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
Mark

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

http://www.jag-lovers.org/xjlovers/xjfaq/efirich.html

David

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:

Mark

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.
ANYWAY.,
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.

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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…

frank
xj6 85 Sov Europe (UK/NZ)
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Try putting a new 190F safe thermostat and replace those
temp sensors, that should make a lot of difference.

                                                 Walter
                                                78 xj6 ser.2

Status update. I drove the 85 XJ6 to Seattle last week, good hour or so on the highway. I brought my IR temp reader. and the block, radiator, and water rail didn’t got above 72c (ish). So looks like I’ve got the wrong thermostat installed. Ugh…

I guess this will be where I’ll start. I guess I will be taking care of the Aux fan at the same time. What’s weird, is the airpump temp sensor is available, but the fuel temp sensor isn’t.
I’m going to do some experiments to see if the airpump temp sensor produces the same results as the fuel temp sensor. Why? for the same reason dogs lick their junk. because they can. :smirk:

What fuel temp sensor? Do you mean the coolant temp sensor?

David

Mark,
What fuel temp sensor? Do you mean the thermo vacuum valve?

Paul

yes the coolant temp sensor. sorry for the confusion. The bit that tells the cold start relay that 's well, it’s cold; which in turn initiates the cold start relay. That sensor.

Gents, let’s try to straighten out some of the terminology here, relative to the Series III XJ6 4.2

We shouldn’t do it, but all of the devices on the coolant rail could be called “temp sensors” because they all sense temperature as part of their job.

The Thermotime switch (TT switch) is forward-most on the rail. It operates the Cold Start Injector (CSI)

Next is the temperature sender for the dashboard gauge.

Next, third from the front, is the Coolant Temp Sensor (CTS) for the fuel injection system. It communicates with the ECU in the trunk.

Rearmost is the thermo-vacuum switch which operates the air injection pump diverter valve and the air switching module. This switch is not used on all cars, USA or otherwise. In some cases, market dependent, this location on the water rail had different switches (EGR operation, for example).

The fuel temperature switch is on the fuel rail. It is plumbed inline with the fuel pressure regulator and dumps vacuum when fuel reached xxx-degrees. This increases fuel pressure. It can be bypassed by simply running the vacuum hose from the regulator directly to the vacuum nipple on the engine. Early Series IIIs did not use this switch at all. Some of those cars were retrofitted with the switch, some not. I think it became standard issue in 1982.

There is no cold start relay on a Series III 4.2

Cheers
DD

3 Likes

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There is no fuel temp sensor, Mark - there is a thermal vacuum switch related to fuel temp. And the air temp sensor on the AFM…

But I second checking whatever can be checked…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)
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