I just bought an 84 xj6. picked the car up yesterday and drove it home, about a 2hr trip. there were a few issues that croped up on the trip and I would appretiate any advice on how best to address them.

a breif description of the car. as I said it's an 84 it only has 21,000 miles so it's obviously spent most of it's life in the garage! it appears to have been very well maintained and the seller claimed the car was driven around the nieghborhood once a month or so to make sure everything was in working order...

ok now to the issues:

1.) the cruise control doesn't work.. hopefully just a fuse? but if not any ideas?
2.) the steering rack has a noticable leak / leaks. is this common and are they easily rebuildable?
3.) there was a noticable vibration on the highway at speed. It feels like it's coming from the rear I say that because it's not coming through the steering wheel. I'm hoping it's just a tire issue. the tires are old and hard and possibly out of balance due to cord shift? what else should I check here?
4.) this morning when I went to move it from the driveway to the shop it didn't want to start. after lots of cranking it finally fired (I assume the fuel in the rail bled back out over night?) and ran fine but when I got it inside there was fuel leaking from the short lines between the fuel rail and the injectors. all the lines have been recently replaced and the clamps were not very tight. I tightened them all up and it seems to have solved the leak but I doubt this was the cause of the starting issue?

I'll stick with these issues for now and in the meantime I'm going to change the oil and maybe through some spark plugs at it just to have a starting point for future maintenance.

thanks,

rgg

 

Fuse, yes, check it first. Then check the vacuum supply to the bellows. Also, the bellows often shrinks and the seal to the end plates is lost. These can be disasembled and re-sealed.

A note on fuses: you're not just looking for a blown fuse. Often the fuse isn't blown but the end caps and holding clips are corroded and simply need cleaning. Also, beware of a fuse that "looks" OK but where the wire is broken under the end cap where you can't see it.

A great many of the infamous Jag electrical problems are caused by fualty/dirty fuses and/or electrical connectors





Rebuildable, yes, but not many DIYers have good luck doing it. Most buy a rebuilt unit from one (of the many) reputable Jag suppliers





Those tires have got to go on general principle anyway....and they are the most likely cause of the problem. However you might have a driveshaft center bearing iusse or a stiff u-joint. But...go with new tires and see what happens






Hard to say. Assuming the lines and filter are clear a healthy fuel pump will recharge the fuel rail in just a few seconds so the bleed-down isn't really a huge issue. Lack of fuel pressure and flow, though, is a big issue.

Pull the fuel filter and empty the contents into a clean container. What you see (or don't see) will be an important clue and will help determine your next steps.

Post back for more details on any of the above, if needed.


Cheers
DD

 

Thanks Doug!

1.) cruise control. I replaced the fuse with a new one. I haven't driven it since so I can't report on weather or not it was sucessful. the reason i suspect it's elec in nature is that there is no light coming on telling me the cruise is on.. does one exist on these cars?

2.) Steering rack. I will order a rebuilt unit ASAP.

3.) Vibration. Definitely agree with the on principle remark; in fact I suspect they are probably the original tires... yikes!!
I put the car up on the lift and I cant see or feel anything noticable in the driveline so hopefully tires will solve the problem.

4.) Fuel. where is the fuel filter located? I followed the fuel line from the rear of the car (hard line) to the front where the hose attaches then up to the fuel rail and I see no filter anywhere?
the reason I was suspecting it was a drainback issue is because once it starts it runs fine throughout the rpm range. if it was lack of pressure or flow I would expect it to be real evident at high rpm?

new question. what is the prefered spark plug for these cars? I pulled one plug just to have a look and was suprised to find Bosch platinum.

thanks again for all the help!

rgg

 

Nope, no cruise control light. Jaguar was still a bit backwards back then. Jaguars didn't even *have* cruise control until the Ser III came out in '79. What you have in a Ser III is "the most modern of all antique automobiles" :-)





In the spare tire well, right front corner






Makes sense, but sometimes problems defy logic and, besides, you gotta start somewhere so it might as well be a quick-n-easy freebie check :-). These cars are a bit notorious for fuel system rust so it has to be eliminated as a culprit.





Heh heh...sorta like "which is the best oil?". Everyone has opinions and favorites. Many Jag die hards prefer to stick with Champions (R12YC, as I recall). That's what I'd use, personally.

Cheers
DD

 

By the way, when you order your steering rack make sure to order new mounting bushings as well. The originals are probably shot. Most owners prefer newer-design urethane bushings...better steering feel, longer bushing life.

Any of the usual Jag parts specialists will have 'em.

Cheers
DD

 

Doug,

I hear ya on the spark plug question!

I asked because I was suprised to find platinum plugs in it. while they are great plugs for modern cars I know from some of my other old cars (all much older than this one) that they don't do well in cars w/o modern fuel injection sys. I just don't know how up to modern standars the jag sys is?

will do on the rack bushings. the steering is kind of vague and I suspect a new rack and bushings will be a huge improvement! do you have a favorite parts supplier that you can recommend?

Thanks,

rgg

 

I've been using Coventry West (800 331 2193) for years. Motorcars Ltd also has a good reputation but I've never used them. There are many others. Lots of Ebay vendors, too.

No matter which supplier you use be cautious of too-good-to-be-true pricing. Some parts are "brand x" replacements. Generally speaking parts are inexpensive enough for these cars that you can afford to ask for known quality, name brand items.

Others will chime in with their favorites

Agreed on spark plug remarks, by the way.

Cheers
DD

 

Doug,

spent most of the day on the car.

The starting issue is getting worse and is now hard to start any time you shut it off and let it sit for more than a few min.
I replaced the fuel filter and confirmed that I have good fuel flow. I dodn't have a guage to check preasure so I can't confirm that but I did confirm that I'm loosing preasure soon after the car is shut off. the diagram shows a check valve in the system. where is it? and does it really matter that it's not holding preasure? I'm starting to suspect it's more likely a sensor somewhere or something else not flow or preasure related??

on a positive note I put a set of tires on the car and that completely eliminated the vibration, so at least I can check that one off my list!

there's several other minor issues but for now I'm going to focus on the starting problem before tackling anything else..

thanks.

rgg

 

There is a check valve on the airbleed assembly, which is the brass contraption with hoses and fittings near the fuel filter.

A faulty check valve might result in needing an additional couple seconds of cranking but that's about it. A healthy fuel pump will pressurize the lines and rail in about 2-3 seconds.

You mentioned "good flow". Does the pump operate while cranking? Easy check: put the gearshift in "D" and turn the key to "start". You should hear the fuel pump run.

A fuel presure test really IS required for a proper diagnosis, though. I see a new tool purchase in your future. But first check your spark while cranking. Is it yellow or orange? If so, it's weak. You want a bright blue spark.

Next, remove the plug at the coolant temp sensor and jump the terminals together with a paper clip or such. Try starting the engine and report back if anything changes.

Cheers
DD

 

There is a fuel pressure regulator (is this Doug's check valve ?), which contains a spring-loaded blow-off valve to return surplus fuel to the tanks. This will normally allow the correct pressure to be maintained in the fuel lines, although obviously not for ever when the pump is not running, but foe several hours at least. Once the fuel pump starts it will repressurise the fuel rail very quickly at Doug says. Of course the blow-off valve can leak badly and fuel pressure may therefore not be to the correct value. The car will probably still run, but not so well. he other thing is the engine temperature transmitter, if this is not indicating a cold engine, not enough fuel will be injected. There is also the cold-start injector which is switched on for a cold engine, then keeps injecting, (I think) until engine start is detected. The cold start injector really squirts fuel in !

 

No, the check valve is back by the fuel pump...not same thing as the pressure regulator.

Yes.....A leaking regulator can really cause problems as raw fuel is drawn into the engine. Or, sometimes, the regulator doesn't leak but it won't regulate the pressure. Too high ressure flooeds the engine, too little starves it. Only a pressure test will tell.

The cold start injector works off the starter circuit for a maximum of about 8 seconds in sub-freezing weather. The cold injector is grounded by the thermotime switch which heats up to prevent too much cold start fueling. And, yes, it squirts fuel like crazy !

Cheers
DD

 

thanks Fraser,

unfortunately I didn't get to work on it today (had to do real work) but I'm begining to suspect the preasure regulator may be the culprit. the condition is getting worse to the point where it happens anytime i try to start the car after sitting more than just a few minutes, so I think the cold start systems are probably not to blame. I need to get a fuel preasure guage so I can find out exactly how much preasure I have. the thing that puzzles me is the car runs great after it starts and if it was a low preasure or flow issue I would think it would run poorly especially at high rpm??

rgg

 

Well, sometimes symtoms don't make much sense and diagnosis means finding out what *isn't* the problem as much as it means finding out what *is* the problem :-)

Did you jump the terminals in the coolant sensor plug?

Cheers
DD

 

Doug,

I didn't have a chance to work on the car at all today. as soon as I do I'll do the fuel pump test you recommended and jump the temp sensor. I'll let you know the results.

rgg

 

This indicates to me the cold-start system is defective, so you need to check the thermotime switch. Trouble with ageing fuel injection systems is there are so many separate things that can go wrong or fail !! It was all so easy with carburettors and distributors.

Question: one it has started is it OK in all conditions and revs ?

I had many happy, (and many unhappy), years with a Series 3. The happy years were towards the end of the 14 years (YES !!!), when I had got the car really sorted out to my satisfaction. I was really sorry to see it go to a new owner.

 

Ok I was able to get back on the car this evening. I did the fuel pump test Doug reccommended and the pump is definitely working, in fact when I do that it preasures up the fuel rail and she fires right up. I rigged up a guage and the fuel preasure looks good. book says 36.25lbs; my guage isn't that accurate but it reads 36 to my eye. when I shut the engine off it leaks down to around 20lbs in just a few min and then slowly bleeds off further. 10 is as low as I saw but I've left the guage on and will see what it reads in the morning. it's interesting how quickly the rail preasures back up when I do Dougs test but doesn't seem to when trying to start it... I've heard some electronic FI sys cut the pump off after a few seconds of the starter turning and the engine not starting, do you know if the Jag has such a cut out?

unfortunately I did the pump test and subsequint start up before jumping the cold start so wasn't reall able to do it on a true cold start but will in the morning.

thanks for all the help,

rgg

 

Frasier,

it does run good in all conditions and revs and as I said in my previous post once pressured up it started right up when dead cold??

rgg

 

Good !




Strange





Nope. No such cut-out on yours. The pump should operate as long as the key is held in the "start" position.

Try this: bypass the entire fuel pump control circuit. Unplug the fuel pump relay and run a jumper wire from the battery "+" post to the white/green wires in the relay plug. You shoud hear the pump run. See if anything changes with the starting.

(You probably have 2 white/green wires at the relay plug. Jumper to both of them and/or whichever one makes the pump run. You'll hear it)

Cheers
DD

 

Thanks Doug,

I'll try verify pump opperation while cranking. I was by myself this afternoon but I'll try to get someone to crank the car while I check pump and then watch the preasure guage and see what's going on there too.

is the check valve the hex plug looking thing on the purge valve? or is it all one unit? I can't help but think if I eliminate the leak down my problem will be solved?

rgg

 

The goofy brass contraption next to the spare tire is the "air bleed" and the check valve screws into the side....looks just like a hose nipple but it has a one way valve inside.

If the check valve is bad it'll delay starting for the amount of time it takes for the pump to repressurize the fuel rail...usually 2-3 seconds.

Cheers
DD