1951 M38 Running Very Rich

Robmbeau · Post by **Robmbeau** » Mon Jan 07, 2019 7:31 pm

Hello,

My 51 M38 has been sitting for the past 5 months as i have been rebuilding all of the axles.

nice weather on Sunday for Pennsylvania in January so took it for a ride and it is just nor running right. Black smoke and a rough idle. I had to increase the idle to get it to run half decent. once driving it did run ok.

had trouble getting heat in it so I do think the thermostat is stuck open so it never really got warm even after an hour drive.

i turned in the carb screw to try and lean it out an no real change.

i think I need to rebuild the carb but figured i would ask.

On another note I upgraded to 11" drum brakes and what a great change. too many people where i live for the stock brakes.... Wilwood dual master as well.

Post by **wesk** » Mon Jan 07, 2019 8:33 pm

Get your manual out and do the step by step, item by item troubleshooting. Taking action to replace or rebuild without troubleshooting usually will result in several shot's in the dark and extra money and labor spent fixing or replacing items that are broke.

Simple things to always check when she runs rich are:

Choke plate not open

manifold heat valve or heat riser stuck open & heating which makes the air hot and thin.

Float stuck down overfilling carb

Float cracked and fills with gas and sinks overfilling carb.

Float setting too high.

Float needle not sealing at the seat.

Air filter over serviced with oil and restricting air in.

Induction leak.

Robmbeau · Post by **Robmbeau** » Mon Jan 07, 2019 8:49 pm

wesk,

Some great advice.
i found a troubleshooting manual for the carb but not one for the M38. Can you point me in the right direction?

Thanks

Post by **wesk** » Mon Jan 07, 2019 9:12 pm

TM 9-804 M38 Operator's Handbook early version and TM 9-8012 M38 Operator's Handbook later version both have entire chapters on troubleshooting. If you don't have either then download the free copy of TM 9-8012 and it's revisions in our Downloads section.