I have a problem with my truck and I can't figure out if it is electrical or fuel related or both. First off, let me tell you what I got. I have a 1977 F100 with a 351 Windsor with a little over 27000 miles since rebuild. It has an MSD igntition system and an MSD Blaster2 coil. The distrbutor is a Ford electronic distributor. I have removed the mechanical fuel pump and installed an electric inline fuel pump mounted on the outside of the driverside framerail between the tank and the engine. I also installed a transparent fuel filter just before the fuel pump as per directions. The carburetor is a remanufactured Autolite 4100 from Pony Carburetors. Here is my problem. I will be driving on the expressway at 70 or just down a backroad at 30 and it will run just fine and all of a sudden it shuts off like I killed the power to it. Here is what I have done to try and fix the problem. I changed out the MSD billit distributor and put the Ford electronic one back in, I swapped my MSD 6a ignition module for one that I had for another project which is an MSD6 AT module and it did not fix it. I also checked fuel pressure with an inline fuel gauge which is at 7 psi even when the engine shuts off. I also decided tor strait wire the ignition from the module straigt to the battery and mount a rocker switch under my dash instead of it running through my ignition switch. All my ignition swith does now is supply power to the starter to turn it over. The switch also lights up so you can see that the ignition is getting power. I figured that if when the engine shut off and the light from the switch shut off then I would no that the ignition was not getting power. Well, when the engine shut off shortly after I put the switch in the light on the switch was still lit. It never flickered. You name it I have probably already done it. I have run out of ideas. When the engine shuts off it want fire back up for either where between 10 minutes to 24 hours. The other day I was driving to work and the engine shut off I had my dad pull me home and once we got it home my dad took a can of starting fluid and sprayed down in the carb as I turned the engine over but it would not start. So he sprayed about half a can of it and it barely fired up and began to run. It should have fired up with just a single shot of that stuff. I know one thing is for sure. None of this started to happen until shortly after I replaced my bad alternator for a heavier duty 70 amp alternator from Advance Auto Parts.

Please help

Matt
Jacksonville, FL

P.S. I have some pics of my truck in my gallary that I took of it a few months before I changed the carburetor.

 

How's your wiring at the coil? I had a problem on a different vehicle where the wire that supplies power to the coil would work its way off. When that happened, it just died as if I had shut it off with the key. When I reattach the wire it starts right up and runs fine. Because the coil is downstream of the ignition switch, you wouldn't notice a power loss at the switch. The large connector at the coil that Ford uses would make it difficult to tell if the wiring was loose or corroded.

What do you have to do to restart it?

 

The wires come straight off of the MSD ignition and are secured tight.

 

Be very careful when using starting fluid, a 1/2 a can is a good way to wash off the cylinder wall's and do some damage to the motor.

How close is the fuel pump to the tank? Remember that an electric fuel pump is made to pump the fuel not suck it.

When it shut's down have you checked at a spark plug to see if there is spark?

 

The fuel pump is about 3 feet away from the tank. And as far as getting it started, I just have to weight it out for a while. Like I said earlier it takes any where from 5 min to 24 hours before it might start again.

 

When it shut's down have you checked at a spark plug to see if there is spark?

 

did you have to splice the wires for the larger amp alt? or just use the factory plug/connectors?

 

It mimmicks the ignition box. If you're sure both those boxes are good, I'd swap the coil for a known good one and see if that is what is letting you down. Did you change the voltage regulator with the alternator? If you thought the dizzy was the cause and that's why the swap back to the Ford one, is the electronic pick up in the dizzy at fault? Just shootin in the dark at what you haven't mentioned yet. Hope you get it figured out, cause I'm curious about the solution.

 

I would try the coil, sometimes when they heat up they quit working and once cool they work again, the same is true for just about anything electrical. For sure like was said when it happens again see if you have any spark.

 

There is a test that you do to see if the ignition and the coil is bad. There is a connector that connects the distributor to the brain box. what you are supposed to do is disconnect the 2 wires and jumper wire on the end of the plug. Then you disconnect the coil wire from the distributor and put it near ground. Then you remove remove the jumper wire and if everything is good the coil should zap the ground from the coil and you will here a pop or ping. Well, I did this with the jumper wire fast and each time I pulled it out the coil would trigger and zap. So the coil is very well. And this is right after the engine shut off so the coil was warm at the time. The coil would also trigger the engine to turn over as I disconnected the 2 wire plug from the distributor. I found that as long as there was fuel in the cylinders after trying to get it started that the engine would continue to spin each time I unplugged the 2 wires from the distributor.

 

I just thought I'd let you all know that I am pretty sure I found and solved the problem. My brother and I decided to take a look at my truck today and he said that when the engine shuts off again that I should attach a spark plug to one of the spark plug wires to see if there is fire to them. So, when the engine shut off I attached a spark plug to a plug wire and turned it over while he watched and sure enough it had no spark. So the next thing I did was grab the volt meter and check for voltage to the MSD box. There was only 1.5 volts getting to it(same as the voltage from a AA battery). So I traced the main power lead from the box back to the solenoid and found that when I wiggled the wire while the engine was running it would stumble and then shut off. I reworked the connection and so far no problems. So it ends up that whenever I would hit a pot hole or anything that would jar the truck it would die because of the loose wire.

 

Glad you got it figured out