1973 2500M ignition issue

[Jmulloy]

Hoping someone can help with this problem.

While driving the car I hit a small bump, which caused the car to lose complete power and come to a dead stop. Was able to restart car on full choke and drive it home. Ran ok, but not great. When I got the car home, I popped the dizzy cap to see if something was a skew and upon seeing nothing replaced the cap. Car wouldn't restart. Only way I could get it started was to rotate the dizzy about 180 deg, but obviously this wasn't the solution.

I took it to a local mechanic who replaced my Crane xr700 with a Pertronix system including a Flamethrower Coil. Seem to run ok when I left the shop and then the RPMs started dancing around like a yo yo. 2K rpm to 0 and back to 2k. Mechanic is telling me that my SU6 carbs need to be rebuilt, but I think something else is wrong.

Any help is greatly appreciated.

John

 

[Deleted member 8987]

The 180 out is a common malady, even affects professional mechanics. You plugged the wires in wrong.

The only safe and reliable way to replace a cap is remove the old cap with all wires still installed.
Ensure position of cap relative to distributor body (i.e. don't rotate it).
Install new cap, holding old cap above in exact rotational alignment, move one wire at a time.

The jumping tach is often a related issue with electronic ignition upgrades, and I cannot recall the exact fix, as I eschew electronic ignitions.

Probably covered in other sections of this website.

Usually a bump and die is wiring...corroded connector, corroded or loose ground.
Check voltage to coil or electronic ignition with key on, ensure fuel pump running properly.

Dave

 

[Jmulloy]

The 180 out is a common malady, even affects professional mechanics. You plugged the wires in wrong.

The only safe and reliable way to replace a cap is remove the old cap with all wires still installed.
Ensure position of cap relative to distributor body (i.e. don't rotate it).
Install new cap, holding old cap above in exact rotational alignment, move one wire at a time.

The jumping tach is often a related issue with electronic ignition upgrades, and I cannot recall the exact fix, as I eschew electronic ignitions.

Probably covered in other sections of this website.

Usually a bump and die is wiring...corroded connector, corroded or loose ground.
Check voltage to coil or electronic ignition with key on, ensure fuel pump running properly.

Dave

Thanks Dave. I didn't unplug the wires on the dizzy when I removed the cap and replaced it in the exact same position prior to removal.

Can you point me to some info on the jumping tach issue?

John

 

[Deleted member 8987]

There are three ways for the distributor to get out of position. If the gear slips, but that won't be 180. Replacement rotor that's 180 off (seen it in other cars) is number two, wires replaced in wrong sequence is last and the only viable source in this situation.

 

[Deleted member 8987]

Actually, there is a fourth, seen it a couple of times.

Folks carefully mark position, remove distributor, tear it all down, re-assemble with the spring pegs for dual counterweights 180 out...the rotor is part of that separate shaft, and it will now be off 180.
Points or electronic don't make any difference to firing order, but a new plate or breaker can move the timing a bit.

 

[Jmulloy]

Actually, there is a fourth, seen it a couple of times.

Folks carefully mark position, remove distributor, tear it all down, re-assemble with the spring pegs for dual counterweights 180 out...the rotor is part of that separate shaft, and it will now be off 180.
Points or electronic don't make any difference to firing order, but a new plate or breaker can move the timing a bit.

Thanks Dave. I found a disconnected wire on the tach and a loose ungrounded wire next to it. Jumping tach problem gone.

I can get the car to idle nicely, but when I get it on the road and stand on the gas I'm getting sputtering and an occasional backfire from the tail pipe. Still a timing issue or do I need to start looking at fuel delivery issues?

John

 

[Deleted member 8987]

Have you used a timing light to see where it really is?
Got the proper coil for the new ignition?
Easy things first.

 

[glemon]

I agree with Dave, and will also add that the things you have been messing with (ignition) are more likely to be the problem than the thing you have presumably left alone, the carbs. Does it still do the sputter and backfire when fully warmed up or only when cold? Did it do it before the dead stop issue that started it all. One thing that concerns me is that the fix was sort of a shotgun approach, swap out and replace a bunch of stuff and see if it works now, don't get me wrong I have done it myself, but then you still can't be certain that you fixed the original problem.

Fuel delivery is usually and all or nothing type of deal if you are simply talking about getting gas into the engine, as far as getting the right mixture, that is a whole nother can of worms. I would check the timing first, if you don't have a timing light, the old Triumph manuals talk about setting the timing by feel/rpm, as you advance the timing (by turning the distributor towards the direction of the spinning rotor with the motor on and a thick leather glove on your hand) the engine should speed up, turn it until it gets to its highest RPM, then back it off just a little (if you back off to the point where RPMs drop appreciably, you have gone too far) you should now be in the ballpark of good timing for the engine to run well. If it is warm it up and take it up a hill in third at about 2500 rpm or so, if you get "pinking" (kind of a clattery noise coming from the motor) as the British call it, you are to far advanced, and need to back off a little, if you don't get any you can try to advance it a little and see if you get any then, for optimal timing you should be just off the "pinking" threshold.

Timing lights are good to show if your vacuum and mechanical advance are working right, but I lived for years without one and never blew a motor up.

Anyway, since timing must have been messed with, and since the timing being off often leads to backfires, I would check that first, a would suspect something in the ignition if you hadn't gone to a Pertronix, but they are pretty much just on (working) or off (not working) unlike points which can give a weak spark with bad points or a duff capacitator. Another simple test is to run the car in the dark and look for any arcing (electrical sparks) on the cap or plug wires.

 

[Jmulloy]

Thanks for the response. The car "pinks" when its hot or cold. I'll try your approach.

John