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Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

I have replaced 3 distributor caps, the lastest one only lasted about 15 miles, do the distributors wear out. The caps have a line going from one lead to the next inside of the cap. I don't feel any play on the rotor but it might not take much. Any ideas? I have another one but the electrical hook up is broke, can the electrics be swapped?
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79 924 NA

Paul · Posted: Sat Dec 25, 2004 5:15 am Post subject:

Pop your cap, then grab the rotor and try to push it back and forth to see if the shaft has play. If it moves more than a little bit, this might be the cause.

What damage is being done to your cap?
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

It move a little, the inside of the cap has little cracks (spyder web) like that go from one terminal towards the next terminal. Also, the terminals themselves have burnt spots on them. (Terminal - little metal inside the cap that the spark plug wire attaches to).
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79 924 NA

Paul · Posted: Sat Dec 25, 2004 6:00 am Post subject:

Sounds normal.

Are you having other problems that replacing the cap solves?
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

The car had been running ok, it did not have a fast idle when started up. I tried to fix the AAV, but ended up ordering a new one. Then when I got it all back together it ran for crap. Then went back to basics - set timing, which i noticed that when the plug wire for #1 was remvoed the car ran better - wasn't missing. looked at the cap and the inside had the spyder cracks, so went bought a new cap and car started right up and ran great. Went out for a little ride then started missing again, pulled #1 wire and it stopped missing, took new cap off and spyder cracks again.
My original cap had these cracks but the car ran ok the cap was red, the new ones from Advance Auto parts are black P/N 22-5008. Don't know that it makes any difference. You have any other ideas?
Also, as a test I switched spark plugs and no difference, also switch spark plug wires and no difference ( just for #1 spark plug)
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79 924 NA

Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

I have another distributor, only thing is that the electrics inside look different
one currently on the car has # 0237 003 005 the extra one is # 0287 022 019

They look basically the same on the outside, can the electrics be changed, my extra one the electics are junk, broke plug for 1 thing.

To change the electrics is it just take the c-clip off and it all comes out?

Thanks
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79 924 NA

Paul · Posted: Sat Dec 25, 2004 9:05 am Post subject:

Time for a compression test, especially if you have been slowly losing coolant.

Also are you running a stock coil and ignition module? Are your ballast resistors still installed (to check start the car and tell us what the voltage is from the + side of the coil and ground).
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White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

gohim · Joined: 02 Nov 2002 Posts: 4459 Location: Rialto, CA

The distributor runs on a couple of solid bushings that are pressed down into the "tube" section of the distributor casting.

Any competent machine shop can disassemble the distributor, and replace the bushings if they are worn.

Although they all look alike and will plug into the head, there were different distributors, and they work differently. The early Euro cars had points in the beginning, that's one part number. The US cars have always been pointless, but there have been a couple of different vacuum advance setups and the type of pointless ignition was changed.

So, I would hesitate to try to plug in a distributor with a different part number.

A small amount of play in the distributor shaft is acceptable. I would suspect a generic cheap distributor cap and rotor may be the real problem here. In my experience, when a distributor is wobbling during rotation, and it is due to wear, the damage or "cut/scrape" line in the inside of the distributor cap will not go all the way around. If there is scraping/cutting all the way around, I would suspect an incorrect rotor (the tip is too long), or a incorrect distributor cap (too small inner diameter). The clearances inside of a distributor have to be tight between the rotor and the terminal contacts inside of the distributor cap for the spark to jump properly for good performance. If the cap or rotor are incorrectly sized, scrapping is going to occur, or the air gap will be too large, causing a weak spark.

I would recommend that you make sure that the distributor housing bolted to the back of the head mounted so the distributor is located as far down as possible. The reason is because if the distributor was incorrectly mounted in the high position, when the hood is closed, physical contact would occur between the hood and the distributor cap, which would push the distributor cap at downward angle, and could cause the distributor cap to move over sideways, causing contact between the distributor cap and the rotor.

Then, you should bite the bullet, and buy the correct Genuine Bosch Distributor Cap, and Rotor to install, and see if the problem was cured.

924RACR · Posted: Sat Dec 25, 2004 11:45 pm Post subject:

I'm underlining the last line of gohim's comments there - make sure you get a genuine Bosch cap and rotor. I had horrible problems with erosion of the contacts on the cap in the racecar, causing a slight miss at 5000rpm, and it is only happy with true Bosch parts there...
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Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

I will try and find a Bosch cap & rotor on Monday. It has not been leaking any antifreez and has been running really good.
I do notice that both distributors have some movement up and down.

I have the distributor slightly loose so to adjust the timing, I will push it back and tighten it down and see if that works. I know that is a tight fit as I had my old wires arch out on the hood of the car.

I will also call around to see about having new bushing installed.

Thanks for the advice and have a Merry X-mass.
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79 924 NA

Paul · Posted: Sun Dec 26, 2004 7:58 am Post subject:

This is the distributor housing mentioned above. Make sure the bolt that has yellow crayon on it (above the VW symbol) is mounted the same as this picture.

_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Lizard · Posted: Sun Dec 26, 2004 4:31 pm Post subject:

I second Paul's motion, make SURE that the distributor housing is positioned correctly, it can be in 2 potitions and 1 causes failures, however if the car doesnt miss with cyl #1 unplugged, you are having other issues as well,
how are you setting the timing?
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Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

Thanks Paul for the pic, I just looked at mine and mine is mounted on the other hole, it has been this way since my son put the different head on about a year ago. I will loosen it up and move it. I have used a timing light hooked up to the #1 plug and also hooked up to #1 terminal on the cap, both results seamed ok.

I think that maybe having been mounted incorrectly the cap would get moved by the hood, so will try that first. As I said the car ran ok with no real problems but maybe my new plug wires are a little bit taller and the hood places a little pressure on the cap.
So out to the garage.
Thanks
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79 924 NA

Johno · Joined: 14 Oct 2003 Posts: 53 Location: Greendale, WI

I put in a new Bosch cap and rotor and the car once again runs very good. I also changed the mounting bolts on the distributor, won't hit the hood of the car any more.

Thanks all for their input/help, Paul thanks for the photo that made it clear about moving the distributor back.
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79 924 NA

dubrict · Joined: 22 Apr 2011 Posts: 150 Location: Horseheads NY

This thread is very old, but how much play is acceptable in the distributor? Mine has about 1/8 inch
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1979 924 NA
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