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Will a wet distributor cap cause tach oddities? (jumping & incorrect readings by 2x)


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12 replies to this topic

#1 Syonyk

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Posted 07 January 2006 - 11:38 PM

Well, my ignition system has been driving me nuts lately, and I'm pretty sure it's just the damn distributor cap causing all my problems.

The distributor cap seems to keep getting water in it. The first time was from half an hour sliding sideways through 8" of snow, the second time was kind of random, and it's happened a few more times. Tonight I took it out with a few other people, and after about 15 minutes I started to get ignition breakup, and the tach was jumping around.

I pulled off to a gas station, dried it out, and managed to pull the center button out. I wedged it back in, and things started & ran, but the tach was still jumping around. After another 5 minutes, it smoothed out & behaved.

The odd thing was that while the tach was jumping around, it spent a significant amount of time at near twice the indicated RPM. It was hovering around 6.5k RPM indicated while I was doing 65mph in 5th gear. When the ignition stopped glitching, it dropped right back down to the proper 3000 RPM.

So, I guess my questions are:
1. Can a wet distributor cap cause the tach to jump around like this, and read twice the correct RPM?
2. How the FSCK do I keep the inside of the cap dry? I'm giving up on cheap aftermarket stuff & going with OEM Subaru parts, but I'm getting annoyed at having to spend time fighting with it.
3. Is there any reason to suspect other ignition system parts (coil, sensors, etc) of having issues, or is this all explainable by the cap?

-=Russ=-

#2 Syonyk

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Posted 08 January 2006 - 12:56 AM

Ah... crap. A bunch of searching on jumping tach stuff, and it looks like I may have a bad distributor in addition to the issues with the cap. Is there any chance a failing distributor could somehow let moisture into the cap? Maybe from the crankcase or such?

-=Russ=-

#3 Ryanb

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Posted 08 January 2006 - 01:03 AM

not sure about the last question, but i do bet on the the disty. i had the same issues and a new disty did the trick. i have a used one laying around I will send you for 15 plus shipping if you are in need.
And no i'm not saying it's your disty to try and make a sale, just trying to help you out because the board always helps me out.

#4 edrach

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Posted 08 January 2006 - 01:32 AM

Jumpy tach is often caused by a worn bushing and shaft wobble. Wet distributor is more likely to cause it not to run at all. I used to have that problem with an old 510 Datsun years ago. I found spraying the distributor cap on the outside with something called LPS greaseless lubricant. It's heavier than water and displaces it and solved the problem on my Datsun. Most good auto parts stores carry it.

#5 Syonyk

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Posted 08 January 2006 - 02:03 AM

not sure about the last question, but i do bet on the the disty. i had the same issues and a new disty did the trick. i have a used one laying around I will send you for 15 plus shipping if you are in need.
And no i'm not saying it's your disty to try and make a sale, just trying to help you out because the board always helps me out.


Understandable, I often post parts I have for sale if there's a related thread. It's rather helpful IMHO. I may take you up on that.

I'll see how it behaves tomorrow, but I think that it might be time to swap out the disty, coil, and put a new cap/rotor on, and keep the spares in the back.

-=Russ=-

#6 ballitch

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Posted 08 January 2006 - 02:29 AM

the last time i had that problem was when my voltage regulator on my alternator was going out, got new alternator and it was a okay.


~Josh~

#7 wesley willis

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Posted 08 January 2006 - 05:05 AM

when i first got my hatch i had a jumpy tach. thought it was the alt, but i was wrong. a new dist did the trick.

#8 Syonyk

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Posted 08 January 2006 - 12:15 PM

I *just* got a new alternator under a month and a half ago.

Now, onto the more practical issues:

The stumbling, I have no doubt, was due to the wet distributor cap. The jumping tach may have been unrelated, but if I can get the distributor cap issue cleared up, will the jumping tach cause any problems, or is that something I can drive with for a while until I get around to replacing the distributor, if it is at fault? Basically, should I look for spare parts to keep in the back now, or do I have a while? I haul across the midwest with alarming regularity in this car, and it's my only snow-capable vehicle, so if it's something that could fail completely at any moment & strand me, I'll get replacement parts now.

-=Russ=-

#9 hooziewhatsit

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Posted 08 January 2006 - 08:30 PM

if the disty is anything like the experience I had with one that failed... it worked for a couple days, then I couldn't reliably start the car after that. Put a new disty in and it fired right up, and has been fine since.

So... that being said, it probably wouldn't be a bad thing to have a spare one in the car just in case (and maybe a timing light)

IIRC, there should be a rubber seal on the disty to cap connection to help it stay dry? Does yours still have that? I'd try to get the wetness issue cleared up soon, then go from there (like you said you would).

#10 clutchcargo

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Posted 08 January 2006 - 08:55 PM

I had this problem a while back, my vote is for spark plug wires.
I bet if you continue to drive, you'll eventually see that it will start skipping as well.
GL

#11 Syonyk

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Posted 08 January 2006 - 11:23 PM

The plug wires have about 10k miles on them - they should be fine.

I'm going to screw with it when I get home, and see if there's any play in the shaft. It sounds like getting a spare disty would be a Good Idea, before it starts getting cold/snowy again (a motorcycle & RX-7 don't exactly make good snow cars).

-=Russ=-

#12 bella

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Posted 09 January 2006 - 10:31 AM

the last time i had that problem was when my voltage regulator on my alternator was going out, got new alternator and it was a okay.


~Josh~


I hade same problem but because my alternator diodes.

Paul

#13 clutchcargo

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Posted 09 January 2006 - 12:53 PM

The plug wires have about 10k miles on them - they should be fine.

I'm going to screw with it when I get home, and see if there's any play in the shaft. It sounds like getting a spare disty would be a Good Idea, before it starts getting cold/snowy again (a motorcycle & RX-7 don't exactly make good snow cars).

-=Russ=-


Mine had 6k on them, one of the wires was bad. I spent a bunch of money replacing items that didn't need replacing because I didn't believe it either. It doesn't cost anything to ohm test them.




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