I installed an auxillary tank and bypassed the oil pressure sending unit to run the main lift pump. Now the main lift pump runs during the glow cycle and will continue to run until the key is shut off. I'd like to change this to run both pumps off the OPS, or some other simple means, to ensure the pumps stop if I crash. Does anyone know of an easy way to do this? Is it worth it?

Behellis1----Let the OPS control a relay that in turn would power your pump's from a Seperate fussed circuit.

Just don't crash:rolleyes:

Can I purchase simple relays with the approparite internal switches? Any thoughts on what to look for and where to look?

If you just want to run both pumps, a simple on/off relais would do. It should have 4 contacts; two of them are to switch it on and off, the other two are for the power supply that is switched on/off by the relais.

There are usually numbers at the contacts of the relais. The numbers tell you the purpose of the contacts. If I get it right, they are as follows:


30: power supply, being switched by relais (from battery)
87: switched power
85: ground to operate relais
86: + to operate relais


That means contacts 30 and 87 get connected when you apply current to 86 and have 85 connected to ground; otherwise they are disconnected.

Every place carrying car parts should have them. Just make sure that they use appropriate voltage and can switch sufficient current, as there may be 12V and 24V versions. 12V relais can usually switch up to 30 amps.

If you want/have a switch in the cabin to turn on and off the secondary pump at will, you can use a second relais, operated by the cabin switch, in the wire going from the OPS relay to the second pump. Then, if the OPS relay is switched off, the second pump won't run, regardless of the switch.

But you might want to turn off the primary pump once the stock tank is empty. I don't think the pump would last long when running without fuel.

To get that, you can use a relais operated by the OPS to supply power to another relais. The other relais would be operated by your cabin switch, and it would switch _between_ the pumps, i. e. powering either one or the other, but not both at the same time. That requires a special type of relais to switch power supplied by the OPS relais between the pumps, and numbers on the contacts of it will be different than above.

Don't forget to use fuses as appropriate in the power supply wiring and in the wiring that supplies operating power to the relais. I would add a light to the cabin switch to show which pump is turned on.

Olee- thanks for the great post. This is very helpful

I'm glad that it is --- I'm also getting great help and info here, so it's good being able to help others when I can. This is a great place :)