Damp weather charging problems

[Brandywine68]

I'm having trouble finding a gremlin in my 68 coupe, On cold damp mornings it starts fine runs great for about 30 seconds then goes way rich or loses ignition or both. It does this till it warms up and then runs great for the rest of the day until the next morning. Sounds like a common problem right? Ive tried everything. New carb, MSD ign, Dist, battery, coil, alt, volt reg, stereo, checked all wiring bumper to bumper, cleaned and tightened all grounds, disconnected all electrical components and still had problem, put back in the mech fuel pump. I've done more I'm sure but I don't remember right now. It acts just like a miss adjusted choke (Electric) black smoke and everything but my amp gauge goes into the negative and the lights dim. Its eaten voltage regulaters in the past and two red top batteries. Thats why I'm thinking its electrical. After it warms up it purrs like a kitten. I've bypassed the resitor wire and the ignition switch all together. The only things I have left are the plugs and wires. I'll change them tomorrow if its nice. Any suggestions? 68 coupe origional 6 banger, converted to 302 mild, Holley 750 vaccuum electric choke, T-5 conversion.

Also I get 12 volts at the coil while its running poorly. This makes me suspicious of the high tension side. The cap, rotor, wires and plugs. What do you think?

 

[MitchGT]

try disconnecting your electric choke. also, don't you think that a 750 cfm is a bit much for a mild 302? I know it's a vacuum secondary, but that still sounds a little big. If the problem ends up being the electric choke, you might think about putting on a new 600 cfm vacuum secondary. I had one on my modified 289 and it ran great.

 

[Brandywine68]

Yes it probably is too much, but it runs great. I had a 600 Holley on it and changed to the 750 trying to fix this problem. I disconnected the choke a while back and it made no difference, however, today it was cold and raining so I heated the carb and choke area with a heat gun before I started it and it made a difference. I will try adjusting the Choke again for about the third time. Thanks for your reply. It helps to feel I'm on the right track.

 

[tos]

Just out of curiosity how is your choke wired (where is its power coming from)?

 

[blk 02]

Yes it probably is too much, but it runs great. I had a 600 Holley on it and changed to the 750 trying to fix this problem. I disconnected the choke a while back and it made no difference, however, today it was cold and raining so I heated the carb and choke area with a heat gun before I started it and it made a difference. I will try adjusting the Choke again for about the third time. Thanks for your reply. It helps to feel I'm on the right track.

If you disconnected the electrical choke then dosent it stay closed? I'm pretty sure that it requires 12 volts to heat the bi-metal spring and open the choke. I would ensure that your choke plate is open.
Graham

 

[Brandywine68]

I disconnected it just to see the difference. If I remember correctly it didnt run well enough to tell.

The choke is wired through my ignition circuit with the resistor wire bypassed so I have 12 volts there always.

This morning I went to adjust the choke again as promised and it was fully clockwise at the stops that holley put in. Little pins that keep people from over turning the cap and damaging it. My choke wasnt coming off fast enough so I needed to go more clockwise. I've been down this road before obviously because the cap was turned to its stop, so, I pulled out the stop pin and turned it a little more. This morning it ran great but it wasnt very damp out, still I have some confidence that the problem is fixed. stay tuned and thanks for your help.

Basically I found out a good way to troubleshoot choke problems. When its cold and damp out, heat the sucker up with a heat gun before the first start, if you have no problems, the choke probably needs adjusted. I'm guessing if this works that the base adjustment was just off enough to take the cap adjustment out of its range.