Ailing 73 Limousine

[Lars Kneller 8246]

A couple months ago I was driving my 73 Formal and it started missing a little.  We stopped for dinner and (thankfully) it ran fine on the way home.  It did well all summer until 2 weeks ago when driving home from a car show.  It started missing again, got progressively worse and (again thankfully) then quit just as I pulled up to my home. I managed to get it running long enough to get it back into its garage space and it stalled again.  When I attempted to start it, it backfired loudly and now won't catch at all.  My concern is the timing gear has self destructed.  Any other thoughts?  Thanks!  It currently has 49,000 miles on it.

["Cadillac Kid" Greg Surfas 15364]

Lars,
I am sure you checked for fuel and spark before guessing at timing gear, so you are most likely correct. Age seems to have as much to do with the nylon gear deterioration as mileage.  The easy way to tell if the chain slipped is to get #1 cylinder to TDC on the Compression/power stroke and see where the timing mark is.
Greg

[TJ Hopland]

Ya if the normal 'tune up' stuff is in good condition timing chain/gear would be suspect.  I would not expect it to fit exactally what you describe but at this age who knows.   You if the engine is fairly clean inside you can see the top edge of the chain and gear by pulling out the distributor.  If the engine is dirty it can be hard to tell but if it was bad enough to fail I think it will be obvious.

[David #19063]

Hi Lars,

Check the cap real well for any hairline cracks.  If the cap is old the plastic could be deteriorating.

Check for any loose, off, or split vacuum lines.

Make sure the distributor has not loosened and caused the timing to be way off.

I'd throw in a set points & condensor that you know are good for sure.  I have had the same issues on a couple occasions and had the points be the culprit.  Although, on one occasion it was the nylon teeth, but my '69 LeSabre 400 had 105,000 miles on her.

With 49,000 miles I would not be as concern with the nylon timing gear.  But I have been wrong before.

But a weak or weakening coil could cause similar issues as well.

I would lay my money on points, cap, rotor, vacuum, or timing.

[kelly]

I would agree with the concept of the nylon coated gear not  being the first, or most likely suspect.  When valve timing jumps, it doesn't get any better for even a little while.  It might not be a bad idea, if you are concerned, to also plan on a replacement of the timing set at a time of your choosing rather than at roadside.
Kelly Martin

[35-709]

Easy enough to check the timing chain/gear as Greg Surfas describes since it is a concern with those plastic gears.  But my opinion is the same as Kelly's, it wouldn't get better for awhile and then get worse again.  I would be much more suspicious of the coil, condenser, or maybe even the points.  Let us know what you find to be the problem.

[Glen]

I think there are two problems here.  The original problem which is intermittent and may be hard to find.  But when the engine backfired it could have caused the timing chain to jump.  So now the engine won’t start.

Or the intermittent problem just got worse. 

The first thing is to check the timing like Greg says.  Mostly because it is the easiest to do.  And will eliminate the timing chain if that is not the problem. 

Glen   

[TJ Hopland]

I have a 73 with 59K on it and the cam gear is as bad or worse than one of my other cars with 150K.  The 78 I bought 2 years ago (around 100K, sat for 11 years) looked pretty good, only slight cracks visible through the dizzy hole now has parts missing out of it with only about 3k miles on it since last inspection.  I checked it because I saw plastic bits in the oil last change, normally the bits dont seem to come out, they just get stuck in the oil pickup.   The bits also could be valve guide seals since they were a similar material that also does not hold up well with age. I think there are many factors in how well these hold up, mileage alone does not seem to be the largest.  Pulling the dizzy to check that will also give you a chance to check the dizzy bushings, if they are real warn the dwell tends to float around and not run as well as it should.

Another odd thing I have had happen a few times over the years is something rots out in the charcoal canister and gets sucked into the carb.   Most of the time its connected direct to the bowl so there are no filters.  The little bits of charcoal are about perfect to plug up the jets.   An inline fuel filter was/is the trick to keep the system hooked up and somewhat functioning if you dont want to disconnect it.

I have had a few cases of points sticking open recently, it seems they dont build them like they used to.  Also seen more shorted condensers recently than I remember back in the day.  On a friends car this summer the wire that went to the points and then through the dizzy body to the coil had an internal crack so when the advance started to move it would loose contact.  It would idle or cruise fine, the rest of the time it would hesitate and buck.  He was ready to tear the motor out.  We only found it because I wanted to check the dwell with a meter vs. the gap method.  Dwell was off also.  Correct dwell and a new piece of wire and it was running better than ever.

People often forget to check and replace the short bits of fuel line between the sender and the steel lines that go to the front.  A cracked hose there usually does not leak since its often the high spot in the system.

[Guidematic]

 A timing chain will not go bad, then fix itself for a period of time, then go bad again. When they go, they go. That's it. All too often people blame the timing chain, and then replace it only to find things no better. It seems to be today's catch all, like carbs were awhile ago.

If you do suspect the timing chain, do a compression test. Compression will be low across all cylinders and be even. Also, when cranking the engine, it sounds like all the spark plugs have been removed. Do this first, then move on depending on the results.

Mike

[Lars Kneller 8246]

The experts of the forum are once again correct!  It turns out my problem was a loose distributor cap.  I hadn't noticed that one of the attaching clips (the rear one) had somehow got pulled up and when I turned it and thought it was holding the cap down, it wasn't.  When I replaced the points their gap was too wide.  Once I adjusted them and got the hold down back into place and properly attached, now she seems to run fine. I did run the check suggested on my timing gear and everything was fine.  Thanks for everyone's help!

[David #19063]

That's great Lars!

It's nice when it turns out to be something simple and inexpensive that you can fix yourself.

Also, thank you for taking the time to lets us know what the problem was.