List:
I had one of those dumb moments when I left the ignition turned on without the car running in the garage. I didn’t know this until a few days later when I went out to start the car and the battery was dead. Recharged the battery and started right up. Thought I was in good shape until I notice the car doesn’t run well and back fires even at idle. backfires less with the choke on then with it off. Doesn’t do it much on acceleration, more so with foot off the gas and idleing. I have the SNGB electronic replacment system for the OPUS system installed. Could the coil or amplifier get damaged with the igntion on for extended period and not running? Any thoughts would be greatly appreciated before I go down the path of diagnosing and checking systems. The car is 73 S3 2+2 V12 auto. Recently installed plugs, plug wires, and cap. New fuel pump and fuel filters. Car ran perfect before the ignition issue. Thanks in advance.
Jim Henningsen
Hi Jim,
The thing that caught my attention was that you changed the ignition wires and cap, if it were me I’d go back and triple check the order of the wires unless your sure it ran great after you did this. I would think that the amp would be all or nothing so I think that is less likely, I would try a different coil and see what that does. Could you have knocked a vacuum hose loose?
JMTCW,
Cheers,
LLynn
It ran great after installing the plug wires. I reseated all of them on the plugs and dizzy. still same. possible vacuum line. will check those. I do have a backup new coil that I can change. It also backfires through the carb. I am also going to check the fuel pressure as i thought the fuel pump might have been damaged from being left on without the engine running. Very frustrating. Thanks for the reply.
Hi Jim,
I know the feeling. I doubt it’s your fuel pump but I suppose it’s possible. The pump should put out about 3-4 psi and with the V12 it has a return feed to the tank.
Try the coil and see what happens. Good luck,
Cheers,
LLynn
You certainly can fry a coil if you leave the ignition on when the points happen to be closed.
If you’ve got points.
kind regards
Marek
Get the point ? …
The point being that the OPUS and the Lucas CEI ignition work by providing an ignition pulse when a magnetic pulse is received through a little transformer. Transformers don’t work on dc, but use ac, so it is the action of the change in current passing into the input circuit of the ignition which makes it work, not any particular static dc value which may (or may not) be present. Have a read of Bywater website for an explanation of how each of them works.
The Barrat ignition “upgrade” as I understand it is just a cleaned up and partially reconditioned Lucas CEI. A similar upgrade could be had if you just get one out of a trashed XJS and spend some of the money making good years of neglect.
kind regards
Marek
Thanks for the feedback. Turns out the auto tranny vacuum line for the vacuum actuator came off when I put the rains shield on. Put it back on and back to normal running. Thank goodness! I put two hose clamps on that line at the manifold so it doesn’t come off again.