Engine: No power until fully warmed up

[Leroygsmith]

The previous owner told me that the Patrol needs to be fully warmed up (at least 5 minutes) before driving.
I can verify that it has no power (can't climb a small hill) until it has been fully warmed up.
The engine has a NIKKI carb, with a manual choke.
I have not done a compression test, I will when I return to Ecuador in November.
Can anyone give me some pointers on how to trouble shoot this issue?
Thanks, Leroy

[Flaggoni]

From what I have heard and experienced, (on my stock 68) these things don't warm up quickly. When cool out, I'll add a little choke to accelerate from a stop for about the first 2-3 miles of driving.
Things are just a little too lean to fully atomize the fuel until the intake manifold warms up.
The exhaust manifold should have a heat-riser valve to divert exhaust up thru a passage in the INTAKE manifold to help heat up the manifold to better vaporize the mixture.
Often, this is stuck or missing.
Also, the diverted exhaust passage that goes up and across and down thru the intake was found to be completely clogged on the three intake manifolds I've looked at. You'll need to separate the intake and exhaust to view this condition.
My warm-up time got much better after digging the crud from that passage.
Also, you could be having carburetor/Venturi icing. Most, more modern vehicles using newer carbs will have some provision to warm the air prior to the carb. Normally this is done by routing the intake air across the exhaust manifold.
Looks like the fuel level in the carb is easy to view. It needs to be correct to obtain the correct mixture. Also, make sure the carb accelerator pump sprays as it should. Also, others mentioned possible vacuum leaks related to weak power brakes, they also will cause a lean mixture that will be most problematic when cold.

[Leroygsmith]

Thank you for the insights and sound reasoning. I would not have thought about the preheating.

[Esteban]

The tips from Flaggoni are an eye opener!

In addition to that, I could only think of a starving accelerator pump or very reduced main jet.

Good luck!

[Leroygsmith]

Thank you. I have a Gunson Colortune which, once I get down to EC, should be able to tell me a lot about the carburetor performance.

[moore_rb]

Also to help speed up the warm-up process, make sure there is still a functional 180 degree thermostat in the engine's top coolant neck. Typically, when a thermostat sticks or rusts shut, it finds itself removed, and tossed in the trash.

If the compression is good on all 6 cylinders, then making max power is going to be all about tuning - Correct initial timing (10 degrees BTDC), good points (or better yet a Pertronix electronic ignition module), and a carb that has a good idle mixture setting, a functional accelerator pump, and the right size mainjets for the altitude you are driving, are all important considerations.

Also, do a visual verification that the non-original carb was installed so that the throttle linkage actually allows the butterflies to open fully when the pedal is floored...

[Leroygsmith]

Thanks, that's a good checklist. I also suspect a missing thermostat because the climate is so temperate (typically low temp never goes below 48 degrees) that the PO may have considered a thermostat as unnecessary.