Challenger 1800 Power Loss on One Engine at WOT

[jscheibmeir]

Looking for some help with a problem that's driving me crazy. I recently cleaned the rave valves and replaced the diaphragm and filter in the carbs. Both engines will start fine and idle fine; even mid range is good but when I push both to WOT they both will go up to 7000 sometimes but the left engine will fall off to 5000 RPM especially under a load. For instance if I turn and it does it out of the hole too but I can get it to go back up to 7000 RPM with the right engine by pulling the throttle levers back and then slamming them forward again. But will drop off again as soon as there is load on it.
Has anybody ever had this problem?

 

[howie099]

Could be fuel related or cavitation. I would clean out the carbs on that engine and look over the drive lines

 

[jscheibmeir]

Thanks for the ideas howie099. I recently went through the carbs. I did notice that the blue plastic shaft protector on that engine has slid back and is getting chewed up in the impeller. Do you think that could cause some cavitation?

 

[howie099]

Could nic up the impeller some. Some people remove those. I am shocked it is still there. Lack of power wouldn't be cavitation since the the engine would still rev out, but you just don't move

 

[jscheibmeir]

It moves I can get up to around 40mph when both engines are close to 7000 RPM but the left engine will fall off to 5000 RPM with any kind of load. Then after it falls off I pull the throttle levers half way back and push them wide open again and it will match the other engines RPM's until I turn or put a load on it again.

 

[ialonso]

It moves I can get up to around 40mph when both engines are close to 7000 RPM but the left engine will fall off to 5000 RPM with any kind of load. Then after it falls off I pull the throttle levers half way back and push them wide open again and it will match the other engines RPM's until I turn or put a load on it again.

My guess...Fuel Flow or carbs.

How's your fuel pump? How's your fuel filter?

Others have been lucky in rebuilding carbs with no issues. Mine always end up with a lingering problem, and I just replace it. If you have one carb per cylinder they are not cost prohibitive to replace (IMHO) vs. the aggravation of remove-reinstall to troubleshoot.

 

[snikwad003]

What he said and fuel valves?

 

[jscheibmeir]

It was actually acting this way before the carb rebuilds. It has accelerator pumps on it, do you think it could be the external accelerator pump?

 

[howie099]

Fuel pumps are external. Most people swap to the universal mikuni's and just JBWeld the extra nipple. One person here did add the internal fuel pump back on his challenger 1800 and he said they work fine. I am pretty sure you have 2 carbs per engine so that adds up real fast if you get all 4.Usually swapping the carbs between engines will let you know if its a carb issue or something else.

 

[snikwad003]

The fuel pumps are in the mag carbs only, the accel pumps only squirt while applying throttle then they are doing nothing so they dont do any thing at wot.