ISX400 Tune

[Waterloo]

Here is the Cummins Inline that most all of us use here...

https://www.ebay.com/itm/Cummins-INLINE-...SwIJlZ9U~7

The gearing and that transmission is a tough nut to crack to keep the rpm's up above that 1500 rpm's, I run mine at 1700 rpms all day long. Try not to drop below 1500 as much as possible, especially when loaded.

The issue you run into when running below 1400 rpm's are the liners, you lug the motor, the liners in time fret, or break loose and damage the head. It is normally the #5 liner. Then you in frame.

When outfits like Walmart order these trucks, they spec them stupidly so that any mouth breather can drive them and return good fuel mileage. They do the least maintenance possible on these units and then sell them off before they fail.

These new trucks are designed with a life expectancy of 500,000 miles, that is why you see so many being sold off with 300,000 miles +/-.

Now, the fuel pump, is it still painted red? If it is, I would rebuild that immediately, as odds are it is the factory original. They have a normal lifespan of roughly 400,000 miles under ideal circumstances. When they fail, if the truck is not shut down immediately, catastrophic engine damage is normal. The metal flows through the oil system, and basically destroys the entire motor. If caught in time, it is still a $10,000 to $15,000 repair.

Me, I would pull the pump and rebuild, that way you know it was done properly.

Then, get under the top, you really need to inspect the cam shaft and lobes. It is rare for these motors to get this far along in life without carbon packing, which leads to cam and lobe damage. Odds are, it has never had the overhead ran. So I would do that the same time I did the fuel pump.

The gearing, when you get some weight on you will be going WTF, as the truck will not get out of its own way with those gears. I would look at some 3:55's or around that ratio for the best performance and fuel economy.

Sounds like the emissions are intact, that is a good thing, it means no one has messed with the ECM. You will need that Cummins reader and software to stay up on that stuff, as it can get very expensive down the road when these systems need maintenance. A shop will empty your wallet, you will need be proactive and keep up on these systems, which means learning how they work and how to repair and maintain them.

I would also visit the Amsoil web site and order their bypass oil filter kit and install that. You will need that to keep the soot down in the oil. Your motor will thank you.

Oil changes, every 12,000 miles or there about, up to 15,000 max on that motor. If there are signs of carbon packing, changing the oil every 3,000 miles may be in order, roughly three to four times, to clean the soot and carbon out of the motor.

There is more, others will chime in...

Oh, you can thank the EPA for all of this...