SOLVED: 911 Oil pressure sender, Can't figure out why it won't work - bad sender(s) Options

[nditiz1]

So I have a distribution block on my engine. A grease gun hose goes from the standard top opening to this block. The block has a large hole and a small hole. The small hole has the standard idiot sensor. This works fine as the light goes off in the dash. A 911 sender is screwed into the large hole. I have a wire going to the gauge in my dash. If I ground the wire to the engine, the gauge pegs at 5 bar/above. The sender is a 0-5bar, the gauge is a 5 bar. What am I missing here? I have even swapped the sender and still I am not getting a reading.

[Superhawk996]

Sender needs a ground path back to the block.

A rubber grease gun hose won’t provide one.

A metal braided hose works better but can still get flaky over time without a dedicated ground to the sender.

[nditiz1]

I thought about that as well. I believe the distro block is made from aluminum or stainless steel. That block is bolted to the engine sheet metal. I even added an extra wire to the outside of the sender to test continuity. Maybe I still have a continuity issue.

[Superhawk996]

Maybe I still have a continuity issue.

Engine tin isn’t a reliable ground. Try a dedicated ground from engine case to your sender.

[nditiz1]

Will do. Also, I may actually have 2 bad senders. The one was unknown that I had on originally. I just put it back on and the gauge pegged as though the spring was broken internally. The other one had a worrisome connector at the top (spins) which could indicate it is not making a connection any longer internally. I will buy a new sender.

[Superhawk996]

Will do. Also, I may actually have 2 bad senders. The one was unknown that I had on originally. I just put it back on and the gauge pegged as though the spring was broken internally. The other one had a worrisome connector at the top (spins) which could indicate it is not making a connection any longer internally. I will buy a new sender.

(IMG:style_emoticons/default/biggrin.gif) neither of those are good signs.

Little troubleshooting lesson for general info:
That is why swapping parts to troubleshoot is a bad plan. With the continued enshittification of aftermarket parts this is more relevant than ever.

A multimeter checking continuity won’t lead you astray.

A) check continuity from sender case to metal engine case
B) check continuity on the signal wire back into cabin to back of gauge.

When I was taught troubleshooting long ago in tech school, they would substitute bad spares. If you tried to troubleshoot by swapping spares you would go in circles and fail.

[nditiz1]

In theory I should be able to blow compressed air into the non working sender and get some kind of resistance correct?

Edit: IF it is working as it should

[Superhawk996]

In theory I should be able to blow compressed air into the non working sender and get some kind of resistance correct?

Edit: IF it is working as it should

Yes but with a caveat - you’ll probably need an air nozzle with a rubber taper tip to get somewhat of a seal. I’ve done it in past with rubber nozzle and it worked OK cant vouch for metal tip air nozzles.

The other thing is an analog multimeter will work better. A digital auto-range may not be able to adjust to the varying resistance fast enough to give you a reading very well. Set the digital multimeter to a fixed range (assuming yours can) and it should read resistance better.