Hi guys!

Does anyone has a 94 Xj6 wiring diagram for the starter/alternator circuit?

Idk if anyone has had this issue. Car starts hard, if at all and only with jump. Starter doesn’t seem to get enough amperage to crank well. The battery was old so I put in a new one. Starter relay in the little computer under dash works and is not crispy. The alternator is pumping out 14v (checked at the pos post on firewall) but it doesn’t reach the battery....

Don’t have a specific diagram in my files so flying blind a bit.

Thanks in advance

-Neil

 

Hi Neil,

You can download the Electrical Guide here:

Jaguar XJ40 Electrical Guide 1993-94

Corrosion on the various battery power connections and grounds is a common cause of poor battery charging. I would suggest as a starting point (sorry, no pun intended) that you disconnect the battery negative cable, then disconnect and clean the following connections:

Battery cable terminals and battery posts
Battery negative cable ground point at the right inner wheel well
Firewall jump post on the engine bay side
Battery power cable at the starter
Engine ground strap
Electrical connections at the alternator

It would also be a good idea to clean the engine bay ground points that are referenced by the engine control module. There are two on the intake manifold, and one on the firewall behind the cylinder head.

To clean these grounds, I disassemble all the nuts, washers and eyelet terminals, clean with a small brass-bristle brush (never sandpaper, which leaves scratches that promote future corrosion), flush with zero-residue electronic cleaner and allow to dry or used compressed air before reassembling. The nuts need to be snug for an air-tight fit, but don't overtighten and break a stud.

Other potential problems include the battery power connections at the fuse boxes, cracked solder joints in the fuse boxes, and the firewall battery power connection on the passenger compartment side. But these are less likely to cause your starting problems.

Other issues that can contribute to hard starting include worn tune-up items (distributor cap & rotor, spark plugs & wires, air & fuel filter, etc.), a failing crankshaft position sensor (CPS), a failed fuel pressure regulator (FPR) and/or fuel check valve (inside the fuel tank), a failing coolant temperature sensor (CTS), etc.

Remember to never work on the battery power or ground connections unless the battery negative cable is disconnected.

Cheers,

Don

 

Don you’re a mensch! Thank you for the diagrams.

When I changed the engine I had to make a plug from the suppression module to alternator. I found the blade clip connector for the ground to be disconnected. Cut out the blade clips and soldered a plug in this time. Glad it was an easy fix once found.

Thanks again!

Neil