Good morning everyone. My 91 Sovereign stalled out in my driveway on Thanksgiving. I've been trying to troubleshoot the problem since. It appears to be fuel starved. When I spray starting fluid into the intake, the car will fire right up for a second. The fuel pump hums nicely when I turn the key to "on". I cracked open the fuel line at the rail and fuel is pumping out when the engine is cranking. I picked up a stethoscope to check the injectors, and I don't hear any clicking when trying to start the car. My assumption right now is that something is causing the injectors not to fire. Any thoughts on how I troubleshoot this? Thanks in advance.

 

I'm presuming it's an immobiliser issue. I had similar problem with an s class mercedes. Injectors were immobilised as infra red pick up was not reading the key fob signal.

 

Look at the rev counter when you crank the engine over. Is it registering the cranking rpm's?

How's the distributor cap/rotor/wires?

The immobilizer switch is located in the driver's side footwell btw

Larry

 

Mine was intermittently cutting out a few years back - turned out to be fuel pump.


+1 Lawrence - When cranking - are the RPM's registering on the tach? Crank sensors are common fault as they age.


What happens if you bang the fuel tank with your hand when it cuts out - does it start or keep cranking?

 

Hi Robert,

The first thing I would suggest is to check the Vehicle Condition Monitor for any stored diagnostic trouble codes (DTCs). Turn the key to position II (ON) but do not crank the engine. Press and release the VCM button on the trip computer to the right of the steering wheel, and watch for a message to appear in the small window below the speedometer where the odometer/mileage display normally appears. DTCs are displayed as "FF" or "Fuel Fault" plus a two-digit number, such as FF22 or Fuel Fault 69. Write down any message that appears and post it here so we can help.

The Inertia Switch in the driver's footwell is designed to shut down certain circuits in the event of a collision, one of which is the fuel pump, so if your fuel pump is running and you have fuel at the fuel rail, your inertia switch has not been tripped.

As Larry mentioned, if your tachometer is not reading approximately 200 rpm while cranking, suspect the crankshaft position sensor, a common cause of a cranks-but-won't-start condition.

Assuming you are using a long screwdriver or socket extension as a "stethoscope" to listen to the injectors and are not hearing any clicking, it would be worth confirming the injector power supply. With the ignition in position II (ON) but without cranking the engine, all six injectors should have battery power (approximately 12 volts DC) on either their Pink/Blue or Pink/Black wire. The other wire is grounded by the ECM to fire the injectors, which all fire at the same time. An inexpensive noid lamp can confirm that the ECM is providing the injectors with the proper ground signal to fire them.

A couple of known issues relate to corrosion on the ECM electrical connectors due to water ingress and corrosion on the ground points referenced by the engine control module (ECM) due to their exposure to the elements in the engine bay. It is always worth cleaning the grounds, two of which connect to studs on the intake manifold and the third is on the firewall/bulkhead behind the cylinder head. Disassemble the nuts, ring terminals and star washers, clean everything thoroughly with a small wire brush (not sandpaper - scratches promote future corrosion) and zero-residue electrical contact cleaner spray. Allow to dry and reassemble. If that makes no difference, remove the right-hand knee bolster and check the electrical contacts at the ECM for any signs of water ingress or corrosion.

You can download the Electrical Guide for your car at this link:

Jaguar XJ40 Electrical Guide 1991

One other Parthian shot: Are you certain there is sufficient fuel in the tank? The fuel level sensors are known to fail and can stick at a level that tells the gauge there is fuel in the tank when the level is actually too low for the pump to pick up.

Cheers,

Don