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Old 07-30-2021, 10:09 AM   #1
philcobill
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Question Can't get engine started after changing timing gear

This past week we changed the timing gear in our Special Coupe. I have only been able to start and idle it three times and drive one time since then. The following is a list (not exhaustive) of things I have done so far.

1. Changed out carburetors (three of them). There is adequate fuel flow at the carburetors.

2. Put in new "modern" points and the condenser, and set them to 0.018-0.019.

3. Cleaned and re-gapped the spark plugs to 0.035.

4. Set the timing according to Les Andrews in the Model Mechanics Book. I also consulted various YouTube videos on the subject. While setting the timing, I made sure I rotated the cam clockwise before tightening the screw. I used an indicator light which was off at notches 0 and 1 on the spark advance lever, and on at notch 2.

5. Double checked, and cleaned and tightened all wiring including the coil to distributor wire and the wiring in the terminal box.

6. The distributor has "modern" Nu-Rex plates in it. I checked the wire between the plates for shorts, there were none.

7. The three carbs are a Tillotson, a loaner Zenith, and the original Zenith that came with the car. I know the Tillotson may have clogged jets.

8. I have tried various GAV setting on the carbs.

9. There is the perfunctory 6.3 volts at the terminal box, the red wire, the starter, the alternator, and the points.

10. When we installed the timing gear three people checked, double-checked, and triple check the meshing of the timing gear and the crankshaft gear.

11. The ignition cable is turned into the distributor the correct amount. (I have no reason to believe otherwise because there is spark at the points, is this a correct assumption?)

12. The timing gear was not shredded, and the fibers were intact. So I imagine that nothing from the timing ended up elsewhere in the engine.

Behavior

1. The engine turns over all right, but I am running down the battery. I was able to start the car one time and drive it around the block using the Tillotson carb, but I barely made it back home because the car was sputtering so badly. I imagine the sputtering could be from the clogged jets in the carb. Additionally, I was able to start it for about 30 seconds using the loaner Zenith and the Tillotson, but not yet with the original Zenith.

2. The engine backfired so loudly it sounded like a gunshot, and stopped. I could not restart it right away after that.

3. The engine sounds like it can catch, firing a couple of revs and then stopping

4. Before driving the car around the block on the Tillotson and while idling it, the engine sound was the best I have heard out of it. The idle was much quieter than before.

I wonder what am I doing wrong. Is there a something I am missing? Is the above behavior indicative of a timing gear not in sync with the crankshaft gear (off be a tooth)? I don't imagine that is possible because I have been able to start it and idle it at least one time.

I want my car back. Before the timing gear went out, the engine would fire almost instantly after I pressed the starter button. It is darn frustrating not being able start it.

Bill

Last edited by philcobill; 07-30-2021 at 10:29 AM. Reason: wording change
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Old 07-30-2021, 10:34 AM   #2
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Default Re: Can't get engine started after changing timing gear

What happens if you try setting the spark control rod at different settings while starting? Does the behavior change at all?
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Old 07-30-2021, 11:22 AM   #3
Patrick L.
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Default Re: Can't get engine started after changing timing gear

Check compression and post results.
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Old 07-30-2021, 11:22 AM   #4
Bob Johnson
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Default Re: Can't get engine started after changing timing gear

The cam gear can be off 1 or 2 teeth and the engine may start and run but run poorly. Recheck the timing gear alignment.
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Old 07-30-2021, 11:24 AM   #5
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Default Re: Can't get engine started after changing timing gear

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The cam gear can be off 1 or 2 teeth and the engine may start and run but run poorly. Recheck the timing gear alignment.
You want him to quadruple-check the timing gear alignment?
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Old 07-30-2021, 11:34 AM   #6
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Default Re: Can't get engine started after changing timing gear

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Do you have a spare known good distributor to install?is the battery at full charge?
Carbon tip in distributor cap good?ground to engine with an auxiliary cable?
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Old 07-30-2021, 11:52 AM   #7
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Default Re: Can't get engine started after changing timing gear

Compression is between 70 and 73.5
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Old 07-30-2021, 11:53 AM   #8
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Default Re: Can't get engine started after changing timing gear

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Originally Posted by Brentwood Bob View Post
Do you have a spare known good distributor to install?is the battery at full charge?
Carbon tip in distributor cap good?ground to engine with an auxiliary cable?
No, yes, yes, and yes.


The car ran just fine before the timing gear went out
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Old 07-30-2021, 11:55 AM   #9
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Default Re: Can't get engine started after changing timing gear

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The cam gear can be off 1 or 2 teeth and the engine may start and run but run poorly. Recheck the timing gear alignment.

Just for a sanity check, is there someway to check before taking the engine apart in case it ends up being unnecessary?

Last edited by philcobill; 07-30-2021 at 12:19 PM.
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Old 07-30-2021, 12:19 PM   #10
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Default Re: Can't get engine started after changing timing gear

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Originally Posted by alexiskai View Post
What happens if you try setting the spark control rod at different settings while starting? Does the behavior change at all?
I did not have it running long enough to determine this well. When I drove it around the block, I concentrated on just keeping it running when it was sputtering, and was playing around with the GAV control mostly.
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Old 07-30-2021, 12:20 PM   #11
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Default Re: Can't get engine started after changing timing gear

When looking down #1spark plug hole find the spot that both intake and exhaust valves are slightly open( put in 3 rd and move some till one valve opens other closes, move till they are in "balance ", at that point the piston should be at top center---- this works for most internal combustion engines----- if cam is retarded power will be low, usually a lot of intake noise, and the ignition has to be over advanced
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Old 07-30-2021, 12:20 PM   #12
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Red face Re: Can't get engine started after changing timing gear

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Originally Posted by alexiskai View Post
You want him to quadruple-check the timing gear alignment?

That may end up being what we do. However, I would like to fully explore other options and eliminate other possibilities before dismantling things again.
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Old 07-30-2021, 12:24 PM   #13
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Default Re: Can't get engine started after changing timing gear

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Originally Posted by philcobill View Post
I did not have it running long enough to determine this well. When I drove it around the block, I concentrated on just keeping it running when it was sputtering, and was playing around with the GAV control mostly.
I'm talking about adjusting the advance lever while you're trying to start it. If the timing is off, either due to a bad gear or something else, you'll sometimes see it start easier if you put the advance lever in a position where normally you wouldn't put it. Just something to try.
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Old 07-30-2021, 12:24 PM   #14
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Default Re: Can't get engine started after changing timing gear

Phil,

There is a way to check the valve timing without taking the engine apart. Also the ignition timing without depending on the timing pin in the front. You have to go back to the basics of how an engine works. Here is how.

Take the spark plugs out. Turn the engine over by hand until the timing pin inserts into the dimple in the cam gear. Now, verify that the number one piston is actually at top dead center by inserting a piece of wire or wood to reach the top of the piston and then rocking the engine forward and back with the crankshaft pulley. Depending on how stiff your engine is you may need a wrench on the crank shaft pulley nut.

Once you verify that the #1 piston is actually at TDC then proceed to check the valves on #4 cylinder. Both intake and exhaust valves should be just barely open.

If the timing pin did not accurately indicate TDC or the valves were not both barely open when #4 was at TDC then the cam timing is off. This could be due to a number of causes, perhaps a manufacturing flaw.
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Old 07-30-2021, 12:29 PM   #15
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Default Re: Can't get engine started after changing timing gear

Something with your new timing gear doesn't sound right. Why did you change it?? Was something else starting to go south leading you to change the timing gear?? Compare the old one to the new one. Any differences?? Do you have a nice blue spark out of the coil when cranking the engine?? The spark may look good when flicking the points but cranking the starter might be dropping the voltage too much to provide sufficient spark.
Good gas??
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Old 07-30-2021, 12:31 PM   #16
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Default Re: Can't get engine started after changing timing gear

I did computer programing for much of my professional career. Often when I was helping someone fix their program they would say "it was working yesterday but it stopped working today". I would ask them what changes did they make since it was working. At first they would say "I did not change anything". But after more questioning they would finally would admit that they did change something but the change should not have caused the problem. Almost all of the time the change that they made caused the problem.


Since the car was running fine before you worked on it, I think that whatever you did caused the problem. So it is highly likely that there is a problem with the cam gear alignment.


Bob
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Old 07-30-2021, 01:04 PM   #17
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Default Re: Can't get engine started after changing timing gear

One other thing. Do you have good fuel flow into the carburetor??
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Old 07-30-2021, 01:11 PM   #18
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Default Re: Can't get engine started after changing timing gear

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Originally Posted by philcobill View Post
Compression is between 70 and 73.5





I asked this to help without having to remove front cover again. Tooth mis-alignment will affect compression.

70# is high. I think too high for a stock engine/cylinder head.

Is there a chance that the crank was turned while the original gear was off, before the new one was put on ?

There were some gears quite awhile ago with the dimple in the wrong position.

Try removing the sparklers and confirm TDC in #1 with the dimple in place. You see feel the piston top with a piece of wire stuck in the hole at an angle. Just be sure to not feel a valve moving instead.[ that has happened]

Last edited by Patrick L.; 07-30-2021 at 01:32 PM.
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Old 07-30-2021, 01:49 PM   #19
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Default Re: Can't get engine started after changing timing gear

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Originally Posted by Bob Johnson View Post
I did computer programing for much of my professional career. Often when I was helping someone fix their program they would say "it was working yesterday but it stopped working today". I would ask them what changes did they make since it was working. At first they would say "I did not change anything". But after more questioning they would finally would admit that they did change something but the change should not have caused the problem. Almost all of the time the change that they made caused the problem.


Since the car was running fine before you worked on it, I think that whatever you did caused the problem. So it is highly likely that there is a problem with the cam gear alignment.

Bob
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Old 07-30-2021, 01:56 PM   #20
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Default Re: Can't get engine started after changing timing gear

. Before driving the car around the block on the Tillotson and while idling it, the engine sound was the best I have heard out of it. The idle was much quieter than before.
That's the clue I think....Timing off doesn't come and go. Does this engine fire right off with starting fluid? You changed carbs, but if it is fuel the thing will fire on starting fluid....Nice voltage at points, I would (because it's easy and can cause your symptoms) change the cap and rotor. If you can't replace them clean the top of the rotor where it contacts the cap. Be sure the plugs are sparking by removing each one and cranking motor with it grounded to the head.
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