GM EFI ignition troubles, requesting smarty-pants!!!

[Stumpuller6.5]

I look after a couple of Vortec 305 gensets that use MSD igntion components, (minus the plugs that are delcos.) that are having issues burning up the caps and rotors. These units typically run 1200-1500hours between services (has a large kidney filter system with large capacity of oil) and every time need the caps and rotors changed.

Well I was just out this morning and had to change cap and rotor on one of the units that had only 818 hours on it, it was missing and backfiring before it got to the point it would not run and/or start.

Changed them out and it was good to go, the other unit had 612 hours and was getting bad too.

I would like someone to figure out wtf is causing this issue. Distributor is OEM, ignition module is OEM, the coil, wires cap and rotor are MSD parts.

See pictures below.

Any thoughts?

 

[Bigredmariner]

Bad batch of electrodes? Have any of you guys tried to go back to GM stuff just to see how the GM caps hold up?

 

[drperry]

The MSD coil could be putting a little more oomph into the spark, causing premature wear.

 

[Zembonez]

Too much voltage.

High energy systems work great on drag cars, but they don't run for long at a time. I'd bet an OEM set up would work best here.

 

[drperry]

The cap and rotor can stay MSD, but definitely go back to a factory coil.

 

[Bigredmariner]

I did a little searching, the copper strap on the rotor looks like it is angled down in the pic. Makes me think that is wasn't in good contact with the caps' button allowing it to build too much heat and fail prematurely. Googled a few terms and found a few snippets on MSD's site leading in the same direction I was thinking. Basically MSD ignores the fact there is a problem, but the ones who have bent that contact strap up have reduced their failure rates.

I have a #8579 Small Diameter Billet Distributor for 302 Ford. This is used with a MSD 6T and High Vibration Epoxy Coil. I have been very pleaded with the funtion of the complete system and have not had any problems. Yesterday I purchased the new "Black" cap that you recently introduced. The dimension differences between the OEM cap and this one are of concern. Why for example are the lower ends of the brass terminal posts within the cap designed to actually be over .160 inch above the tip of the rotor, instead of allowing the rotor to pass "next" to the post? It appears that the posts are machined in such a way (cut on a lathe after assembly) that the rotor tip was intended to pass in a spining motion, but in actuality they are .160 above the rotor tip instead of "Next" to it with a normal air gap as in OEM design & application. It also prevents the spring tang from contacting the center button in the cap unless the tang is bent up quite a bit. There has been much concern on other forums regarding what was perceived as poor service life; I believe this to be the reason.???????????

 

[Black02Silverado]

One other thought, how old is the distributor its self? Maybe some wear in it?

 

[Stumpuller6.5]

It did it before with the stock coil, not as bad though. I will have to check and see how many volts are going into the coil....

That is interesting about the tang on the rotor, wonder why they wouldn`t have it bent up enough... may have to try that.

 

[bubbatrucklover]

You would think MSD would admit and address the problem. I always thought them to be a good company for aftermarket spark needs.

I personally like Accel but, still them and Mallory are what I thought the top 3 are.

 

[Stumpuller6.5]

I went back this after noon and bent the tang up a bit, probably 1/8". I also determined there is up to 3.0 ohms resistance from the negative on the battery to the ground a the rear of the block. I will make some new ground cables to go from the back of the block to the battery. For now I temporarily ran some small gauge wire that I had in the truck from one of the screws in the distributor cap to the negative on the battery. When it comes due for its next service I will see the results and install the bigger grounding cable from block to battery.