55.2-59 Problem with gauges

[jeffs56]

Hey guys I’m hoping you can help me out on an issue I’m having on my gauges. I have the intellitronix gauges for my 56 Chevy truck. The oil gauge jumps back and forth. It does it at idle and when driving. Any ideas?

[jeffs56]

Sorry it’s not letting me post the video

[dsraven]

not familiar with those gauges but would suspect the oil pressure sending unit. thats a pretty common sending unit fault. first ensure it is the correct unit for the gauges, then if so, i recommend to do a manual pressure check where you unscrew the sending unit, screw in a T fitting, screw in the sending unit to one side of the T and a manual oil gauge to the other side. start it up and compare the two gauges as well as get an actual gauge reading.
if you have an LS engine it is also a common problem for them to haver a problem with the oil pump pick up tube O ring seal where the tube goes into the front engine cover. it leaks and sucks air into the oil pump along with some oil, hopefully. air compresses so the pressure gets erratic as the pump does its thing. google it for info.

[jeffs56]

I have a vortec 350. The gauges that I have are a analog gauge set

[dsraven]

Is it just the oil gauge that's acting up? What does it do with key in run but engine not running? If it holds at zero then I would try disconnecting the sender. That should pin the gauge at one end and hold steady. Then ground the sender wire and the gauge should pin the other way and hold steady. If that works then try a new sending unit.

[jeffs56]

So when I turn on the gauges all the gauges power on and then the oil gauge goes back down to zero like normal. So what would you try?

[dsraven]

an old fashioned electric analog gauge is simply a gauge needle balanced between two electromagnets. one magnet has a steady current supplied with the key in run. this is the one that draws the needle to zero. the other magnet has current supplied but has a variable ground, varied by the sending unit, so depending on how much ground there is the magnetism on that side can be zero or, with a full ground, it can outweigh the magnetism on the other side and pin the gauge at max. some needles are sitting in something that slows their movement so they are not as sensitive to quick variations in voltage, some are not. I would say that if the gauge was fine and just started doing this lately then do the above test with the wire at the sending unit and if the gauge reacts well everything points to the sending unit. thats the cheap fix anyway. a newer style electric analog gauge may be driven by a stepper motor. here is a link to explain better than I can. maybe it will help.
https://www.autometer.com/blog/faq-p...E&gclsrc=aw.ds

[mr48chev]

Web site is down for repair or ?? so it is hard to study the details.

My experience says that outside of a bad unit 60% of electrical issues are because of ground connections or bad =loose connections. The first thing I'd do is check every connection between the sender and the gauge and the ground for the gauge.

You might want to pull the plug on the alternator and run the truck for a minute and see if the gauge makes any change. Alternators have been to mess with other electronics if they aren't perfect.

[nvrdone]

Just wondering if I understand all this - does the gauge ground thru the sender? If so did you use any sealant on the sender? if so that could be causing an intermitant ground causing the problem.

[dsraven]

there are some reviews of the intelitronix systems on the summit site. it seems like sending units are a common frustration item and cause problems with the gauges and correct readings. if the wiring checks out I would do some manual tests with a regular mechanical oil pressure gauge "T"d into the oil gallery with the existing sender, or it it is too tight , space wise, simply use another oil gallery port for the manual gauge. there should be one near the oil filter. this will allow you to compare actual to what the gauge is dash reading.