HELP!!

I've had virtually the ENTIRE fuel system rebuilt on my maroon 1994 XJ6. It started out needing a fuel pump, then a tank, then all the lines. . . So now, it starts great but my mechanic cannot keep it running. He says the car dumps so much fuel into the system that the it floods out after a little idling time.

As I see it (and of course I'm a total novice here! First time Jag owner), the only potential culprits now are: the injectors (but they're the originals that have always been on the car); the fuel rail; or the fuel pressure regulator.

Where do we go from here? I'm so close to the finish line I can almost smell it but we've got this last hurdle to clear first. Any suggestions will be GREATLY appreciated! Thanks in advance.

 

Hi Leroy,

Welcome to the Jaguar Forums! It's great to have you with us.

My first question is this: How well do you trust your mechanic to work on a Jaguar? Replacement of the fuel pump is a very common issue, but replacement of the fuel lines is typically only necessary when the lines have been damaged by trying to remove the fuel tank without disconnecting them from the underside of the tank. Replacement of the fuel tank itself is quite rare and I would have to suspect the mechanic damaged the original tank somehow by not following the proper removal procedures.

The next step I would recommend is that you check the Vehicle Condition Monitor (VCM) for any stored diagnostic trouble codes (DTCs). To do so, turn the key to position II (Ignition ON) but do not start the engine. Press and release the VCM button on the trip computer to the right of the steering wheel. Now watch for a message to appear in the small display window below the speedometer where the odometer/mileage normally appears. DTCs are displayed in the format of FF or Fuel Fault and a two-digit number. Write down any message exactly as it appears and post it here and we'll try to help.

There is almost nothing that can go wrong with the fuel rail itself aside from blockage or a leak.

The fuel pressure regulator (FPR) is a common failure point. Typical failure modes are loss of ability to maintain pressure in the rail, which leads to hard starting and lean running, or a deteriorated diaphragm that leaks unmetered fuel through the vacuum hose fitting directly into the intake manifold, which leads to rich running. You can pull the vacuum hose, crank the engine, and check for signs of wet fuel at the vacuum hose fitting on the FPR, which indicates diaphragm failure.

The injectors can stick and leak, though it is uncommon for all of them to do so simultaneously. Was your car sitting without running for a long time? The injectors can be cleaned and renovated with an inexpensive kit available on eBay. See my photo albums at the link in my signature.

Have you given the car a good tuneup? Air filter, fuel filter, spark plugs, plug wires, distributor cap & rotor, clean all the ground points associated with the engine management system (especially the two on the intake manifold and the one on the firewall behind the cylinder head), clean all the grunge from the insides of the air intake plumbing and throttle body, etc.?

Two other common causes of rich running are a failed coolant temperature sensor (CTS) or problem with its electrical connector or harness, or a lazy or stuck oxygen sensor (O2S).

Please let us know if you find a DTC stored in the VCM and if so, I'll tell you how to look for additional codes.

When you get a chance, please visit the https://www.jaguarforums.com/forum/n...-intro-must-5/ and post a required introduction so we can learn something about you and your Jaguar and give you a proper welcome.

Cheers,

Don

 

THANK YOU DON!

I now have a comprehensive to-do list. I will follow up and let you know how it works out!

 

I had a similar problem, also took a few seconds to start & fuel pressure regulator cured it. Now it starts instantly & idles properly.