Fuel pressure guage question

[panzerq]

Hey everyone, Ive got a 99 2500 24v cummins, nv4500 tranny, edge comp box, 125 injectors, and a fass 150 fuel system. 

 

Ive got a few questions about my gauges, they are all autometer cobalts. the EGT and boost ones work fine. the fuel pressure one has not worked since I bought the truck. Ive been messing with it lately to see whats wrong, and heres what ive tried to do.

 

When I first turn the key on, the gauge goes a little below the zero mark and dose the calibration.

 

I unplugged the harness from the sender,(the sender is ~2 months old and has a snubber before it), when I unplugged it the gauge slowly pegged its self out. I think I read that it means its grounding out somewhere?

Sender is plugged in on the outlet on the fass pump

 

I tried grounding the body of the send to the frame using a jumper cable but it didnt work.

 

Also the harness with the 3 wires was cut and extended so it could reach up to the gauges, all of the spots where it was cut are tapped up and no wires are showing.

 

Any ideas on what I should check next?

 

Thanks!

Edited March 13, 2014 by panzerq

[Ilikeoldfords]

If it were mine, I would take those spliced spots and either solder them, or use a butt conector. Just something other than tape to reattach them to make sure the connection is good and clean. Are the spliced wires spliced together correctly? I mean, are the right wires spliced to the right wires?

[mulcher812]

if you have a volt meter you can check each wire to ground using the ohm setting and it will tell you if you have a ground problem. The other thing to check is voltage to the sender and from the sender to the gauge. If you put 12 volts in you should be getting something less than 12 volts back to the gauge. So after do a little research if its a 15psi gauge and it has been over pressurized it will may also cause it to fail.

[panzerq]

thanks for the replies, finally got a chance to test it with a multimeter, its a cheapo cen tec one from harbor freight, and it was on the 200k setting in ohms.

 

there are 3 wires coming out of the sensor, i had the key on but the truck off and I tested the wires

 

purple- when i would touch the purple one the guage would go from pegged out to hovering at 3 psi

 

grey- it read 78.5(read that after being blank for a few seconds of holding it to ground, when i would take it off it would read 78.5)

 

black- it read .4

 

 

also how where would i tap the wire to check for the voltage between the guage and sender? unplug the harness from the back of the guage and the sender then use the volt meter or something on the wires? 

 

Thanks

Edited March 15, 2014 by panzerq

[panzerq]

ok so i was poking around at the wiring for the gauge under the dash, and a wire on the diagram that shuold be connected to a "good engine ground" is connected to a piece of metal under the dash, im guessing i should connect that one to the negative o the battery?

[Ilikeoldfords]

Most of the time the metal under the dash is a good ground. It couldnt hurt to check though. You could try running a wire out to the neg post and see what happens.

[Texas CTD]

Image #28. I used that for a ground on my pyro.

 

http://www.dieselmanor.com/diy/CMS-G2gauges/CMS-gen2gaugeinstall.asp

[FrioFreddy]

panzerq-

On my '01 Ram CTD, I installed a Glo-Shift FP guage downstream of recently-installed Airdog 100. In conversating w/ Mfg re: troubleshooting, they mentioned that the guage itself gets 12vdc for powering the logic, then reduces that to 5vdc which is the source to the sensor on two wires. The sensor then sends a variable signal on a third wire, depending on sensed pressure, back to the guage which interprets this signal as a pressure. Just sayin- maybe don't look for12vdc at the sensor. Check with mfg. to find out a range of volts (sensor output) on which? wires at the sensor while operating. Also maybe install a plugged pipe tee between the snubber and the sensor where you can screw in a mechanical guage to verify pressure, then remove the guage and replug the tee afterward. Also, check to see if the splice joints are soldered.This could correct any twisted-wire problems- poor connections will do worse on lower voltage.

Edited March 24, 2014 by FrioFreddy