ignition --timing
 

I have a HP500 and having trouble timing my motor. It seems that when I put the timing light on and give it a total of 32 degrees timing and shut down and restart the motor the timing either jumps up to around 40 degrees total. It also sometimes goes back to 28 degrees. I notice when I put the timing light on and hold the mark the mark is jumping back and forth (the light) It feels like to me like there is something wrong with the ignition system because when I accelerate the motor the advance timing is not advancing. Anyone ever run across a problem like this?

Re: ignition --timing
 

First try a different timing light. I've seen the lights with the advance knob in the handle cause problems :( .

Re: ignition --timing
 

also the pick up lead on the #1 plug could be reading another plug??

Re: ignition --timing
 

Then check the rotor. It has to be tight on the shaft, no looseness at all. Its supposed to be locktited on. Usually, if the light is bouncing around at idle, its a loose rotor.

Is it a stock ignition or msd or something like that? Change modules in any case.

Re: ignition --timing
 

Thank you for your help. I have checked all that you have said and still the same problem. This is a stock ignition. The next thing is to try and change the module.
I'll keep you posted and again open for suggestions...

Re: ignition --timing
 

before you go and change the module you may want to check two things,
1) if thunderbolt ign check the hall effect pick up in the dist, merc has a redesigned sealed unit the older ones will rust and short

2) check the dist gear at the bottom of the dist and the bronze shaft bushing ( wiggle the shaft should be no play)

Re: ignition --timing
 

What GOODT said, I had a broken roll pin in a distributor gear that gave me fits for a couple of weeks.

Re: ignition --timing
 

What Year Is The Motor? and did you ground the wire (purple)

Re: ignition --timing
 

If it's a '99 like your profile says, then it's a Thunderbolt V and , like Baja said, you need to ground the timing shunt to enter base timing mode.

Dave

Re: ignition --timing
 

And It Should Be Set At 14.AND A TOTAL OF 34

Re: ignition --timing
 

Usually the sensor in the disributor either works or it doesnt at all. Ive never run into a wacky one, they just quit. I didnt want to mention the distibutor gear so as not to scare you, there are other cam shaft issues that could do this too, if the cam was walking forward and back. Pray its not that. if you check and verify all the easy things, then the dist gear and cam shaft end play are next.

The modules are expensive from merc, try and borrow a know good one from somebody to trouble shoot before you buy one, the old ones seem to last forever. Im still running on the old t-4 metal boxes with pigtails.

Re: ignition --timing
 

base timming is 8 deg