Hey guys, I had another post on putting a new starter on my car, and now the battery going dead. The wiring harness shows a diode in the start circuit on the 89 XJS. My new starter came with a diode in the pigtail, but since my wiring didn't have one, I didn't use it. I still don't understand the use of a diode on the start circuit. Either way, I went back, and installed it. I thought I had it whipped, but within 12 hours, the battery was too dead to do anything but make the starter click. It seems to drain down to a certain point, and that's as dead as it gets. The lights on the lower part of the door panel will come on, but the brighter ones on the dash don't once it drains down. But it doesn't drain it completely dead. This is a new problem.
The car has 14.1 volts at idle once I start it, and when battery is fully charged, the battery has 12.3 volts. I have a digital volt meter, but not sure what I should do from here. Do I take the negative? Positive? end off of the battery, and using the amp scale, in between the battery post and cable, and start pulling fuses one by one? Any help, advice appreciated. I really thought I was on the way to start driving this car.....

 

I had the same problem, replaced the starter then the battery and DEAD the next day. My problem was stupidity. The rear courtesy lights were on and I didn't realize it cause I always worked on it during the day.I clicked the far right button on the dash panel and I haven't had a problem since.

 

Thanks for the quick response! For the very reason that you gave, I leave those rear lights in the middle position so they never come on. I turned off the lights in my shop, with the battery fully charged, and stood there for several minutes looking for any type of light on. I have the truck light disconnected.

 

sorry, i dont have an immediate suggestion or recommendation for your problem.

but i wonder... for how many of us have these cars had us standing alone in a dark room with the lights off for several minutes... and i'm talking about those of us without a draining battery.

 

Getting back to the task you did, as in you replaced the starter motor.

There is a wire on the +ve stud of the solenoid that travels via a steel tube TO the +ve of the alternator.

Just a thought that there may be a terminal touching somewhere from when the nut on the starter was tightened. That wire/s inside that steel tube may have degraded insulation that is leaking volts after being "disturbed" during the replacement tugging and pulling that would have taken place.

Put your DVM into the -ve lead, set on amps, and see what drain is going on. Carefull here as most of these DVM's are only rated at 10amps DC.

To flatten a fully charged battery in that time frame is a SERIOUS drain.

 

I have/had a serious battery drain as well. I pulled all fuses and none of them changed the drain. Finally started pulling relays, and with a test light hooked up, I pulled the fuel pump relay and the light went out. Testing continuity of the relay showed that one leg of the NO legs was closed. This is a relay with two 87 pins, which should both be open when not energized. I have a new relay coming that I will be installing today.

Probably not your problem, but I know others have had drains not caused by lights on etc. that maybe never took the time to try pulling relays.

Good luck.

 

I recall the metal tube. I also had to do some tugging, to create a little more leeway in installing the wiring on the the new starter, as it is oriented differently than the original starter. I've heard of a wire "shorting", but never "leaking". Would the metal tube feel warm to the touch if this were happening? I'm also going to try pulling relays after I try pulling fuses. I have worked on this car pretty steadily since purchasing it last August. I really would love to get to drive it before the driving events around me are over for the year lol.

 

Another thing I have noticed now that the main wire has been mentioned, is that my volt meter would stay at or around 13 volts when running. It now stays down around the 9 range. Drove it about 30 minutes tonight, and it wouldn't restart. I have to have something pretty seriously wrong here.

 

Be careful there is nothing worse than a flaming Jaguar.

 

Ok guys, this one has me stumped. I am looking under the car this evening. The main wire going from the starter, through the metal tube, and to the alternator looks fine as much as I can see. Appears to have no stress on it at all.
I am a residential builder. My DVM will measure DC volts, but only AC amps. it has a 40 amp range, and a 200 amp range. When I disconnect the negative side wire at the battery, and measure voltge between the negative side of the battery, and the negative wire, I get a solid 13.7 volt reading. I don't know what, if anything that tells me. It appears to get the starter back off of this car, I'm looking at removal of the exhaust, and right side downpipe. I am not one to just start changing out parts, without knowing that what I am changing out will make a difference. At this point, it appears pulling the wire and the metal tube off, and having a new wire made, seems my next logical move. Any suggestions appreciated.

 

Here are my suggestions SC6:

The starter and the alternator are connected at the starter post. Then a single wire goes to the RHS (US passenger side) firewall post. This post is always live and is fed from the LHS firewall post (US driver's side) which itself is connected directly to the battery positive post by a long cable under the car. Why not try to track down the 'leak' as follows:

Disconnect the RHS firewall post leads that go to the started/alternator. Put the meter across the post and the disconnected leads and see if the leak is there.

If so, disconnect the alternator to starter lead and see if the leak is still there.

If so, disconnect the starter and connect the alternator directly to the post lead and see then. This procedure should show if the leak is in one or other or both of these items.

There is a very good chance that, in any case, the leads between the alternator and the starter (this is a double lead for some unknown reason) are pretty shot, so well worth renewing with a single heavy duty cable in any event. Grant Francis (great antipodean prophet of the XJS) very sagely suggests a new single direct connection to the firewall from the alternator and getting rid of the 'via the starter' OEM idea.

good luck

Greg

 

As Greg said, but you really should invest about $20 and get an Automotive type DVM, that has DC Amps. Place that DVM set on AMPS DC between the battery terminal and lead and note the Amp draw, which is maybe 5+ amps.

The 13.7V at the lead you mentioned, only indicates the battery is fairly well charged.

Expanding on Greg's suggestion, I would be reaching up and disconnecting the cable that is on the solenoid post that goes via the tube to the alternator, tuck it away somewhere safe for now. Refit the nut with the battery only cable attached. Remove that same wire at the alternator, and tuck it away somewhere safe, it is now a DEAD wire, and the alternator is NOT in the system at present.

Now connect that new DVM between the -ve battery terminal and the battery lead and set on AMPS DC, note the draw. If it is minimal, the fault is in that tube wiring (COMMON), or a diode in the alternator leaking to earth (COMMON enough). If the amps is still above about 0.5amps (NOTHING on inside the car of course), you still got other problems.

If the draw is acceptable get some 6mm 50amp wire, and suitable terminals (different markets talk in wire "gauge", we dont). Make up a new cable from the alternator to the battery +ve post on the RH firewall buz connector. Sooooo, from the alternator to the chassis rail, up the rail towards the firewall, and route to that +ve connector. Use 2 wires for 100amp rating.

Now do the amp test again, and note the draw.

I still reckon this is something to do with the starter motor task, or a dud solenoid (NOT common).

 

Ugh....This is pretty discouraging. From the looks of it, I will have to take down the exhaust, the right side downpipe, and remove the starter, just to start looking into this. The original starter at least had the post to the outside of the starter where I "may" could have disconnected the wire going to the alternator. On this starter, the post is toward the inside, (toward the block). I had to install the wires on the starter, then bolt the starter on. Absolutely no other way. I still wonder why we love these cars, lol

 

Mmm, that has me thinking now.

The original starter had very little room at the solenoid wire area and the cylinder block.

Your need to pre-install the wiring may have caused the insulation to fracture as the starter was "pushed" into position, and may even be touching the cylinder block, and thus causing the short/leakage you now have.

At least you dont have the steering gear in the way as we have. That starter down here is near the same labour as taking the whole engine out. Been there done that, never again.

 

Ok guys, I charged my battery with the ground disconnected. Hooked my battery up the next day, and it was dead. Well, almost dead. Charged it again, disconnected the wire that feeds the starter, on the firewall, let the car sit over 24 hours, battery dead again. The battery doesn't go completely dead. It just gets down so far, and stops. I took the battery out this evening, and am charging it over night, then taking it tomorrow to be tested. Am beginning to think it may be the battery

 

Yep.

I need a drink, your shout Greg.

NO malice meant, PLEASE, but at least you may be getting somewhere. How old is the battery???.

Charge the battery, DO NOT connect it, let it sit as is, is it down on charge next morning, that is a battery issue.

 

The battery appears very new. However, it was in the car when I bought it last August. The date was not punched out, so not sure.
Chrarged it all night last night, took it today to two different places and had it tested. Both show it bad. The weird thing is, it shows a 81% charge, 12.7 volts, but almost not reserve. Appears it has lost its amperage?
Anyway, bought a Optima battery for it, as I like the idea of a Gel battery inside my trunk. Hope to get it in, cables secured on firewall asap, see if the problem is solved???

 

Well, I guess this ends this thread, problem. Fixed the problem. How coincidental. Put a new Optima in the car, and it starts quicker than ever. Drove the car a good bit last night, let it sit for almost 24 hours, went out just now, and the car started imediately. Oh well, my granfather always said that the KISS method worked most of the time. Thanks for the responses!

 

Congrats! Another off the list and back on the road.