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Difficult / No Start when warm ???

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George Zeck

George Zeck

Jedi Warrior
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Hi All -

Having some difficulty in starting my car lately. When cold - vroom, no prob. After 10 min or so of driving -- it's either difficult or won't start at all. This is <span style="font-weight: bold">opposite </span>to everything I've ever know about cars.

What's changed lately - I've added a Weber carb setup. This now has given me 'choke control' (which was stuck on before 100% of the time).

A friend mentioned that me that since I do not have a heat shield as I did with the SU's), maybe the fuel is getting too hot in the bowl inside of the new Weber. Causing something called 'vapor lock' (never heard of before).

When she gets tempramental (the car) - it just turns and turns but never kicks. Ususally IF I am luckly to get her started, it's with a heck of a lot of gas pumping.

Anyone ever experence this with a <span style="text-decoration: underline">WARM </span>car??? Any ideas on how to fix it? Maybe add / modify a heat shield ??

Tx-

George
 
Sounds like classic vapor lock to me. Did you go to headers at the same time?

Yes, a heat shield might help, as well as routing fuel lines away from exhaust heat.
 
*edit* I also think they make a thicker, more insulating DGV-to-intake gasket as well, but you'd want to check carb-to-hood clearance to see if you have the room to run it.
 
Have you changed your timming to get the carb to Run good/ with out mid throtell hesation? runs really loose so to speak. Advanced the timming? If you did give up a degree or two it should clear up. hmm... oh I had this problem.
Ifyour running a 948 I can give you some jet numbers to start with. the DGV setup comes prrty heavy for a stock 948.
 
I dont think it is vapor lock. the runners on a DG manifold are as long as my arm. Tuning the DGV to run good - fair -aceptable? takes a little tinkering and a hand full of jets and some reading to really get the jest of how to make things just rite. heres a link to what is probley the best discription I have found on tuning one of these beasts.
it for a 510 datsun but the same basic procedure

https://dimequarterly.tierranet.com/articles/tech_weber_tuning.html

excellent info
 
Just for grins you may also want to look at your coil. Sometimes when they get old they stop working when they get hot. Replace it with another one before you spend too much money on the carbs.
Bill
 
I believe the timing is good. Car runs wonderful (when it starts). So to me (a little uneducaated on the topic) -- that would eliminate the carb tweaking.

The fuel line does go a little close to the header (new this season) - maybe I'l either re-route it or try some insulation or sorts.

I'lll run it for a while and check to temp of the coil. It's Petronix and ~ 4 years old ( 10k miles). Is there an easy way to test this (volts ??)

Clearance is really tight (hood to top of carb) - I' d prefer not to make it any worse, but if I have to, I have to.


At least I have a 'direction' to start looking.

Thanks all.

George
 
I agree with BillM.

Go the coil first. As it warms up the insulation in the coil breaks down......
 
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