Hello everyone,

Sorry for the lack of updates with my Phoenix based XJ6, but I've been busy working and saving money to begin body work. Previous problems were completely resolved when I replaced the fuel pump with one from jagbits. The Jag has driven fine through the summer up until this last week, where another problem has reared its ugly head. After driving in the midday sun, The Jaguar seems to crap out, (sputtering choking stalling, after idiling in traffic. this doesnt happen immediately mind you, it seems time or temperature related.

I first decided to replace the old thermometer and gasket with new ones. I drove the vehicle to work this morning, no problems, but the trip home wasnt as fair with rushhour traffic in play. several conversations with the folks at checkers have steered me towards 1. the new fuel pump is overheating, or 2. the fuel filter (which i have just purchased another) is clogged.

Any commentary is greatly appreciated, I'll be posting a video recording this upcoming sunday!

 

I doubt it. I would supect more the crank sensor down on the front of the engine. When they get hot the resitance goes up and they no worky. The best way to test for this is use a heat gun and while reading the ohms between the terminals. Heat the sensor and watch for reistance change. If you think its fuel pressure you need a gauge and adapter to go inline of the rail. I tape mine to the windshield so I can watch it while duplicating the fault. The fuel pump is in fuel to keep it cool which is why I dont recommend people run the fuel down below a quarter tank. then its not sitting in much fuel to cool the electric motor. A dirty fuel filter wouldnt give you a temp related failure either, but should always be changed at least every 60k.

 

I'll check the sensor to be sure, but (and I'm just making sure) This is a 86 XJ6, the fuel pump ,filter, and switch are located below the boot, near the spare tire (a very confined space).((Clarifying the problem; When checking the fuel pump when this problem occurs, the pump itself is extremely hot, given enough time 10-25 minuets, it always returns to working order.)) The fuel pump is not "in" the fuel. Unless this is a term in which I'm not familiar with, and in that case please excuse my misunderstanding. In any case thanks for the help thus far brutal.

 

Your '86 does not have a crank sensor or a submerged pump. I think Brutal is thinking "96" instead of "86".

Replace the fuel filter and empty the contents of the old one into a clean container. If there's a lot of rust/gunk, then that's what's in your fuel pump. (Some add filters ahead of the pump to prevent this from happening). Post back on what you find.

Other possibilities are the ignition coil and the ignition module, both of which often act up after getting hot. If you have a volt-ohm meter these can be checked....of course they have to be checked *while* they are hot for the results to be meaningful.

Cheers
DD

 

see why you get wrong info with out yr model engine. Iassumed you have a intank mounted pump. then could be an issue. pumps normally get hot while running and thats a big reason theyre put in the tsnk to use the fuel to cool it. maybe you should coolit next time with iceto quickly cool. or you may just be getting good old vapor lock in the fuel lines, more an issue with lower pressure carbed engines not high pressure injection

 

aye, I fubbed up that one royally brutal. my apologies! Doug, I'll switch out the fuel filter as soon I get a bit of daylight, and report back accordingly. If the filter doesn't remedy the problem, is it possible to "cool" the fuel pump ? or would it need to be replaced.

The ignition module and ignition coil have both recently been (within the past....4 month) been replaced.

 

Doug, The lil ******* was full of redishbrown fine mud, I suspect rust in me tanks which is a terrible thought since I haven't the slightest idea as how to remove the tanks and repair/ or/ replace.

 

You can drain the tanks or pump out the gas, remove the tanks (big job), and send them for professional cleaning. Most radiator shops do this. Or...some guys clean 'em themselves with a hose. Sorta depends how bad they are.

Still others clean 'em in the car.

Or.....

Buy 6 or 8 inline fuel filters and put them in the lines between the tanks and the pump. You need filters with 1/2" nipples...NAPA has 'em. Drain old fuel, install filters, add fresh fuel. Run the car until you sense the filters might be clogging and replace them again, repeat again and repeat again. In essence you are using filters to clean your tanks. When the filters no longer clog replace the fuel pump again. I know of a couple guys who met with success this way. Minimal effort, about $100 for filters. It really depends how much loose crud in in the tanks. Worth a try, IMHO.

Whenever you change the filters you'll need a piece of 1/2" diameter wood dowel or similar to quickly plug the hose or you'll have a flood of fuel from the tanks.

The tanks drains are underneath the plastic covers on the bottom of the right and left valance panels. You'll have to remove the panles to remoe the plastic covers intact. Some guys just break the covers away.

Cheers
DD

 

Slight correction: the filters go between the fuel tanks and the changeover valve, which is ahead of the pump.

Cheers
DD

 

Quick question Doug, are/were the Stock tanks plain old steel ?

 

Hmmm. You mean were they treated with something or galvanized? I don't know. Good question! Someone will chime in.

Cheers
DD

 

Nah, normal steel, painted on the outside for good looks, hah, who can see them anyways. That is the ones down here that I have been involved with, maybe US cars are different, mmmm.

Just to add to what Doug has already stated, and to possibly ADD to your misery, your pump is dead set toast by now, due to all that "redish mud like stuff" that is in the filter, has gone through the pump to get to the filter, sorry, but thats life.

Those inline "pre filters" are a must in my opinion if you have an external fuel pump, which you do.

 

Status update: Successfully removed both tanks, both full of black rust as suspected. Going to take them to a shop and have them flushed out and bathed to remove all the rust inside.

Just as a note, my xj6 actually has fuel filters before the fuel switch, which seemed to have been hidden atop the fuel tanks near the wheel arch (poor design me thinks) these ones are tiny and i plan to replace these and my fuel pump.

 

Do you have pics of these filters? Very curious....

Cheers
DD

 

Yeah I'll take some pictures when I get some sunlight.

 

You also need new intank sock filters. Check out eastwood.com for fuel tank internal coatings so you dont end up with the same issues in the future even though theyre gonna be boiled out. Unless the radiator shop have a coating they do, but dont leave it undone.In years past when I delt with these issues(before plastic tanks) many times I also found corrosion in the metal lines and the injector rail. along with plug/partially plugged injector screens. You can replace fuel lines. and on the rail I would pull this off too and have it boiled out as well. While you have the injectors out you should have them sonic cleaned flow checked and rebuilt with new screens and o rings. this shop does this for $18 ea with quick turnaround
www.injectorrx.com

 

took your advice brutal, had them boiled out and coated, it starts up again now. The fuel gauges dont seem to respond thoe, hard to tell what that could be.

 

The fuel gauge senders are mounted in the tanks, right behind each taillight. They should have been removed for the cleaning process I would think. The senders have a swing arm and a float. Often, rust and scale build up inside the senders and the swing arm gets stuck in place. The senders can be opened up and cleaned out carefully inside.

On mine, they were both stuck and I was able to bend the little tabs on the sender "case" to open it and free up the swing arm. Also, make sure the sliding contact wipes smoothly across the resistor coil. You can use an ohmmeter to check for a smooth continual change of resistance as the sender arm is moved through its range.

 

they were removed, and functioned perfectly before, and now do not. Im thinking they were put improperly or just died sometime during the change.

other then that, jag has developed a new problem:

has developed a miss, chugs and chokes while in idle not often, but sometimes when given gas after idiling, it dies.

I assume this is my fuel pump which is still clogged with previous debris. any comments ?

 

Fuel senders are side-specific, maybe they were reinstalled on the wrong sides (left sender in right tank...)?

Does the chugging/dying problem happen on both the right and left tanks? Did you verify that fuel is returning to the tank that is in use? The return must be working for the pressure to be right. There is a little tube at the top of each tank you can see with the gas cap removed and the spring-loaded flap pushed down with a screwdriver. It should have a steady stream of fuel draining into the tank that you have selected with the engine running.

Fuel pump suspicions should be addressed by using a fuel pressure gauge when the problem is occurring. Fuel pressure is also dependent on the fuel pressure regulator. The regulator has a vacuum line which can be pulled off to see if any gas has leaked out of the regulator. Replace the regulator if gas leakage is found on the vacuum side. Some Google searching will give you the basics of using a gauge and how to test fuel pressure. The specifications are listed in the manual, or someone here can provide them.

You did not mention it but I would assume the in-tank filters were replaced. These are the white colored nylon mesh ones that push over the ends of the pickup tube just inside the drain plug hole.

Someone earlier mentioned how the rust particles can accumulate in the fuel injector screens, and the injectors may need to be removed for cleaning and rebuilding by a professional service. Doing that and flushing out the lines would probably make a difference after all the tanks and filters are repaired/replaced.

Then you can move on to other possibilities once you know the fuel system is clean and all injectors are good. A slight vacuum leak could be causing an erratic signal from the air flow meter, which would interrupt the idle smoothness. Make sure the air flow meter connector terminals are all clean and making good contact. A little dielectric grease on the terminals would be a good preventive measure to help maintain the connection quality.

Spark plug wires can allow misfiring to occur if they are old and deteriorated. Spraying a fine mist of water on the plug wires while it is running can help show that they are indeed bad. If it starts missing worse when wet, replace the wires, and use a small amount of dielectric grease in the boots.