Engine/Transmission (1998.5 - 2002) Fuel pressure gauge or isolator?

[SnoKing]

So yesterday I notice the Pricol mechanical fuel pressure gauge said I only had 13 PSI. Normally is high teens and low twenties. So I put my shop gauge on the VP-44 and read normal pressure. So I changed the filter (20K and 3 years on it), and everything was clean and nice.

So I hooked the shop gauge up again and compared watching both gauges, the Pricol claims to 13 matching the shop gauge and stops while the shop gauge continues to climb. Turn it off and when the stop gauge drops below 13 the Pricol gauge start down the rest of the way with it.

So I am thinking this is a gauge issue not an isolator issue. Your thoughts????

SNOKING

 

[wlowe]

I would agree that it sounds like your Pricol guage is losing its accuracy above 13 psi. How old is the pricol guage. Is there an isolator already installed, if so I would try removing it to see if it's restricted.

As a side note, 20 psi seems a little high for the injection pump. I'm running a pusher pump in series which increases pressure to over 20 psi, so I plumbed in an aeromotive fuel pressure regulator to keep it at 14 psi. I have two electronic fuel pressure gauge senders hooked into the regulator, an isspro and an Edge attitude. Both run within a pound or two of each other. The regulator is plumbed between the filter and injection pump. It is isolated from the injection pump with about three feet of hose, and returns fuel to the tank through a bypass hose. Makes priming the fuel filter super fast and easy.

 

[SnoKing]

I had thought about that, and will give that a try. Lots of other things going on right now. SNOKING

 

[KATOOM]

Mechanical gauges usually dont loose accuracy over time unless the internal mechanism has been over abused by the hammering of hydrodynamic fluid pulses. So as long as you have a snubber device plumbed inline protecting the gauge then I would assume the problem is related to the isolator before assuming the gauge is inaccurate. The line post isolator is closed loop, which means if the isolator leaks any amount of coolant then the line post the isolator cant apply proper pressure to the gauge and the readings will be inaccurate.

 

[SnoKing]

Mechanical gauges usually dont loose accuracy over time unless the internal mechanism has been over abused by the hammering of hydrodynamic fluid pulses. So as long as you have a snubber device plumbed inline protecting the gauge then I would assume the problem is related to the isolator before assuming the gauge is inaccurate. The line post isolator is closed loop, which means if the isolator leaks any amount of coolant then the line post the isolator cant apply proper pressure to the gauge and the readings will be inaccurate.

That is what I have been thinking. I was going take the anti freeze line off the gauge and see if it re-centered the diaphragm. It has not been apart in many years. It is like the diaphragm has moved towards the outlet, and runs out of travel. I have a custom made rubber hose between the filter outlet and the isolator. The needle has never bounced. SNOKING

 

[KATOOM]

My isolator leaked twice. Once causing the diaphragm to protrude completely in the wrong direction. After the second time it leaked I got tired of messing with it and built a SS braided line with JIC fitting to the gauge. I know thats taboo (as I felt that way about it as well) but accuracy is now spot on. And I also have a "T" fitting plumbed in the line with one of the OEM test port shrader valves so I can confirm with a test gauge.

 

[SnoKing]

Loose the tube on the back of the gauge to reset the diaphragm and tighten it again. Gauge is working again. May have to feed it some more anti-freeze. SNOKING

 

[KATOOM]

Glad you got it worked out.

 

[SnoKing]

I believe this is the isolator I have.
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They sell a new diaphragm if it come to that.

http://www.dieselmanor.com/dm_products/DM-CGI600-115.asp

SNOKING

 

[KATOOM]

I had the cylindrical isolator. I understand the one you pictured is good too.