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VANtastic Blues - Ignition Timing

1982 dodge B250 van, 3/4 ton, 318

Question: can the ignition timing mark change location over time with wear and tear (I don’t really mean can the grooved mark move but not sure how to word this)? 12 degrees advanced gives low vacuum (about 16, should be 20-22) and vehicle lags and struggles to start. Is it possible that the new distributor is bad or installed wrong? Please read recent history below and any suggestions are much appreciated!

problem 1: van wouldn’t start after running for a while. needed to cool down then would fire up.
Solution1 : mechanic replaced just the distributor pick up. I watched him do it and he never loosened or removed the distributor. when first started it ran terrible. timing was way off. Mechanic earballed the timing and the pickup gap and it was never right

Problem 2: van would only start if I over advanced the timing. I would then retard it slightly for cruising but didn’t seem to hold timing well.
Solution 2: new mechanic adjusted timing with timing light to 12 degrees advanced and properly set the gap. Ran great for about 1 hour then started pinging again.

Problem 3: could not get the timing to hold. I bought my own timing light and discovered that the ignition was 25 degrees advanced but I could see the timing mark that the mechanic made at 12 degrees and called to confirm that they adjusted properly.
Solution 3: another new mechanic replaced the distributor completely and earballed the timing. next day still wouldn’t start, had to advance timing to get it running. mechanic then bypassed voltage regulator in ignition switch during starting (probably bad lingo here) and this significantly helped but still not running right.

Problem 4: van just not running right. only getting 10 mpg, used to get 16mpg! it sounds like it is missing, still has problems starting. Timing is definitely still a problem. sometimes it will start when I release the ignition.
Solution 4: I reset the timing to 12 degrees advanced. While running it sounds pretty smooth but I have low vacuum and power loss. I tweaked and advanced a little more but still struggles to start and doesn’t run very well. There seems to be excessive vibration too.

Have a VANtabulous day! Thanks!

This is a pretty old van. I’m guessing it has well over 100K miles on it? It’s entirely possible the timing chain (the chain that drives the camshaft) has stretched or even jumped a tooth or two on the sprocket. If the chain is stretched, the valve and ignition timing (since the distributor is driven from the cam) will wander. This will cause the behavior you’re experiencing. A severely stretched chain will be noisy and in some cases can even wear a hole in the timing chain cover.

Before you condemn the chain though, when was the van’s last tuneup?

I put in new plugs and plug wires just after the pick up was replaced so within the last 3 months, other tuneup stuff has all been done since June. I suppose some plugs could be fowled since it has been starting so hard for so long.
The van only has 90000 miles on it but I will look into the chain and trouble shoot for that.

Yes, it it possible for the outer ring of the harmonic balancer (the part with the “groove” that you line up to the numbered scale to set the timing) to slip around and make it impossible to accurately set the timing.

It is also possible that the timing chain and gear have worn enough to make engine timing (including the valves and not just the distributor) erratic and impossible to set properly. Even though it only has 90,000 miles it’s still 32 years old.

I also remember there being trouble with wear on the distributor drive gear bushing inside the engine and there being a service bulletin and updated parts but I think that may have been for newer engines than yours.

Have a mechanic who is experienced in older cars check for timing chain wear.

Rough earball timing, retard the timing till rpms start to drop, then advance 1/8 to 1/4 turn. Does this have points?

great! Thanks folks and thanks asemaster for making sense of my question!

I will try the rough earball timing and definitely check out the timing chain wear. My service manual talks about points in the trouble shooting, pretty sure yes but not positive. It is a brand new distributor though.

Unless you unplug the vacuum advance and plug the line, the timing will be advanced much more than the 12 degrees it was set at. This is normal. Remove and plug the line then set the timing. Once you plug the vacuum line back it will change. Also, the mechanical advance weights inside the distributor cap will change the timing with increased RPMs. They must be lubed to work properly.

If your van has points in the distributor then it has been altered from original–backwards. Is your engine still in original configuration?

not positive but after looking at some online photos I don’t think it does. With the cap off it just the pick up. However, I have a new distributor that I have not had the cap off but I assume it would be the same as the last one. It was original configuration before recent work.

the mechanic that replaced the distributor told me that he did not set engine to TDC to install the new distributor, said he didn’t need to. (I was having trouble setting TDC, lack of tools, which is part of the reason that I took it to a mechanic)

Is it possible that it is installed off?

The distributor should have an offset tang so it’s a matter of just dropping it in.
Does this van still have the Lean Burn system on it? That is an early electronic spark control system that was pretty much cursed by everyone on the planet. It was quite common to eliminate the Lean Burn due to problems.

Yes, the distributor can be installed with the engine at any position, only an idiot could get it wrong on that engine, but the timing still needs to be checked and adjusted following distributor replacement. Even with just a timing light it should be possible to see if the timing chain is loose or worn.

Just make sure you’re unhooking and plugging the vacuum advance as mentioned.

I didn’t even consider that your van probably has “Lean Burn” or “Electronic Spark Control”, which is an early engine management system. They were never the greatest, but they were pretty much reliable. I had several Chrysler vehicles with this system. You will not be able to accurately set the ignition timing with the vacuum line attached to this unit, which is mounted on the air cleaner most likely. The unit will be working against you if the vacuum line is attached.

A panoply of problems are possible with this symptom. My guess – on a vehicle of this vintage – is that there is play in the point the the distributor gear meets up with the gear inside the engine that drives the distributor shaft. But it could be any of the above comments too. Your mechanic will just have to eliminate them one by one, making his/her best guess where to start.

"My service manual talks about points in the trouble shooting, pretty sure yes but not positive. It is a brand new distributor though. "

Point gap and timing go hand in hand.

finally got a chance to work on the van again. it does not have a lean burn system, I’ve attached some photos below. today when I was playing with the timing I tried leaving the vacuum hose connected and removing and plugging it and also increasing the idle speed. My timing light shows 10 degrees btdc for each, nothing changed. any thoughts on that? thanks

actually I’m a little confused. just realized that the 12 degree btc mark on the pulley lines up with the 10 degree btdc mark that is static. does that mean 12+10? should the 12 degree mark line up with the 0 on the static mark? it still doesn’t change with the vacuum unplugged tho

I am confused also. Are you talking about the timing mark on the flywheel, that has nothing to do with the pictures.

My experience w/ignition timing checks using a timing light, the crank-shaft pulley only has a notch (representing crank TDC) and there’s a fixed gauge mounted to the block running from -15 BTC to +15 ATC. Can you post a photo of how it looks on your vehicle?

Vacuum-controlled advance work differently car to car. My Ford truck has both a vacuum advance and vacuum retard. The advance doesn’t do anything at idle. Only the retard affects idle timing. That’s how it works on my truck anyway. So the fact that the timing doesn’t change may be normal.

When you unplug a vacuum hose during a test, if you don’t plug the now open end of the hose air tight, that will allow extra air into the engine so the idle rpm may increase. Double check that you are plugging it air tight. If you are, it is possible the device it plugs into has a diaphragm that is leaking. Can be easily checked with a hand vacuum pump.