I picked up an 1986 XJSC with a 3.6L I6 this past week. Took the car for its first drive a few days ago, made it about 40 miles, and then one mile from home on the way back it ever so gently lost power and glided to a stop on the side of the road. I couldn’t help but laugh…other cars have left me high and dry in much worse situations, so she was pretty gracious, all things considered. The car got towed home and I’ve been troubleshooting what happened. Things I’ve checked so far:
Gas–not totally sure the fuel gauge is working, so I put in some more fuel but it wouldn’t turn over even with a jump.
Battery–fully recharged it and car cranks just fine but won’t start (it’s about 5 years old though and I think it needs to be replaced)
Then last night I got ready to pop out a spark plug to test and found this:
Plugs 2 and 5 are clean, but the rest of the plug leads look like some version of this. Seems to me that water and/or coolant got in there somehow, but how? Are my spark plug leads also bad? I don’t want to swap out the plugs if they’re just going to get drenched. Gotta love these cars…find one problem and it leads you directly to another…
Any ideas are appreciated. I know I’ve got a learning curve ahead. Thanks, all!
First thing to try is the Crankshaft Position Sensor.
Kinda normal to have water and/or oil in the spark plug wells.(things happen)
I always blow them out and sometimes pour or spray a small amount of solvent into the recesses if oil has collected.
New cam cover gasket kit is needed if there is OIL but water can get in from rain or washing the engine.
Just clean the rubber boots if they are ‘electrically’ sound otherwise.
Now seriously, are you able to crank it? Is it dead or.choking or puffing?
Start from basics - like fuel and air filter. Both can conceal nice surprise.
2.While turning key to the ignition listen to the sound of the fuel pump - if it’s not there - there’s your root cause.
Small sump tank below main tank has an internal mesh filter - with classy British sheet metal of which your XJS is made of (including fuel tank) - expect loads of ginger flakes in the sump - these may cut off.the fuel supply.
Open the bonnet and turn the key to the ignition - pump should prime fuel lines - observe the one on top of the engine going directly into fuel rail - it should move a bit, that’s your prehistoric fuel pressure indicator.
Check the spark on each cylinder - ancient art, easy
Come back to us with conclusions
Ignition problem shall not cause uniform power loss, it’s rather fuel/air related.
Unless you’re absloute “JaguarLover” from UK and you’re only inspired with ‘The Saint’ series - changing plugs and consumables won’t hurt you more than intentional neglection…
Thanks, J. I haven’t checked the air filter–I’ll take a look. I did check for the fuel pump, and it makes a buzzing when they key is on. I’m wondering if the fuel gauge is lying (it says the tank is 1/2 full) and I may have run the tank too low and sucked some crud into the fuel filter. The fuel filter was replaced less than 10k miles ago, BUT it was an awful lot of years ago. Spark plugs were also replaced around the same time (but the PO replaced them three times in less than three years, which seems very weird).
Thanks for the tip on the sump tank. I bet you’re right that it’s full of crap. I’m not really in the mood to deal with clamping off fuel lines, so if I rule out everything else, to the shop we go.
I’ll give the rest of your suggestions a go and report back. Thank you!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
6
Waaay back when, I was at an Autozone when some geezer limped in with a pickup truck that would barely move under its own power. I watched him and a couple of the clerks looking under the hood when one of them unscrewed the wing nut on top of the air cleaner and lifted off the lid. He then lifted out the filter and dropped it on the pavement, where it left a dense black ring.
I’m pretty sure that same limping truck was my first vehicle. My closest near death experience in my truck was probably when it lost power on a steep downward slope with a busy intersection at the bottom. I had to stand on the powerless brakes with my entire body weight and pray.
This is my opinion, stop trying to start it ,drain the oil ,gas and coolant and replace with new . Change the plugs, wire’s, cap and rotor. Set up an alter to the Prince of Darkness (lucas) ,cross your fingers do a cart wheel and turn the key . It worked for me
Good call, Robert. That’s going to be my approach now, I think…clean everything up and rule out basic consumables that are easy to replace. I should have done that right off the bat, but the PO had the car in the shop the week before I bought it so I (foolishly) assumed everything would be in working order when I got it. Live and learn!
Update: spent some time in the garage this morning with help to do some diagnostics. Cleaned all the plug leads, vacuumed rusty crud out of the spark plug wells, checked the spark plugs (good). We pulled the air filter housing completely off and I washed about 1/4 inch of caked on black goo off it with simple green, soap, and water. Disgusting. I’ll pop it back in when the air filter I ordered arrives. Also checked the oil level (good), coolant (good), power steering fluid (low, which is weird since it was supposedly just serviced prior to purchase…), and checked the fuel pump again. Pretty sure the fuel pump is not working. We can hear current running to it, but nothing beyond that buzz. Didn’t see the fuel line move when the key was turned on. Shot some starter fluid into the intake to see if we could get it to turn over, and it would just barely catch and then die again. So it seems there is definitely a fuel delivery issue on our hands.
This week’s plans: replace the battery, wait for parts to arrive, replace air filter and put the housing back on after parts get here, then tow to the shop to get the fuel issue sorted and have the oil and fuel filters changed. I’m going to ask them to check/clean the sump tank, too. The boot definitely smells like fuel, but I’m guessing that will continue to be a problem unless I decide to take out the whole tank and redo everything.
You’ll probably need to do what I just did with Superblue (and posted about the ordeal earlier re: post-engine washing) - ended up replacing the spark plugs wires (inc. the one from coil to dist. cap), the dist cap and new plugs. That finally got things running again like they were before I got dumb and washed the compartment a bit too much.
Oh, and as to batteries, I posted recently how apparently you can’t trust them once they hit the 3-year mark, no matter the quality, warranty, etc. Any time after that and they can just go on ya … My personal XJS maintenance schedule for the future now includes: new battery every 3 years, new plugs wires, plugs and dist cap (and probably rotor) every 2 years, regardless of mileage …
One thing to notice when cranking is whether the tachometer responds as normal. If it moves only VERY little at best while cranking = (usually) CPS bad.
I went ahead and sprung $15 or so on Ebay for one of those “ignition tester” fountain pen-like gizmo/tools a couple of weeks ago. Neat, in that you can move it all around on the plug wires and actually see (via inductive pickup light) the juice going through the wires, the regularity of the timing of those pulses, and how strong they are in intensity (i.e. by the brightness of the light flashes) at any particular point. You can quickly and easily determine whether “fire” is not flowing through the ignition system like it should be at any point(s) between the coil and the plugs.
Next up to purchase, a noid light for the injectors.
Yep, a visit online to Parts Geek’s website for new air filter(s) is definitely in order (they have several brands to choose from for the XJSes, some of which are the cheapest ones around).
If your 3.6 is like the 4.0, you should hear the fuel pump “hum” (almost literally) during its short prime period, while sitting inside the cabin. Don’t think I ever heard a fuel pump “buzz” before.
Update: after taking too much time to think about it over the weekend, I’ve decided to just pull out everything in the boot and do a fuel tank/sump tank overhaul. It’ll have to be done someday, so I might as well do it now. If anybody has any tips beyond The Book (which I read), let me know! I’m definitely going to replace the sump filter with an in-line fuel filter as part of the process. Here goes nothing…
Whew, is that a whiff of “Shipwrights Disease” that I smell? Tips can’t help solve that Steady yourself and prepare for the long haul. Vaya con Dios mi hermano, vaya con dios.
My personal XJS maintenance schedule for the future now includes: new battery every 3 years, new plugs wires, plugs and dist cap (and probably rotor) every 2 years, regardless of mileage … 
Don’t think I ever heard a fuel pump “buzz” before. 
Steady yourself and prepare for the long haul. Vaya con Dios mi hermano, vaya con dios.