I've had a long time intermittency with my ignition system. When I put my latest engine (a 390) in my 76 F100, I didn't use the Duraspark box as I didn't have a magnetic trigger distributor. At first I used an FE distributor with a Crane optical trigger, triggering my MSD 6A box. Later I acquired an FE magnetic trigger distributor that triggers the MSD 6A box. I use an MSD blaster coil. Several years ago I began having ignition cut out at the same time I was suffering pin hole leaks in my radiator. Eventually I got myself a nice new radiator that doesn't leak. I was attributing ignition cut out to the coolant spray fouling my ignition parts. Alas I occasionally would have episodes where I couldn't start my truck. As I read MSD instructions for troubleshooting, I found that if I disconnected my trigger harness from the distributor, and shorted one pin to the other, it would trigger the coil. I would often do this test, hear the coil spark, reconnect, and the truck would start. Over the last year I haven't driven the truck much because I had a carburator that failed. Since I've fixed the carb, I've been having an increase in electrical intermittencies. Recently it's taken, pulling the coil wire off the distributor cap, then shorting the trigger wire, seeing a spark, putting it back, and then the truck will start. I was suspicious of the magnetic trigger inside the distributor, but then remembered that I'd had the same problem with the optical trigger. The other day, the truck died randomly (thankfully two blocks from home) and i couldn't get it started at all, even scabbing in a second MSD 6A box. I noticed a break in the coil wire insulation. I replaced the coil wire and got the truck started. Often I can start the truck the first time I try during the day, park somewhere and when I come back 1/2 or more later, have to fiddle with the connections to get it started. I was looking over the MSD tech site yesterday and realized that they tell you not to use solid core wires. I've been using solid core wires I think the entire time. I'm waiting for authorization to post on the MSD tech forum, and will ask there, but want some insight here as well. Before spending a C-note on a set of MSD wires, is it possible that the using the solid core wires have damaged either my box or my coil. I've thought about going back to the Duraspark, but some wires between the dash and the box have been cut, and I don't have the trigger wire between the distributor and the box. I also don't think I have the proper (stock) wiring to the coil anymore. I've also been tempted by the idea of using DUI as a wiring simple solution. Ideas?

PS how come my profile picture doesn't show in my signature even though it indicates in my signature that it will?

 

At first glance, this sounds like an intermittent wiring problem (such as a loose crimp terminal) or a ground issue. Are you able to find specifications for the MSD coil that let you check it, such as primary and secondary winding resistance?

 

Grounding connections have occurred to me, I'll revisit my grounding points, clean and tighten. As far as the two power feeds into the MSD box, they have 11.7-11.8 Volts usually when I check. I have no idea how to check coil resistances. I remember 8-9 years ago going round and round w/ auto parts people about testing coils and whether or not the power to the coil was suppose to be 12V or less. The MSD box provides the coil power now. Just tonight I got two blocks from home, the truck died for 5 min. I didn't disturb any grounds. This intermittence is eroding my confidence to drive my truck.

 

I would try to isolate the problem. Since it seems to happen on a regular basis, it may not take too long to narrow it down. The first thing I would do is run hot wires from the battery to the system, bypassing all the truck's wiring. It will be fairly inconvienent to open the hood and take the wires off the battery all the time, but hopefully it won't take to long for it to fail or not. If it still fails to start, then you know the problem is with the ignition system itself.

 

I'm starting to think that I may have a carburetor flooding problem. I reconnected my grounds. I notice that every time I test for spark by either listening to my coil buzz or ac tually pulling my coil wire and seeing it zap against the power steering pump bracket that I see and hear what I'm looking for. The pattern seems to be that I have no problem starting the truck initially. I just went outside and fired it up for 5min, no problem. After 10-15 min of running, or if I park somewhere for awhile, that it dies and I can't start it for 5-10min. I does smell gassy while I'm trying to start it. I had a shop rebuild the carb recently. I don't have much experience with carburetor repair. I tried to rebuild an old Holley 2V once with help from friend, and it didn't work out. I'll need to go to a carburetor specialist. The last two evenings that I've gone on test rides, I've had the truck stall out and leave me futilely fooling with my coil trigger wire and coil wire. My theory is that somehow, fuel is pooling in my intake manifold to the point that it floods the engine, and then I have to wait for it to evaporate. I probably have multiple issues, I've had no power at my dash powered voltage gauge a couple of times briefly when playing with the harness between the charging system/ignition switch, but I haven't had THAT happen since I tightened and cleaned my grounds. I may have to move this to the engine board. Also? How do I shrink my picture to show up next to my name at the beginning of my posts?

 

The next time it stalls and you suspect it's flooding, hold the pedal to the floor and try to start it. This will help determine if it's actually flooding or not. In some extreme cases such as a stuck needle and seat in the carbuertor, you can look in the throat of the carburetor and actually see fuel pooling into the intake. In very extreme cases, fuel will dump out of the bowl vents.

 

Where you have your picture now is called your "signature". The little picture is called the "avatar".

Just stick your picture in the "avatar" settings. If it says it's too big, you will have to open a program on your computer(usually one that comes with a digital camera) and get the picture and shrink it in that program, and then upload it to the avatar.

 

I took the truck to a carb specialist who ruled out the carb, but did make some adjustments to it for me to improve idle. They told me the MSD box was bad. It started right up for them and ran for 20min and then quit suddenly, they couldn't restart it. They said no voltage at coil. The compared coil readings to an identical MSD Blaster 2 coil that they had, and it had identical readings. They said replace the box. I had them install my spare box that ran OK for a year in another truck I used to have, and has never been under the hood of this truck. When they finished the truck, it ran fine. I took it home and parked for several hours. When I went out to drive later, I couldn't start it. I again pulled the coil wire and shorted the trigger wires to witness spark off the coil wire. I got spark, put it together and it started right up. I haven't had it stall while driving so far, but I don't get what's going on. Can the coil have an intermittency that doesn't always show while taking ohm or voltage measurements? MSD tech has reported to me that the solid core wires shouldn't damage the box, just cause missing and timing fluctuation. I don't want to buy the expensive wires until I know that it will solve my problem. When the truck wouldn't start, there was both 12V present at the main power wire, and 12V at the ignition switch lead as well. When I couldn't start it after getting it home, I noted that I did have voltage in the cab. BTW, my picture is a bit to big to make into an Avatar, and I can't find a way in my new MacIntosh to resize the picture yet.

 

I am not sure what you mean by shorting the trigger wires, but what I would do is buy a momentary switch and wire it to the starter relay, so you can turn the engine over under the hood. Wire one side of the switch to the batttery +, and the other side to the "s" terminal on the solenoid on the fender. As soon as it won't start, I would open the hood, take the coil high tension wire off, and hold it next to the block and use the underhood button to turn the engine over(make sure the keyswitch is in run) and check for spark. If you have spark, plug it back in and see if it will start, using the underhood button.

If all you have to do is unplug the coil wire, crank the engine, and then plug it back in and it will start, then that is a really weird problem.

P.S. When using this underhood start button, make sure the tranny is in neutral or park.

 

You don't have my argument about it being a weird problem. I nearly needed a tow home today. The different MSD box didn't solve anything. What I mean by shorting the trigger wire is this. There are two wires between the distributor and the MSD box with a connector. The wires go between the magnetic trigger in the distributor and the MSD Box. MSD has a test where you disconnect the connector and touch a wire to each side of the connector to close the circuit between the two wires. This is like the trigger signaling the box to spark the coil. I'll try getting the under hood starter, I once had one before so I'm familiar with how it works. When my truck was dead, I clearly could make spark with my method, but for about 20-25min this time, I couldn't fire the engine. I thought I ran out of battery and called my wife to call for a tow. Then of course I was able to start and make it home. If the remote starter switch works does this prove that I have a bad ignition switch at the dash? Why is the engine stalling out and shutting off after I've gotten it started? A poster on the MSD site suggesting that I may have a bad ignition switch. He has played with old El Caminos and Bel Aires and has had similar problems that were solved by replacing crappy switches. Meanwhile I may buy a 79 4X4 that is supposedly somebody's dependable daily driver for $1300. I feel like something in my wiring harness to the ignition switch may be shorting out or getting hot. When the shop couldn't start the truck yesterday, they claimed the coil wasn't getting any voltage. I don't really know how to duplicate their test. Voltage at + while key is on? Or while cranking?

 

Ok, thanks for the explanation. If you you can short the wires together and get a spark, and but it back together and it won't run for 20 minutes, that tells me there is something wrong inside the distributor.

Since you can short the wires together and get spark, that means you have voltage to the MSD box from the ignition switch correct? So I think you are good there. Also if this works, that means the box and the coil are good too. What are we missing? The wires are not being shorted together when the engine is running. Whose job is that? The pickup in the distributor correct?

Does this sound logical? I don't know how your dist is configured, but I have heard of intermittent problems with distributors, were they have the points or the pickup mounted on a moveable plate(moved by the vacuum advance) and the wires are too tight or just worn out that go from the plate through the side of the dist to the coil or in your case the box. This plate moves continually, and these wires are special ones with many many strands, just like meter lead wire to keep them from breaking internally. But it still happens, and you can't really tell sometimes because the insulation is good, but the wire is broken internally.

 

I've been suspicious of the magnetic pickup, but have been led to believe that they aren't intermittent when they fail. Seems inexpensive enough to replace. I started the truck this afternoon and couldn't get it to fail. Ran for 1/2 hour shut down and then ran again an hour later. I do occasionally loose power to the dash and switch. That is solved by rearranging the Charging system to ignition switch harness until I hear my seatbelt buzzer. That shows up on my volt gauge and of course I can't even crank the motor, so that issue seems different than the engine dying. My dizzy is a stock Ford distributor with the magnetic trigger. I've been tempted to try the Davis DUI, or perhaps an aftermarket Dizzy by MSD or other good aftermarket maker.

 

Replaced the magnetic pickup last week. I haven't had a symptom since. Problem apparently solved. Thanks for your input