Datsun Roadster Forum-311s.org

OK, I give up. this will turn out to be something simple, but I'm running out of things to check.

When I shut it off, it keeps running, AKA post ignition, engine run on. sometimes rather violently.

I have the engine running reasonably well, mixture and carb sync are close to right, timing set.I found a vacuum leak and fixed it, new plugs, a bit carboned up, but not bad. Ignition is shutting off.

Only thing odd is the rear carb wants the mixture screw about 1/2 turn from fully closed (lean) to get mixture set right.

Any input is appreciated.

You've got the culprits in your sights...Timing and the SU's (assuming you have the right grade plugs and that the ignition is shutting off completely!) If a cylinder or two is running hot or has a hot spot (too high of compression, carbon, corrosion, etc.), an engine will diesel. Combine this with bad timing and carb tuning and the cylinder will run hotter and it will be worse.

A band aid till you can get it tuned...Set the ebrake firmly, turn the key to off, dump the clutch in first and floor the gas pedal. As horrible and maybe as bizarre as it sounds, this kills the engine nicely. TR

TR,

I don't think he was looking for the "oakie" way to shut off his car. Sounds like a timing issue. Check the gap on the points and the advance. Your carbs should also be set pretty close to one another.

That method would work if I had a driveshaft installed.
I don't have points, Crane electronic. Timing is at 16 btdc, 3rd small mark clockwise from big mark, and mixture is close to right, runs badly on 1 carb, same front and rear.
Ignition is definately turning off, anyway it is dieseling, running backward without ignition system. Replaced plugs with new Bosch Platinum, took out Champion N8yc, 1 step too cold

May have found the problem(s)

1, carbon crap in combustion chamber, will add Techron and waterpistol the carbs
2. 87 octane gas in tank, forgot to get 93 octane, used the lawnmower gas can to fill up. only a gallon left, so will put in 5 gallons of 93 with the Techron and run it.
3. As per temp gauge and meat thermometer stolen from wife running normal temp, but electric fan thermo may be no good, hasn't kicked on automaticly yet.
4will put in a set of NGK plugs in case Bosch listing is off in heat range.

5 worst case, off comes the head and clean it up and check thickness/compression ratio.

Keep the thoughts coming, one of us will get it.

Hi Dave, Just curious, you mention you have Crane ignition, does it use a magnetic pickup made by Crane or are you using some other type of EI dizzy setup with the Crane.. Bill

I had a big block in a Suburban that used to diesel, and I'd just floor the gas to flood the combustion chambers with a cool(er) fuel/air mixture. It worked until the time I did it and it back-fired through the exhaust. It blew one of the mufflers wide open and set off car alarms in the area. Thank goodness for Midas and their guaranteed-forever mufflers!

It's a Crane XR-700, optical led pickup with shutterwheel, very simple. The xr-3000 version lets you run 12 to the coil, this one uses ballast resistor. Future plans call for MSD, so get rid if ballast then. There is a thorough write up at Cranes site along with the installation manual

Hi Dave, that sounds like a neat setup. I'm still using my points to activate my MSD 6al box. Another thought comes to mind, did you regap your plugs to a wider gap.
When I went to the MSD box and coil I regapped the plugs to .047-.048, not if it's the perfect gap, but it works for my setup.... Bill

I set them at .030, still runnung 8 volts at coil.

I take it you are using the stock coil! Plus even though you only have the 8 volts and are running through the ballist, are you sending more volts to the plugs with the crane unit and coil. I always thouht one would have to increase the gap on any EI setup. Dave, I admit I'm not familiar with the crane unit so this is all guess work. Bill

using a Crane Fireball coil. Basically a coil is a coil, just some have internal resistance so they don't need a ballast. If you go from 8 volts to 13.5 volts, you increase the spark voltageby almost 50%. The MSD actually runs way above 13.5 volts, but for a very short duration.

Check your idle speed. If I shut down while it's idling at 1500 rpm, the car diesels a bit. 1000 and below it doesn't diesel.
I'm running a Crane XR-3000 w/ PS92 coil.