Well I got my new overflow valve installed, but it didn't fix everything I had hoped it would. I still have major pulsations in fuel pressure. If I don't restrict the hose running to the gauge with something (I used vice-grips for a while, then a fuel shut-off valve cracked open just a tiny bit), the gauge needles bounces back and forth about 5 lbs. very quickly, like a clock pendulum, but quicker. I think it has damaged my new Isspro gauge, because even when I had the line off to install the shutoff valve, the gauge didn't drop below 13 lbs. What could be causing this pulsation?

Jim

 

The lift pump is the cause of the pulsations. They all do that, it's the nature of the beast. They will destroy a gauge in short order without a snubber of some kind (needle valve almost closed works for most guys).

 

Oh great, so I just blew my new gauge because of self-stupidity. My wife will just love to hear that as I'm ordering ANOTHER new gauge!

Jim

 

Hey, at least you know now. Can you imagine how hacked off she'd have been if you threw a new lift pump at it to try to stop the pulsation?

 

Never know, your vendor might replace it for free.
Don't know about an Isspro but on some gauges it's easy to remove the glass, pull the needle off and push it back on reading zero and still have it read correctly.
Might be worth at least a look before ordering a new one if you have to pay.

 

But without having a way to verify...how will he know its reading correctly at anywhere but zero?

If its new, id try to send it back for warranty instead.

 

Take my word for it, they will still read correctly if you move the needle.
Hate to admit but I've allowed quite a few water pressure gauges to winter freeze over the years. They end up reading 10-20 psi when it's supposed to be zero. Moving the needle makes them read right on again.
Some gauges even have a screw inside that you can use to zero the gauge.

You are right that getting a new gauge would be the best outcome.

 

Well my gauge seems to read correctly when the engine is running...it reads about 15-17 psi when I'm running. But when the truck is shut down, and I unhook the line (when I installed the shut-off), it only went down to 12 or 13 psi.

Jim

 

Any suggestions for a snubber?

 

I know there is a part number fopr a snubber somewhere here...just cant remember where.

I think a grease gun hose might help dampen the pulses some.

 

This is what works great for me
http://www.grainger.com/Grainger/wwg...mId=1612835462

If link doesn't work go to http://www.grainger.com and search for 6MN31

 

__________________________________

Thanks Bill, but I already have a needle valve in place and its still pretty bad.
I had no problems on the 24v with the same set-up but the 12v a tough one.
I drilled and tapped the FF housing post filter and threaded the needle valve in there hoping the filter housing would buffer it a little but no go. I have to have the valve closed so much that the gauge is to slow to be effective.

 

I tried a fuel shut-off for a small engine, but it doesn't do a good job. I only used it because I happened to have one. I get it set so it works well, but either the pulses or the vibration of the engine...even with the valve up near the firewall, well up on the line...makes the valve self-adjust and by the end of a 75-100 mile drive the gauge is pulsing again. I want to come up with a solution before spending any more money on another gauge.

Jim

 

If you tighten the packing nut under the valve handle the adjustment will stay fixed. Assuming it has one, some valves don't, that's why I use the Grainger valve.

What size and kind of line do you have going to the gauge?
If the line is soft or large it will make the gauge much slower to read especially if the needle valve is cracked way down.

You can always hook up a $10 water pressure gauge from the hardware store to see what works and to verify if your Isspro is the real problem.