Bought a 91 Cummins about 2 weeks ago its a one ton 4x4 5 speed and it runs great no problems and its all stock but i pull trailers and i was pulling a smaller 4 horse trailer the other day so i decided to turn my fuel pin and turn that little gear one and a half turns to get a little more power for pulling, thats all i did and i was pulling a hill when my temperature went way up and so i stop and coolant had blown out my radiator cap. Well right before i pulled i decided to turn my pump back to stock just cuz i was worried about it and my mileage hadn't been as good since i turn it up. Could the pin have anything to do with the radiator overheating and blowing the cap? it still runs a little hot on the interstate after i filled it back up with coolant. Also now that I'm home and driving it around town and slower roads the temp stays normal but it seems like i have a little less power in 3rd and 4th gear... what could that be? The little lip on the bottom of the fuel pin is pointed toward the cab when its stock right?

 

You can't turn a stock fuel pin or a star wheel down far enough to cause any over heating, the over heating has nothing to do with the fueling , you should address that issue separately, as for the power loss you probably have the fuel pin turned a little less than before. an m&h 2 fuel pin Is a good start, but don't go to far with out gauges, cause that with the pump maxed your getting close with the egt trouble. good luck, its a slippery slope

 

Likely incorrect:
Is that an intercooled or non-intercooled '91? Because if if it's an early non-intercooled '91 you most certainly can do enough to make pump mods overheat it while towing, where before it didn't under the same circumstances.

 

its non-intercooled and i also messes with the "smoke screw" thats in the top plate on the fuel pump but then put it back to stock... if i backed the screw out a little to much could that make a power difference? what would you suggest i do with it all? im not sure that it even has a thermostat in it im going to replace it or put one in regardless thanks for the help fellas

 

The non-I/C 1st gens have a less efficient radiator, larger injectors and (obviously) no intercooler. You have to be pretty careful about adding fuel if you are working it. You should put everything back where it was and go from there. Change one thing at a time to see how it does. It won't pull very hard for long under high load with added fuel unless you get a better turbo on it and some other upgrades to let it breathe and cool better.

 

what he said^^^^^ Also, when you turned your star wheel, did you take note of witch way the fuel pin was facing? If not who knows how much more fuel you added.
This is why you don't do fuel mods with out 1st, installing a pyro gauge

 

yeah pyro guage is next i figured out my fuel pin and and star wheel its all back to stock and the trucks running fine but pyro guage is next priority... thanks