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Spark or Fuel?

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bugedd

bugedd

Jedi Knight
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Recently I had my local Weber guru rebuild the used 40DCOE I picked up and put the suggested brass in it that was suggested by Pierce for a stock 1275. My car is, to the best of my knowledge, stock with the exception of a header. It was running better than ever, then recently it started coughing a bit. Idle seems smooth, but under light acceleration, it coughs and stutters. Fuel pump is a newer electric pump at 4psi, filter is new.
The ignition is a Cooper S mechanical advance dizzy, Pertronix electronic replacement for the points, newer plugs, and cap and wires that are unknown age but look okay.
What is a good way to determine whether its a spark or fuel issue?
 
I'm betting fuel. YoAu can buy a spark testor or remove a plug and see if it has a bright blue sark. That said, ifvit has a strong spark it will be across the whole range. Could be a mixture issue (my guess) or a vacuum issue. If it was an SU i would say it is an oil in the damper issue.
 
I agree with JP-sounds like it is a "lean misfire". I think that Webers have accelerator pumps and yours may be clogged or the "reverse valve" may not be holding well enough.
BillM
 
I'll drive it to my guy Monday with those suggestions and see what he thinks. Thanks for the input!
 
Okay, my Lucas DLB 105 coil seems to have an issue. Randomly, I decided to run the car with the bonnet up and listen and heard snapping, then turned off the garage lights and saw arching. Its between the positive terminal and the coil wire to the dizzy. What might cause that? I refitted the coil wire, and all seems well, but its still arching. Is that a wire problem or coil problem? The coil is new, but that really means nothing. The wires however are older. What to replace?
 
First thing that I would do is to wipe off the coil (just clean it). The combination of some dirt and some humidity will cause that arcing on the outside. If that doesn't stop it (it isn't really too much of a problem) then I would start looking for a new set of wires.
I think that this is a red herring- not the real issue.
BillM
 
If cleaning the coil doesn't fix it, there might be a crack in the insulator. Then, the only solution is to replace it. This is obviously a problem, so I'd fix it before worrying about anything else. That might be the whole cause.
 
I put on new wires today, runs great. Just a crapped out coil-to-dizzy wire. Easy fix thankfully.
 
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