Engine No-Crank Troubleshooting, Series III XJ6

The purpose of this checklist is to diagnose a "no crank" situation on the Jaguar XJ6. The specific details pertain to the Series III 6 cylinder models although most of the basic steps apply equally well to earlier versions. Basic hand tools, a 12 volt test light or multi-meter, jumper wire, wire brush, and sandpaper are all that's required as far as supplies go.

Ok, here we go... you turn the key and nothing happens or, at best, you hear a click-click but that's all!

1. Is the battery fully charged? Put a battery charger on it or take it to a battery shop for charging and load testing. If it fails to pass muster you'll obviously want to replace it and if it has failed at a relatively early age you may want to have the alternator checked. Even if this solves your problem you may want to read on and perform some of the following tasks just on general principle.
2. Assuming for this step that the battery is OK, you'll want to check the battery cables. Remove the cable from the battery. Use your wire brush to clean the terminals ends on both cables and the posts on the battery. Reattach the cables to the battery and snug 'em down. You'd be surprised at how many "no start" problems are corrected by this 10 minute task! By the way, the yucky stuff that you clean off will eat into paint and your clothes - clean it off! A paste made from baking soda and water works well here and can be easily rinsed off.
3. More cleaning. Do it now while you're in the mood, you'll be glad you did in the end. The battery negative cable grounds to the body at the right fenderwell. Remove the cable and clean the cable end with your sandpaper until you have shiny metal and similarly clean the ground point on the body. Reattach firmly. Now, on each side of the firewall are two junction posts which are distribution points for battery voltage. These need regular attention. You'll need to disconnect the battery (again..sorry...read on. If you plan to clean everything just leave it disconnected) or you'll have sparks everywhere when you disconnect all the cables from these posts. Clean the posts, cable ends, nuts and washers very thoroughly with your brush and sandpaper and bolt it all back together nice and snug.
4. Yes, more cleaning. You'll need to get under the car for these. Under the car, right side, adjacent to where the engine and transmission come together is a heavy braided ground strap. Remove, clean contact points and cable ends, reattach. Once done there you'll have to check and clean the connections right at the starter. This may get tricky and the car will need to be lifted a bit for access. Use heavy duty jack stands and give your Jag some good shakes before crawling under ! Make a note of how the wires are conencted to the starter before removing them for cleaning. Clean the wires and terminals and resecure tightly. This environment is tough on terminals and dirty, loose connections here are a common cause of "no crank" conditions. As long as the car is lifted you may as well get under the alternator and remove the wires and do the clean and tighten routine there as well. Loose, dirty connections here are a common cause of battery run- down.
5. Battery good and all connections clean and she still won't start? Time to shift from maintenance catch-up to trouble-shooting. The starter relies on a signal from the starter relay (on Series III cars, a silver relay on the firewall----probably simlilar on others). The starter relay will have a white/red wire which leads to the starter solenoid on the starter motor. Disconnect this wire from the relay and, using your jumper wire, apply 12 volts. Your are bypassing part of the circuit here. If the starter works, then you have a problem upstream. See Step 6. If the starter does not work then you have a faulty starter, faulty solenoid, or a wiring/connection fault on the white/red wire. If the wiring checks out OK then it's time to replace the starter with a remanufactured unit which will come with a new solenoid.
6. You're here at Step 6 because the starter worked OK when you by-passed the control circuit. Here's how to check the starter control circuit. Using the test light or multi meter, make the following voltage checks at the relay: brown wire at terminal C2 should have voltage at all times. If not, check for a wiring/connector fault between the relay and the right side firewall post. The white/yellow wire at terminal W2 should have voltage whenever the key is turned to the "start" position. If not, check for a wiring fault beween the relay and the igntion switch or check for a fault at the switch itself (try jiggling it and/or check that the switch has input voltage from the heavy brown wire). Terminal W1 is the ground for the relay and carries a black or black/green wire which leads to the neutral switch. This wire should be grounded when the transmission is in "Park" or "Neutral". If not, check for a wiring fault on this wire between the relay and the switch or a faulty/mis-adjusted switch. Some models may have a white/blue wire at the relay which by-passes the ignition ballast . It has no direct bearing on starter operation.
7. If all these voltage checks are OK then you likely have a faulty starter relay. You can opt to replace it or, if desired, disassemble it and clean the contacts. Many Jag owners have been sucessful in resurecting a dead relay with a good cleaning.