Understanding ignition switch & circuit
 

Thought I had an ignition switch issue when I first tried to shut off my 77' 930. The hesitation got me thinking I might have an ignition switch problem, but I soon learned that it's the nature of the beast. Would someone please explain what's going on here: why the delay? How do the components interact? where are they located? Thanks in advance!

I first have to presume that the '77 is no different than my '87 with regards to the ignition shutoff delay relay. There is a silver rectangular "can" on the relay panel in the engine bay (left side). Said relay will keep the ignition (i.e., spark to the plugs) active for a second or two after you turn the ignition key to OFF. It serves to keep the engine running without the pumps, just on residual fuel pressure, to bleed down the fuel in the lines. The reason being to minimize or prevent leakage of fuel through the injectors after the engine has been shut down.

Mark, thanks for the reply. Makes sense. When the can goes bad, do you know if it will prevent engine shut-off? I went out for a drive today, and when I returned, the motor would not shut down. I replaced the ignition switch, but no difference. Had me wondering if the time delay function was causing trouble.

Potentially it might behave like that. I just replaced mine few months ago. First symptom in my case was draining of battery. Not much, but after two weeks without driving the battery was empty.

When it got worse, the engine shut down took longer, but still manage to switch off. I would not be surprised that in some cases it just don't let stop at all.

New parts are now in black case and slightly larger, but fits in well.

My ignition shutoff delay has not worked in at least 8 years (no delay at all) - I guess it would be a good idea to replace the box (they're really pricey though, right?)?

So, does your motor shut down right away?

Yes, shuts down right away like any "normal" car (no delay at all when the key is turned to "off"). The delay has never worked since I have owned the car (about 8 years or so) - I knew it was supposed to have a delay (and the reason for it), and that the silver box on the rear fuse/relay panel was the controller/relay for that function, but have never done anything about it.

Thanks Ronnie. Lately it feels like my old days with Triumph, BSA, and Norton. Lucas electrics, (aka), "the prince of darkness."

anohter fuel head query
 

Disregard - trying to do new posting.
Alan

I used to ride vintage Triumphs. I'll never forget replacing my headlight. Right on the box
it says "Lucas Prince of darkness"
Not real confidence inspiring.