STRANGE ISSUE WITH MSD 6AL

[narnturbogq]

I'm trying to get my Patrol RB30 turbo conversion completed, http://www.outerlimits4x4.com/ftopic170799.php , and ive fitted a MSD 6ALN, and ive encountered a strange issue.

I can get the engine running, and it will rev sweetly, but i cant get it to idle under 1500 rpm approx. (as the tacho doesnt work with the MSD), as soon as the revs drop the engine stalls. Ive done some tests and ive isolated the problem. I got the engine running and pulled the no.1 plug lead off and fitted a old spark with the gap opened to 2.5mm, and its throwing a massive spark, but as soon as the revs drop the spark cuts, stalling the engine, and 50% of the time the spark cuts out for 3-4 secs approx. then sparks again for 2 sec causing the engine to run-on, but it runs backwards!!!! but only for 2 secs.

Ive wired the MSD up as per the diagram in the instructions, so im after any suggestions to fix the problem.

[LUX90]

Was it a new or second hand unit? If it was second hand I wonder if it is set up to run on the wrong number of cylinders. It tells you how to do it in the instructions
http://www.msdignition.com/uploadedFile ... ons(1).pdf

For the running on issue, they will normally need a diode in the alternator to stop it backfeeding and making the engine run on.

[narnturbogq]

It was secondhand but ive cut the loop as per instructions so its not that.
Ive looked on the MSD site and on the net, and im wondering if there is electrical interference coming from the spark plug leads, ive got brand new bosch high performance leads but im not sure if they are compatible.

[clm434]

What coil?
Are you running a crank trigger?

Few more details to fill in the puzzle

[narnturbogq]

Im running an MSD Blaster SS coil that is brand new.
The electronic dizzy on a rb30 patrol engine has a relucter the is like a sealed unit so i cant get to the two wires that you would need use for that type of trigger for the MSD, so I've used the dizzy output wire that normally drives the coil, which is like a points style signal, which is ok according to the paper work is fine. It reads for points or electronic amplifier signal.

[JrZook]

Im running an MSD Blaster SS coil that is brand new.
The electronic dizzy on a rb30 patrol engine has a relucter the is like a sealed unit so i cant get to the two wires that you would need use for that type of trigger for the MSD, so I've used the dizzy output wire that normally drives the coil, which is like a points style signal, which is ok according to the paper work is fine. It reads for points or electronic amplifier signal.

Sounds like you have a very weak triggering problem. Have you checked the reluctor pickup coil spacing to the metal wheel? Also a reluctor/sealed unit setup is quite different to dissy points pickup. The two wires out of the reluctor alone will produce an AC waveform that the MSD can detect but since you still have the sealed unit attached to it, the reluctor drives a zero crossing circuits and then a power transistor to switch the coil. Thus depending on the actual manufactures setup it still requires to be powered somehow. Id suggest trying a 1k ohm resistor placed where the coil used to be (battery -> resistor->dizzy) and then connect the white trigger wire of your msd between the resistor and dizzy. With this in place the msd will have a definite state when the power transistor is turned off (points open).
not 100% familiar with the std nissan dissy/reluctor setup , if you have anymore info or pics of it throw them up. In particular the wiring to that thing.

Hope it helps,
Dan

[narnturbogq]

Ive taken a couple of pics of the inside of the dizzy.

This shot is side on with everything pulled forward so you can see the back of the module, im guessing the orange bit is the wire coil.


This is front on, as you can see there are only two visable wires, the white and black wire is 12v+ coming in, and the green/blue wire was originally connected to the negative side of the coil, ive since cut the wire and connected the white trigger wire from the MSD to this (the pulse wire for the lpg lockoff controller is also connected to this wire as well)

Hope this sheds a bit more light on what im up against.

[JrZook]

So whats the LPG lock off controller actually do? I could be robbing the MSD of signal at low rpms. Ps how easy does this thing start? Surely your not cranking above 1500 to get it going.

Dan

[ANDREWGQ 351]

I agree, i had a similar problem with the LPG controler dropping the MSD coil out. Just give the LPG box direct 12 volt to see if that helps.
if it does then find another engine running 12 sigal to run the LPG box, its only a twin input relay really.

[narnturbogq]

The lockoff controller is a safety feature to shut the gas of if the engine stall ie: after a crash, and works on sensing the negative dv pulse from the coil (spark).

I was thinking that i might be able to use the MSD tacho output to give the lock controller its signal and see if that works.

[jessie928]

The lockoff controller is a safety feature to shut the gas of if the engine stall ie: after a crash, and works on sensing the negative dv pulse from the coil (spark).

I was thinking that i might be able to use the MSD tacho output to give the lock controller its signal and see if that works.

you dont need to attach it to the neg post of the coil

coil the wire tightly for about 1 inch around the coil lead and this will be enough to work the lockoff

Jes

[jessie928]

SO did you fix the bugger yet?"

JEs

[narnturbogq]

Ive had no time, flat out at work, and was pitcrewing at round 4 all week end. Im going to keep on it. Will keep you posted.