Itinerant Air-Cooled

Have a '74 automatic with a 1800 and dual webber carbs.

And I also have a hot start issue.

Engine starts up just fine when cold. Drive for a while and stop. Starts back up just fine. Drive for a while. Stop. Starts just fine again. Drive it a while longer, stop, and it won't start. It cranks, but it just won't catch.

Replaced the points about 400 miles ago. Engine replaced 1000 miles ago.

Thoughts?

kiltgy wrote:Have a '74 automatic with a 1800 and dual webber carbs.

And I also have a hot start issue.

Engine starts up just fine when cold. Drive for a while and stop. Starts back up just fine. Drive for a while. Stop. Starts just fine again. Drive it a while longer, stop, and it won't start. It cranks, but it just won't catch.

Replaced the points about 400 miles ago. Engine replaced 1000 miles ago.

Thoughts?

What is your starting procedure when warm?

Check dwell (44-50*)

Warm-to-hot engine starting procedure:

As soon as you start cranking the engine, slowly press accelerator to floor and leave it there until engine catches. Don't let it rev up. This is true for all carbureted engines on hot days.
Colin

Yep. That's what I have been doing. Unfortunately it is not working. I will check the dwell when I retrieve it this morning.

"As soon as you start cranking the engine, slowly press accelerator to floor and leave it there until engine catches. Don't let it rev up. This is true for all carbureted engines on hot days.
Colin"
Yeah yeah? You answered my question too. Bus2 is cranky to start when hot after sitting for a spell. I will try this.

This is probably old news, but I just replaced my carb float with a hollow plastic model due to frequent hot flooding. That and a readjustment of idle seems to have cured my hot start irregularity...for now...

Dwell is rock steady at 49. I'll go a bit easier on the gas when starting hot in the future.

Just out of curiosity, is this something that electronic ignition would help alleviate?

Based on what I have read, this seemse to be an issue of air starvation, not ignition. I will say that my fuel injected, electronically IGNITED Vanagon does not have this issue...very often. I suspect that this is due more to the injectors than the ignition.

cegammel wrote:Based on what I have read, this seems to be an issue of air starvation, not ignition. I will say that my fuel injected, electronically injected Vanagon does not have this issue...very often. I suspect that this is due more to the injectors than the ignition.

Seeing as my breaker points-equipped cars all start reliably enough in Hell, no, I would not assume the electronic ignition is going to fix what has been determined here to be "fuel percolation when warm" problem which afflicts all carbureted engines to varying degrees.

Flooring the accelerator simply helps to lean the mixture as best we can, it is not related to "air starvation" so much as a surfeit of fuel.

Colin

Ah! Fuel percolation! That explains the hissing and spraying when I removed the carburetor top the other day.

cegammel wrote:Ah! Fuel percolation! That explains the hissing and spraying when I removed the carburetor top the other day.

The way I understand it, is the fuel that expands (boils?) in the pump- to-carb hose needs somewhere to go. It can allegedly bypass the needle valve with excess pressure that the factory Pierburg pumps are designed to bleed off. I have noticed an extremely significant decrease in hot-start cranking time with mine, though ONE time it did take almost ten cranks. Of course this was parked right next to Chloe, so for all I know the bus was just nervous.

cegammel wrote:Ah! Fuel percolation! That explains the hissing and spraying when I removed the carburetor top the other day.

Next time, look down the throat of the carburetor.
If you can see/hear dripping/hissing with fuel vapor smoke, it suggests a too-high float level among other issues.
Colin

Dual Webers, which ones? Fuel pressure regulator installed? float levels correct? Right size venturis for your application? Jetting in the ballpark? From your description I would think fuel delivery is your problem if you're running IDF's, maybe to much fuel pressure and wrong float levels, wrong size idle jets, carburetors not balanced and synchronized, to name a few problem areas. Ainokea