Help with Ignition problem

Fuel starvation?

Jim S.

 

Sounds like a plugged fuel filter or weak pump.

 

Does it only occur when the engine is warm, or doesn't that have any effect?

 

To expand on these observations, try this. Remove the top cover from the carb air box, fire 'er up and idle 'til she quits. When all's quiet, leave the key on...is the fuel pump still ticking? If not, it should be: Check out the pump. If the pump is ticking, turn off the ignition, quickly move back to the engine bay, lean over the carbs & move the throttle rod to WOT & observe if any fuel is squirting out of the accel pump nozzles. If not, close throttle & open again. Still no fuel? It it is most likely fuel starvation caused by a failing pump or intermittent power or ground to the pump, dirty filters (don't forget the small screens at each of the carb inlets), sclerosis of the fuel lines, or debris in the tank(s).

Now, if fuel is squirting smartly out of the nozzles, try to immediately start. If she lights off, let her idle 'til she quits & repeat the process one more time to ensure that you are indeed getting fuel. If she quits & you are still getting fuel, replace the top cover on the air box, pull a plug lead, hold it close to the plug & have someone crank her over. Listen for the "zap/zap/zap" (careful..., you don't want to FEEL the zap/zap/zap) of ignition. If no sparking, you likely do have an electrical gremlin.

Let us know the results of the above & we'll have a bit more to work with.

Now, when I rebuilt the carbs on my Dino, I installed a clear plastic filter in the rubber line just before the carbs. If lil' bits become trapped in that filter, the carbs will be saved & I'll know that something's not kosher with the fuel storage & delivery systems. And, if the fuel level drops to nil in the clear filter, I know I've lost fuel pressure. 'not original, but it helps me keep an eye on the condition and flow of the fuel.

Good luck,
Coop

 

Could be crap in the fuel tank too.

Had this problem once. Car would run for a few minutes, then quit. You shut er down, wait a minute, start her back up, runs for a while, quits again.

We had crap in the tank. When the fuel pump started it would suck the junk onto the fuel inlet, we'd burn what was in the lines, car would die. Shut the car off, fuel pump stops, junk floats off the inlet, rinse and repeat the cycle ad nauseum.

In our case it was leaves. someone had tucked a small handful into the tank causing the problem but I'm guessing anything could do it.

Might be worth a look at fuel flow to figure it out.

DM

 

The most common defect of the MSD 6A series is one or both inverter transistors failing, in that scenario the MSD 6A is completely dead or creates a very weak spark. You should not have a points capacitor in your setup as the points just switch a small current to trigger the MSD CDI.
For checking the MSD 6A, immediately after the engine dies pull one of the spark wires and connect a spare plug, which you then put on the engine or ground. Now try to start the engine again. If you can see a spark at the spare plug and the engine does not start on the other five cylinders, its most likely fuel starvation.

 

Excellent point.
Don't forget that just prior to entering the carb's float bowls there is a fine mesh screen as a final filter/surge device. Easy to check that point also.

 

Power for the ignition goes through the ammeter. You should make sure the terminals and connectors on the back are clean and secure. If the connections become corroded or loose, resistance will increase causing subsequent heat build up. It can develop into an intermittent problem that is hard to diagnose.
Aloha,
Mark

 

could it be a partial ignition coil failure. i.e able to charge until it gets warm, then leaks? Quick change of coil would confirm.
Kevin

 

Is the power input to the MSD protected by a fuse or a relay?

One of my cars had MSD on a relay and when it tripped off, this would happen......a larger fuse solved the problem.....

MSD does make a nice coil that will tolerate sideways mounting, never understood how Ferrari got away with that on the oil filled ones, a no no.......