Hi guys ,ive been working on my 1998 jaguar xjr for about a year now , the problem im having is it will crank but wont start. Ive fixed a lot of little things ,and im getting fuel to the rail and spark and compression but no start . It will start with starting fluid but it wont stay running. I used a test light and noticed there was no power going to the injectors. Can anyone point me in the right direction as to why it wouldn't have power to the fuel injectors or even a link to a forum that has the fuse diagram and wiring diagram would be helpful. Thank you and advance

 

Link to Gus's jagrepair.com site, my go to site.
http://www.jagrepair.com/images/Auto.../jagxj1998.pdf

 

Hi Dhighlife27,

With the ignition ON, the fuel injectors receive a constant 12V supply on the Black wires with Red tracer lines from the fuel injection relay, which is in the row of relays on the right side of the engine bay. See the relay and fuse box location diagram on pdf page 30 of the Electrical Guide manual that BobRoy provided the link to.

The fuel injection relay receives its battery power from Fuse 5 (10A) in the Engine Management Fuse Box on the left side of the engine compartment. The ignition-switched control voltage for the relay comes from Fuse 5 (10A) in the Engine Compartment Fuse Box.

Upstream of those fuse boxes are the Ignition Positive Relay and the Engine Management System Control Relay, but since your engine has spark and will run on starting fluid, I think you can assume those relays are working.

The schematic for the injectors is shown on Page 2 of the Engine Management System schematic (pdf page 45 for S/C engines).

By the way, unless your test lamp is "computer safe," using it on a modern computerized vehicle can be dangerous, since even with the resistance of the bulb the lamp can draw enough current to fry sensitive circuits in expensive components like the Engine Control Module. Better to use a digital multimeter with high internal resistance (for example, 1 megohm or greater), or one of the newer "computer safe" test lamps.

Please keep us informed.

Cheers,

Don

 

thank you ! Im a weekend worior so im gunna test that this weekend and let you guys know , also if i pressed the inertia button , could that make it not send power to the injectors? Because my understanding is that it will only reset it .

 

Yes, when the inertia switch is activated the button on top extends noticeably. Depressing the button resets the inertia switch.

Cheers,

Don

 

So i tested all of the fuses under the hood and in the trunk , and switched around relays , all of them tested good , but im still not getting power to the injectors, im at a loss!

 

Hi Dhighlife27,

Have you measured for battery voltage from the Red/Black wires at the fuel injector electrical connectors to a good ground point? Measuring across the two terminals at the fuel injector connector may not produce a DC voltage your meter can read. The injectors are individually grounded by the ECM to open their solenoid valves, but this happens so briefly most digital meters cannot react quickly enough to display it. You might be able to read an AC voltage though. A more reliable test is to connect your positive test lead to the connector terminal for the Red/Black wire and connect your negative test lead to a good ground point in the engine bay.

Have you measured for battery voltage at the appropriate terminals of the fuel injection relay and the fuses I mentioned in Post #3? If you have and found no voltage, you'll have to work upstream following the schematics until you find the failure point.

Cheers,

Don

 

No when i tested it i tested for DC so ill try to test for AC and see what what happens , if not ill go hunting for the failure. Thanks you for all your help ill keep you updated on the progress.

 

Measuring a pulsed square wave as AC may give you a clue but won't be a definitive test. A more reliable test is to measure the DC voltage from the Red/Black wires on the fuel injector harness connectors to a good ground point that is not the other wire in the fuel injector connector, since it is grounded by the ECM only periodically to open the injector. One of the ground points on the left fender/wing in the engine bay would be good.

Cheers,

Don

 

Hi, I was reading your response and found it very helpful, thanks fore that.
I have a separate question I hope you will find time to answer. Mine, Jaguar xj8 1999 year starts fine, but immediately, looses power and culprit was found that it switvhes off injectors going into Bank 1(A1 and A4), Bank 2(B2 and B4), suffice to say it cuts of A and D, and G.

What could be the problem? Can error codes in the Body control module like key circuit failure cause this? Regards

 

Hi dharry078,

I don't feel like you are giving us the complete picture: You imply that you have a BCM Diagnostic Trouble Code (DTC) flagged for a key circuit failure, but you don't mention if any Powertrain (P-prefix) or Network (U-prefix) DTCs are flagged. Can you tell us all the codes that are flagged, assuming you or your mechanic have the capability to read proprietary Jaguar codes beyond the generic P- codes? The Engine Management System manuals may be helpful in diagnosing your malfunction, along with the DTC Summaries and Workshop Manual:

Jaguar Engine Management Systems & Advanced EMS Diagnostics 870A Book A

Jaguar Engine Management Systems & Advanced EMS Diagnostics 870B Book B

Jaguar DTC Summaries AJ26 1997-1999

Jaguar X308 Workshop Manual

Cheers,

Don

 

Thank you Don for your response and interest in assisting.
Although my problem was solved, I did flag 5 P Codes. P0354, P0351, P0356, P0357, P1367.

I did trace the problem, THANKS TO THIS FORUM FOR THE WIRING DIAGRAM, to Pin one from the Ignition ECU to the 24 gray connector that have been severed by a roddent that took the wire for its lunch.
Fixed the wire and even considered entering it into the rally. Needless to say, the client had been with this problem for the past two years as he bought the car from a disgruntled man becasue of the same problem. He changed engines, a gearbox, and same problem, and he had given up on it until he came to me, and I came to this Forum.

Thank you