I have an '03 xjr that I've increase the sc crank pulley size as large as would fit. On cool days I max out the injectors. I thought I read that you could swap out the 4.0 liter xjr injectors with the injectors from a 4.2 liter xjr provided you change the fuel rail. These injectors should allow enough more fuel to satisfy my system. Anyone else try this?

 

I am not sure that switching to the 4.2 would make a difference if they actually fit.If fuel on the top end is a problem I would lean more to having a good set of rebuilt and tested injectors and then start experimenting with increasing the fuel rack pressure. The injector will be open for a duration controlled by the ECU so I would think increasing fuel delivery during that duration would help.
The other alternative would be to have the ECU remapped to give a longer fuel duration.
You might want to also replace the fuel filters to be sure they are not inhibiting fuel delivery under high demand.
One last thought is if you feel you are not getting enough fuel on the top end it might be that your secondary fuel pump is wearing out.

 

I appreciate your response but I've considered all the options you mentioned and tested the injectors I have and under full load at 28°F at approximately 4000 rpm's, the injectors are at 100% duty cycle and I still maintain 45 psi fuel pressure. I guess I didn't give you enough parameters to see where I'm at. I've reached the limitations of the injectors and don't want to bump up the pressure. The pintle valves in the stock injectors won't like it and use more current.... I checked the flow of both the 4.0l and the 4.2l injectors but wasn't sure of the physical lower fit of each. I'll look up the dimensions of each and go from there. Thanks again for your input.

 

avos probably went down this road in getting to 600HP then 700HP - ask him?

 

Hi all,
Update. Towed the jag to our shop, raised on a hoist cracked lines to fuel filter cycled key no fuel. Bypassed both relays and still nothing. Removed tank (wasn't terrible) Bench tested both pumps, DOA. nothing from either one. I can't imagine both pumps dying at the exact same moment. Are these R models capable of running on one pump? Speculating that one pump may have died in the past and wasn't noticed then when the second pump expired over the winter we had a no start. I have a new set op pumps/strainers ordered for the morning we should know by the end of day tomorrow.
Thanks all for the input/experience/great ideas.
Niels

 

Neils,

Tell me where you intended to post this "update" and I'll move it.

Graham