2nd Gen Non-Engine/Transmission Fluctuating fuel pressure on isspro ev2

[GVance]

Hey guys, just a quick question about my new fuel pressure guage. I installed the sending unit on my AirDog 100 where the low pressure indicator usually goes. Everything seems fine but the needle on the ev2 guage fluctuates constantly between 15-19 psi cruising and between 13-16 psi at WOT. Is this normal or have others had similiar experiences? Does output pressure at the AirDog fluctuate that much? Im also wondering if there is an air bubble under the sending unit that needs bled out. What are some of your guys ideas?

 

[ILIANBG]

Hi. How do you have the gauge plumbed from the Airdog to inside the cab? I have my Isspro tapped into the line right before the VP, but I have an isolator on the firewall. Then from there- a line filled with antifreeze going to the gauge inside the cab. I don't have any issues since the install, 4~5 years ago. I was told by the vendor that a snubber is used when an isolator is not there. But then I did not want diesel fuel going in the cab. If I was tapping into the Airdog like you, I would have installed an electric fuel gauge, like the Westach- so just a small sender is mounted at the Airdog. From there is easy to run the the small wires into the cab. So, let us know how you did it, I'm interested to know.
Ilian

 

[GVance]

Thanks for the reply! The Isspro ev2's are the electric version of their gauges, so it is a electric sending unit mounted into the 8an hole provided on the AirDog where the low pressure light normally would go. I wouldnt think a snubber would be neccesary in that location, plus Diesel Manor states they use a "heavy-duty" sending unit in diesel applications that does not require a snubber. Im just trying to see if anyone elses electric FP gauge fluctuates or if I was lucky enough to get a "special" one! And to answer your question on install, I ran wires along AirDog harness, through firewall grommet and mounted the gauge in a steering column mount. I really like the results and leaves me room for a boost, egt, and transmission temp gauge in the A-pillar.

 

[ILIANBG]

This must be a new product from Isspro. When I bought mine from Diesel Manor, only mechanical was available. It's nice they made an electric option.
Just a thought- I had fluctuations when I installed the Airdog, but turned out to be a problem in the tank, on the bottom of the plastic assembly. There is a fine mesh, and was almost totally clogged up. I found out that when I dropped the tank to replace a faulty fuel level sender. That was few years ago. I have to do it again- it shows erratic fuel level again.
So, after I installed the Draw Straw-no more fluctuation in pressure. I am not saying you have that problem, just passing the information.
Ilian

 

[HHhuntitall]

The first EV2 sensors went on the market in '06. I'm guessing what you're seeing is electrical, either fluctuation in voltage going to the pump or going to the guage. Where do you get your power source for the guage power? Also, do you have the wires from the sending unit going over or running with the power feed to the fuel pump?

 

[GVance]

ILIANBG- Thats a good thought, that could be possible that there may be a restriction at the draw straw... may be something to look at in the future if I see a steady decline in pressure.

HHhuntitall- I didnt think about fluctuation of output voltage from the alternator affecting the AirDog. . there maybe something to that as the original owner removed the passenger side battery and battery box. Ive been trying to hunt down a battery box and will then purchase 2 new batteries. . Im sure my starter will appreciate that! I sourced the 12v ignition from the wire suggested on the Diesel Manor install pages, and double checked that source with a tester for power. As for wiring the gauge, I wrapped the 3 wires for the sending unit in 3/8 wire loom and ran it along side the AirDog loom all the way to the engine bay. Thanks for all the suggestions!

 

[HHhuntitall]

Running the wires together may be causing the eratic readings in the guage. When the pump is requiring more voltage, the magnetic field generated from the higher amperage could be causing interferrence in the sensor field being sent to the guage in the dash. Are the fluctuations erratic and quick, or slow and fluid? If they are slow, I'd suggest they are a result of pressure fluctuations. If they are quick and erratic, I'd suggest an electrical problem in the sending unit or guage. If they fairly slow and not that jumpy on the guage, I'd think they would be related to the pump and fuel. How well do you have the fuel tank vented? Also, as far as voltage fluctuations, I'd think if you had the pump wired properly(not saying you don't) it shouldn't reflect small fluctuations in voltage. Perhaps if you have other large amperage absorbing accessories, it could. Naturally, it will cycle with the grid heaters in cold weather, as they pull a large amount of amps. The A/C compressor could be pulling enough amps to cause the fluctuations if it is fed off a nearby circuit of the Airdog, explaining the erratic readings, as well. Always check your gounds, too.



Hope this helps.

 

[GVance]

I would imagine that the gauge is reading properly just instead of moving fluidly from say 17psi to 19psi it kind of jumps from one to the other. not real erratic like electrical interference. . maybe I will try to take a video. Im going to contact Isspro to find out if this gauge should show psi changes like that. The fuel tank seems to vent fine, no pressure build ups or vacuum created in the tank so I assume that its fine. But now I have a new problem. . The wire I tapped lost power for some unknown reason. Heres the wire I tapped,

3-Gauge Install Pictures

So whatever that wire ran is now dead and instead of tapping another wire that "looks" important, I used the accessory wire off the back of the cd player... I love this truck!!