Distributor Cap Failure

[tmaull]

Had an interesting failure this summer. Distributor cap failed. It was relatively new, new engine build. Failed approximately 250 miles into a long trip. I had taken it on and off a few times the previous weekend. Guessing something messed up the rotor contact? Evidence of arcing at the center. Anyone ever seen this?

[tmaull]

[7783911]

Yes, i saw similar failure with non oem cap, replaced with proper Bosch and all is good in the world

[tmaull]

This one is a Bosch part - pretty sure I’m the cause of the issue, but curious to see what folks think.

[wildcat077]

Possibly one of the clips became disengaged at one point and caused the cap to have bad contact , causing the arcing ! !

[porsche930dude]

Iv only seen that once on a honda civic. I stuck a pen spring in there and he was back on the road.

[kcook320]

Weird you just posted that. My 1980 911SC wouldn't start yesterday. Looks like the coil is bad and the distributor cap is cracked. Doesn't look to have arc'd - almost like the crack was while it was non-running. Must have been a flaw in manufacturing and the cold weather caused it to crack I am guessing????

[da Vinci Dan]

Did you put it on? The reason I ask is that i have noticed when I replace mine that it can sometimes not seat fully even after the L shaped retainers are locked down. It sometimes needs a slight shift / pressure / wiggle and then it fully clicks into place.

A misaligned cap may explain your problem. Bosch parts are usually pretty well made. However, I have had a few duds over the past couple or years. So, It may also be the case that their quality is declining.

[tmaull]

Originally Posted by da Vinci Dan

Did you put it on? The reason I ask is that i have noticed when I replace mine that it can sometimes not seat fully even after the L shaped retainers are locked down. It sometimes needs a slight shift / pressure / wiggle and then it fully clicks into place.

A misaligned cap may explain your problem. Bosch parts are usually pretty well made. However, I have had a few duds over the past couple or years. So, It may also be the case that their quality is declining.

Yes, several times. Pretty sure that’s exactly what happened - either I damaged the rotor, or misaligned the cap. Interesting that the car made it so far tho. It still ran, just on three cylinders.

[schoward]

I used to always use the Bosch ones until replacement maybe two years ago. At that time I noticed the fit of the new Bosch one wasn’t as perfect and sure enough it chipped a tooth within weeks. My local imported parts shop only had the beru cap on hand, which when I went to install looked and felt higher quality than the Bosch and fit was good too. I don’t know if Bosch isn’t what it used to be but the beru one is what I’ll prbably use from now on. Been two years and fine. I will say a spare cap and rotor is always in my kit when I do long road trips. Even lightly used ones are good insurance.

[Walt Fricke]

I vote for a manufacturing defect - the center contact isn't centered, so the rotation of the rotor created sideways forces which broke the Bakelite or whatnot the cap is made from, at which point the center contact fell off.

But that's assuming the mold is what places the center in the center - if it is machined in later, then maybe the thinner casting side was enough weaker that it failed?

I love the ball point spring fix. Glad I read this.

[mo-mon]

Happened to me about a year ago when I tried to save a few bucks and tried the Beru. I had a bad feeling during the install as it never seated as good as the Bosch. Went for a cars and coffee and on my way home, engine stumbled & upon checking, cap was tilted & rotor was toasted. Limped home & replaced with the old Bosch cap & rotor until I was able to order a new set.

[wrxnofx]

Originally Posted by mo-mon

Happened to me about a year ago when I tried to save a few bucks and tried the Beru. I had a bad feeling during the install as it never seated as good as the Bosch. Went for a cars and coffee and on my way home, engine stumbled & upon checking, cap was tilted & rotor was toasted. Limped home & replaced with the old Bosch cap & rotor until I was able to order a new set.

I don’t know that the Beru cap and rotor are a step down in quality. My ignition wires are Beru and I’ve been very happy with those. So this time I went with a Beru cap and rotor. Drove the car 4600 miles to and back from Rennsport Reunion with it. No problems whatsoever.

The Beru cap had lockdown tabs that required a lot more downward force than the Bosch before I could rotate them. Maybe that was your problem.