Got new engine running...but it won't stop

[Corwin]

Okay, so I got the new engine running and held it above 2500RPM for a good ten minutes. But then when I try to shut it off it just keeps running.

Even pulled the coil wire off and it still kept going! Then I pulled the ground off the battery and it sputtered and eventually died. Anyone help me with this?

I've got an MSD box, coil and distributor all look to be connected properly.

[blacktruck]

msd getting feedback thru the voltage reg maybe?
talk to msd about where to put a diode 'tween the vr and the msd box

[joetron]

what carb?
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[Corwin]

It's an internally regulated alternator. The MSD box is wired directly through the battery but has a third wire that goes to the ignition-switched wire.

Carbs are dual Kads, just rebuilt.

[joetron]

have you lots-o-carbon in the heads?

could create a condition called dieseling, where the carbon basically turns into a glow plug.


when it keeps running, does it run smooth?
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[Corwin]

The heads are brand new, so I wouldn't think so. It runs at higher-than-normal RPMs, but idled fine.

I say idled because it won't start now - I get a scary loud clanking noise when I try to turn it over. Not good I assume, but just possible that the valves ne re-adjust?

[junior55]

The MSD run-on above is a definite thing... BUT you said you pulled the coil wire????

All MSD's need the backfeed diode on the alternator for sure!
How it runs without the coil wire is a miracle.
Was this a full out run ...or just a deiseling stumble run as mentioned?

[Corwin]

It was full out, like nothing happened. I did have the power wire for the box touching the ignition wire, maybe it was feeding through? No idea.

This diode though - which wire would that connect to? Pretty sweet how the two MSD manuals I have say nothing about that. Gotta love it. Question though - the MSD box is only "connected" to the alternator in the sense that they're both attached to the Battery...

I did figure out the clanking noise though - the new starter was TOAST. Was a high-torque performance starter too. POS. Put a stock starter on it and just like new.

[junior55]

The diode placement was a modification required by any transistorized device getting its "on signal" from some backfeed somewhere instead of completely from the on-switch.
I know several fuel injection computers will not shut down cleanly unless this diode is in place.

[Corwin]

Well maybe I'll give them a call about it. I got the engine running fine and broke it in but it still keeps running. I played around with the timimg a bit and it's better (at least cuts off when I pull the coil wire now).

Can you tell me more about the diode - what it is so I can find one and how I need to wire it in? I'm assuming on the ignition-switched wire but maybe not...

Thanks again guys for all your help.

[buggofast]

do you have any auxillary fans running on the engine for an external oil cooler maybe?

[Dale M.]

Start up car.... kill ignition... If you have run on , pull D+ wire off Alt or remove lamp from idiot light circuit .. IF engine dies you have a back feed through idiot lamp circuit.

An alternator (D+ lead) can possible back feed voltage through you idiot light and through connections at ignition switch to back feed you MDS box (control ciruit - RED wire to ignition switch) . Back feed does NOT have any effect on main +12 volt supply and ground leads wired directly to battery.

Solution may be to put idiot lamp lead on accessory position of ignition switch or put a isolation diode in line between idiot lamp and D+ terminal on alternator... Band on diode points towards D+ terminal on Alt.

Diode can be simple Radio Shack item (called Rectifier Diode) with a rating at least 3 AMP at 50 VOLT....

Also on MSD 6 box, if you are using magnetic pickups in dist, you can use white wire from box as a ignition disable switch... You just need to connect white wire to one side of switch and other side of switch to ground... If switch is "ON" on MSD box is disabled and engine will not start... MSD box is effectively grounded out and will not fire coil. If switch is OFF system runs as normal... Neat little ant-theft circuit if switch is hidden.

Dale
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All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[Corwin]

Awesome, thank you for that - really helps. I'm going to try all that today.

I actually did wire the white line to a kill switch behind the back seat (Ghia).

No auxiliary fans.

[Corwin]

Worked like a charm - thanks!

Took it for a spin around the neighborhood and I wouldn't say it was smooth sailing, but it was pretty fun!

[Dale M.]

Diode or rewire idiot lamp circuit to acc. side of ignition?

Dale
_________________
“Fear The Government That Wants To Take Your Guns" - Thomas Jefferson.

"Kellison Sand Piper Roadster" For Street & Show.
"Joe Pody Sandrover" Buggy with 2180 for Autocross (Sold)
============================================================
All suggestions and advice are purely my own opinion. You are free to ignore them if you wish ...

[Corwin]

Diode - couple of bucks at Radio Shack.