Does your coolant temp sensor have a part number? If we confirmed it’s the same part as used on the V12, that would tell us more about how your EFI works.
Morning Kirbert,The 3.6 – early 4.0 and early 5.3 all take a coolent sensor with jaguar part number DBC 3728 – as soon as it stops raining here I will do the test to see if it is the sensor.
Rgds
Gerald
Kirbert,
Does the v12 6CU has a limp mode if one of the sensors / potentiometers is disconnected???
It has a default value for the oxygen sensors if they are disconnected. Other than that, I don’t think so; if a sensor fails, the car just runs like $**t. There is no OBD system.
Hi Rooinek,
I’ve a 1985 XJS 3.6 Manual Cabriolet (Oblong Air Box & header tank on right hand side ) My ECU in boot is the following spec LRZ185 3.6L Six 85 - 87 Lucas 8CU (DAC3831)84488
Its 11 years of ownership & rolling restoration. Had my fair share of cut outs & then runs fine moments.
Below are tests & parts I had to replace due to similar symtoms hope this helps
Regards
Player022
Check these items:
AIR TEMP Sensor ( can cause error fueling status to ECU & cut out ) Car can be driven with disconnected & warmed up: try paper clip bridgin in connector. ***replaceded after Car would to start then cut out , disconnected would run fine one warmed up **
TPS ( throttle Possition Sensor ) Check with multi meter that you get smooth indication of voltage from 0.32 /036 to 5V as you turn throttle capstand. This failing can cause over fueling ,cutouts and stalls. did a 150 mile highway jouney no problems butas soon asI hit stop and start traffic in city died & would either over fuel or start then die.fixed once replaced imagine a crackeling volume pot on a stereo…now its controlling your injector pulses.
Fuel Pump ( A ; Check Relay B: Check connections Clean & tighten use electrolite grease ) After a cut-out check you hear the wurring ( priming fuel system ) of pump prior to cranking.
Fuel Rail: CHECK?/Test Fuel Pressure regulator & Fuel 3 way vacuum Valve ( brown unit on rail with vac pipes affects pressure to rail based on fuel temprature.
Injector Harness: (Check for wire breaks & bad/ corroded connectors, hiden faults in loom can reak havoc, check continuity of each sensor to plug & plug to ECU ** had to swop mine , found companny her that can build like oem **
FULL LOAD VACUUM SWITCH (affects fueling ) Test for correct switching ? disconnect vacuum line & block at switch & manifold. *** currently investigating an Idle issue its top suspect as I’ve had AAV valve rebuilt***
ECU: Check temprature after cold start & try cooling with fan or spray.
these guys do test & Repalcements ECU’s https://www.atpelectronics.co.uk/ they also show both the ecu’s you have : the unit that works was only in production for Years 83 - 84 and your spare unit 84 - 90.
AJ6 Engineering in UK are Jaguar ECU & performance parts specialists S6’s & V12’s especially ( suggest you contact Roger ( a guru ) there to find out why a DAC3831 ecu wont work with your car)