Jaguar Repair: SIII injectors not firing on start, air flow meter, fuel pump relay

Question
my 84 jag was starting to run rough so after a compression ck i needed to rebuild the engine. the new engine is in and it will not start.if i remove a couple of plugs and dip them in fuel then it starts. i have a noid light so when the engine is running all injectors are firing. it does not matter if it is hot or cold when cranking the noid light does not illuminate so the injectors are not working whilst cranking. i hot wired the csi and it started each time,but i think 12 volts fried the csi as that no longer works. i live in a warm climate so it would never cut in anyway.using a remote jump switch on the battery and turning the ignition on it still will not start. i even hot wired the coil used the remote starter but still the injectors don't fire. with the fuel on the plug and the noid light plugged in when i crank the engine the noid light only comes on when the engine fires. i found water in the fuel tanks so i flushed the hole system when it was clean i removed each injector but kept them connected to the fuel rail turned the ignition with the sifter in drive to keep the pump running, i then touch briefly each injector with a 12 volt hot wire and they all had a good strong cone spray pattern so i figured they were fine. only did this to sort out the rough running problem. so i have two problems will not start without adding fuel directly to the plugs (aerostart gets it going now) and when running does not have a smooth idle ,but seems to accelerate and drive ok, after a long run the plugs are clean so it not running rich

Answer
Hi Warwick,

You have several issues that I don't understand. One is the fuel pump running. The US version turns on the pump when air is entering the air flow meter and opens the vane which triggers the fuel pump relay. Nothing else can turn the pump on.

Second is the cold start injector. It is operated separately from the injection system and the only part of the system that is shares with the injection system is the fuel. It is powered by the Start position of the key and grounded by a thermo-time switch in the coolant rail on top of the intake manifold (usually the large switch in the forward most position) The thermo-time switch will only ground the injector when the coolant is cold but it will also disconnect the injector if used several times as it has it's own electric heater.

Third is the injectors. They are powered not by 12 volts but by a pack of resistors mounted low on the front inner fender. The ECU in the trunk is what grounds the injectors in groups and does this two times per cylinder firing and not in any time with the valves. Thus the build up of carbon on the under side of the intake valves at around 65 to 75,000 miles.

If you are at a point that the car runs good once started You should closely look at the cold start system. A simple test we do to see if the cold start system is at fault is to just spray starter fluid into the intake to start the engine and if it starts ok when warmed up then it is most likely the cold start system is failing. Even on a hot day in Florida here the cold start system must operate.

There is one other factor you should look at. The Series III XJ-6 had an odd problem even new. They require a deep charge battery. To see if this is a problem on any ser III Jag we just connect a good jumper battery to the car as though it had a dead battery (even though the car battery will spin the engine quit fast but not start) If the addition of a jumper battery makes it start then it needs a new deep charge battery. If this is the case the battery in the car can be used in any other brand car for possibly several years.

Howard

Howard