I have an 85 XJ6, that was running fine, then one morning I started, and got misfire, and would not startup. I managed to start by cranking few time, with the gas pedal on. But soon as I drop below 2500 rpm the car stumbles and dies. Even when I have the gas pedal pressed, I can not lower gradually to say 1500 rpm, just drops from 3K down 500 or so, then dies.

I assume the fuel pump must be ok, since I can keep it started over over 3K rpm. I had changed the fuel filter a year ago or so.
Can relays, fuel regulator, AFM or fuel blockage contribute to this type of problem.

Guidance is much appreciated.
-Kadeer
85 XJ6
2004 XJR

 

Update:
I just put the key to ON position with it in Drive, and I do not have voltage at the fuel pump.
How is it possible the car will rev over 3K rpm without the fuel pump running. Unless the pump starts up later after the car is started, and gas is floored.

 

Turning the key 'on' won't power-up the pump circuit.

Try the same experiment but turn the key to 'start'. The pump should run. If not, post back

Cheers
DD

 

Let's begin with something easy.

Check the duct from the Air Flow Meter to the Throttle Body. Is it secure? No holes or rips?

Cheers
DD

 

no holes or rip to the throttle body.

Doug, I turned the key to the 2nd position, without starting it, no power to the pump. I read if you put it in Drive, and put turn the key 2nd position, the pump should activate. No voltage on the wire.

Is it possible, that because my car has a 3/4 full tank of gas, that the fuel is flowing to the rails without the pump running, I am parked on a slight incline down.

 

Doug, just went out to try your suggestions. Thank you for your guidance. I turned the key to position 3, start, and the pump was working. I also verified with jumping the fuel relay, 30&87.

Then I rechecked the throttle body lines, turns out the clamp of the throttle body was loose, and pipe was not fully in from the AFM. Soon as I put it in place, everything went back to normal. Starts and idle fine now.

Surprised to see how erratic the car was with partly unmetered air.

Thanks again.
-Kadeer

 

Love to hear the solution to a problem!!

 

Just a huge vacum leak!!!!!