I installed an Isspro 40psi fuel pressure gauge about 2 months ago. It has been running about 12-14 psi unloaded on the hwy and 8-10 towing about a 10K lb trailer.

This morning when I got to work, I noticed the fuel pressure was about 22-24. Went to lunch, still the same. On the way home this afternoon, it dropped a little but still hovering about 20-22.

I've always been concerned about losing pressure but can't imagine why it would increase like that. I have the gauge connected at the IP with the banjo bolt, grease gun hose and snubber (in that order).

The truck is basically stock as the sig says below. The lift pump has apparently been replaced since it is in the tank. Can't think of anything that would make more pressure except something maybe restricting the flow in the IP.

 

Those are the highest stock fuel pump pressures I've ever heard of.... something doesn't seem right. Do you have any way to plumb a mechanical gauge to check the electric one against?

 

I was under the impression it was a mechanical gauge installed. If not I would assume the sender has quit working. I have had too many problems with the electrical fuel pressure gauges to mess with them any more...

 

The needle still bounces around some (just like always). When I start it up, I see it drop to zero momentarily then come back up.

 

Check to make sure the sender is grounded properly, if the sender is actually functioning, that would be my best guess...

 

What do you mean by "snubber"??

You don't need a snubber if you have the in-tank pump. It may be plugging and holding pressure. That pressure is way to high for an in-tank pump anyway so something is not reading corrrectly.

 

Some companies have recommended running a snubber before the sender to isolate harsh harmonics from the Cummins/cp3. I ran a short piece of fuel line from my cp3 to sender for years without a snubber with no ill effects.

 

An isolator maybe, not a snubber. A snubber is whole different critter, you only need those on a reciprocating piston pump.

OP, please define whether you have a snubber or isolator. Pressures are way too high for an in-tank pump unless somebody put it in wrong and blocked the by-pass in it. If thats what happened then the pressures are about right for what the pump will develop.

 

I haven't done any work on the truck lately, I'll look for a ground problem though.

 

Snubber - dampens the pulsations. Geno's tech support recommended using it.

Anyways, it can't "hold" more pressure than the pump puts out so it does seem that the gauge has a problem. I don't know what kind of pump is in the tank. I bought the truck with the pump as it is. I installed the gauge myself.

 

Def a snubber, not an isolator. Also, you can see the sintered metal in the end of the fitting (before I hooked it up).

As I said in the original post, I've been running it for a couple months. Just started doing it this morning.

I have the gauge connected to Port A using the tapped banjo bolt from Geno's.

 

I could put a tee in the line after the snubber.

 

That would work but as stated earlier check your grounds... I run an Autometer sender and it has been rock solid for 50,000+ miles.

 

Thanks...

 

Don't need it on a vane pump, there are no pulsations to deal with. All you need is a 24" grease gun hose from the banjo to the sender.

If it is an electric gauge, you never specified, then its probably the sender, ground, or gauge. The 12-14 is more than any manual gauges registers on these pumps hence my comment about the pressures. A reading of 7-9 psi is the norm.