Impco Propane System Follow Up

[Steve@Advance]

Back before Christmas I posted about my propane powered Mitsubishi lift truck smoking and running rich.

This is an Impco system, Type J vaporizer, RK lockout valve, factory installed on an FGC 20 truck.

Well, I went through the fuel system. Put repair kits in both the vaporizer and the lockout valve, took the "carburetor" apart, cleaned it up.

Everything looked good, the vaporizer was filthy, but cleaned up well. Nothing difficult or questionable about any of it, I feel good about how it's starting, running, no leaks.

But it still seems rich. Blows blue smoke, some at idle, bad under load. It has a strange smell, not antifreeze, not exactly an oil smell. It never ever needs oil, not fouling plugs, not overheating or loosing coolant.

There is a high speed mixture adjustment, very difficult to access, but I have turned it to lean and it seems to have no effect, even loading the engine with the hydraulic pump, it makes no difference. I don't have a combustion analyzer.

Any ideas? Does rich running propane appear as blue smoke?

 

[Janicholson]

If you can manage it, put on a different propane source. Barbecue tank or? and see if it changes. I have seen some propane that was very different. Have you owned it long enough to have seen it run correctly? if so was there a period of change to the smoking condition? Jim

 

[Dieseltech]

The Impco 300, 300A, and 425 carb/mixers I'm familiar with have two settings, full load and an idle mixture setting. The model E vaporizer also had two lever spring choices, orange for 1/2 inch WC for 300A and Century carbs, and blue for 1 1/2 inch WC for the 425 Impco carb. Not sure if the model J regulator had two spring choices. Is the carb an Impco? Maybe CA 50? It has a full load setting and an idle mixture setting too. Also, the E and J regulators can have an EC1 light load mixture device, I've never seen one though, only in the Impco Service Manual.

 

[matthies]

Does it run any better without the air cleaner hooked up? Just a thought maybe filter is dirty and looks clean. Seen this on a couple diesels.

 

[Steve@Advance]

matthies I haven't tried pulling the air filter, but I will.

It's been blown out many times but a long time since it was replaced.

Thanks!

 

[Steve@Advance]

Dieseltech, the carb is an Impco, I will have to look at the model number again.

I'm assuming everything is matched up, all factory equipped, correct springs, etc. It has run well for the 15 or so years we've had it.

There is an idle mixture screw, it has minimal effect, but I keep the idle set pretty high. If I set it any lower it dies when you bottom the tilt cylinders, the operators complain.

There is a main mix adjustment, a half-cylinder looking restrictor thing inside the fuel inlet hose fitting on the carb. I can turn it full open or full closed, doesn't seem to make any difference just listening to it or watching the smoke.

I'm thinking an exhaust analyzer is going to be necessary to get a final answer. Ever used one?

Thanks!

 

[Steve@Advance]

Jim, we've had it for about 15 years. It's always smoked just a little, but has suddenly gotten worse and stinks up the shop.

It's been through several tanks of fuel since this started, they are exchange forklift bottles.

As I was putting it back together I tested each component with the fuel on to be sure the lock out and vaporizer weren't leaking by. They appeared to be functioning properly.

Thanks!

 

[Janicholson]

Coolant and small amounts of oil consumption make nasty stink. Combined with the acrid smell of Propane could do it. A coolant leak down test and a combustion gasses in coolant test are in order. The engine may nor be worked hard, and as such might have wear from cold starts. Jim

 

[amscontr]

The Impco 300, 300A, and 425 carb/mixers I'm familiar with have two settings, full load and an idle mixture setting. The model E vaporizer also had two lever spring choices, orange for 1/2 inch WC for 300A and Century carbs, and blue for 1 1/2 inch WC for the 425 Impco carb. Not sure if the model J regulator had two spring choices. Is the carb an Impco? Maybe CA 50? It has a full load setting and an idle mixture setting too. Also, the E and J regulators can have an EC1 light load mixture device, I've never seen one though, only in the Impco Service Manual.

Are you familiar with Impco propane fuel systems on a 1992 GMC Topkick 427 Tall Deck?

 

[Janicholson]

Are you familiar with Impco propane fuel systems on a 1992 GMC Topkick 427 Tall Deck?

Welcome To these Forums. The original post is 5yrs old. dates are often overlooked when a search finds a topic. Jim