Worn distributor?

'89 XJ 4.0L

I pulled my distributor today to replace the gasket (actually the gasket wasn't even there) and I noticed that the middle of the gears were all worn and shiney. By worn I mean that the middle was about half the width of the ends of the gear.

Similiar to this: http://lh5.ggpht.com/_qIfzkfjR_Nw/RgbkLBOyNLI/AAAAAAAAAi0/rk4_NYddonY/PICT0039.JPG

Just not quite as extreme. The cam gear is also worn in the same manner. Should I replace the distributor? Or not even bother? I realise that if I replace the distributor I might as well replace the cam, but if I replace the cam I gotta replace the other cam-parts and it turns into an engine rebuild, which I don't want to do. I've been quoted at $110 for the cheapest distributor here.

Could this really affect my timing? Also I noticed that there's a lot of up and down play, as in about a quarter to a fifth of an inch, between the distributor and the metal casing of the distributor.

You can get just the gear drive for the distributor and just replace that, for about $30. I've seen it at www.rockauto.com and I'm sure its available at other places. Usually its just a roll pin tapped in with a hammer through the gear and shaft on the end of the distributor.

They design the distributor drive gear to be softer than the cam, so that you don't have to replace a cam because of distributor problems. There are engines with a plastic gear drive, I "think" most jeeps have bronze gear drives, which is softer than the steel cam. You can't see the cam gear through the hole with a flash light to check?

Up and down play in a distributor is normal, brand new can go up and down the amount you describe.

Can it affect timing? Don't know what kind of engine control the '89 4.0L had, if you have a CPS, then it shouldn't, because the CPS triggers the ignition. Most engine switched to CPS triggering by the mid-80's. In this case, the distributor just serves to "distribute" the spark from the coil to the spark plug that needs to fire.

If you don't have a CPS and the ignition is being triggered by the distributor, then yes badly worn drive gear might affect ignition timing. You should be able to adjust it with a timing light. BUT, that much play in the gear may get the timing off again and soon.

Of course if the distributor is off bad enough, the contact point in the rotor/cap might NOT line up when the PCM is firing the coil, and thus the spark will NOT get distributed to the spark plug. Since the PCM is constantly advancing and retarding the ignition timing, it might line up sometimes and work and NOT line up other times and NOT work. In this case, the motor might start and run at low rpm fine, but suddenly cut out at higher rpm.

That is why there is such a specific procedure for installing the distributor and making sure its lined up properly in the manuals.

Renix engines have a CPS. You should at least replace the gear if it's that worn.Chances are the bushing is worn also though. I bought a new[not reman] distributor for under $100, a reman was about $60.

Yes you should change that whole dist out. With gears that worn it has been either pushing hard on the cam gear or the metal in the dist gear was too soft