Jaguar Repair: injectors are firing!, noid light, thermal time

Question
Howard,
I'm sure your clear on all the things I've checked in attempts to get the injectors to operate. They were not indicating that they were working when hooked up to noid lights, and thats when I started this troubleshooting process. Then after finding nothing noticably wrong I dicided to take out a fuel injector and observe it to be sure it wasn't spraying. Low and behold........the injectors ARE SPRAYING! I've been chasing a ghost problem! still the fact remains it only starts on carb cleaner. I've noticed that I get a strong spark off of the coil, but a weak very small spark at the plug. The amplifier module,coil,distributor cap, and rotor button have all been replaced. Is it normal to get a weak spark at the plug? Does the fact that it will start on carb spray rule out a possible ignition problem?  

Answer
Hi Mario,
Great, all you need to do then is to correct the cold start valve. (you either have a faulty Noid light or it is the wrong one. If an injector operates then it will fire a Noid light easily.)

The ECU does not operate the cold start valve. It is powered up by the starter relay (terminal W-2) and grounded by the thermal time switch. (forward most sensor in the coolant rail) The thermal time switch grounds the cold start valve when the coolant is cold but will break the ground and not operate if the starter is used too often in a short period of time. As the coolant heats up it too will break the ground thus not allowing the grounding of the cold start valve.

My experience has noted that the solenoid of the cold start valve still works when the valve fails so checking the "Click" of the valve does not diagnose a failed valve.

A good sure method of testing the valve is to remove the valve and take a piece of fuel hose and connect it to the fuel rail and to the valve. take a jar and drill a hole in the lid the size of the end of the valve along with a small air bleed hole and insert the injection end of the valve into the jar and remove the air cleaner can and turn the key to "ON" (not start).  

Connect a grounded jumper wire to one pin of the valve and hold a second jumper wire (powered) and open the airflow meter flap and touch the second pin of the valve with the powered jumper. You will see the spray in the jar. The spray MUST be in a large cone shaped spray. if it dribbles or is a thin straight stream, the valve is failed. (Common) sometimes you can improve the spray pattern by running injection cleaner through the valve.

Howard