Help with Ignition problem

My 246 GTS developed an ignition problem recently. It will run for approx 5 min and then cuts out. After waiting 5 more mins it will restart and run for another 5mins, and then the same thing happens.

It doesn't seen to matter whether its been driven or just ticking over in the driveway then same thing always happens.

It's got an MSD 6ALN ignition system. So far I've changed the rotor arm, points, capacitor, and coil and still it happens!!

For the 5 mins its runs it actually runs well.

My question is what to try next - Is it likely to be a distributor rebulid or does the MSD module need replacing?

 

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?

 

It happens straight from cold.

I've not checked for fuel starvation, but don't think that's it. It will rev freely before cutting out, and after doing so is completely dead (Just turns over). After 5mins it will restart instantly.

When it first happened I thought it must be the capcitor, so changed that, plus the rotor arm and the points (which were badly worn). That made no difference. So then changed the coil, even though it wasn't getting the slightest bit hot.

If anything since changing the capcitor, rotor arm and points the problem has got worse.

 

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

 

OK.

It's definately an ignition problem. Have checked fuel and that's all OK - pump still clicking away and plently of fuel squirting into the carbs.

However definately no spark at the plugs. I'm begining to suspect the MSD ignition unit and am contacting MSD to get their opinion.

 

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.......

 

I've already changed the coil, but made no difference

 

Have just changed the MSD ignition unit and all is well again. Not taken it out for a lenghty run yet, but she ran for approx 35mins without a problem.

MSD thought it must be a bad heatsinking problem on the unit, and as this unit isn't repairable, a new one was fitted.

Looking forward to taking it down to the Goodwood Revival in a few weeks.