While my newly tuned DRD 5500 Cab and Chassis was out doing some hard work this week, I had a weird issue while pulling hills on the interstate (40k Combined weight).

It would build boost into the normal range for this truck (26-28), and then like a switch was thrown, it would instantly go down to like 12 or 13.

Then about 15 seconds later, it came back and built a normal range boost.

Then it would start a cycle of 15 seconds on/off till I got to the top of the hill.

I stopped and threw a new air filter in there and thought I had it till it started again a few miles up the road.

So I found that if I regulated the boost with my right foot and kept it under 20 to 22, it would be fine; I just needed to gear down a few more times than normal.

I called up the road and found a parts store with a rear fuel filter in stock and changed it out in the parking lot. Problem gone!!!

It wasn't time for filters yet, but I'm guessing bad fuel?

Also, I'm guessing the truck was going into some protection mode due to insufficient fuel or fuel pressure?

Shout out to DRD for answering an email unrelated to the tune!!!



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