Single terminal oil pressure switch for Rover SD1 V8?

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alc59
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Single terminal oil pressure switch for Rover SD1 V8?

Post by alc59 » Tue Apr 02, 2019 5:33 pm

In my Grinnall Triumph TR7 which has a Rover SD1v8 engine the 3 terminal oil pressure switch has failed - it's weeping lots of oil.

It only has two wires going to it, so I have in mind to replace it with a one terminal switch, because the 3 terminal switches are difficult to get and expensive. Can anyone let me have the part number for a one terminal switch that will fit?

Thanking you in anticipation for your help
Al



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Ian Anderson
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Re: Single terminal oil pressure switch for Rover SD1 V8?

Post by Ian Anderson » Tue Apr 02, 2019 8:19 pm

http://www.ldpart.co.uk/shop/shop.php?c ... d=sidd6fb2

Could this be what you are looking for?

Not sure about thread size thoughIAN
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

DaveEFI
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Re: Single terminal oil pressure switch for Rover SD1 V8?

Post by DaveEFI » Wed Apr 03, 2019 8:40 am

The three terminal switch controls the fuel pump on the SD1. Later carb cars did this with a single terminal one and a relay. The injection versions also used a single terminal one.
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Allan Robinson
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Re: Single terminal oil pressure switch for Rover SD1 V8?

Post by Allan Robinson » Tue Oct 01, 2019 12:07 pm

Hi all, I have a Dax Rush with a 4.6 RV8 using an SD1 front end and oil pump. I would like to introduce the fuel pump cut off safety feature and from previous posts it would appear that I have two options.

1.) Buy a 3 terminal oil pressure switch is a quick solution for circa £25. (I have found a new one on eBay)
2.) Use a single terminal oil pressure switch for circa £3 but would then need to purchase a relay to control the fuel pump.

I have been using a Facet Red Top fuel pump for many years now via a 10 amp fuse and the advantage of a relay being that 10+ amp relays are readily available. Although a 3 terminal oil switch is a quick solution I have no idea what sort of current these oil pressure switches are designed to carry. Any ideas or experiences?

I also I do wonder why Rover changed from a 3 terminal to a single terminal with relay?

I look forward to viewing any thoughts or opinions.
Many Thanks
Allan

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Re: Single terminal oil pressure switch for Rover SD1 V8?

Post by DaveEFI » Tue Oct 01, 2019 1:57 pm

The three terminal switch doesn't seem to be the most reliable device, judging by posts on the SD1 forum.
When injection arrived, the fuel pump cut-off became an inertia switch. (The purpose is to prevent fuel spilling in an accident - not to protect the engine) So it made sense to change to the same simple oil pressure switch and a relay for the carb cars too.

If starting afresh today, I'd say the single terminal switch plus a relay the cheaper option. If you already have a relay controlled pump, even cheaper.

You'd fit the switch in the ground side of the relay coil, so extra current though it minimal. Depending on how you wire things, you may also need a diode (or two) to prevent any interaction between the warning light and relay.

Here's the circuit of how the SD1 did things.

Image
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Allan Robinson
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Re: Single terminal oil pressure switch for Rover SD1 V8?

Post by Allan Robinson » Thu Oct 03, 2019 7:16 pm

Many thanks Dave for your valued feed back. From your comments I agree that the single terminal switch controlling a fuel pump relay would be the better solution and that is the way I will go.

Thanks again
Allan

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