JLG 600A dual fuel problems

[Sportywind]

We purchased a JLG 600A boom lift about 6 months ago and have had a lot of problems with the dual fuel system. It runs fine on propane but when you try to run it on gasoline you have to hold the throttle arm 1/2 way open and it runs very rough and smokes terribly like its running way too rich. If you let go of the throttle arm it dies immediately. Parts replaced include fuel lines, fuel pump, fuel filters, carbureator, and fuel pump relay. We have even tried running it on non-ethanol fuel. Also when you try to start it on gasoline it will surge continuously like it cant find the correct idle position. Any ideas would be greatly appreciated.

 

[lantraxco]

Check float setting and main jet, does it have an adjustable main jet, with a needle?

Are you sure the propane is being shut off when you switch over to gasoline? If it's still getting propane that could cause an over rich problem. Try turning the tank valve off and running it a while?

 

[Sportywind]

Check float setting and main jet, does it have an adjustable main jet, with a needle?

Are you sure the propane is being shut off when you switch over to gasoline? If it's still getting propane that could cause an over rich problem. Try turning the tank valve off and running it a while?

The only adjustment I can see on the carb is at the base and I have tried turning it in and out various numbers of turns to no avail. Seems to make no difference at all. I have started the machine first thing in the morning, no propane tanks turned on, switch set to gasoline. It will start after several times cranking and that's when it does it's surging as if trying to find the proper idle. It also smokes and runs very rough during this time and will eventually die out.

 

[lantraxco]

Which engine does this machine have, the Ford?

 

[Sportywind]

Yes it's the Ford 4 cylinder engine.

 

[lantraxco]

Here's a link to a service manual that may help. Is the automatic choke opening?

http://www.cigpower.com.tw/up-files/parts manual/Service_3120718_09-23-05_ANSI_English.pdf

Carb is on page 3-63.

Could also be a timing issue, might want to check that. I don't see that in the manual though?

 

[Sportywind]

I have the service manual but thanks for sending the link....I plan to investigate more on the carb and choke tomorrow morning when it's nice and cool. The guys have been running it all afternoon (on propane) so it's too hot to work on today. If it was a timing issue it wouldn't run on propane.

 

[lantraxco]

Not necessarily, propane behaves a lot different than gasoline, dual fuel setups usually use a compromise between the two if I recall correctly. Somebody will correct me if I'm wrong I hope.

 

[willie59]

Not saying it will fix your problem, but whenever you switch from one type of fuel to another, i.e. propane to gasoline, you need to have the engine running (like on propane) then flip the fuel switch to the center position and run it until the engine dies. In the center position both propane and gasoline are turned off by their respective solenoid valves. Running it until it dies purges the system of the fuel that you were running it on, in this case propane. Now flip the fuel switch to gasoline and crank it until it starts on gas.

Again, not saying thins is going to fix your problem, but I wager your problem is related to long time use of alcohol gasoline, that stuff is nasty for small carburetors, but do make sure the choke is fully opening when engine warms up.