Is there any adjustment on the S-III Fuel Injection

Obviously I haven’t taken the time to dig through the manual(s) on this one, but…My Little Green Bean XJ6 plugs are black. not wet black (oil), just black. This tells me she’s running a bit on the rich side. Is there an fuel ratio adjustment? Needless to say there isn’t an OBD scan tool plug to check with - so, I’m curious.
Compared to the '86 which I’m not sure what it runs on because it seems to run forever on a tank(s) of petrol; The Green XJ6 blows past everything except a filling station.

I’m open to thoughts on this matter.

Thanx as usual

Try taking a look at Doug’s guide on troubleshooting over rich mixture.


Thank you @Dwomby I will look at the temp sensor. I recenly replace the coolant, & thermostat which was lazy to stuck open. I will throw a meter on this one to figure out what the issue is.

thanx again, You’ve saved me a ton of time :slightly_smiling_face:


Yep. Adjusting the spring on the AFM is not the best idea, apart from that the idle mixture bypass is adjustable but the problem should be with the temperature sensor, fuel (regulator) or cold start injector… in that order. Maybe lambda. At least you have XJ6es to compare to!
Another David

Thank you David,
Didn’t even think about “adjusting the spring” That sounds like a bad idea to me.
I’m about to start on the temp sensor first (Another Jag Mods video), then the fuel regulator I replaced the Lambda sensor about a couple of years ago. The light came on, swapped it out, then spent a week or so trying to get the light to go out. Finally figured it out. PUSH DA BUTTINN Mark… :crazy_face:

I’m pretty confident that’s the temp sensor. or cooked wires to the sensor all of the wires around the intake is cooked. I’m holding off as long as I can to replace the birds nest of wiring.

I’d like to redo all of the under the bonnet wiring, but I haven’t found a source for the OE color wires. I really don’t want to be “That Guy” or “That PO” that everyone talks shit about.
Fuel regulator. Any suggestions on to accomplish this without taking a petrol bath? I’m assuming the pressure is checked at the output of the regulator? I’ve checked fuel pressure on the '86 at the beginning of the fuel rail. but maybe that test rendered inconclusive results it was 35 psi cold start. Probably over thinking as usual.

To stop getting showered in petrol disconnect the fuel pump (or relay) and start the engine until the fuel pressure has dropped.

The regulator is basically a spring valve, Mark, opening to the return line (‘output’) at the spec pressure - keeping the
fuel rail pressure at spec. The 'output pressure is basically zero - and not relevant to fuel pressure testing.

Two pressure readings are relevant; ‘raw’ (pump) fuel pressure - measured at the hose connecting pump to fuel rail. An ‘as new’ pump delivers 100+ psi, a ‘good’ pump some 70+ psi - below some 40 psi the pump won’t run the engine at high loads…

‘Regulated’ fuel pressure is normally measured connecting the gauge to a CSI hose, or a ‘T’ at the rail inlet hose - the point is to measure fuel pressure inside the fuel rail. Which is spec’ed to 36,25 psi +/- 0.725 psi - running the fuel pump only.

As an aside; the ECU computes fuelling based on constant rail/manifold pressures - a membrane in the regulator uses manifold vacuum to adjust rail pressure…

xj6 85 Sov Europe (UK/NZ)

Try putting a new 190F safe thermostat and replace those
temp sensors, that should make a lot of difference.

                                                78 xj6 ser.2