Fueling & Injection - help with fuel schrader valve!
12-19-2005, 09:41 PM
i got time to install the sending unit of my fuel pressure guage on the fuel rail via the schrader valve. i pulled the pin in it using the tool to unscrew it, and hooked up the sending unit, but still no fuel presure reading? is there something else in the schrader valve to remove?? why am i not seeing any fuel pressure?
There is nothing else to remove. What kind of gauge is it? Is it analog or digital, readout at the fuel rail or remote?
just checking to make sure, but when you say you "pulled the pin" you mean you used a valve core remover and actually unscrewed the entire assembly right (pin and body)?
Some people take pliers, yank out just the pin without the other stuff off, and wonder why it doesn't work.
12-19-2005, 11:14 PM
Kind of stupid but does the car run? If its needle type it may be stuck a bit, tap it...
12-19-2005, 11:31 PM
yes, i removed the pin with the valve core removal tool, so i got it all out. the car starts and runs fine. the guage is the Cobalt C2 electrical guage..so it has the sending unit attached to the fuel rail on the schrader valve.
the needle isn't stuck, im sure b/c when i got the gauge, it was reading 60psi, but when i hooked up power to it, it made a sound like "errrr" and needle went to 0psi...so i dunno.
i have another mechanical fuel pressure gauge so im going to hook that up and see if its reading pressure. if it does, i guess its the sending unit...
damn ebay and faulty sellers!!! i paid freakin 135 for this guage!!! guy had good feedback to...we'll see...
thanks for the tips guys!
12-19-2005, 11:37 PM
I responded to your email.
It was me who sold you the gauge.
Only thing I can think of is the sending unit.
Gauge was working fine when I removed it.
If it doesnt work, send me the unit back and I'll paypal your money back.
12-20-2005, 12:05 AM
The gauge does make an odd clicking noise when you start the car and I think it should go to zero, this is normal. This is how it calibrates itself when it starts up.
As a last resort option, you could remove the sender from the rail and turn the car to on, NOT start, and see if fuel comes out of the end of the rail. You will want somone holding a bucket to catch the fuel if it does come out. If there is fuel, then the sender might be damaged which is a very possible idea. Also make sure the wires in the wiring harness arent cut or grounded. Make sure the harness in plugged in all the way into the back of the gauge.
12-20-2005, 12:12 AM
the gauge does calibrate to zero everytime you start the car.
I dont want AJ to feel like i'm going to screw him over. If it is the sending unit, then thats an easy fix. You can get them new from Autometer.
The gauge was working perfectly when I removed it from the car. Only reason I sold it is b/c I'm installing larger guages in my AC vents in my TA.
Like I stated above, Send me the gauge back and I'll refund your $135.
12-20-2005, 12:23 AM
Hate to say it, but the sending unit is around $100. I'd talk to Autometer before buying a new sending unit.
12-20-2005, 06:33 AM
Do you see a reading if you just put the ignition switch in the 'ON' position without starting the car? What did you use for a power source for the gauge? Make sure it is un-interupted during engine cranking or the gauge won't calibrate correclty when you start the car.
Good Luck, Ken
12-20-2005, 01:11 PM
Jp is an honest guy, and i appreciate that! thanks bud
ok, as for the gauge...im getting nothing even when i turn the ignition (ie system primes itself).
the power wire, i guess, may be hooked up wrong. i wired it to a pre-existing power source, which could be the problem. i will re-wire this and go from there. i'll just route it directly to the battery.
on a side note, i did cut the wires going from the plug harness to the sending unit in order to get it threw the fire wall. that plug on the back of the guage is huge and i couldn't fit it threw the wall no where. but i put the wires back together properly and tightly, i wouldn't believe there is a problem there...
on a side note, that red power wire, it is for the power for the sending unit??? or for the guage?
thanks guys! i really appreciate all the help!
12-20-2005, 04:15 PM
AJ I emailed you the .pdf file from autometer's website for installation.
When you turn the ignition to the "ON" position, does it make the "err" sound? It should do this every time you turn the ignition to the "ON" position b/c it self calibrates itself everytime its given power.
If you are turning the ignition to the "on" position and its not even making the "errr" sound then thats your problem. The red wire needs to be re-done.
The red wire gives power to the unit so it can "read" the information from the sending unit.
The red wire needs to be connected to a 12V ignition source. Not the battery, if you do this, the gauge will have power at all times. In other words, a wire that is powered when the car is in the "on" position, but has no power when the car is off. Finding a wire running from your ignition is the best thing to do.
Just get a test light, poke a wire w/ the car off. Should be no power. Now turn the ignition to the "on" position. Test the wire again, it should light up the test light.
12-20-2005, 05:02 PM
you'll also want to use the test light to make sure the wires you cut are getting power. Test the wire before/after the firewall w/ a test light to make sure its getting power on both sides
12-20-2005, 06:46 PM
brother, i feel like an idiot. i didn't even think of wiring the red to the ignition, but i didn't know either... i'll have to find a good wire from the ignition to tap into.
since GM uses basically the same wiring harness in all their vehicles, whichwire did u tap the red into? or where???
thanks again bud!!!
12-20-2005, 06:59 PM
no problem man. Easy mistake. Honestly, I dont know which one i wired it to. I just used a test light and tested a couple 'till i found one.
Just get a test light and do what i suggested in the post above. Find a wire. Test it w/ the car off. No electricity. On the same wire, test it again with the ignition in the run position. Test light should illuminate.
Let me know.
12-21-2005, 09:41 PM
i got it working for me! turns out, the red power wire i had tapped into was incorrect. but its all straight now! thanks for all the help guys!!!