1980 720 Cutting Out on hills?

[sackcheck]

I wasn't quite sure where to post first so I guess I will start in the 720 section

 

My 1980 720 kingcab, l20b started cutting out while climbing hills with slow gradual grades (was fine on steep short steep grades). At first I just dropped down from 3rd into 2nd and the whole engine stalled, I pulled over popped the hood and didn't see anything obvious so I waited 5min and I took off and the problem went away. So I thought it was just a dirty fuel filter. I changed the filter and it still happens. I was coming home one day and it happened again after I came over a bridge and continued driving to examine the problem further. The rest of the ride home had no grade at all, but I wasn't able to get over 55mph without it cutting out and dropping me down to 40mph. I tried fifth, fourth, third, 1/4" throttle, 1/2" throttle, full throttle and no change it would just cut out harder when at higher rpm.

 

 

Things I know that are wrong with the truck but have had no effect cause they have been that way for over a year now are: A/B valve is disconnected and plugged due to cracked vacuum line, the gas level in the carb is a tad high after rebuild last year, alot of steam coming from tail pipe when warming up even on a warm day but haven't lost any coolant due to it, and for some reason don't know why I randomly hear this clicking of a relay under the dash from time to time, theres no pattern sometimes its slow sometimes its a fast on off click?

 

I also installed a new fuel pump (mechanical) early last year, and installed a manual choke last year too (quick classy fix works fine).

 

 

I'm kinda off limited on time to track down a cause do to all this rain and no garage to work in. So any ideas where to start would be awesome Thanks!

[datzenmike]

Take the air filter off and look at the round glass 'bull's eye' on the front. The fuel level should be near the dot in the center. If set too low it can run out on hills.

 

They are cheap and easy to get at so change the fuel filter again. Cut the old one open and inspect the contents. If full of dirt the tank is likely got lots of crap in it still.

[sackcheck]

Well the old fuel filter was stained red and clogged with rust. I checked the fuel level and its level with the dot on the glass. I noticed the little rubber accelerator pump boot is cracked again. And I found this tiny nipple coming off the vacuum line that goes to the brake master cylinder, I looked every where for a loose hose or another nipple its size but found nothing. Is this some sort of test nipple? Should I plug it?

[datzenmike]

The small line coming off the brake booster should have a rubber cover plug over it already if you have a standard transmission. If you have an automatic this line should have a rubber hose going to a hard line that goes down the back of the motor to the transmission.

 

Well the old fuel filter was stained red and clogged with rust.

 

I realize that, I said to check the new one. If the old one was full of rust it's a very good chance that there is more rust in the tank and the new one is also plugged.

 

They are cheap and easy to get at so change the fuel filter again. Cut the old one open and inspect the contents. If full of dirt the tank is likely got lots of crap in it still.

[sackcheck]

The new one is clean, I can see it flow and no rust particals yet. I guess I'll just pull the carb for a cleaning and see what I find. Just trying to avoid pulling the carb LOL, I need a pair of child hands to get to those nuts:)