Are Caps Checkable?

[seattle_fleetwood]

This is going to make me sound like an idiot, but is there a reasonably easy way to check the effectiveness of the cap and rotor on a '91 Deville? A new cap is only 25 bucks, so I'm thinking it's just easier to be sure by replacing the old with new, since I have no way of knowing how long the ignition parts I have have been on the car

[Scotty]

1) look for cracks

2) look at the contacts in the cap and check them for looseness, bad wear, white corrosion or oxidation.

3) look for carbon tracking

4) There is a small carbon nub in the center make sure it is not badly worn, don't pull the coil out there is a rubber seal in there that gets compressed the first time its installed that you may create looseness in.

5) check the rotor for a worn contact and worn center spring (that contacts the carbon nub)

6) look for carbon tracking around the rotor

[an01sts]

Those are excellent visual checks; however, there is no visual check for a cap, meaning that a cap can look to be in exceptional shape, but it can still be bad.

This sping is an excellet example: I have a 30' Proline w/a with twin 350's. When I was getting ready to take it off winter wood, everthing fired up fine. On the day I was going to float it, one engine wouldn't fire. I could tell by listening that it would almost sputter, and it had fire. I dinked and dinked with it because a week or so earlier it fired up instantly.

I inspected the cap closely as Scotty pointed out, and the cap was perfect with zero wear. I thought about yanking the other cap because it's a boat (Break Out Another Thousand) and the cap is $75. No! You cannot use GM cap because the marine dist is totally different.

I hated to play hit of miss with $75, but it's a miserable set-up to work on, and yanking the other cap would have become a major nightmare, twice the nightmare as yanking the one cap.

Because I had exausted every other possibility, I bit the bullet and played hit or miss with the a new cap. I installed the new cap, and when I hit the key, it didn't even crank. Instead, it just went VRROOOMMM!

If it's running fine, it's probally okay. But I don't have problems with preventaive maintaine, replacing things before they take a crap. (If it's running fine, and you see anything that Scotty points out, replace it because it will probally bite you in the *smurf*.) If you have a problem and you have exauseted all your avenues, except the cap, the only way you can verify the defective cap is with a known good one.

[Scotty]

THats good advice, you really can not check how much the contacts and rotor contact have worn creating too much of a gap between them when they are in place. Its really cheap enough that is probably best to start with new pieces and be done with it.