Yes, electric gauge.

I checked the connections and for a good ground. Looks good.

The pressure has gradually dropped over time and is now running about 18 unloaded.

I don't know what kind of pump is in the tank since it was that way when I bought it. Are there a lot of choices for in-tank replacement?

Still weird.

 

Just had a new lift pump put in the tank. I run an Isspro gauge with an isolator going into the cab and the same banjo tap at the CP3. I always used to see 8psi idle, 5psi cruising, and 1-2 psi wot with the old pump. New pump shows 13-14psi as idle now and 8-9 psi cruising without much more of a drop under heavy throttle. Maybe the new in tank pumps are stronger?? Do the 6.7L's use the same one?

 

I don't know much about the pumps.

Mine has gradually gone back to the way it was when I first installed the gauge. Still Wierd.

 

Update:
After a week at the initial pressures of 12-14, the reading has gone back up to 24-26 psi. I only drive the truck 1-2 times per week. Just highway driving then occasionally pull my 10K lb gooseneck.

 

I know this is an old thread, but I just finished solving the problem.

The gauge has been reading 40psi (max) for the last year and a half. I just never got motivated to fix it since I typically only use the truck for towing and forget about it.

It wasn't an electrical problem. I found the following troubleshooting guide on Isspro's website.

http://www.isspro.com/TROUBLESHOOTIN...leshooting.pdf

Went through it step by step to find out that the sender is putting out a signal for 40 psi. Called Genos, they referred me to Isspro. Told tech support the story. Bottom line is they sent me a replacement sender under warranty. I have had the system for about 2 years, which I told them, and it never has worked correctly.

Ultimately good service, but a little slow in responding to phone messages.