Fuel pressure gauge losing pressure

[kman522]

I have an Autometer fuel pressure gauge for my Cummins that constantly loses pressure the more I drive it. I seem to have a air leak and I have tightened every single connection. My T connector is between my lift pump and my fuel filter, is the best place for my T??I have a isolator on it. Fuel flows into a piece of equipment I bought with my gauges........so there is no actual fuel coming into the truck via the gauge.Should my T for my fuel be after the fuel filter?????

[Mopar1973Man]

More than likely you are having issues with the isolator really common. What you need to do is reload it with coolant and rebleed the line again. Also remember to reset the piston too.(Personal opinion)I really don't like the isolators at all. Like in your case the isolator is case of your inaccurate fuel pressure readings. So you'll go the fight to re-setting the isolator and double checking everything. Then if you check the pressure with a different gauge directly connected to the fuel you might find a difference in pressure. I've been direct plumbed now for over 8-9 years and never had a issue with fuel in the cab. Also I'm using air brake line after check out the burst pressure I found out air brake line is rated to 700-900 PSI burst pressure. I hardly doubt 15-20 PSI is going to do it. Also it the same line used on bigger trucks...

[JAG1]

I would put the 'T' after the filter just before the injection pump. That way you can tell what the vp is getting after the filter

[dripley]

I would have to agree with both of the gentlemen above. I also have a mechanical gauge in the cab for over 1 year with no issues. It is tapped into the fuel line before the vp, but after all filtration.There is a test port on your vp where the fuel line connects to the pump. It is a scharder valve with a cap on it. You can hook up a test gauge there and double check your pressure. That is if you are still stock.

[Mopar1973Man]

As long as the gauge is after the last filter you can hook up anywhere in that line. Farther from the injection pump the better it will protect the gauge from water hammer damage which affects both styles electric and mechanical.

[kman522]

Thanks fellas, I am going to move my line this weekend after my filter and direct plum it to my gauge.