I'm planning on getting a fuel pressure gauge. Need to know what max fuel pressure to expect. The book says 43 psi at idle is spec so I would guess I need a gauge that goes a lot higher.

60 psi or less. The higher the psi, the more out of range. Like a torque wrench, you'd run a 0 to 75ftlbs for 60 and below, where a 150ftlbs torque wrench, you'd use for say lug nuts on a car in the range of 104ftlbs.

Gotcha, Hub. Thanks. A sensor gauge is like the gauge on a torque wrench. It's more likely to be accurate over a smaller range than a wide range--especially if it only requires a very small range.

Where would I put the sensor? I believe it is often placed at the butt end of the fuel rail but that is only about 1/2" diameter.

What's the difference between fuel rail pressure and just plain fuel pressure? They make gauges for both.

From a truck site but the same info should apply:

http://www.cumminsforum.com/forum/3rd-gen-performance-parts-discussion/41078-fuel-pressure-vs-rail-pressure.html

Fuel pressure-to make sure your in-tank lift pump is pumping OK, so you don't burn out your CP3.

Some would say a rail pressure gauge is a good thing if you've really bombed your truck. With enough fueling mods, you can drain the rail too fast, and a gauge would tell you that.

Fuel pressure is more important as far as making sure the truck is operating correctly. However, rail pressure is key in setting up your power adders and tuning your truck.

SO i say get both. The rail pressure gauge is cooler to watch anyways

This just a guess, I might be wrong, so say fpp is key on, it stops once the rail is pressured. Rail pressure while not running is going to have the same number as fpp. But once the engine starts, rp is going to drop times 4 cylinders in demand times said rpm.

So I'd find a T-fitting off the fp side of the hose and read what the book says to look for. Once the rp drops the pump kicks in to keep the constant. Besides, there's a little bit more room at the pump than the rail.

That sounds accurate. It's maybe 2 and a half feet of hose. I don't see how the pressure could be different inside the rail if the rail is fed by that hose. There is no other component to obstruct flow between the fuel pump outlet and the injectors (like there might be on a car) so all the way between, the pressure should be the same.

A reply at 1441r.com seems to corroborate your assumption.

http://zx1441r.com/forum/viewtopic.php?f=9&t=4147&sid=54180184e7e5d93de8fc1d1edac879fa

Typical test pressure is ~47 so rail pressure will be close to that but not exceeding it. These systems are brutally simple compared to a modern car, where the ECM controls the fuel pressure constantly by modulating the pump voltage.

However, he goes on to recommend installing the sensor to the rail.

You'll definitely want fuel pressure gauged at the rail. That's what the engine sees.

I suppose the rail would be better just incase some kind of obstruction should develop after the pump like a kinked hose or sediment. Problem is, you could have healthy fuel pressure in the rail and still have plugged injectors. That is at least as likely to happen as a kinked hose or sediment.

* Last updated by: Rook on 11/20/2017 @ 9:31 AM *

So I'd find a T-fitting off the fp side of the hose and read what the book says to look for. Once the rp drops the pump kicks in to keep the constant. Besides, there's a little bit more room at the pump than the rail.

Looking at the book, they show a T fitting adapter for the fuel pressure tester. The T is in a hose that connects between the fuel pump outlet tube and the fuel rail just like the stock fuel hose does. If I go with the fuel pump as the source for my gauge sensor, I will probably need to cut the stock hose and put such a T into it. Sounds a lot easier than drilling into the rail.