Oil Pressure Gauge - Sender unit

[1971Series88]

Help - please...

I have no oil pressure readings on my gauge - I checked the voltage and I am getting juice to the gauge fine.

So the Q I have is - how do you tell it is the Oil Pressure Sender unit with the problem, or the actual Smiths gauge (original) itself?

I checked out the sender unit costs....WOW! over $300!! eeeek!

Series 2a, with the twist off oil filter adaptor - other than that - all is stock.

[stonefox]

I'd put in a early 2a capillary /Temp gauge.

[siiirhd88]

The electric oil pressure gauge works like the fuel and water temp gauges, with the sender varying the resistance to ground. The circuit should have stabilized 10v or so on the input to the gauge, and then the wire runs from the gauge to the sender. If you ground the wire at the sender, the gauge should go upscale to max pressure. If so, the sender could be bad or it doesn't have a good ground to the engine block. If it doesn't peg upscale, check for an open circuit from the gauge to sender.

The senders do go bad, and when replaced need to be mounted in a specific orientation.

Due to cost, when I use electric gauges I use VDO senders and gauges.

Bob

[jac04]

The senders do go bad, and when replaced need to be mounted in a specific orientation.

Bob- I've never heard that the senders need to be oriented a certain way. Is that correct?

[antichrist]

I'd put in a early 2a capillary /Temp gauge.

x2, without a doubt.

[siiirhd88]

The Lucas type of senders for the electric oil pressure gauges usually need to be in a specific orientation. Older senders can have the word "TOP" that needs to be oriented at the upper end when mounted. The newer senders just have a small stamp mark on that should be at the upper end.



Bob

Bob- I've never heard that the senders need to be oriented a certain way. Is that correct?

[1971Series88]

x2, without a doubt.

OK so I bite - what is one of these capillary gauges - and where would one buy one?

Thanks to all for the feedback...I will try grounding the gauge and see if it moves the needle....cross my fingers the gauge is bad!

[stonefox]

It a dual sided gauge, Oil pressure works on a capillary action .There is no electrical connection .Its damn near fool proof. The temp side is a probe direct into the head. I have a couple used ones. You can get them new on ebay but they are pricey. I think they are NLA but I could be wrong. I couldn't find it on RN,but that doesn't mean its not there.

[TedW]

Rather than using a sender, a capillary gauge is connected to the oil supply by a (usually) copper capillary tube that sends oil (under pressure) to the gauge - which reads said pressure. Generally more reliable (and accurate) than electric gauges.

I replaced the electric gauge with a mechanical (aka capillary) one on my 1970 when the sender crapped out. No problems since.

I have a few extra gauges kicking around if you're interested. I don't think I have any of the connector tubes, though - although I'm sure they are available from sources like Moss Motors. PM me if you're interested.

[SafeAirOne]

The Lucas type of senders for the electric oil pressure gauges usually need to be in a specific orientation. Older senders can have the word "TOP" that needs to be oriented at the upper end when mounted. The newer senders just have a small stamp mark on that should be at the upper end.

Hmm...interesting. I must admit, you've got me wondering what's going on in there that it needs a "top" side. Then again, I've seen the craziness inside the Lucas SIII exterior lights switch, so the pressure sender doesn't really surprise me.

[Alaskan Rover]

Rather than using a sender, a capillary gauge is connected to the oil supply by a (usually) copper capillary tube that sends oil (under pressure) to the gauge - which reads said pressure. Generally more reliable (and accurate) than electric gauges.

I replaced the electric gauge with a mechanical (aka capillary) one on my 1970 when the sender crapped out. No problems since.

I have a few extra gauges kicking around if you're interested. I don't think I have any of the connector tubes, though - although I'm sure they are available from sources like Moss Motors. PM me if you're interested.

I totally agree, TedW, the mechanical guage is usually more reliable than the electric. My original electric guage had crapped out before I purchased the vehicle. I eventually replaced it with a mechanical guage feeding off a capillary tube. I think the guage kit was S & W or some such (easily available at any parts store and there is an assortment of guages on hand at a auto parts super store like Pep Boys in the US or National Tire in Canada. The guage fit the original hole perfectly and the capillary tube fitting fit the original hole for the sending unit perfectly as well.

In trhe case of most of the over counter guage kits like I purchased, the capillary tube is nearly opaque plastic, rather than copper...but mine has given no problems whatever over the many years it's been installed. Just make sure you route away from any hot exhaust manifold, but it attaches to block on opposite side of manifold anyway, so that isn't hard to do.

[antichrist]

Nissonger sells the parts for the gauges, including the capillary tubes. They used to sell the gauges as well and the last Smiths I got from them had the plastic tube. Older gauges had a flexible metal tube (sort of like the connection pipe for a gas appliance). The gauges can use either tube.
There are a lot of after market 52mm mechanical gauges, SW, AutoMeter, VDO, etc.

[siiirhd88]

The small copper (and plastic) capillary tubes use small compression fittings and work well. I have had failures at the compression fitting on the engine side connection from the copper tube work hardening due to flex and vibration, even after making a spiral pigtail. I now use a grease gun flex hose attached to the engine and mounted to a fitting on the inside of the wing. The grease gun hose is 1/8" NPT and is a high pressure hose available anywhere. Attaching the copper tube to a fitting on the wing eliminates the copper flexing between the engine and wing. I've used a 1/8" NPT 'T' fitting soldered/brazed to a mounting tab to attach the fitting to the wing, with the ports attaching the flex hose, the 1/8" NPT to copper tube compression fitting and a GM low oil pressure warning light switch.

I've only had one failure of a mechanical oil pressure guage where the bourdon tube failed. It filled the dash with oil.....

I prefer the mechanical guage for reliability and accuracy, and the electrics for ease of installation.

Bob
'02 D2 SD
'02 D2 SE Kalahari
'97 RR P38 Vitesse
'80 SIII 109
'75 SIII 88 V8
'68 SIIA 109 V8

[1971Series88]

hmmmm...thanks for all the replies. I am/was always leary about routing hot oil into the cab...I have a healthy distrust of plumbers and plumbing in the house as well! Ask me why ....I will give it some thought.

Thanks Ted for being my "parts guy"

[73series88]

i got a sunco manuel oil presure gauge
tapped the end where the door knob sender would have been.
and fitted the oil gauge line
the rover electric gauge parts are so expensive and so many things to go wrong
16 bucks at the local parts store.
ive been running that for almost 4 years
sometimes simple is better.
aaron