When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
1986 XJS won't turn over, even with a jump, after re-installing battery
Greetings folks! My 1986 XJS V12 had a dead battery. It would try to crank but wouldn't start. I figured rather than jump it I would remove the battery and top it off with a charger. Two things occurred when I was removing the battery which I assume are unrelated but will mention just in case. First, I removed the battery terminals in the wrong order (positive first) and saw a little arc. Second, there were a pair of wire connections (small plastic plugs with two round terminals) bound to the positive battery cable which were unplugged. I wasn't sure if they came unplugged when I was removing the cable or if they had been that way all along but I plugged them back in. I'd be interested to know what they're for even if they are unrelated to the problem.
When I replaced the battery, which checked out when tested, all of the lights and accessory electrics worked fine and the battery gauge listed it in the normal range. But now when I try to start it I get nothing. There's a little mechanical 'click' similar to turning the key to any other position but there's no sign the starter motor is doing anything at all. The fuel pump doesn't start with the key in any position. Jumping it, which has worked in the past when it was just a dead battery, had no effect. I'd love to fix this in-house since getting it to the shop is a bit of an ordeal. Any ideas on what I should look at would be greatly appreciated.
The 2 Brown wires under that plastic cover on the battery +ve cable are for the relays just alongside the battery, under that trim panel. They would have been connected prior to your intervention, as the car will not start with them unplugged, and since you say it did run, thst di my conclusion.
HOWEVER, when replugging them be REAL CAREFUL, that you actually slide the "female" bit over the "male" bit, and thats ALL I will say on that terminology, use your own imagination. It is SO easy to slide them down the side of each other, which will see the fuel pump not work, duh.
The cranking has NOTHING to do with those 2 wires.
The click is more than likely the starter relay "clicking", and not passing the current to the starter. The relay may have burnt contacts inside, very common, and a simple clean, usually gets it going again.
Follow the heavy White/Red wire from that relay on its journey TO the starter motor, and somewhere just near the rear of the RH inlet manifold, you will see a connector (male/female again), and that sucker is a PITA on any good day. Unplug it, clean it, replug it.
Other than that, the battery terminals are NOT clean and tight.
This is just a brief list, the real one is real looooooong.
Lets know the findings please.
Last edited by Grant Francis; 04-01-2015 at 01:56 AM.
Thanks for the help! The good news: I fiddled with the connections of the wires on the +cable and now I can hear my fuel pump hum for a couple seconds when I turn the key.
The bad news is I'm having trouble locating the starter connections I need to check. I was only able to track bundles of small-ish wires from the battery and didn't see anything promising under the bonnet either. My shop manual says the starter is buried deep on the passenger side of the engine so I'm not sure if I need to approach it from above or below, or if the connections I'm looking for are somewhere else. Directions based on landmarks this photo of my engine would be great... if it's anywhere near the top. If reaching it requires major surgery I'll probably need the mechanic to take over.
A couple more questions:
Would a voltage drop test at the battery tell me anything useful at this point?
The struts that hold the bonnet open are no longer doing their duty. Any suggestions on how/where to replace or repair them?
The starter wires on the starter itself are buried very deeply. Checking them is a real pita. The wire going from the battery is tied directly to the starter. If you study the wiring diagram, you can actually find the wire that is the "start" wire that goes down to the starter solenoid. Very easy. Right on the right side near the rear of the inner fender. If you apply 12 volts to this wire, you can actually cause the starter to engage without much effort at all. If you can't, the starter motor, or the solenoid itself is suspect.
As far as the hood struts, replacing them is your option. There is a crossover that fit another vehicle, that makes them very inexpensive compared to Jaguar. You can find them on eBay fairly easy. The really inexpensive thing, is a clamp looking nut, that you install on one of the strut rods, and lock it on the strut rod at point you want it to stay.
Looking at your picture, that starter relay will be under the plastic cover right at the hood latch on the right side of the inner fender near the hood.
So, I removed the plastic cover hiding the starter relay and didn't see the three relays I had expected, but rather one little relay in the middle, one empty tab where another little relay could have been placed, toward the front and a metal cap with a red sticker on it toward the back. The sticker read "Important, +VE feed to... etc.". I nudged and tried to follow the wires in and out of these relays and I also fiddled with the cables, relays and wires immediately around the battery and reseated the battery itself. In all of this I never actually found the starter motor so I had a friend start it while I was looking at the engine, hoping I could find it by sound. The engine started. I have no idea what I did. Maybe my friend is just lucky. It has started every time since.
In unrelated news, after letting it run for ten minutes the oil pressure indicator never raised above the lower quarter of the gauge. I'm thinking that's not where it's supposed to be...
I would now CAREFULLY and ONE AT A TIME, remove the wires from those relays, and then CAREFULLY squeeze the terminals on each wire a little bit. This will give them a much tighter "grip" on the relay spade connector. This is a common problem, and that is the real fix for it.
The starter motor you are so desperate to locate, is tucked under the RH exhaust manifold. It is invisible from above, and barely visible from below. It is HUGE, and weighs about 15KG, and is basically Black. They give very little trouble in the big scheme of things. The associated wiring is more problematic.
Your fiddling has disturbed the wires at the rear of the engine. Located dead centre of the engine, under the 1" metal cross pipe, is the oil gauge sender unit, it is the one on top and is the larger of the 2 in that location.
Carefully fiddle with that units wire again, and MAYBE you will restore the dash gauge, and maybe not. It is a fickle arrangement at any time.
I've got a bad feeling the reading on the oil gauge may be legit. It moves when I turn it on, just not to where it ought to be. Is there a reasonable way to verify?
The XJ-S oil gauge is a mongrel, and many, many owners worry sooooo much about it. The V12 has the best oil pump/oil system, of any engine ever built.
I have never seen one go bad.
The oil sender, and dash gauge fiasco is numerous that I sorted over the years.
The sender is the main reason for gauge errors, BUT, as a quick search will devulge, the dash assembly is also at play here. A 2nd earth wire is almost mandatory for proper instrument operation, as is "retightening" ALL the small screws on the circuit board, ETC ETC.
Fwiw, out of 8 V12 JAG's over the years, only one showed good oil pressure on the gauge. My car now will actually show 0 oil pressure at hot idle, and I've done the instrument cluster refresh
03-31-2015, 11:04 PM
1986 XJS won't turn over, even with a jump, after re-installing battery
