1986 Jaguar XJ6 Fuel Pump

I have a 1986 XJ6 that has been sitting for around 15 years. The car is in great shape and has been kept in a garage. The problem I’m having is the fuel pump doesn’t prime when the ignition is turned on, but when you crank the car the fuel pump will kick on. My question is what causes this maybe some sort of relay or wiring problem. I don’t even know where to begin.

The pump is triggered by the ‘air-flap’ in the L JETRONIC airflow meter!!!

How would I go about troubleshooting the problem? I appreciate the help.

There is no priming function. The pump circuit operates with the starter, as mentioned, then when the engine draws air the air flap switch takes over.

There’s a write- up in the FAQ section

Cheers
DD

You can trick the system into priming by putting the gearshift into D or R and then turning the key to Start. This will operate the pump…. but not the starter

Cheers
DD

Ok I will be sure to try this I just replaced the pump and filter and couldn’t get the fuel system to prime. Thank you

Carson,
Welcome to the list.
I f your car sat for 15 years you will likely have several issues facing you. I recommend that you drain all the fuel from the tanks, and remove and replace all fuel hoses in the trunk and engine bay (and replace the fuel filter) before you ever try starting the engine. You do not need to add the hazard of high pressure fuel leaks to your challenges.
Other people who were in your situation before with cars that sat too long and posted about it had lots of fuel system problems including stuck fuel changeover and return solenoid valves and very old cracked and dangerous fuel injection hoses. Fuel Injection hose does not last forever.
Good luck.
BTW, I have been a member of this list for 22 years now and pretty much everything that can be discussed about these cars has been covered many times. The list of Frequently Asked Questions (FAQs) and the archives are full of helpful information waiting to be mined. I use them often and can usually find exactly what I need in a few minutes of searching.

Paul

1 Like

Thank You for the reply, I had planned on replacing all the lines and the filter but I wanted to be sure the car would run first. Do you know what size hose I need to replace the line and where I would be able to buy it?

Carson,
There is a variety of sizes of fuel hose used in the Series III XJ6. I replaced all of it in the two Series III XJ6s that I used to own and sold but don’t have those cars or the details any more. I have a Series III XJ12 now and some of the hose is different than the XJ6. I think that most of it is 5/16" fuel injection hose, at least forward from the fuel pump. The fuel lines from the fuel tanks to the changeover valve is a bit larger, perhaps 1/2". I know that this has been discussed many times on this list. I recommend that you search the FAQs and archives for more detail.
Here is a link to the FAQs for your convenience: https://www.jag-lovers.org/xjlovers/xjfaq/

Paul

Carson,
There is a variety of sizes of fuel hose used in the Series III XJ6. I replaced all of it in the two Series III XJ6s that I used to own and sold. I have a Series III XJ12 now and some of the hose is different than the XJ6. I think that most of it is 5/16" fuel injection hose, at least forward from the fuel pump. The fuel lines from the fuel tank to the changeover valve is a bit larger, perhaps 1/2". I know that this has been discussed many times on this list. I recommend that you search the FAQs and archives for more detail.
Here is a link to the FAQs: https://www.jag-lovers.org/xjlovers/xjfaq/
BTW, this is an international list so it would be helpful to know where in the world you are located. If you are in the USA, most of the fuel hose can be obtained at local auto parts stores like Autozone or O’Reilly’s. Sometimes I had to go to a local NAPA or mom & pop auto parts store for unusual dimension fuel hose.

Paul

carson, paul has good points…there’s fuel pump relay on the fire wall engine bay, easy to check power to fuel pump. test light to fuel pump then ignition on, that will tell you if the message from maybe the ECU is sending the signal

:slight_smile: quote=“Carson_Rothwell, post:3, topic:433630, full:true”]
How would I go about troubleshooting the problem? I appreciate the help.
[/quote]

Not really 'trouble’shooting as yet, Carson…:slight_smile:

The gear lever in ‘D’ and cranking is a verification of pump function as Doug says. Also, prop open the AFM flap - the pump should run with ign ‘on’, verifying AFM switch function.

Frank
xj6 85 Sov Europe (UK/NZ)