Delayed shut down with MSD.

Denny S. · #1 (**permalink**) 01-29-2002, 06:46 AM

Not being to familiar with MSD ignitions. My question is this.
When I turn off the key the engine takes 4 or 5 seconds to shut off. I'm not referring to dieseling. It just doesn't shut down immediately. Is this correct ?

jeff_taylor · #2 (**permalink**) 01-29-2002, 08:32 AM

Denny,
Check out a thread in the "Shop Talk" section called "Ignition Switch Problem". This very same thing is discussed as a problem with some electrical systems and MSD ignitions. I believe you can find it back around page 4.

Geary L. Sarno · #3 (**permalink**) 01-30-2002, 08:06 AM

This is not related to MSD but I had a similar situation with my first Cobra buildup. I wired a Black Magic 150 fan to the "Run" terminal of my ignition switch instead of the "Accessory" terminal. The engine continued to run for about 15 seconds after the key was removed. The fan continued to spin for a few moments after shut down becoming a generator and feeding the ignition curcuit. I could remove the key - get out of the car and walk a short distance before the engine would stop.

justa6 · #4 (**permalink**) 01-30-2002, 08:08 PM

Here is another possibility.

If you have your ignition wired off a place that the hot side of the alternator comes into you can get this same effect. The Alternator can (when turning) power the MSD. This usually happens with a GM alternator with an internal regulator ie a "one wire" system.

Regards,

cdog · #5 (**permalink**) 02-05-2002, 04:33 PM

The easy fix is to put it in third and release the clutch slowly just as the key is turned to off...

Double Venom · #6 (**permalink**) 02-05-2002, 09:04 PM

Denny,

Gary is right. I have answered this question a dozen times.

You need to take the Fan out of the system. It has nothing to do with the MSD box.

Either re-wire and get it out of the ignition system completely or
go to Radio shack, pick up a diode, wire it into the fan wiring..poof you problem is over.

No offense intended, but using the clutch is a good way to heat up / score and ruin a good clutch!
DV

HighPlainsDrifter · #7 (**permalink**) 02-05-2002, 09:32 PM

The run on problem is the alternator supplying current to the ignition[msd] module.This is a common problem the tech guys see at the drags every weekend.They will turn off the main power cut off switch while the engine is running for safety reasons at the track,if it keeps running you don't pass tech. The cure is to wire the main output lead from the alternator though the ignition switch or wire a relay into the alt ckt as you would a fan relay.
Perry.

Double Venom · #8 (**permalink**) 02-06-2002, 05:34 AM

HighPlains,
I see your point, and think it is a very valid one. But, this problem is also quite common with these Cobras and Streetrods that don't even run MSD's.

If Danny didn't have the problem before the MSD then, I have to assume that you win the prize! An extra cookie at the DVSF!

You are coming...no?
DV

renaissance man · #9 (**permalink**) 02-06-2002, 06:17 AM

I just fixed this very problem. MSD even states that "run on" is a common occurance in their manual. Stating that, "electric fans sometimes feed through to the ignition causing a small light inside to remain on telling the system to stay powered up". Put a 1A 100v diode in line and your problem is solved. If you don't have a manual I can email the proceedure to you with pics. I have an MSD 6A. If that's what you are running, let me know.

justa6 · #10 (**permalink**) 02-06-2002, 06:51 AM

Thought I'd throw a twist into this discussion on MSD's.

I tried the new MSD DIGITAL 6 which has all kinds of "goodies" built into it. 2 Rev limiters, various ways to control timing, and higher current to the coil than the regular MSD 6. Well we could never get it to work correctly. I even had MSD send another one to see if the unit was bad.

At least in my application it simply didn't work above around 6500 RPM. The motor would rev above that but the tach would go crazy and the engine would go flat, as if the voltage suddenly dropped.

I tried a 6AL with the rev limiter chip but no digital functions. Plugged it in and the motor pulled hard to 8200 Rpm where it hit the rev limiter that we set. Worked perfectly...

Don't know if this is because of my application, although MSD tech said it would work on the Buick V6.

FWIW,

Frank Coppola · #11 (**permalink**) 02-06-2002, 06:55 AM

OK, I admit it. I am a closet-run-on case. I just didn't want to fess up. I feel much better now, knowing I have such great company.

Renaissance Man, would you be so kind as to send me the procedure so I can deal with my "problem".

Thanks!

Monster · #12 (**permalink**) 02-08-2002, 08:52 PM

I just got an MSD6A that I will be installing tomorrow and in the "Installation Instructions" pg6 it talks about "engine run-on". Specifically on early ford externally regulated systems. A diode is supplied with the install kit and the instructions outline the procedure. go to www.msdignition.com for troubleshooting and download versions of the instructions.

good luck,
Mike "monster"

Dave Wharran · #13 (**permalink**) 02-09-2002, 07:16 PM

Independent of the type of ignition, as reported earlier in the post, if you have an electric fan on the radiator or an oil cooler, and it is hooked on the same circuit as the ignition, after you turn off the key, the fan will act as a generator and provide enough power for ignition (and ECU if you're using one) for several seconds (seen as much as 5 seconds) after the key is turned off. The engine keeps on running like you never turned the key off. I've seen this happen on several different vehicles. Unnerving at first till you understand whats going on.

Dave

renaissance man · #14 (**permalink**) 02-11-2002, 01:08 PM

ENGINE RUN-ON
If your engine continues to run even when the ignition is turned Off you are experiencing
engine Run-On. This usually only occurs on older vehicles with an external voltage regulator.
Because the MSD receives power directly from the battery, it does not require much current
to keep the unit energized. If you are experiencing run-on, it is due to a small amount of
voltage going through the charging lamp indicator and feeding the small Red wire even if
the key is turned off.
Early Ford and GM: To solve the Run-On problem, a Diode is supplied with the MSD in the
parts bag. By installing this Diode in-line of the wire that goes to the Charging indicator, the
voltage is kept from entering the MSD. Figure 6 shows the proper installation for early Ford
and GM vehicles.
Note: Diodes are used to allow voltage to flow only one way. Make sure the Diode is installed
facing the proper direction. (Cathode toward regulator).
Ford: Install the Diode inline to the wire going to the #1 terminalGM: Install the Diode in-line to the wire going to terminal #4.

justa6 · #15 (**permalink**) 02-11-2002, 01:21 PM

OK guys here it is.

If you turn off your key and the engine continues to run
Its being caused by

EITHER: The Ignition system is being powered by the FAN (if its running) or the Alternator or you miss wired the darned ignition, or when it happens, as in my case, the idle RPM is high as is the compression...

Whew, glad we got that one straightened out...

Regards to all,