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Username Post: Symptoms of low voltage to ignition        (Topic#354162)
vabeach56wagon 
Valued Contributor
Posts: 3118
vabeach56wagon
Loc: Chesapeake,VA,
Reg: 04-22-02
12-01-18 11:23 AM - Post#2753003    

What are the symptoms of reduced voltage to the ignition system (resistor in place) when using an MSD cd distributor?

Thanks

paul

Original builder of the Gobstomper - '56 210 9 passenger wagon now in other's hands. Current Ride is '69 X33D80 Z28 Camaro



 

Ecklers AutoMotive

Shepherd 
Frequent Contributor
Posts: 1554

Loc: Lake George, NY
Reg: 11-11-15
12-01-18 12:26 PM - Post#2753007    
    In response to vabeach56wagon

Poor spark strength, possible misfire under load. Does this system use resisted voltage or direct 12v?



 
acardon 
Ultra Senior Member
Posts: 11105
acardon
Loc: DFW TEXAS
Reg: 03-25-05
12-01-18 01:40 PM - Post#2753011    
    In response to vabeach56wagon

  • Quote:
(resistor in place)



Why are you using the resistor with a box? Remove the resistor, connect ign1 and ign2 terminals of the ignition switch together and wire them to the box. The box should get constant power direct from the battery or starter terminal.

Don
66 Corvair (driving)
57 2dr HT (driving)
56 2dr HT (waiting to be restored)


 
IgnitionMan 
Valued Contributor
Posts: 3510

Reg: 04-15-05
12-01-18 04:34 PM - Post#2753028    
    In response to vabeach56wagon

First, let's clarify.

If an MSD box is used, ANY feed volts into it via its small diameter red wire is fine between 6.0,and 16.0 volts even a resisted input. That is MSD's specifications, NOT mine. The small red input wire on those boxes is simply an on/off switch to run the system, not voltage sensitive.

Now, the MSD "Ready to Quit" stand alone type distributors are NOT a CD, never have, nor ever will be, but, they do need unresisted full battery level feed voltage input. These systems are a TCBI.

Not always, but those systems, such as a true HEI, that favor full battery volt input, can have slight starting issues, but unless the distributor components are compromised, usually run just fine if a resistor is left in place in the power feed circuit.

Idiocy that causes those system's performance issues is generally when the limits are exceeded. Largest run issue is too large a spark plug gap. Over and over again seen are problems when spark plug gaps on all these systems are exceeded, above the absolute end limit of .045. A larger spark plug gap and low input volts will cause issues.

The over .045 larger plug gaps on MSD boxes only manage to kill the boxes, and/or create misfiring.



 
vabeach56wagon 
Valued Contributor
Posts: 3118
vabeach56wagon
Loc: Chesapeake,VA,
Reg: 04-22-02
12-03-18 09:45 AM - Post#2753188    
    In response to IgnitionMan

Thank you. In this instance the PO installed a no-name strange-looking standalone CD type distributor...

I replaced it with a spare MSD 8361 "ready-to-run" which I had in storage. It has never before been used. At the positive coil side I have 12+ volts. Plugs are gapped at .035. It'll idle and under load will transition to just under 2000rpm but won't take any more full throttle. Acts almost like a weak rev limiter. I have not yet replaced the coil. That will be done today.

I have another MSD 8360 pro-billet but that would require installing the 6AL I have and I would prefer not to do so if possible.

Of course, it could be a gargantuan vacuum leak I don't know about!

paul

Original builder of the Gobstomper - '56 210 9 passenger wagon now in other's hands. Current Ride is '69 X33D80 Z28 Camaro



 

Ecklers AutoMotive

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