Timing changed while running

[utexasrick]

Finally took out the boat after replacing the engine with a rebuilt engine. It's a 4.3 with thunderbolt IV. I set the timing and it was running fine out of the water and in. I drove it around for a bit at a little higher than idle speed and everything seemed good. Then I tried to increase the RPM's to around 3K and the engine just shut off while accelerating. Could not get it to restart and had to be towed in. When trying to restart, it would turn over a little bit then stop then turn over some more. Finally got a chance to take a look at it today. Fuel system looked good, fuel pump turning on, oil pressure started to increase as it turned over without spark. Wires do have spark. Then I checked the timing and at TDC. The rotor is pointing to the next firing cylinder (6) instead of #1. It seems like somehow the timing is off by one cylinder. How can this happen? I checked the distributor and it was not loose, still bolted down. Anyone ever seen this before? Not sure if the distributor can jump a tooth while being bolted down as there seems to be almost no play.

 

[tpenfield]

Re: Timing changed while running

I'd pull out the distributor for a look at the gear teeth, etc. Also take a look at the cam gear. . . .

 

[Bondo]

Re: Timing changed while running

Finally took out the boat after replacing the engine with a rebuilt engine. It's a 4.3 with thunderbolt IV. I set the timing and it was running fine out of the water and in. I drove it around for a bit at a little higher than idle speed and everything seemed good. Then I tried to increase the RPM's to around 3K and the engine just shut off while accelerating. Could not get it to restart and had to be towed in. When trying to restart, it would turn over a little bit then stop then turn over some more. Finally got a chance to take a look at it today. Fuel system looked good, fuel pump turning on, oil pressure started to increase as it turned over without spark. Wires do have spark. Then I checked the timing and at TDC. The rotor is pointing to the next firing cylinder (6) instead of #1. It seems like somehow the timing is off by one cylinder. How can this happen? I checked the distributor and it was not loose, still bolted down. Anyone ever seen this before? Not sure if the distributor can jump a tooth while being bolted down as there seems to be almost no play.

Ayuh,.... With a Timing Light,..??..??

 

[utexasrick]

Re: Timing changed while running

Ayuh,.... With a Timing Light,..??..??

set timing with light, when it checked it, I just pulled off the cover and its definitely pointing at the #6 cylinder

 

[utexasrick]

Re: Timing changed while running

Well pulled off the distributor, teeth seem to look good both on the drive gear and rotor. Almost no play in up and down motion of rotor. Then I tried rotating the rotor by hand while the distributor was installed and it moved! I think that is the problem. Didn't take much force to move it also. It's possible that at higher speeds the rotor is slipping from the shaft. Not sure how it is assembled so that will be the next step to take it apart. The rotor should not be able to rotate if the drive shaft is not rotating correct?

 

[Don S]

Re: Timing changed while running

There is a roll pin in the gear that keeps the gear from turning on the shaft. Probably sheared. Hold the gear and turn the rotor, that will tell the story.

 

[utexasrick]

Re: Timing changed while running

Found the key on the inside of the rotor was sheared allowing it to spin on the shaft. I'm 99.9% positive that was the issue. Going to see if I can find a new one and retime the engine. Hopefully no more break downs.

 

[Don S]

Re: Timing changed while running

The only key is a part of the rotor, you need a new rotor.

 

[achris]

Re: Timing changed while running

The only key is a part of the rotor, you need a new rotor.

Part Number -13524A6