the problem in the first place. I can just strip it back and re-use it rather than having to buy more fancy low impedance wire. The route with two 1/8 female connectors was the path I had figured to be the most feasible at this point. I butchered the old connector with a hack saw to make sure it really was just 2 tiny spade connectors but I live in a pretty small town and these are even sort of difficult to come by. Where are Weatherpack connectors sold and how much would they run cause I start college in a couple weeks and lets just say I dont have much spare change laying around right now. _________________ "The phoenix asteroids..." |
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924RACR
Joined: 29 Jul 2001 Posts: 8794 Location: Royal Oak, MI, USA
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Posted: Sat Aug 08, 2015 9:32 pm Post subject: |
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McMaster-Carr (mcmaster.com) is an excellent place to buy any basic electrical connectors etc, along with fasteners in general. I just got a couple of sets of weatherpaks from them myself, for my racecar.
Only problem you'll have is crimping them; they require a special tool. Maybe if we can locate some already with pigtails (already wired, with loose ends) you could splice these in as needed. _________________ Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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Talby
Joined: 05 Aug 2015 Posts: 8 Location: Montana
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Posted: Thu Aug 13, 2015 5:43 am Post subject: |
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So I found some 1/8 female spades the other day and made a new connection.
Apparently this wasnt the whole problem, so I did a little more searching and fount that a small black wire travels from the starter motor to the 1.5 ohm resistor wire. Not sure what purpose this serves but the schematic shows it would only send voltage to the coil while starting the vehicle.
It looks to have been rubbing against the heat shield which eventually caused it to melt and break in two so I spliced a new wire directly to the 3 pole connector by the battery compartment. Sadly, she still didnt start after all that and now I have absolutely no idea what to do.
When I attached a gap tester to the wire leading to the distributor cap I could get a spark when turning the key on and off, but when the engine is turning over it doent seem to spark at all. I assume that it would but at this point I am not sure of anything (my knowledge is limited to good old fasioned points and condensers).
Again, any advice is more than welcome. _________________ "The phoenix asteroids..." |
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maybeoneday
Joined: 09 Dec 2013 Posts: 82 Location: Melbourne, Australia
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Posted: Thu Aug 13, 2015 5:51 pm Post subject: |
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resistor wire is so the coil does not get the full battery voltage and create a mega spark that burns everything out. Modern coils are internally resisted and as such dont need it, if you took out the wire you would have to replace the coil with an internally resisted one. Hope that helps explain it. _________________ 1977 924 NA Auto |
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Talby
Joined: 05 Aug 2015 Posts: 8 Location: Montana
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Posted: Thu Aug 13, 2015 11:39 pm Post subject: |
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How much voltage should I have at the coil? Last time I measured around 6.5 vdc but that seems like not enough with the amount of resistance at the cap, rotor, and plug wires _________________ "The phoenix asteroids..." |
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maybeoneday
Joined: 09 Dec 2013 Posts: 82 Location: Melbourne, Australia
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Posted: Fri Aug 14, 2015 12:38 am Post subject: |
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Talby wrote: | How much voltage should I have at the coil? Last time I measured around 6.5 vdc but that seems like not enough with the amount of resistance at the cap, rotor, and plug wires |
I have been having a little trouble working this out for a points ignition, however from my research something over 5v is probably ok and what to expect. I have 7.5v but my ignition is not 100% either, however I do have strong spark on 2 cylinders so I think my coil voltage is ok. Remember that the primary and secondary windings in the coil step up the 6.5v voltage to something like 35kv at the lead to the dizzy.
I think that wire to the starter is a trigger wire to tell the starter when to energise. That is, without looking at a wiring diagram i think from its size and where it goes thats what it is (I hate looking at wiring diagrams). _________________ 1977 924 NA Auto |
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Talby
Joined: 05 Aug 2015 Posts: 8 Location: Montana
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Posted: Fri Aug 14, 2015 5:28 am Post subject: |
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Quote: | I have been having a little trouble working this out for a points ignition, however from my research something over 5v is probably ok and what to expect. I have 7.5v but my ignition is not 100% either, however I do have strong spark on 2 cylinders so I think my coil voltage is ok. Remember that the primary and secondary windings in the coil step up the 6.5v voltage to something like 35kv at the lead to the dizzy. |
The problem with my situation is that I dont have spark at any of the cylinders and when turning over the engine I still only read 6.5v at the lead to the dist.
In other news, today I did some more tests to see if I could find a smoking barrel.
Ignition Leads:
8.1kOhms
6.6kOhms
5.9kOhms
7.2kOhms
└Haynes manual suggests≈6kOhms
Rotor:
1.6kOhms
└Suggests≈5kOhms
Primary Windings:
.8 Ohms
└Suggests 1.0-1.5 Ohms
Secondary Winding:
8.1kOhms
└Suggests 5.5-8.0 kOhms
Distributor Cap:
≈30 Ohms
The rotor seems to be questionable but lower resistance wouldnt prevent spark, it would reduce the voltage drop from what I understand. I also checked the resistance of the pickup coil which turned out to be about 1.1kOhms, but I am not sure if that is a normal reading. Perhaps that could be the issue? _________________ "The phoenix asteroids..." |
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Ozzie
Joined: 12 Mar 2005 Posts: 4448 Location: Townsville, Qld. Australia
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Posted: Fri Aug 14, 2015 6:35 am Post subject: |
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get the correct rotor button, a higher spark voltage could cause the plug lead to break down.
Also I have found the short plug leads have lower ohms and get progressively higher as they get longer. _________________ Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance |
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maybeoneday
Joined: 09 Dec 2013 Posts: 82 Location: Melbourne, Australia
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Posted: Fri Aug 14, 2015 9:29 am Post subject: |
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the rotor is the only stand out from what I can see. Also change that un-shielded earth wire off the coil bracket, I used a shielded thicker car stereo earth and it did wonders for my electrics. _________________ 1977 924 NA Auto |
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Talby
Joined: 05 Aug 2015 Posts: 8 Location: Montana
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Posted: Fri Aug 14, 2015 11:09 am Post subject: |
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maybeoneday wrote: | I used a shielded thicker car stereo earth and it did wonders for my electrics. |
How about this...
I had some leftover from buying a sub off a guy in a garage sale (never did get to install it into the vehicle it was purchased for )
As for the dist rotor, I have a hard time believing that is an issue because it was new straight from Bosch 2 years ago when the car was running flawlessly but then again they are only 7 bucks on amazon... _________________ "The phoenix asteroids..." |
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Lefty
Joined: 14 Oct 2013 Posts: 61 Location: Sydney, Australia
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Posted: Fri Aug 14, 2015 6:21 pm Post subject: |
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This may seem stupid
More frequently I have been getting the car turn over but not run. I dicked around for a while with a few things then it went ok. I fluked the solution
The cables entering the moulded plug at the back of the ignition switch ( where the key goes) worked their way loose. It's an intermittent issue now
From under you dash find the wires and push them in hard.
It's worth a shot and takes 30 seconds
Good luck
Lefty _________________ One less beige car |
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