Large fuel consumption

[GaWag]

New guy here.

Impco 425
vff30
model E

AMC 360. Seem to be using a lot of fuel. Sounds like an air leak under the hood. Runs well. Just no range on my 2 10 gal tanks.

Anyone have a diagram pointing out all the adjustments on these 3 components? Can't seem to find any information to this.

Steve.

http://gfsj.org/forums/attachment.php?a ... 1124155919
http://gfsj.org/forums/attachment.php?a ... 1124155919
http://gfsj.org/forums/attachment.php?a ... 1124155919

[C3H8]

IMPCO carbs only have two adjustments. The idle and the power screw. The carb you show in the picture is an IMPCO CT425M-2. The mid range is controlled by the use of the correct air gas valve assembly in the mixer. First step is to check the gas valve under the lid of the mixer. Part number should be AV1-16-2 assuming there is no feedback electronics installed. If it doesnt have a label on it the number 19 should be stamped in the actual valve on the bottom end. The idle is the allen screw on the right hand plate held by 4 samll screws, looking at your picture. It is recessed inside the plate. The adjustment screw is stiff to turn as it has a locking mechanism on it to prevent loss of adjustment due to vibration. Set this at the best idle. A better method is with a gas analyzer. The power screw is inside the opening just under the lip of the mixer. Chrome opening and again uses an allen screw. This adjustment is normally set at the factory to be usable on a average 350 to 400 CI engine. Usually it is best to have a chassis dyno if your going to adjust this. Its only function is to control mixtures at full load and acceleration. Both the adjustments richen mixtures turning them out and lean mixtures turning them in.

[Frank]

Have you checked your distributor's vacuum advance for a leak in the diaphragm? This could explain the air leak you hear and the resulting lack of vacuum advance could explain your poor fuel economy.

[franz]

Just what are you comparing your mileage to? If you are doing a direct gasoline comparison, and are using a gasoline engine converted directly to propane, you may fully expect a 15 to 20% decrease in mileage on propane. If the engine has been enhanced with compression but no cam change, the difference will be less. Add in a camshaft (which is common when optimizing a propane application) and economy may deteriorate again.

Franz

[GaWag]

Thanks guys. I will check the adjustments.

My comparison is the gentleman who sold me the setup said that he could run his 350 powered bronco II all day long on one tank and still have some left over. I know I am heavier than that, but didn't expect to go thru 2 full tanks in one day. His were 10 gal tanks as well.

The distributor is brand new.

I can also smell propane in the cab. I have checked for leaks and will check again but I only seem to really smell it is when I am running.

[Melvin]

There are a lot of variables when comparing two vehicles. Is that a chevy 350 in the Bronco? The AMC 360 can be fairly thirsty even on gasoline compared to a mild 350. Add in gears, transmission, driving style, power etc. and you can see how this isn't a very good measurement.

How is the milege vs. what you were getting with gas?

You don't have to be running very rich to smell propane but I'd be checking for leaks with a soap solution just for piece of mind.

[Eskimo]

No real help, but a friend of mine also has an AMC 360 on 'pane, and he goes through almost 2 forklift tanks in a day of rock crawling, while I still have some left over from one tank at the end of a similar day.

I haven't seen his rig since he's converted it, so I can't comment if he's running rich or not, but that just seems to be quite a bit of fuel!

[GaWag]

Melvin I agree. It was the only comparison I could draw from. As far as running on gasoline, I would just about go thru 1 19 gal tank on the trail. Of course when you are on the trail for 10-12 hrs, Tellico can be very rough!

Eskimo tghanks for the info. Only a couple of us 360 guys in FSJ's running on pane. I am kinda flying blind here.

Thanks for your helps guys. I hope to get a chance to look at it soon!

[fordCourier]

I used to drive one of these beasts. The engine looks great without all that gasoline crap... congrats on the conversion...

If you hear a whooshing sound from the mixer you have the WRONG mixer diaphragm/valve, and yes, it will make the mixture super rich.

Which mixer diaphragm/valve do you need? Depends, the AV1-14-2 did this on mine (the WHOOSH). It was called a "lean cruise" diaphragm. Ran my ford 2.3 so rich is would barely run.

Of course the 360 will suck down any rich mixture you give it... Very Happy

maybe someone else will know the exact mixer valve application for a 360....

In my case I could not geta rich mixtuer problem solved until one day...

I was looking at an impco .pdf with an exploded view of my CA125 mixer...

There was a thin (1/64") copper washer between the valve and the diaphragm in the assembly. Called my local supplier and he sent me a few. After inserting them into the assembly they brought the mixture closer to lean.

Given the wide range of engines, it would seem using these washers should allow for some fine-tuning- but only if you get the valve 'in the ballpark'. I suspect your valve is just too rich.

Of course I also installed a O2 sensor and safecontrols mixture computer so I could see immediate verifiable results from my experiments.