Prime digital FP gauge issues!

[josh young]

I figured I'd start another thread on this issue I've been having. The gauge is a Prime brand, can't find anything about them doing a search. I've been over all the connections under the hood and on the gauge I can find, hit everything with contact cleaner, checked for loose nuts. etc. It has a wire that is made in the gauge, I assume it's the wire to the sender. It also has one for ground and one for power. There is also a purple wire on the top of the gauge that is not hooked up and does not appear to have ever been, I don't know if that's another option or? The best way I can describe it is as follows: When you turn the key to the run position it's right there with my manual gauge give or take 1 psi. The readings start low then go up in the run position. When I start the car the digital gauge readings start to automatically go down to around 10 psi then slowly come back up. It will go back up to the mid 20's, but never as high as it was before I started it. I thought about buying a new gauge but I don't know if it's my issue. I've searched the internet high and low and this seems to be a scarce issue, or at least one that's not talked about. Thanks guys for the information in my other thread, I checked everything I could to no avail. I thought it might be better to start another thread with as much information as I can give in it. If I find the issue I'll update both threads, in case anyone happens to have this issue in the future.

 

[v6turbo87]

The purple wire is most likely to dim the gauge when you turn on the headlights. It is very common with digital gauges. As far as your problem, I would replace the sender not the gauge. Being exposed to engine heat it is more prone to failure.

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[josh young]

That makes sense on the purple wire because there is no change in brightness when the lights are on or off. Thanks!

 

[v6turbo87]

I have a few gauges made by Cyberdyne and they have purple wires for dimming.

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[Chuck Leeper]

Check the ground resistance.
Had a similar issue w/ Autometer ga's. Found hi ohms at the ground side. [Welded studs, internal and external star washers, multiple body/chassis straps.]
Had 22 ohms. Called AM, he said waay too much. Not more than .2 should be attainable.
Since this was a new install, we had problems finding the issue.
Took all the grounds off, re-cleaned, re-installed. .02.

 

[GNONYX]

Is it possible for you to take a picture of the gauge, front and back as well so all can evaluate what type of gauge you have?

 

[josh young]

I'll try to get some pics today. I found the company's website. They are out of Cleveland Ohio.

 

[josh young]

Well I may have figured out the problem. I believe v6turbo87 may have it, a bad sender. Either way it looks like I'm going to be replacing the sender since it has developed a slight fuel leak in the top of it. It's leaking in a little recessed area with what looks like a small pin in the middle / opposite side of the sender wire. It's not a bad leak, just enough to get a little wetness on your finger. In the process of looking at it, I lightly tapped the sender and it seemed to stop the leak. I guess it has a check valve inside of it? I did notice my readings on the gauge was right there with the manual gauge with the key on, but after tapping it a little it went down to around 8 to 10. So maybe I can kill 2 birds at once wit this thing. I'm going to give the company Prime Instruments a call in the morning to see if they still have any parts. They don't show any of these gauges on their site anymore. Is the sending units a generic piece, or are they different with different maker's? Maybe I can get this thread wrapped up soon. I'll try and get some good pics of the gauge and sender tomorrow, just ran out of time today. Thanks a million guys!

 

[Chuck Leeper]

"It's leaking in a little recessed area with what looks like a small pin in the middle / opposite side of the sender wire."
Could be the diaphragm is leaking. That hole could well be a small vent, to allow atmospheric pressure to the dry side of the diaphragm.