Engine Running Problem Post MSD Install

[rr262]

I just finished the install of the MSD6AL (6420) and the 8920 Tach Adapter in my 83 SC. I am presently using a new Bosch Blue Coil (made in S. America) I have a MSD coil on the way, but I had a spare Bosch coil and wanted to test out the MSD install.

The car started up and runs just fine, with the exception that the engine appears to be limited to 3500 RPM. The engine keeps running but will not go above 3500.

Initially, I did not install any of the rev limiter plugs (assume this results in no limit) I also tried it with the 7000 and 8000 plug installed - Same problem.

I have searched the board for something similar but can not seem to find anything.

Any Ideas?
Thanks

Ken

[Steve@Rennsport]

Ken,

Did you snip the wire under the black cap on the upper side of the MSD unit?

Bosch blue coils are NOT the right ones for MSD's. You reallyt need that MSD coil for the system to work properly.

[rr262]

Yes I snipped the wire for the correct (6 cyl) configuration. I should have the MSD coil in hand in the next day or so. Is it possible that is the source of the problem?

Thanks

[wjfk32]

I installed a MSD to my 82SC.. I didn't need an adapter... ..Chk on the 930 Bd.. 930 Rocket - has instructions... Check all connections again... It can be be frustrating.. GOOD LUCK!

OH- I did the master blast 2.

[lindy 911]

Try switching the wires from the distributor. There is a positive and negative wire and they may be backwards. It will run if they are backwards but will do just what you are describing. It will rev to 3,000 or so and no further, usually pretty crappy.

Lindy

[andrew15]

2 things -

1) Use a MSD high vibration coil

2) I can't remember the posting, but I seem to remember that the install instructions from MSD were incorrect - The purple and green wires needed to be swaped from teh instruction where they connect to the green signal / ground wire from the distributor.

Regards,
Andrew M

[jtfreels]

I'm with Andrew, I had the same problem you are describing and yep I had the wires wrong as in #2 of his post.

Jay

[cole930]

Violet MSD (+) wire goes to the shield of the green distributor wire.

Green MSD (-) wire goes to the center conductor of the green distributor wire

Cole

[rr262]

OK....I checked the wires and they are wired correctly:

Green wire to the Green wire in the CDI Plug.
Purple wire to the Thick Black Wire in the CDI plug.

I called MSD and they suggested the following causes:

1) Check if distributor wires crossed (per above). Test by reversing them. (Which I did and the engine ran but at an advanced idle, and still cut out at 3500 rpm)

2) Interference from adjacent wires. Checked the routing of the green distributor wire for other wires that might be causing interference (I did this and it looked fine). I do not have solid core spark plug wires which is suposedly another source of interference.

3) Bad MSD unit. (They said they would give me a RMA so I could return the box if the above checks did not resolve the issue - which it did not).

They also indicated that the Bosch Blue coil was not the cause of the problem.

I plan to install the MSD coil tommorrow when it arrives to see if anything changes (which I doubt) and then get a new MSD unit.

Thanks for all your help and I will keep you posted.

[rr262]

Just to be complete, I got the MSD coil today and installed it, with the same result.

MSD Tech Support is convinced it is the box so I am sending it back and ordered a replacement.

I have gone thru three Permatune boxes (one that had to be replaced before I bought the car) and so I decided to do the extra wiring and switch....

I hope this is not a sign of things to come....

[rr262]

Not Good.....

I quickly wired in a different MSD 6AL box and had exactly the same problem. The car starts and idles perfectly but cuts out at 3500 rpm.

Here's the thing. I have been methodically troubleshooting a cold start problem most of the winter. I checked the operation of the cold start valve and checked fuel pressures (system pressure, control pressure and residual pressure) and they were all within spec.

When the car had trouble starting it seemed like the spark being applied was interment..the car would fire for a bit, then stop. Once the car was started it ran perfectly. If the car was warm, it started and ran just fine.

Given my experience with the permatune box(es), I decided to convert to the MSD.
This seems to have fixed the starting problem completely, but now I have this new issue.

(BTW, when I reinstall the permatune box on the car with a warm engine, the car starts fine an the RPM limit problem goes away. The car starts perfectly with the MSD box, and once started or warm, runs perfectly with the permatune box.)

some data:

1) I am running the MSD blaster coil.
2) I did not replace wires, cap, rotor or plugs, which are all relatively new.
3) Plugs are gapped to the recommended permatune value (.065)
4) Cap and rotor look in pretty good shape and have less than 1000 miles on them.
5) I have a relatively new BERU wire set (p/n 10-8533-613). I am assuming they are not solid core wires (I pulled off the coil lead and looked and it looked braided to me) If someone wants to tell me that they are indeed solid core wires, this is the cause of my problem, and I am a complete idiot for not figuring that out by myself, I would really appreciate it.

I am totally stumped...my suspicions are some sort of EMI problem causing the box to cut out..

Any ideas on this puzzle?

[rr262]

Got it....

I found a thread that described a similar problem. "MSD rev limit set at 3800?" Based on what Geroge did, I disconnected the Tach Adapter and wired the tach wire directly to the CDI plug and everything works fine, including the tach. I assumed I needed the adapter and obviously was wrong. Somehow having the adapter in the circuit was causing the rev limit problem.

Looks like I finally solved my cold start problem by getting rid of the Permatune box...

[Steve@Rennsport]

Ken,

Good to hear that you found the problem. I've had some grief with Tach Adapters so I tend to avoid using them at all costs for the reason you've experienced.

Beru wires are solid core but do have suppression resistors in the plug connectors and those are troublesome. I use Magnecor 8.5mm race wires for a more durable solution, especially with MSD ignitions. Be aware these wires are a tight fit so extra care is needed to ensure they are properly seated in the cap and coil.