turns over, won't continue running without starter

[hymodyne]

.After looking over comments concerning the high idle and rough running I was experiencing, my friend and I had got the car to settle down to about 2700 but no lower. we put the seats in and we had a cool moment- sitting in the car in the seats-with the engine running for the first time. a smile and nod were shared between friends listening to a project coming along, when poof! a loose ground wire contacted a voltage source, probably the back of the headlight switch (not stock), and suddenly we were in emergency mode: I pulled the hot wire away from the rest of the harness, and my friend disconnected the cable from my master cut off switch. damage: one ground wire in the center of the harness, so I had to trace it back all the way to before the melted wire is present, roughly 14 inches of new ground wire was spliced in. I re wrapped all of the larger arteries of the harness and turned over the ignition. It turned right over but seemed to only have spark when I kept the starter engaged. at the moment the starter was engaged, it would turn over. I checked plugs 1 & 6 and each showed consistent spark as I turned the engine over. when the starter was not engaged, the motor would not continue running, again after running consistently for 15-20 minutes prior to the electrical problem. Is there a different wire for starting power and power after the starter is not engaged?

james

[Spider]

The ign system you have is probably a ballasted coil system. A 6 volt coil is feed through a ballast resistor, but when starting the coil is fed 12v from the back of the solenoid, white/yellow wire by-passing the ballast resistor to aid cold starting. once the car has started the feed to the coil reverts back to the lower voltage fed via the ballast resistor.
Hope this helps and if you do not have a manual let me know and I will post up colour codes for the relevant wires to look for.

I have looked in the manual now. Check your fuses one is probably blown after you shorted out the electrics. The one which feeds the coil will have a white wire one side and green the other side. the ballast resistor is in the form of resistance wire connected between a white wire and the white/yellow connected to the +ve terminal on the coil.

[hymodyne]

Update:

Two white ignition wires were disconnected in my search for the end of the fried wire. I put them back in and re installed the ignition and she started fine. idle is down to 2200 without choke.

Getting closer,

James

[piman]

Hello James,

what have you checked on the carburettors? You should be able to get it to idle at 700 rpm without any problem?

Alec

[LadyScrumpy]

have you got a high pressure fuel pump on it?  If you're running too much pressure it might over-rev.

1.5psi is about right for a gt6.  If you're up at 5psi then you ought to regulate it down a bit.

Test the fuel pressure with an old vacuum gauge if you've got somethign that'll go low enough.  We've just done that on my other half's MGC.

I smirk a little every time the bonnet goes up on that thing! hehe.

[firebobby]

My car did this a while back, turned out to be the Ballast resistor had failed, fitted a new one and it stayed running after I released the key :)

[hymodyne]

getting new throttle shafts and bushings fitted soon. Should resolve things. Both shafts were in this shape:

James