Ok just heard that the 95 and so XJR came with 2 fuel pumps and the 2nd one comes on at 3000 rpm??? If thats so I have a 95 and would like to know how to make sure its working. My car seems to lack power an dont want to get up and get moving from a stand still which for a supercharged car shocks me. Any ideas would be great

 

I was in the manuals looking for some info for you and I discovered that the #2 pump comes ON at 4000rpm and turns off at 3200. In another post I gave incorrect info. If you got the "3000rpm" thing from one of my earlier posts I apologize for the goof.

I couldn't find any info on checking that the command for #2 pump is actually happening.

I *think* the connectors at the tank for the two pump can be switched. If I'm right...and and may not be....you could swap connectors and if the car doesn't even start then you'd know the #2 pump was dead. But....if the car does start it suggests both pumps are operational but doesn't confirm that the #2 pump is being commanded "on".

I'll have to mull it over a bit.

Others with chime in, perhaps with better thinking

Cheers
DD

 

Thanks doug appreciate the help

 

This might freak some out, but I tested pump function by jumping power across the relay plug, but would recommend extreme caution if doing that. I had the ECM disconnected for the test, and it merely confirmed that the pump was working. It will not tell you if the command to power up is being sent while running. I am also very curious as to how to confirm the second pump is in fact working under load.

 

This is pretty low-tech, but what the heck....

You could wire-in a simple test bulb to the circuit and string the wires out of the trunk and into the cabin through the windows. When you hit 4000 rpm the circuit should get voltage and the bulb will glow.

Or...use a 12v buzzer the same way. If it's loud enough you might be able to leave it in the trunk and still hear it

<shrug>

Just an idea


Cheers
DD

 

If you can confirm that the #2 pump itself actually operates, using one of the above methods, disconnect it and drive the car.

If it runs worse you'll know it is being commanded on.

I don't really know how much difference it makes when it IS working. I'm not sure if it's there to increase power per se or merely to ensure the engine doesn't go lean and hurt itself.

Cheers
DD

 

You have tested the pump...now test the relay. Apply power to the proper pins and check for continuity across the relayed circuit. OR Stick a friend with a voltmeter in the trunck and run her passed 4,000. .......I'm guessing if the pump wasn't working the fuel curve at higher RPM, when fuel is critical, would through a code for being lean. Your post started out saying she is sludgish off the line. Doesn't sound like a 2nd fuel pump issue. I can spin the tires in my 96 and the tires only have 3k miles on them. The launch isn't breathe taking, but the car is 4200 lbs. I did spank a WV CC the other day.

 

It could be in the the throttle itself. I had that same issue and the throttle cable had stretched and the springs were bad. I think it was actually a recall to replace some of those parts.

When I would step on it it actually got less power the faster I would go.

Now it goes like a rocket.

 

Doug's test light idea is a great one! It would be dead easy to wire in a small 12 volt led, then wind it out on a hill. Mind you, secreting the Mrs in the trunk with a flashlight has its merits...