MSD ISSUE... backfires w/no power at all
 

Ok, before I started the car was running great. (never should have started this)

Car: 1979 911 row 3.0

parts:
MSD 6AL
Magnecor Wire 8.5
new plugs gaped .42" or 1.05mm
MSD blaster 2

Issue:
engine idles ok, but backfires with almost zero power under any load.
I check the pickup wires they are correct.
each of the plug wires is firing
I adjusted timing forward and back no go.

fried two rotors could this the cause or the effect?
I need help, I have two 5yrs old's that want to be in the 4th parade.
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yank the MSD and use the original bosch unit. why do we need these things? the rotor resistor can be dremelled out and a length of solid wire laid in there and then JB weld over the top. sometimes the multi-spark doesn't change over to normal spark at 3K rpm and you get total crap-out/backfire.

I agree with john statement but in all honesty you probably have the polarity hooked up backwards. switch the 2 wires and you will be all set

I did switch the two wire at the distributor. Runs worse.

this is really frustrating.
for such a simple install, this is really troubling.

That sound exactly like what my car is doing with the new MSD. So I just ran over to Checker Auto and purchased the recommended:


Niehoff Ignition Distributor Rotor


It has the solid metal top with no resistor built in. I don't know that my rotor looks like yours but your description fits to a tee. Tomorrow I will go to the shop and see it that is the problem. If it is I will let you know.

Thanks, please let me know. I am going to do the dermal and wire install tomorrow.

Vhat das dis do?


KT

The "Niehoff Ignition Distributor Rotor" Is a rotor the same as a stock 911 rotor but it doesn't have the "resistor' built in...

Rebe911,

You have too much resistance in the system. Lots of us are using MSD, but as John suggests, maybe yours isn't working correctly. If the correct rotor doesn't help, change the plug gap back toward stock and see if that works.

You also mentioned playing with the timing. Set it so that it is correct at 6000 RPM, and don't worry about where it lands at idle. At least then you won't have to worry about the timing being part of your issue.

thanks I will give it a try.

have you checked the mixture and the advance even though you said it was running good before? it could be too lean especially if you have changed the timing and/or changed the CD unit. i would turn the mixture CW jsut to the point of surging or to the point the RPMS want to drop when you let off the gas and it returns to idle. for mine, i have found that edge where the dip in RPMS is, is 3%

Stupid question but does the engine need to MSD Tach Adapter to run correctly?
I would think not.

does it need the tach adapter for the engine to run correctly or for the tach to run correctly?
engine- no, tach- i think so but not sure.

im having issues with mine also. Im going to look for that rotor here in Austin. Is there a recommended plug and gap to use with these MSD's. I have the mm magnecor and a blue coil. my cap and rotor looked worn out after only about 2-3 months!!!:confused:

I had to put the tack adapter on my 80 SC with the MSD unit.

My tack is actually reading right.
it is just the engine is running like $hit. I am going to do the rotor mod tonight and end up the center tab on it for better contact. I believe there is to much resistance in the cap so the spark is happening in the cap once the MSD changes from multi spark to one big spark around 3k

did you clip the wires to set it up in 6 cylinder mode?

I clipped the red wire.

it may be just too lean

What's the plug gap set at? MSD recommends no more than .06" and in a Turbo this may be to wide. I'd set the gap at spec for your car and start with that, then only open up the gap after it runs correctly at spec. Keep in mind that the higher the cyl pressure the harder it is for the spark to jump the gap and your worse conditions are at your peak torque RPM in WideOpenThrottle. Given your description it seems to act up even at very light load just off throttle so this sort of indicates something else may be going on here. Could it be the MSD is somehow not setup correctly? check the basics, like cyl # configuration set to 6cyl mode?

Did you pull the distributor out? Rotor came off OK, didn't take the dizzy out to get it in a vice?

Sure you have got the ignition timing all set up right?

I did not pull the distributor, just the cap and rotor. the rotor came of fine.
The timing was on when I pulled everything out.

after work today I am going to:

mod the rotor
drill holes in the cap (per MSD)
new grounding straps.

anything I missed?

What way does that rotor spin in the SC clockwise or counter-clockwise? I ask because it's rather telling that the bad rotors are burnt on the right edge, most likely spark is occurring far before or after it should. Meaning the rotor may not be near the post at the time of spark. Could be timing is far advanced or retarded. Also keep in mind that maybe for some reason cyl #1 is firing correctly but somehow one (or more) of the others are not? That much damage on the rotor is most likely from the spark jumping a very large distance to the post. The question is why?

the resistor melted and it just happened to bubble out at the end. usually it exits out of the epoxy.

John,

Thanks for the simple answer. If this is the case then a rotor without the resistor or one with it modified should solve the issue. I'm interested how this turns out since soon I'm installing a MSD 6600 (pro unit) into my 84 Carrera.

Thanks.

I believe it spins Counter Clockwise.
I Checked all the wires for continuous spark with the timing light. Looked good for the most part. Every once in a while one of the wires would skip a spark.

Now, correct me if I am wrong, if it is spinning CCW and the damage is on the right side of the rotor as you look at it that tells me it is firing too early and I need to rotate the distributor cap clockwise back.

I keep this post updated with pictures of the fix... just don't make fun of how dirty the engine bay is. She is a project in process.

Correct, would mean firing early.

But first do the rotor mod as already pointed out by John, this is most likely your issue.

I went to the shop today, put in the new Niehoff rotor. Pushed it down firm.

Car started right up and rev good in neutral to 6000 rpm.

When in gear, driving, in all gears revs good to 3500 then cuts out, runs great at 3400rpm.

Any ideas.

What did you put in the MSD for a rev limiter? The default is around 3500 if you didn't put anything in it.

I currently have the 6000 rpm chip in the MSD.

Revs good in neutral.

Not in gear.

In your first post you said plug gap is 0.42" this can't be you must mean 0.042" right? Just double checking, I doubt it would even run at 0.42" or for that matter not possible to even gap them at that value.

Yes .042 is correct.

where did you ground the MSD unit? i missed it if you mentioned it......

Grounded to the fan shroud but I am going to run a 2 gauge grounding strap from that location to the frame.
I am uploading pics of the rotor mod now. they will be posted with in the hour.

Double check your timing. I suspect you are way advanced. Engine runs fine until 3500 RPM when the advance goes so high that the spark cant make the jump from the rotor anymore. It's easy to mistake the 30 degree mark for the Z1 or 5 degree timing marks. When I had this problem it was because the magnetic pickup was hooked up backward. It gave me about 35 degrees of advance at idle.

The green wire should go to green and the purple to the shielding.

-Andy

Non-mod rotor 5.05 kilo ohms
modified rotor 0.0 ohms
the rotor mod:
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Well did everything:
new ground straps
new ground for battery
modded the rotor
drilled holes in the cap (per MSD)
checked wires

still idles good but as some as I let the clutch out if backfires and loses power.
I am going to close the gap down more on the plugs.
from .042" to .035"
any other ideas?

was your original bosch unit dead?