OIL PRESSURE GAUGE JUMPING

[01CHARGER]

I HAVE INSTALLED A NEW AFTERMARKET OIL PRESSURE GAUGE AND A WATER TEMP GAUGE, I HAD A PROBLEM WITH THEM BOTH JUMPING AROUND SO I FOUND OUT FROM A FRIEND TO GROUNG THE ENGINE (WHICH WAS NOT) TO THE FIREWALL, WICHED WORKED FOR THE WATER GAUGE, BUT THE OIL GAUGE IS STILL JUMPING, DO I HAVE TO GROUND THE TRANSMISSION THE SAME WAY?

[Just 6T9 CHGR]

Is is a mechanical or electric gauge?

Both might jump if they are cheapie gauges....I have a cheapie electric one and it jumps a bit at idle

[01CHARGER]

THEY ARE ELECTRICAL