W123 dash panel
 

Is there anyone who does repairs on these. The one in my sons car gives erratic fuel & temp gauge readings. I’d like to get it repaired he’s run out of fuel a couple of times because of it. Also how should i cap the oil pressure line while it’s out?

Not a fix, but I just zero the trip odometer every time I fill the tank. 350 miles/tank on winter diesel and 390 miles/tank on summer diesel are safe numbers for me, W123 300TD w/ 4 spd manual.

Can’t speak for the clock - but if the fuel gauge is bouncing around you prob have a very dirty/sludge fuel level sender - which is in the tank. That would’ve easily accessible underneath the first aid kit. It has 2 very delicate wires that a float runs up and down on - they get sludgy and the prevent the float from properly moving.

I recommend simply replacing the gauge. PM me and I'll fix you up with another gauge.

There is no way I know of to run the engine without a gauge connected to the oil pressure line. When I need to do this I simply connect a gauge to the line (and to the electrical) and that way I can run it without the whole instrument cluster in it.

I hope this helps,

i don't know this for sure, but I image there might be some kind of appropriate square plug/cap that would screw onto that oil line flare fitting - and allow you to drive with out the gauges.

i don't know what size that fitting is - but something perhaps like this? i was at home depot the other day buying an assortment of fittings to attached my air compressor hose to another line - and I noticed these types of cap fittings.

https://www.marshallexcelsior.com/14-od-flare-fitting-cap-brass

The photo is too hazy to be a clear picture but the ends of the Oil pressure line cylindrical in shape with a shallow taper/point/angle on the sealing edge.

They guage end would be harder to block off then the Oil Filter Hosung end.

However, when I went to remove the Oil Pressure Line at the bottom rear of the Oil Filter I found that (The hollow bolt is supposed to rotatate around the line) the hollow bolt was rusted onto the sealing end and the whole line tried to rotate.

In my case I cut the line but other siaid I would have been better off loosenng the gauge and and then the whole tubing could rotate .

ah, yeah that make sense Diesel911. I've not looked at the gauge end in a while, I guess it's not a normal male flare fitting as you point out. my bad!

Pretty sure it’s not the sending unit. I can press on the instrument panel or jiggle the wires under the dash and cause the fuel and temp gauges to swing from one end to the other. Would it be possible to remove my old oil gauge and screw it to the pipe to keep oil from leaking from the pipe while I work on the dash?

I had a leaking oil pressure gauge and didnt have parts to fix so i plugged it with a bolt. worked just fine till i did a new line and gauge mounted where the radio used to go.

Back in 2007 when people had electric gauge fluctuations they said one possible was where the instrument cluster was grounded.

Does anyone know if a thankful of Fuel with Startron and letting it sit with a full tank for several days would eat off stuff on the sending unit? Note there is some sort of enzyme in it
.

I am guessing you did that where the Oil Pressure Line goes into the botto reaf of the Oil Filter Housing.

Yep bottom of the oil filter housing. And it was a brass plug with teflon rather just "a bolt"

Guys guys guys! Hold on.

First OP, you're looking to repair your instrument cluster. The dash panel is the massive thing that covers well, the dash.

Diesel911 has it 100% on point. In fact, this is the first repair I do on any of these old cars.

Save your money before replacing these gauges, fuel sender, and other $$$ parts. Go to your favorite auto parts store and get a ground strap.

Run the ground strap from the back of the instrument cluster to one of the many bolts that attach to the firewall. Any will do. Attach both ends to a screw and screw it down.

Reconnect everything and see if this fixes the erratic gauges.

There's no need to cap off the oil pressure line if you don't start your car. If you have to, then of course cap the line or put the cluster back in.

I have mechanical 123 gauges too I'll sell reasonably.

I'd pull the cluster and check the grounds.
 

It may have been said, I dunno, I only read down to this one of your post.