GRT Avionics

My stock GRT fuel pressure sensor seems to indicate too low a fuel pressure (FP). I have an IO-320 with Silverhawk servo and AFP pump/filter assembly. Most info - and feedback from similar installations - says my FP should be somewhere around 25 to 30 psi. Mine reads 2.5psi with the boost pump off, and goes to 2.8 psi with the pump on. ( The fuel line to the FP sensor comes off the usual fitting on the mechanical fuel pump.) I used the 475 ohm resistor in the wiring, as recommended for higher FI pressures; and I used the offset (+5) and scale factor (59) recommended for same. With the engine off and the Sport EFIS booted up, the FP reads -0.1psi.
Any suggestions?

Rupester,
I had a problem with sensor, resistor and EIS program matching.
I think it was the fuel pressure like you.
Even though I am an IO, I used a VDO sensor (which is what they used to supply before the high pressure sensor)
The root issue was that I did not have the sensor that matched the resistor and EIS instructions.
They have to match, meaning the resistor and EIS settings change depending on the sensor and desired display on the EIS.
I had to come up with my own. Did. Works fine.
Sorry, I don't have my electrical documentation here at the house so I can't give you exacting help at this moment.

Get the sensor part number, compare to the resistor/EIS document. Maybe call GRT.
I'll bring my docs home next trip (probably Sat)

Rupester wrote:My stock GRT fuel pressure sensor seems to indicate too low a fuel pressure (FP). I have an IO-320 with Silverhawk servo and AFP pump/filter assembly. Most info - and feedback from similar installations - says my FP should be somewhere around 25 to 30 psi. Mine reads 2.5psi with the boost pump off, and goes to 2.8 psi with the pump on. ( The fuel line to the FP sensor comes off the usual fitting on the mechanical fuel pump.) I used the 475 ohm resistor in the wiring, as recommended for higher FI pressures; and I used the offset (+5) and scale factor (59) recommended for same. With the engine off and the Sport EFIS booted up, the FP reads -0.1psi.
Any suggestions?

IS the an EIS and GRT EFIS?
Wondering which EFIS and have you looked at the inputs decimal integer setting?

As indicated, it is a GRT Sport EFIS, along with a GRT 4000 EIS. I used exactly the parts (sender, resistor) and set-up numbers provided by GRT. The 4.8V wiring is correct, since the other 4.8V devices wired similarly function just fine.

Kahuna is probably on the right track. Page 19 in the EIS 4000 manual talks about the D/I (decimal/integer settings). Change that Aux to an Integer(I) and it should eliminate the decimal point.

Ben

Will give that a try. Thanx.

Aside: Makes me wonder if I couldn't increase the scale factor ten-fold and move the decimal point over. Just a renegade thought.

Yeah,
Kahuna and Ben are probably onto it. I did have mismatch problem but your case does look like Decimal/Integer setting.

Yep, it was the decimal/integer setting. Once I reset both the EIS and both EFISs to integer, it works fine. (Aside: the GRT setup info made it sound as though I had the option of either decimal or integer for any of the aux points. Experience points to that not being true.)