Series III cuting out

[bchene]

Have owned LRs for many years, and have used the posts on this forum to address many 'unique' LR issues. I am stumped this time and can not resolve a current problem.
My current LR is a series iii, rhd 109 ex-mod with a 2.25 gas engine. When accelerating the engine will cut out and go to an idle. After a period of time, 30 seconds to a minute, you can start up again.
Sitting it will idle all day. When sitting you can goose the throttle, hold it, and it will never cut out.
The same symptoms occur as you start to go up a hill. Starts out fine but by the top, say 100 yards it will start to buck and go to an idle.

The following has been done over the last month.
Fuel lines replaced
Fuel filter replaced
Carb replaced with new Weber (old carb was a zenith)
Fuel pump replaced
Vacuum lines replaced
Electronic ignition module replaced
New dist cap, rotor, wires and plugs
Coil replaced
Vacuum advance checked
Engine valves and timing set

I have not replaced the dist. Timing advance works well and it holds the setting.
Questioned the fuel pump lever (lobe) wear. Engine runs great, compression good, oil pressure good. No overt sign of wear within the engine.

I am at a loss. I am sure I am missing something 'stupid'.
Any help offered is greatly appreciated.

[disco2hse]

Vapour lock?

[ArlowCT]

I have seen a new fuel line cross threaded and allowing air I to the system only under heavy loads. The truck idled fine and drove ok until it was under a load.

[SafeAirOne]

Did you clean the fuel strainer on the end of the fuel pickup tube in the tank? Did you loosen the fuel cap/check for a clogged vent hole?

Did you evaluate the amount of crud/water in the bottom of the fuel tank? When the malfunction occurs, did you remove a fuel line and check for a sucking sound?

Did you replace the condensor (if equipped)?

[JimCT]

The fuel tank valve is clogged. Just took mine apart , 68 ambulance and I have no idea how it was even running.

Did you clean the fuel strainer on the end of the fuel pickup tube in the tank? Did you loosen the fuel cap/check for a clogged vent hole?

Did you evaluate the amount of crud/water in the bottom of the fuel tank? When the malfunction occurs, did you remove a fuel line and check for a sucking sound?

Did you replace the condensor (if equipped)?

[bchene]

Thanks for the notes.
I checked the fittings at the tank, pump and carb. They seem to be even and tight.
I have run the LR with the fuel cap off, no difference.
The filter at the pickup tube has been removed and the tube cleaned. Tank also cleaned.
Under seat fuel tank valve/switch is bypassed with an in line fitting.
I have not been able to check on the 'sucking', but the new fuel lines are transparent and no bubbles are visible when running.

I do not know how to check for vapour lock. Or what it is.

Further thoughts?

[ArlowCT]

My weber card has a filter screen inside it right under where the fuel line connects. Small hex plug removes and comes out with the screen. I have had that plug.

Sounds like it may be a bad fuel pump. I know some people have not been having great luck with them lately. Could be worth putting your old one back on or trying another new one.

[bugeye88]

You could also consider an inline low pressure electric fuel pump, with an on/off switch in the dash. This does several good things, first it will fill the float chamber of the carb for easy starts, it will help deliver fuel to the carb when fuel pump issues arise with your mechanical pump, and it reduces or eliminates vapor lock issues related to fuel line boiling. There are many pumps ou there which will fill the bill. I use a Facet pump. Oh, also place an inline fuel filter before the carb, especially with a Weber 34 ICT as they are very sensitive to crap in the fuel.

Rob

[ArlowCT]

I too run only a electric pump. I was just feed up with all the issues I had with mechanical pumps. It may have been that day on the mass pike when I had my bonnet in the back of the truck because of vapor lock issues that I said enough is enough!

[disco2hse]

Thanks for the notes.
I checked the fittings at the tank, pump and carb. They seem to be even and tight.
I have run the LR with the fuel cap off, no difference.
The filter at the pickup tube has been removed and the tube cleaned. Tank also cleaned.
Under seat fuel tank valve/switch is bypassed with an in line fitting.
I have not been able to check on the 'sucking', but the new fuel lines are transparent and no bubbles are visible when running.

I do not know how to check for vapour lock. Or what it is.

Further thoughts?

This ought to help: http://bennettpump.com/uploads/file_...por%20Lock.pdf

and this...
http://en.wikipedia.org/wiki/Vapor_lock