My fuel gauge is set up as in sig. The pressure is usually 62 at idle. Today at idle its 81. Also, when off, the pressure usually quickly drops to zero. Today it drops to and sits at 16. Obviously, there is some sort of obstruction that is keeping the pressure high. What does a clogged fuel filter do to the fuel pressure? Any other ideas? The gauge works just as it always did on the other 2 settings, which are oil pressure and coolant pressure.

 

I'd suspect a faulty sensor that is giving a 16+ psi higher reading. Swap it with another and see the problem follows it. Also if the wire going from the sensor to the gauge is chaffed and grounding out it will give a false reading.

 

So no chance that there's just something blocking it and pushing the pressure up? Not sure that'd be any better or easier to find. My favorite idea is that just changing the fuel filter would fix it, but I doubt that's going to be it.

 

I would install a new sensor.

 

I can switch the pigtail out from the coolant pressure sensor easily, just unsnap from one then snap onto the other. It's got to either be the sensor or the pigtail. Funny that the sensor responds correctly to throttle changes, just not accurately.

 

Is the gauge fluid filled?

Josh

 

No, it's electronic. A hose off of the bowl at the under the hood filter, with the sender attaced, and a pigtail to the switch and gauge.

 

No, is the gauge face fluid filled, as in anti-vibration or whatever.

I know Autometer fluid filled fuel gauges are known to cause weird readings as the fluid heats up and cools off. As a fix many drill a hole and drain the fluid.

Josh

 

I switched them out and got exactly the same but oposite results. Thus, it is not due to high pressure in the system, but rather, as stated, either the sensor or the pigtail. Since I have this complicated switch I set up to run all these sensors on one gauge, I think I'll switch out sensors first. That way, I can hopefully avoid the headache of getting back into that multiple pole, multiple throw switch.

 

Hmmm, don't know. It's an ISSPRO, but since another of the same type of pigtails gets the same results, I'm saying its the sensor.

 

Good to know. Just throwing that issue out there just in case.

Josh

 

Josh, thanks for the excellent help, as always.

 

Easy test is to take the sensor off and then with a alligator clip
so the sensor has a ground see what it reads.

Sean

 

I think I already know. I have to disagree with myself in that I had ruled out high pressure in the system. That COULD still be the issue. However, I parked the truck for over an hour and when I came back, it still read 16. In my opinion, that rules out high pressure since that system seems to depend on the fuel pump to make pressure. This is proven by the gauge returning to zero immediately when the truck is turned off. In contrast, the coolant pressure will continue to read as the pressure slowly drops to zero as it cools over hours. So it seems that to that sensor, 16 is the new zero and I'm about to find out how long the warranty on it lasts.

 

I agree that if it has not dropped back to "0" then it's a
bad sensor.The fuel system is just loose to hold
pressure that long.

I would not mark 16 as the new 0 because it may not be linear
when it goes up.

Sean