The KA24E engine often suffers from poor oil pressure late in its life. To make sure a lack of lubrication doesn't cause premature engine failure in your 240sx, it's a good idea to inspect the oil pump.

If you want to inspect your oil pump, it is not necessary to pull off the cylinder head. The oil pump is located on the bottom portion of your timing chain cover...directly opposite from your distributor. In fact, your oil pump and distributor share the same geared shaft located inside the timing chain cover.

To remove the oil pump, first make sure that the No. 1 cylinder is at TDC. You may want to make a pencil mark on your distributor to indicate the rotor position at No.1 cylinder TDC. This is an important reference which I will explain later. Unbolt the oil pump from the timing chain cover. Have a pan or rag ready to catch any oil that spills as the pump is removed.

Carefully move the oil pump away from the timing chain cover. The geared shaft should also slide out as well. If the shaft doe not slide out, gently jiggle it loose. Do not try force the shaft out as it will only bind. Once the shaft is removed, the distributor rotor is free to spin any which way...this is where your pencil mark comes in handy.

Anyway, once the oil pump is removed, check the pump gears for damage. They should be able to rotate without any interference. There is also a large plug located on the oil pump cover. Unscrew the plug and you will find the regulator piston and spring. The piston should be able to slide in and out of the housing slowly due to gravity alone. If the piston tends to bind up, regulator is trashed.

By the way, you can get competition oil pump springs from Nissan Motorsports to increase the oil pump pressure.

Inner Spring Part No. 15133-E4620 Outer Spring Part No. 15133-22010

You can use either or both depending on the pressure you want to obtain...some people also stack washers to compress the stock spring a little more. Nissan Motorsports also sells a high volume pump that will flow about 15% more oil than stock...

Part No. 15010-S8000.

To re-install the oil pump, first make sure that the engine and distributor rotor is at No.1 cylinder TDC. Then align the dot on the geared shaft to the dot on the pump shaft sleeve. Use a new oil pump gasket and carefully slide the shaft and pump together until the pump can be bolted once again to the timing chain cover. This might take a couple trys to make everything mate up correctly...just be patient and gentle with the whole process.

I have found that the gearing of the geared shaft will allow the distributor rotor to be either slightly advanced or retarded with respect to the engine. I keep it on the advanced side.