As mentioned in the in the Engine Start post, my engine start wasn’t 100% uneventful. The main problem was the lack of oil pressure on the gauge, but there was the usual selection of leaks to deal with as well.
Oil pressure first: out came the multimeter and the out-of-date wiring diagram from the old manual (2015c). No wiring diagram is provided at all in the new manual (v1.2 and v2.0).
With a basic multimeter, I was able to prove that the oil pressure sensor had power and earth, but there was no connection between the sensor and the gauge. By disconnecting the engine loom, I could prove good connection between the gauge and the chassis loom connector.

With the help of Caterham Cars and an up-to-date wiring diagram, the connection problem was discovered to be the connector between the engine loom and the oil pressure sub loom.
You can just see that the top right-hand side pin isn’t in the correct position. Once this was sorted, the oil pressure gauge sprang into life.
Top hose clamp too large Replacement hose clamp
I had a few coolant leaks as the pressure increased with the engine tempratue. The coolant system must hold that pressure or the coolant will boil before the thermostat opens, because the thermostat opens above 100C. The only real problem with these leaks was the hose clamp for the top hose. The replacement top hose had a smaller diameter so the original clamp was too large to create the seal needed. I ordered a replacement hose clamp to solve the problem.
The rest of the leaks just needed the clamp tightening, and one of the dry sump oil hose connections needed to be tightened.
420R kits supplied in late 2021 have an immobiliser fob attached to the keyring. If you are experiencing problems getting the immobiliser to disarm it may be because the fob is too far away from the pick up aerial when the fob hangs naturally on the key in the ignition. The aerial in question is adjacent to a black disc that is part of the ignition housing. I found that if you touch the black disc with the fob the immobiliser will disarm immediately and you will hear the fuel pump kick in.
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