Diesel Bombers - Fuel pressure gauge

WOT = Wide Open Throttle. Pedal to the metal. Hammer down. Foot to the floor. Generally speaking, maximum fuel, although I'm pretty sure with these trucks in stock configuration that isn't always the case. But for purposes of discussion here, it should be.

Regardless, gauges can need calibration, but I'm not sure how one would go about it. I know a buddy of mine who worked in a speed shop said they once took five Autometer boost gauges off the shelf and hooked them all up to the same air source and they all showed a different reading at the same pressure. Then they did the same test with some high dollar Japanese tuner gauges (Greddy, IIRC) and they were all in perfect sync and dead nuts accurate. I suspect some of those Autometers were a little out of calibration somehow, but the point he was trying to get across at the time is that Autometer "ain't all that". That was many years ago though, before stepper motors and such, and I think all gauges have come a long way.

As for ISSPRO, if you're using an electric gauge, ISSPRO has multiple maps/programs for them that are application specific. If you have a gauge programmed for an electric LP and try using it on your mechanical LP Cummins, it's not going to read properly. I'm sure there are as many programs for the same gauge as there are engine/pump configurations, and it's just a matter of plugging in the gauge to a laptop with the tuner software installed and changing some values, or sending it back to ISSPRO and telling them what you've got so they can set it up with what you need. I would talk to whoever you bought the gauge from and make sure they gave you one programmed for your specific application. I know my ISSPRO FP gauge wasn't right for my truck and I had to send it to ISSPRO to be reprogrammed; I don't think most of the retailers are aware that the EV2 gauges specifically, are factory-match gauges designed to compliment OEM instrument clusters of specific year/make/model trucks. Every combination of face and trim color, lighting color and even brightness of the LEDs are designed to match the factory instrument cluster of a specific truck, as well as the fuel system that truck is known to have. I got the white face/black trim/red pointer/green lighting EV2's for my '98 Ram because I thought they looked nice, but the fact is they were intended for a much newer Ram with brighter backlighting and an electric LP. ISSPRO was able to reprogram it for my older truck and send it back, but if they'd been told what year Ram it was going in when it was ordered the fiasco could have been avoided.

As for the mileage, that is odd. Everyone I know who goes to a FASS, Airdog, etc, claims their mileage goes up not down. This might further suggest something is wrong with the LP, but I'm just guessing.