Mr Gadgets

I am wondering if any one has run a MSD box on a motor and observed the same problem I have been chasing? With a crank trigger and 6AL box I set the initial timing at 15*. When the motor runs, I see the timing jump 90* advanced from the initial.
I am running a EFI along with the MSD and the whole setup has run flawlessly on my previous motor. I have isolated the EFI and run the motor with it shut off with the same ignition problem. I have moved wires and scoped the inputs and outputs, filtered DC, no help!
I have been working on this problem a long time with no positive results.

I have tried, 3 different MSD boxes. Two other ignition systems. Three different coils, 5 timing lights, 3 caps and rotors, etc, etc.

With the timing light on the coil wire, I see no jumping. On any one of the plug wires I see it jump, intermittently.

Any of the engine guys that run motors all the time on the dyno, ever see a problem like this. or anyone else. I have a video of it and can post it if necessary.

MSD is useless in helping with the problem.

Thanks!
Dick

SkiDoc

iTrader: (4)

I know it doesn't make sense, but the only thing you didn't swap was the distributor.

mike tkach

iTrader: (3)

dick,try unpluging the crank trigger and use the one in the distributor,are you useing a msd dist?

ezstriper

Dick, I run a crank trigger in my race car, with a digital box, did you phase the rotor ? also all of this stuff is very sensitive to grounding, make sure the grounds are good...silly question..how are you setting the timing ? by the trigger right ? which dist are running ? pro-billet with pick-up removed ? we run the trigger only(large flat cap) and phasing to rotor is important...and yes depending who you get on their tech line..GFL !!!! try the forums off their website... also you said jumps 90 stays there or moves around ? Rob

Boat1

This sounds like you have a rotor phase issue, the rotor is closer to the next plug wire pin the the cap, thus spark jumps to it. Since you said this engine is also EFI, I'm guessing you are using the distributor for the cam position sensor, ie. you have cut off all arms of the reluctor wheel but one. Typically the EFI wants its signal 50 - 85 degrees before TDC of #1 to signal start of rotation. You must set this phase and then set the rotor phase so that the rotor is pointing at the wire pin in the cap when it is firing, not at TDC. What EFI system are you using?

Mr Gadgets

Gentlemen,
Thank you for your comments..
Rotor phasing.. I have set the phasing. I have the top of one of the caps with about 5 holes in it. I can plainly see the spark jump to the terminal at the proper phasing. I dont see or hear any spark scatter in the cap. I also dont see any carbon tracking in the cap or on the rotor. I have tried three different caps and rotors, one being the adapt a cap with wide spacing.

I have used the dist pickup with the same results.. It is a MSD Probillet with the VR pickup.. same results.
I have swapped in an HEI dist and used same the plug wires and plugs... same results.

90* jump.. with the crank trigger, it is set to 15*, I see it jump to 105*, intermittently.. Some times it takes about 20 seconds or so for it to start and then it does it 5-10 times in about 15-20 seconds. It always reverts back to 15*..

EFI is Megasquirt. It worked before without any problems on my previous engine. It uses the tach pulse off the MSD 6A to sync the injectors, which are bank fired so no cam position is necessary. I have used the MS to control the MSD and same result. I have swapped in 3 different MSD boxes. But the problem has shows up running an HEI. I even ran the motor without the EFI.. removed the tach signal from the MS and squirted fuel into the throttle body.... same results, still jumping. Ran it without the alternator wired in. Using a mechancal fuel pump.
I have all my grounds going back to the battery neg terminal. Heavy gauge wire to cylinder heads from neg battery terminal.
I have run the EFI and MSD on seperate batteries, although they need to be connected to share the same ground.

This is driving me nuts!! Should have been to the dyno in Nov..

Keep those ideas coming!!

Thanks!
Dick

Boat1

Have you verified the .050 air gap from the crank trigger to the wheel. Check it at all 90 degree points. Are you using the mechanical advance of the distributor to control timing advance or does the EFI control the advance.

Mr Gadgets

I did set the gap at all different settings. Tried it tight and very loose up to .125" or so.. and two differnt sensors. Same results.
Remember I tried an HEI dist and used the pickup on that dist and it still does it.

I will be using the EFI to control the advance, when ever I find this problem..

The only thing I have not changed are the plug wires and that will be next..

FIXX

iTrader: (2)

Did you thermo wrap the sensor wire going from the magnetic pickup to the box? their real sensitive and will cause a timing spike..also what timing light are you using,,imy digital snapon one hate's msd and the readings will be all over the place..i use a old fashion standard timing light from sears..

Mr Gadgets

Right now the sensor wire is plugged directly into the box that is laying on a board at the base of the engine. No extension and no shielding. I am using one of five different timing lights.. My old stand by was a dial back, so I bought a DC powered light, then I borrowed an old Sears light, then I bought two of them off ebay (Sears 161.2134). All of them show the same thing.. At first I was expecting the light to be the problem.
When I scope the output of the tach signal on the MSD, I see a pretty decent square wave, indicating that the trigger input is not seeing noise, so I have been told. The tach output is one buffer stage from the input trigger. I suspected noise getting to the MSD box all along. But when I put an HEI dist in the motor and dont use the MSD box, it will still jump the 90*.

I have been working with Pat from TechWest Racing on this problem and he has been a great resource for info. He has done a great deal of trouble shooting on all kinds of MSD and other ignitions. He has been able to give me guidelines for what I should see and tips on how to look for problems. His business is rebuiding MSD boxes.. He modifies them to work better and last longer. He has seen a lot of stuff, but is anxious for me to trip across the reason for this one. One thing I know, He will get both my boxes for modifications when I am done. I have been in electronics all my life and I like what he is doing to the MSD boxes..

Keep those ideas coming..