Electrical/MSD Problem

thumper_302

thumper_302

White Lighting
Okay, 33 years of racing for me, 45 years for Dickie, almost 50 for Norm Benard, and 30 years for abe and none of us has every seen this.

On Saturday we were trying to time my Mustang with the timing light. We noticed that the light was getting multiple pulses.

Dickie move's #1 wire away from the block and onto the heater hose and it goes away. He then moves it back and it comes right back. Dickie then asked me the same questions.

I tell him: Wires are new MSD 8.5, new Cap/Rotor, new pickup, new plugs, MSD is grounded at the battery and the frame, block is grounded with a ground strap, block anker, and a heavy gauge ground wire.

We then check volt with the car off (12.38)

When car is at idle (12.98) and at say 3500 (14.00)

Checked all the grounds and they read (0)

Now, Dickie moves the clamp from the timing light that goes on #1 around the engine bay. he gets the clamp close to the O guage wire going from the starter solenoid to the battery in the back and pick up a pulse fromt the that wire. As soon as we move #1 away from the block it stops. We can also move the other wires away from the block and toward the positive wire and get the same effect.

We worked on it for awhile but we will have to get back to it next week. Basically we are getting an ignition pulse throught the positive side of the charging system. Anyone ever seen this?????????????????????????????????????????????? ????????
 
Don W.

Don W.

Stab it and steer it
Re: Electrical/MSD Problem

:2cents: Cross firing. May be a bad plug wire in the bunch, or bad cap. I know what you said but maybe there's a bad ground from the MSD. Bad connections on the primary side of the coil. :2cents:
 
thumper_302

thumper_302

White Lighting
Re: Electrical/MSD Problem

Everything on the MSD system is brand new, as a mater of fact, the whole damn drive line is brand new. We are getting ignition pulse through the positive side of the charging system but the radio has no ignition noise.
 
Don W.

Don W.

Stab it and steer it
Re: Electrical/MSD Problem

Hopefully no one was insulted just trying to throw some ideas out there.

If it's a single cyl pulse then it might help if you can track down which cyl it is and go from there. Remember; when a coil fires a high voltage is also generated in the primary side (in the "old days" it was absorbed by teh condencer.) so maybe there is some feedback of some kind going on. Is it possable to try a different MSD box?
 
WyoSyclone

WyoSyclone

Active member
Re: Electrical/MSD Problem

I put my notes in red.....

thumper_302 said:
Okay, 33 years of racing for me, 45 years for Dickie, almost 50 for Norm Benard, and 30 years for abe and none of us has every seen this.

On Saturday we were trying to time my Mustang with the timing light. We noticed that the light was getting multiple pulses.

Dickie move's #1 wire away from the block and onto the heater hose and it goes away. He then moves it back and it comes right back. Dickie then asked me the same questions.
I guess you're talking about the #1 plug wire? If so, I'd suspect a break somewhere in the insulation....

I tell him: Wires are new MSD 8.5, new Cap/Rotor, new pickup, new plugs, MSD is grounded at the battery and the frame, block is grounded with a ground strap (How big is this ground strap - one of the braided ones?), block anker, and a heavy gauge ground wire (How big?).

I'd try grounding the MSD with one wire only, large gauge (10), directly to the battery. You may have set up a 'ground loop' issue using two grounds.

We then check volt with the car off (12.38)

When car is at idle (12.98) and at say 3500 (14.00)

Checked all the grounds and they read (0)

Now, Dickie moves the clamp from the timing light that goes on #1 around the engine bay. he gets the clamp close to the O guage wire going from the starter solenoid to the battery in the back and pick up a pulse fromt the that wire. As soon as we move #1 away from the block it stops. We can also move the other wires away from the block and toward the positive wire and get the same effect. (Cracked porcelain on the plug?)

We worked on it for awhile but we will have to get back to it next week. Basically we are getting an ignition pulse throught the positive side of the charging system. Anyone ever seen this?????????????????????????????????????????????? ????????
Click to expand...

From my experience these problems are caused by being induced (physical break in a ground, windings in the coil going bad), or by being radiated into the system (what causes a lot of noise problems in autosound systems). Radiated noises can be either via 'primary transmitters' (eg directly from the coil), or can come from 'secondary transmitters' (something like the hood picks up the noise from the coil and rebroadcasts it). I'll go out to my shop and take a pic of a tester I made to track these kinds of problems down... looks a little weird but works like a champ. From the sounds of your problem I'd say it's either a broken porcelain on a plug, a break in the plug wire insulation, or a bad termination on a plug wire. Hope this helps you track it down :D
 
thumper_302

thumper_302

White Lighting
Re: Electrical/MSD Problem

As for the pulse, it is multiple pulse's when #1 is on the block. When we move the #1 plug wire away from the block it will pulse the timing light correctly.

Above are all good answers.

The wires are the high dollare 8.5 MSD wires and are brand new. Just to cover all our basis we check each wire with an omh meter, ever one was good. My Digital 6 is at MSD right now ready to be picked up and the currentl box is an old 6AL unit. No breaks in the wire cover, again-all new.

Tomorrow we are going to re-wire every thing on the MSD. Check our grounds for the
100th time. I like the spike idea with the alt but the alt seems to be working perfect.

I will take what I have gotten from you guys and when and if I figure it out I will let you know.

Thanks
 
SY2455

SY2455

70's Veteran
Re: Electrical/MSD Problem

Dumb ? follows. Could you be dealing with the multiple spark side of the msd unit ? As I understand it the Msd box will send multiple sparks though 20* of crankshaft rotation. I know when I take my Syclone in for a smog test and the guy hooked up the machine, the machine will go nuts and he can't get a reading on timing until he connects a figure 8 looking thing and lay it atop the motor to get a timing reading. My truck runs really good and get 25mpg on the Hwy and until I put the MSD unit on, the guy would just connect to the # 1 wire to get the reading.
 
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