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Electronical Fuel Pressure Gauge

MrMarty51

MrMarty51

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Miles City, Montana
I installed two sending units from GloShift for their 0 to 30 PSI gauge.
One sending unit at the AirDog lift pump and the other hooked into a swivel JIC adapter fitting at the injection pump.
I have never been able to get a good reading from either of the sending units, thought it was a bad unit so ordered another SU and installed it with the same results.
Once in a while there would be a fairly accurate reading from the gauge, I think but never real sure.
Yesterday, thought, going to get to the bottom of this.
Having the little mechanical gauge from when I was running the other style pumps, teeed into the hose between the FFM and the IP, hooked in that little gauge with surprising results.
The initial pressure buried the gauge. Not sure how deep.
Backed off the FP regulator screw about a 1/4 of a turn and brought the pressure down to about ten, according to the bouncing needle.
Twisted the adjustment back up about 1/8th of a turn and took the average.


And so, with the pressure spiking and dropping so fast I believe that the GloShift sending units are actually creating electronic spikes and causing the gauge to read at maximum pressure, 30 PSI.
I’m not sure if there is a gauge sending unit that could, or would eliminate the spiking from the gear-rotor pump.
Anyone have any advice ?
 
All that pressure spikes and valleys must have wiped out the sending units, or the gauge.
Turned the ign switch to run for the WTS lamp and the gauge pegged 30, front and rear sending units.
@Big T and @ak diesel driver
I think Big T might have the AirDog and AK has the raptor unit.
Do You guys have gauges hooked to Your pumps, if so what brand, and are they mechanical or sending unit electronical ?
 
is the regulator the type that controls the pump electrically or does it just bypass to flow back to the tank? if it just bypasses the flow, then you might need a snubber or bladder to eliminate the pulsing pressure. the IP is creating the pulsing when it takes in some fuel as the injectors fire. mine does this on both trucks with the facet dura-lift pump I have on them. I can't remember if it's the snubber or a bladder that takes and smooths out the pulsation on pumps to give you a smooth flow of pressure.

you might even look into a remote mount pressure regulator similar to what's used on older hot rods when they do an LS swap. that would require a return line but might help smooth out pressures, even aid as a fail-safe so no matter what the pump does, you'll never exceed that set pressure.
 
MrMarty51 said:
The AirDog does have a return to tank bypass regulator.
I’ll check out the pressure snubber systems and maybe try one of those in the IP sending unit before ordering more gauges.
Click to expand...
Back when we were discussing fuel pressure gauges, I posted a link to the snubbers I ordered. I haven't got them installed yet, so I can't give a referral
 
dbrannon79 said:
Does the snubber go inline on the supply to the engine or just to the gauge sending unit? from all the pressure spikes I would think it needs one inline to the engine.
Click to expand...
The snubber screws into the port where the sending unit would normally go, then, the gauge screws into the snubber.

I got on GloShift website and did the search for the snubbers.
Pops right up. Also an explanation how the sending units can be destroyed from the pressure spikes.
I ordered two of their snubbers and two new sending units.
I dont want to have to wait for new sending units to get here if the ones I now have has been destroyed from the pressure spikes.
Now waiting for the postage to get them here. 😹😹😹😹
Just ordered them about ten minutes ago.
 
I was just looking into them. they are a type of flow restriction device. some are adjustable, some are not. but they simply restrict flow so the spike is not seen on the gauge.
 
SnowDrift said:
I have seen stone snubbers, needle valve types and some other type. I am leaning toward the stone type for a fuel pressure gauge - maybe some sort of orifice?. Any recommendations?
Click to expand...
I had a needle valve type and the internal pipe threads threads were too shallow and stripped before it could get tight enough to seal.
I also had a stone snubber on hand so I have been running with that and it seems to be functioning just fine, even the extra mechanical gauge added in, between the FFM and the IP seems to be doing okay with that stone age snubber.
I added age in there because it sounded phunny. 🤷😹
I also installed that mechanical gauge into a T between the FFM and the IP because I had several of the GloShift sending units fail and, to me it gets quite concerning when the gauge is buried at 30 PSI.
At least now with the mechanical gauge permanently installed, if the electronical gauge goes wonky, open the hood to double check that the fuel pressure is inna safe zone.
The mechanical gauge is a small dial faced unit branded by HURST, or some such. Not a lot of money when I bought it.
 
Remember there is another option for fuel gauges. If you add an ISOLATOR
You can safely mount a mechanical gauge in the dash. It takes 2 to do the pre filter/post filter thing.
Basically a blader that has a small compartment on either side. It has a fitting on each side of the bladder, one side for the fuel to go to. The isolator gets mounted outside the firewall. Then the other side has another fitting and you run a line from it to your gauge mounted on the dash. You fill it with an oil- usually mineral oil (baby oil) and when the fuel pressure goes up it pushes the bladder which pushes the oil into the gauge and moves the needle.
Now, if there is ever a leak in the line going to the gauge - it is just a little baby oil that spills and is not a never ending supply of fuel from your lift pump.

When Leroy started selling his fuel pressure tap for the top of the FFM, he offered an isolator.
It does not replace a snubber which takes away the peaks and valleys of psi and also calms down the pumping so you read an average reading instead of exact.

If you use a gear driven fuel pump that does not have the majority of its fuel in recirculating mode- a snubber is often required.
Ones that have say a Fass or Airdogg which use a 1/2” line (required for warranty on AIrdogg, I can’t remember on Fass) and you tap the restricted but always flowing return line with the 3/8” or 5/16” line to the ip- many people report no fuel pulsing problems. The most common return for the 1/2” line: into the filler hose.
 
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