Leaky Tank,carb Adjustment, Transfer Case

[Col Klinx]

Well I finally got plates for my truck and after filling it up ive discovered it leaks gas pretty bad until it gets to about 3/4 tank. Iam pretty sure its the sending unit seal but i don't know why. I put in the new gasket and i think it bunched up and is causing a leak. iam going to drain the tank and drop it wendsday (tommorow) and check it out. Iam hoping this is an easy fix and a cheap fix cause iam broke also i need the truck to get me to school among other places. So has anyone ever had this happen before or have any ideas on how to fix it? Also does anybody know what the engine RPM should be at idle? Ive tried to set it because it seems high but when it goes down it goes way to far. It seems to be really really touchy. My friend had some sears engine tester which ahd a tach on it and it would go from 600 to 1000 but i couldn't get anything in between that. i was thinking 700-800 would be a good place to start though. So would that mean i need to adjust the idle mixture to get it to idle down a little more (the carb is a holley 2 barrel)? And where would i find out what model transfer case is in my truck? besides the leaky tank and moderately high idle the truck runs great.

 

[Ziggy]

Do you have the gasket in the proper place? The gasket goes between the tank and the sending unit. If the sending unit gasket did bunch up, and it is still good, apply some vasoline to both sides of the gasket before you re-install it. This will help seal the gasket. Also look at your hoses for cracks or holes from aging. Examine the split weld on the tank, this is where most holes accure due to water sitting there and rusting the tank. Look for a gas stain on the tank to pin point your leak. Small leaks can be fixed with JB Weld or some sort of epoxy made for gas tank leaks. Bigger holes should be repaired by a professional welder who will repair gas tanks or buy a new tank.

As for your idle, you would have to look at the emissions sticker under the hood for the proper settings. My '79 calls for the timing to be adjusted at 500 RPM, but after that is set, I bump the idle up to about 600-650 RPM. Remember to adjust the timing with the vacuum advance disconnected and plugged.

 

[Ziggy]

I forgot about your transfer case, it is either a NP 203 or NP 205. The NP 205 has a small round plate on the backside with 3 bolts holding it on between the rear output housing and the back cover for the front output shaft bearing. If you don't have this plate, you have an NP 203. Also, the NP 203 has auto hubs on the front, NP 205 has manual hubs.

 

[Broncoholics]

There is some stuff called Marine Tex which fixes leaksin a gas tank. Even hardens submerged in gas if thats your problem. You can find it in most marine supply stores.