Anatomy of 5 port external oil pump

[Robster]

Seems several of us are suffering from erratic oil pressure problems. Not wanting to be left out of the club, my car is producing weird oil pressure readings. I have a Xflow with an external 5 port oil pump because of the dry sump. I would like to remove and check the pressure relief valve, and apart from being a pig to get at, I cannot work out which bit of the pump does what.

 

I have a small plate on the outside of the pump, secured by two small screws. Underneath this there appears to be something like an allen key bolt, but with a large slot in the head. As this is central to the pump, can I assume that this is the end of the shaft driving the pump? Off to the right is a dome head nut with a locking nut underneath it...is this the pressure adjuster? Will removing this get to the pressure valve?

 

If anyone has looked at one of these pumps, can you please guide me through its bit! Should I remove the whole pump to examine...

[EFA]

Robster,

 

A 5 port pum uses 3 ports for scavenge (two hoses go to the sump. the other is the return to the tank) and 2 ports for the pressure stage.

 

The pump has 3 rotors (stages)

 

Each stage has two ports except one. This is a scavenge stage, and it is linked to an adjacent stage which provides the 2nd and 3rd port of this section of the pump.

 

So firstly, idnetify the scavnege stages.

 

The remaining stage is the pressure stage.

 

This is NORMALLY at the back of the pump (i.e. opposiite end to drive pulley) and this vents into a chamebr at the back on the pump where the pressure relief valve is located. The presure relief valve when open simply returnds high pressure oil to the low pressure side of the pump.

 

If you are going to try to fix it, I suggest a full overhaul. The pressure relief valve in my 3 stage pump does collect silicone sealant from inside the engine, but I dissasemble the pump most times I remove the engine from the car, as the pump has to be removed to get the engine out of my car.

 

During the strip doen you will soon figure out how the adjustment mechanism works.

 

 

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[Roger King]

Arnie,

 

The Crossflow pump is completely different to what you have described. Your description is more like the Vx fully external one.

 

The Crossflow pump is driven directly by a gear on the camshaft, so Robster is correct in thinking that what he has seen is the end of the shaft. The slot is for driving a mechanical tacho gearbox (this stuff goes back to the Ark), which bolts on instead of the plate. I don't understand why Caterham supply this version of the pump, because it is freely available without the slot or the end plate which means less joints to leak.

 

The dome headed nut covers the pressure adjusting screw. There should be a lock nut under the domed nut. If you slacken the lock nut and wind the adjuster screw IN, you will turn up the pressure. Don't forget to tighten the two nuts again and note that this will only affect pressure at higher revs; it won't make any difference to tickover pressure.

 

To actually get at the valve you have no option but to dismantle the pump. This is not really recommended unless you are familiar with what you are doing.

 

The design of this type of relief valve means that it is virtually impossible for it to jam open, but they can suffer wear on the plunger or seat.

[EFA]

Roger,

 

"The Crossflow pump is completely different to what you have described. Your description is more like the Vx fully external one."

 

You're right.........

 

Fat Arn

The NOW PROVEN R500 Eaterid=red>

See the Lotus Seven Club 4 Counties Area Website hereid=green>

 

[John]

I too have had problems with fluctuating oil pressure. At fist not too serious, and changing the oil pressure gauge sender showed some improvement. But then, alarmingly, my 25psi light was coming on on cold tickover. Engine removal and pump examination revealed a chewed drive gear on the pump, cam and distributor. The cause is still unknown, but this engine was built perfectly by a top engine builder. The cam, pump and disy were sent back to a well known cam company for examination for an unconclusive answer. They advised that the oil pump drive shaft was possibly bent but I find this difficult to beleive as it worked perfectly well on my previous engine prior to rebuild.

 

IMHO, be safe and get the pump checked properly before any damage is done. Im afraid that fitting a new pump could well be your best option to save an expensive rebuild.

 

John