Hard to start Hot

[timc930]

Having a Hard to start hot issue, so today I bypassed the mech pump and installed a Facet Electric Pump, pulled the carb, took apart, let soak in carb cleaner for a couple hours then reassembled, installed the carb and truck fired right up. I let it idle for around 30 minutes to get good and hot, shut it down, waited five minutes and will not restart. If I hold my hand over the carb body while someone is cranking, I can usually get it to start. Also replaced the coil as well. Weber 34ICH Carb.

[SafeAirOne]

Well...if I were sure it's a carb problem, I'd start by looking for either an air (vacuum) leak at temperature or a fuel flow restriction at temperature, or, less likely but possible I suppose, a vapor lock issue.

Take this with a grain of salt though, since I don't use carburetors myself.

[timc930]

This may be a feed issue, as it fired right up this morning, let it run, shut it down, then it would immediately restart. Once I waited 10 minutes, it would not. I could hear the Elect FP running trying to reprime (pump is loud until it has it's prime), it wold not reprime until I removed the fuel line form the carb, then it began to flow. Going to check the lines coming from the tank.

Regardless of the above, there was fuel in the carb bowl, so it should be starting warm/hot, that's what is puzzling.

[timc930]

So there is nothing restricting the fuel flow to the carb. Looked in tank, very clean. Blew threw the lines. Today, I let the car idle for about 40 minutes and it just shut down. Fuel pump kept running (electric and wired to ign switch) but was very loud because it was not pumping fuel. I have no idea what is could cause an elect pump to all of a sudden loose the ability to pump fuel. Once car cooled off it fired up on first crank.

The car acts as if once the engine gets hot, the fuel becomes a vapor, and the elect fuel pump and the carb are unable to function until the engine cools.

[SafeAirOne]

It sounds like the fuel pump is being starved of fuel. Is your tank properly vented? Does the sound of the starved pump change when you remove the fuel filler cap?

Is the sediment screen on the bottom of the fuel pickup tube clean? Is there an internal sediment screen in the electric fuel pump?

[timc930]

It sounds like the fuel pump is being starved of fuel. Is your tank properly vented? Does the sound of the starved pump change when you remove the fuel filler cap?

Is the sediment screen on the bottom of the fuel pickup tube clean? Is there an internal sediment screen in the electric fuel pump?

No sediment blockage anywhere in system, carb pulled apart and cleaned this week, tank clean, all fuel filters perfectly clear with no sediment what so ever.

Tank is not vented, and I tried removing the cap several months ago when I was working this, but that was with the mechanical pump. But you are exactly right, it does act as if there is vacuum pulling against the fuel flow....

How should the tank be properly vented?

[Les Parker]

You could have a bad fuel cap. It should have a small hole for venting on IIa's and a vent valve on the Series III.
Try it will the filler cap removed.

[timc930]

Looks like it was a problem with venting, creating a vacuum all the way to the carb, as there was fuel in the bowl and it still would not start. Removed the gas cap, so far so good. I have drilled 2 1/8 holes in the underside of the cap....

Been running it all morning, getting hot, shutting down, waiting 5-10 and it has fired right up each time. Drove it a few miles did good. We'll see how it goes....

tim

[bugeye88]

Tim,
Great! Glad it was something so easy to fix. I've seen that happen in modern cars with their complicated fuel systems, but not often with Landy's. At least now you have all the jets in the carb clean and a good electric pump in place.

Cheers,

Rob
Bugeye88

[SafeAirOne]

I have drilled 2 1/8 holes in the underside of the cap....

Two and an eighth inch-holes? Wow, it's REALLY vented now!



Nice job. This is a well-known issue to me, unfortunately. My issue is always a clogged up sediment screen on the bottom of the fuel pickup tube though it's is essentially the same problem as a bad tank vent. Glad it was an easy fix.