Hi from Norway! This is my first post here. I'm helping a frien of mine. He's working on a truck/ motorhome with a Common rail engine. I'm known with conventional diesels but I have limited knowlege of common rail. The issue is that it will only rew approx 2200rm under heavy load/ uphill. Flat or downhill no problem. Neutral revs OK. There is no engine fault light on dash. We had a brief look at filters etc but can not find any obious problem. If we drive uphill it struggels and come back on full power/ rpm after some seconds after flattening out. I suspect the Return valve ? Are there any issues that normally cause this. At moment we don't have OBD code Reader as this truck have 6 pin Connector, not the common OBD2 Connector. Regards Olav

 

If U have dual tanks, check the selector valve, years ago ,I had a gas MH doing the same thing , flat , level ran fine after months of trouble shooting, i found the tank selector valve would leak and allow the system to pull air in, changed the tank selector valve problem solved.

 

Thanks,we will look into this. Olav

 

Also check the pickup tube coming out of the tank, there is a filter on tube that may be plugging up inside tank,,