I've posted twice about my noisy 98 12 valve.(IE loud knock at cruise speed but not much noise at idle or when cold).FYI a weak lift pump was the culpret.Good fuel pressure at low rpm but as rpm increased fuel pressure dropped.I would like to run a fuel pressure gauge in the cab.Who sells the isolator?

 

You don't need an isolator. Most fail in first few thousand miles and allow fuel in the cab without your knowledge anyway.

 

No isolator here. I have a snubber to damp the pulsations from the lift pump, and a ball valve to shut off the flow if a leak were to develop in the line or the gauge. A lot of guys use a needle valve for the same purpose. The valve is kept nearly closed to provide an orifice for damping purposes, and in the event of a leak can be closed. I couldn't find a needle valve I liked, but McMaster-Carr had nice snubbers and ball valves. The whole setup including the gauge and mount cost under $50.

 

So I just install a fuel pressure gauge in the cab?How about the needle valve trick?Does any one sell a gauge that will stand up to the 12 valve?

 

I have access to Mc-Master-Carr,Do you have any part #s

 

Snubber: 4034K1, specify 10 micron
Valve: 4912K71

With the 10 micron snubber, the needle is absolutely steady, so no worries about the lift pump beating the gauge to death. The LP on my truck is a piston style like a 2nd gen, but with a lighter pressure spring. When I ran an underhood mini gauge without a snubber, it was hard to judge pressure from the pulsations and the gauge died after a couple weeks.

My current gauge is an AutoMeter water pressure gauge I bought for $10 from http://surpluscenter.com/. They have some 60 psi pressure gauges that would work well with your "water" pump.

Yes, the gauge is installed in the cab with plain ol' nylon pressure gauge line, just like an oil pressure gauge would be.



There's nothing wrong with the face of the gauge, that's a reflection.

 

Don't think there is a gauge or sender made that can stand up to the pulsations a 12 valve produces without using something to dampen them. Needle valve or snubber both work.
60 psi is the best gauge range, doesn't matter what the gauge says on it, it will be compatible with diesel. Surplus center always has an 60psi Autometer Industrial that says either fuel, water or air on it for about $10

Needle valve installed on pump inlet banjo bolt

 

Thanks for all the help guys

 

Would it be best to go with copper line instead of the nylon? I was looking at the surplus site and am thinking about going with the 0-35 psi with 1/8" fitting and using there 1/4" needle valve. Would I be ok with this for my 12V?

 

I have found copper to be worse, it work hardens and cracks from engine vibration. And we all know how the Cummins likes to vibrate. Stick with nylon. If you are worried about abrasion, slide it through a length of 1/4" fuel line or wiring loom to protect it.

You need a 60 psi gauge on a 2nd gen 12 valve, the piston pump on that engine can put out 45-50 psi. On a 1st gen with a stock LP you could run a 15 psi gauge, I have a low pressure piston pump that puts out 18 psi when the engine is defueled at high RPM, hence the 35 psi gauge.