Have an Autometer electric FP gauge that is not functioning. Looks like the sending units go bad on these after a while, and retail at $100. Before buying this replacement part, are there methods to troubleshoot/diagnosis this piece as the problem? All wiring looks good…so it comes down to the sending unit and the gauge? Needle is stuck on zero, shows no signs of ever wanting to move.
Do you have an air compressor with a regulator? If so, fab up or find fittings to adapt the sensor to the line. Make SURE THE REGULATOR IS BELOW 100PSI!!! Then connect it up and see if it reads. I’d suggest getting the pressure around the 20 psi mark to start.
This would probably be easiest with a t-fitting. One end a male air fitting, the other end a female, and the t being the sensor. Then hookup a blow-gun to the female end so you can adjust the pressure easily and/or open the blow-gun and make sure the pressure changes on the gauge.
I would test the gauge… that’s a 3 wire sensor, power-ground-signal disconnect the sensor, use a AA battery to generate a voltage across the ground (prob green or black)/signal (probably white) wires. If the gauge moves, i would suspect the gauge is OK and the sending unit is cooked.
Conversly, with the car in a state where there is rail pressure and the sensor connected, backprobe the signal wire and see if you have a voltage that ISN’T 5v or 12v… also check the power wire for 12v/5v signal…
If you’re not getting voltage to the supply wire, you can test the sensor by applying power and ground and measuring the signal voltage.
if you have any questions, LMK
Your test would only whether or not the sensor was seeing pressure… I’m pretty sure his car runs or he at least knows he gets rail pressure, so a test that simply duplicates a different pressure scenario isn’t going to tell him anything.
I wasn’t thinking that. I was thinking even if he was getting FP how to test the sensor out of the car to eliminate that instead of the gauge. U did it the other way and tested the gauge. A combo of both would be best to test both the gauge and sensor.
Blowing air into the sensor is exactly the same as using a fuel pump to build fuel pressure with the sensor installed on the rail… he knows he has fuel pressure, idk what blowing air on at the sensor would possibly tell him…
I listed methods for him to test both the sensor and the gauge, without the hassle of removing anything but an electrical connector.
Does the needle cycle to max and back to zero when you turn it on? Im nearly positive mine does (I have the same gauge). It probably does this so that the stepper motor in the guage can index the needle back to zero. Im not sure if it does this regardless of the sender being plugged in or not. I can check quick after work and let you know what it does with the sender unplugged.
Ping this message if you dont hear from me by like 7pm.
Yes it does…but if my problem is electrical, how would this go about solving that?
If I’m getting this right…I can unplug the electrical connector into the sensor. This is pretty simple and easy to get to since the sensor mounts at the front of the engine. The 3 wires are red, black, and purple. In your example I’d be using the AA battery to connect the black(ground) and purple(signal) wires?
Yes, if the gauge doesn’t move when you do this (with the key on), it’s fucked. when you have the sensor unplugged, check the red wire for +5 or +12 volts too, with the key on.
