Hot starting problem with Webers

[ckissick]

I tried the search, but...

I have a 1970 911E with a 1978 3.0L with Webers. Yesterday on a hot day (about 90 degrees), the car wouldn't start after sitting for about 15 minutes. It cranked fast, but no start. I tried, waited, and repeated for about 2 hours before finally towing it to the nearest Porsche wrench. He got in and it started right up.

So what causes this with carbs, and how can I prevent it from happening in the future? It never did it before in 8 years. The carbs are rebuilt and in good condition, and the car runs great once it's going.

[john walker's workshop]

any pumping makes it worse. just open the throttle about 1/3 and crank until it fires.

[Steve@Rennsport]

Charlie,

John's advice is golden, of course,....

I hope you installed the insulator kit between the heads and manifolds.

[ckissick]

I do have the insulators. I had tried starting it the way John suggests, but no luck. The mechanic who got it started said he turned the key with his foot off the gas, waited 2 seconds, then floored it.

Is there anything to be done to prevent it from happening in the first place? (I suppose PMOs would solve it, but too much $$$ for now.)

[Arctic Rat]

Just a thought, had similar starting issues. The problem was from the points being out of adjustment. If your not using points then disregard.

My points had worn enought that they did not provide much of any spark, the engine will crank real easy allowing it to flood,put the proper gap into the points and fired right up ran great.

Good luck
Joe D

[john walker's workshop]

sooty plugs don't help. most carbed engines have them. try some denso irridiums in a hotter heat range. you might look down the 6 throttle bores with a mirror and flashlight after it sits hot for a few minutes to see if any drooling is going on. every engine is a bit different on how it starts the best. maybe yours likes a wide open throttle to let lots of air in.

[Steve@Rennsport]

At this juncture, it bears mentioning that fuel pressures and float levels must be perfect. Further, one should confirm that the floats, "float" and needles are not sticking.

Today's alcohol-laden fuels are not kind to carburetors and one must be diligent about setup & maintenance.

Lastly, one cannot troubleshoot carburetors if the ignition system has issues. Make sure you have a nice fat blue spark at the plugs when cranking.

[unclebilly]

Is it possible that the carbs have not been drilled to prevent percolation? Could the carbs be percolating them selves dry?

[RWebb]

Originally Posted by Steve@Rennsport

....
Today's alcohol-laden fuels are not kind to carburetors and one must be diligent about ...maintenance.
...

Steve - can you outline the proper maintenance & its scheduling?

[Steve@Rennsport]

Originally Posted by RWebb

Steve - can you outline the proper maintenance & its scheduling?

Sure,....

Given the physical properties of ethanol and its corrosive nature, its important to:

1) Always store the car with a full tank of gas to prevent condensation.

2) Use a good healthy dose of Stabil in the fuel at all times.

3) Annual inspections of carburetor floats and needles.

4) Annual replacement of fuel filters. We use a filter unit that incorporates a water separator before the carburetors.

Hope this helps,

[ckissick]

Good tips, Steve. But what's Stabil? Did you spell it right? I googled it and just got Adidas shoes.

[TimT]

Sta-Bil

[Steve@Rennsport]

Originally Posted by TimT

Sta-Bil

Thank you, Sir,...

Its a superb fuel preservative.

[carrera turbo]

hello there all

i have rebuilt a few sets of carbs in the past few months. mine on my 2.7 race car. my car starts in 80 DEG. weather like fuel injection. so two different guys wanted me to rebuild there carbs and make theres run as mine does. all are plumbed the same and vented they all even run the same filters and rain shields.

so one runs great starts ok hot but a 2.2 i cant get to start hot without holding throttle part way down or cranking for 8-10 seconds. it is jetted and synced very well. i even adjusted the valves for him because i thought this might help. no difference. all ignition parts are good timed and it just is hard to start. i think he is a little upset that his car didn't turn out as well as the other two but i cant get it any better. he said it runs better than it has in the last four years and has always been hard to start.

does he just live with the hard start ? he has the insulators between the manifolds and heads. car starts good cold runs well hot.

sorry to hijack

cheers ed

[Grady Clay]

Try this:

Originally Posted by Grady Clay

Here are a couple of important links for prior Pelican threads.

“Hot Start with carbs”
http://forums.pelicanparts.com/showt...hreadid=154032


“Weber circulating fuel system”
http://forums.pelicanparts.com/showt...hreadid=205823



The Pelican Search function will yield more.

Best,
Grady