SO much for my charcoal cannister theory. The tube from the charcoal canister to the breather tube into the intake has already been plugged/disconnected by a previous owner. However, I did get her started today and this time left the gas caps wide open to see if it made any difference. It might just be psychological, but it seems like it runs a little bit better. The vent tube leading up to the canister valve and the canister is still hooked up, so I'm guessing the valve on the canister is bad. I will just cut the canister and valve out of the system and maybe put a filter on the end of the vent tube to stop debris from getting up in there.

I still suspect the problem is bad gas. But there are other problems with the fuel switcher that I want to sort out later. I'm guessing the return valves do not seal properly, so fuel is returned to both tanks. When I had the overflow, it stopped when I opened the other gas cap because the changeover valve itself probably has leaky seals and allowed the pressure to be relieved to the other tank.

 

As for the fuel sender, I was reading that Techron (which I'm adding into the tank with the fresh gas) can supposedly help remove some of this gunk on the fuel sender and hopefully make it work again!

 

Well, I finally tried to flush out the fuel tanks. We ended up clamping the fuel hoses in the trunk and letting the fuel come directly out of the tanks and into our gas cans (via a hose). The fuel that came out was definitely stale--it was very dark yellow-almost like urine when you've not been drinking enough fluids.

After all of that, and filling each tank with 5 gallons of fresh gas and Techron, the car was still running like crap. It will idle, then you can try to get it on the gas. Sometimes you can coax it to 3000 rpms, sometimes you can barely coax it above idle. At this point, the car had been running for maybe 5 minutes--if that gives you any idea whether or not the new fuel actually made it up to the engine.

On a hunch, I decided to change the fuel filter. It was pretty filthy, rusty fuel poured out one end. I put the new filter in, after clamping the hoses in the trunk. It took quite a bit of cranking to get the engine to start back up again. When it did, it was like magic! The engine ran perfectly! For a few minutes anyhow. Eventually the engine was back to running the way it had before.

Does anyone have any idea what's going on? Is the fuel in the tank really that rusty that it would clog a new filter in a matter of minutes? I am thinking of draining the tanks again using the same method and seeing what the fuel looks like.

But the fuel that came out of the tanks didn't appear rusty (no floating bits) to me, so I imagine the fuel coming out of the tank this time was also not rusty!

The other thing I noticed was that the fuel pump is VERY noisy. The amount of fuel that it seems to pump out is very very slow--about a gallon every 20 minutes (which is why we ended up having to give up and drain the tanks from the trunk area). Is this normal???

I will post a video of the fuel pump shortly.

 

How about some arithmetic?

Presuming 10mpg.

Then, 1 gallon/20 minutes = 3 gallon/60 minutes.

Implying, 3 gallon/hr * 10mpg = 30mph.

In other words, at 10mpg that flow rate would support at best 30mph cruise ignoring increased consumption during acceleration.

So .... probably not adequate.

 

Hhaa, I did the arithmetic but I was hoping that there was some cheshire-ish magic going on to keep the engine running.

But yeah, it makes perfect sense now that the fuel pump is bad. What is a good cheap fuel pump? I don't want to spend a ton of money on this if I don't have to--plus I won't be driving it that often.

 

Noisy 83 Jaguar XJ6 fuel pump - YouTube

Here is my fuel pump...

 

Before you rush off and buy a new fuel pump, have you cleaned the gauze filters at the bottom of the tanks ? These are attached to the large plugs at the bottom of the tanks, accessed via a hole in the rear 1/4 panels. If these are blocked the pump will struggle to pump fuel.

 

Thank Fraser. This is definitely good advice. Unfortunately I've already ordered the pump (a $70 one off RockAuto.com).

It seems as though the gauze filter in the bottom may not be my problem, since the fuel flows very quickly out of the 7/16" hoses from each fuel tank. Of course, if this doesn't work that will be the next thing I check, but maybe I'll have a professional do it because I really don't want to be messing with all of this fuel again!

I'll keep you guys posted.

 

I drained my tanks and let them air dry for awhile while working on other things. I found there was a thick layer of sediment on the bottom that had to be loosened with a brush I taped to a stiff wire and vacuumed out/blown out with shop vac. Maybe the flushing you did was inadequate, and you have good initial flow but still alot of sediment stirred up once you start driving. I would recommend taking off those drain plugs at the bottom and removing the senders (behind the taillights), and cleaning the tank until you are certain you have removed the maximum amount of stuff. Also a good chance to get the senders working, I doubt Techron will do it after seeing the condition mine were in. Just make sure to pre-order the gaskets for the senders and drain plugs, as well as the in-tank filters.

You can also install pre-filters (NAPA 3248) in the 7/16 hoses before the pump to help catch residual sediment before the pump eats it. Make sure the in-tank filters that Fraser mentioned are in good condition so large chunks aren't getting past.

Some relevant info:
https://www.jaguarforums.com/forum/x...p-issue-41947/

 

I replaced the fuel PUMP (edit), and it was running great! (I'll upload a video later.) It revved up freely and didn't seem to exhibit any of the hesitation and stalling it was plagued with before.

I let it idle for about 5 minutes and then took off for a drive around my parking lot. Out of the parking spot it seemed great. No signs of hesitation or stalling. But then I rounded the corner, and started to get on the gas. All of a sudden the engine stumbled and stuttered and cut out. I let it rest a few seconds, and then restarted it. It cranked, and finally started a few seconds later, only to struggle at about 100 rpm and finally stall. I let it roll back down the hill and into a parking spot.

The new fuel pump seems to be working well, and I know there has been a lot of speculation about the fuel tanks being rusty, but other than some rusty looking stuff in the fuel filter, I haven't seen any signs of rust, even in the fuel that came out of the tanks when I drained them via the fuel hoses (pre-filter and pre-pump). And I also doubt it would cut out that fast.

I jumpstarted it (it has a weak battery). Again, it would only crank, and the engine wouldn't catch or even try to catch. I suspected that perhaps the fuel pump was not functioning--but I jumpered the positive terminal of the battery to the fuel pump connector and I could hear it purring away. I also tried jumpering the fuel pump while cranking the engine, which did not change anything.

Because of this, the only thing I can think of is that the fuel pressure regulator is busted, now that there is a functioning fuel pump in there. I figured I'd give that a shot, ordered one on Amazon.com for about $40 shipped (should be here tomorrow--can always return it if I don't want it). Because it is busted, it might just be allowing most of the fuel in the fuel rail return to the tank, which won't allow it to build any pressure. Have you ever heard of a fuel pressure regulator going out right after changing a fuel pump? Perhaps the fuel pressure regulator was busted all along?

Is it possible that the problem is the inertia cutoff switch? I didn't touch that thing yet, but I don't know if that would cause the problem because I also tried cranking the car while the fuel pump was jumpered and running (unless the inertia cutoff switch also disables spark?).

 

SORRY, I meant I replaced the fuel PUMP. I am editing the post.

 

I have posted on this before,as I have had direct, (and unpleasant), experience of it...............

There is a tiny pair of contacts in the MAF box that supply 12 volts to the fuel pump relay when the car has started. Until the air flap moves they are open, when the car starts the flap moves an arm out of the way and they close. This is bypassed when the engine is being turned with the key to start it or one could never start the car. Only the contact mounts provide the closing pressure, there is no spring, and over time the springiness of the contact mounts diminishes. It is really p**s-poor engineering, IMHO, but there we are, we have to live with it, there will never be any factory mods now.

These contacts can fail to pass volts at any time, and did several times to me whilst I was going along at speed, and caused some rather dangerous situations; really brown pile in my pants, sort of thing !

You can check this with a long pair of leads with a 12v light bulb on the end. Connect up to the fuel pump terminals in the trunk, lead the bulb into the car, where you can see it, then watch the bulb illuminate as you start the car. The light should stay on. If the engine suddenly fails to run whilst you are in motion, and it is these contacts, the light will go out, thus proving no supply to the pump via the relay.

There is a mention of this in these website pages (page 3 Airflow meter problems)

Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

 

Thanks, Fraser. I will try to look into it. Couldn't I avoid doing all of this by listening for the fuel pump during startup? I heard that if you put it in drive and crank it, the fuel pump will run as if it was attempting to start, but the starter solenoid will be deactivated.

I wonder if this is too much of a coincidence. I think I'm going to test the fuel pressure regulator today when I get home and see if that is indeed the problem.

 

Also, I want to measure fuel pressure. Where is this Scraeder valve everyone is talking about, and if I bought a fuel pressure gauge, do I simply hook it up and go?

 

OK, you can hear the pump running on starter motor cranking as the contacts are bypassed, and probably while the car is ticking over, but what you need to check is when the engine stops/fails while you're tootling along the highway. Is it the pump has stopped due to lack of volts via these contacts ?

The instant you see the light goes out the engine will start to fail. In my case each time it happened, I would take a deep breath at the roadside if I had just been overtaking somebody, (rather worrying when the engine fails as you're rushing past !), then try to restart the car. In all such cases it always restarted straightaway, that was why I had such trouble finding the cause. I was told about the bulb test by a local shop and then worked back to these contacts using the wiring diagram. I too, tested the inertia switch, by shorting out the leads, but no joy.

FWIW I got the car reliable and in good order, but it took me 14 years !!

 

1983 XJ6 after replacing fuel pump - YouTube

There is a video of me starting the car. Skip to 2:00 to hear it run.

It runs beautifully in the video. I did a number of experiments. I tried cranking it and cranking it and the same thing seemed to happen--it wouldn't catch. Then I tried jumpering the fuel pump and letting it run for a while. Then I put the fuel relay back on and started the car normal. After some cranking, it did start the engine, and sometimes it will run perfectly smoothly but only for a few seconds. Then it will start misfiring and eventually die.

Jumpering the fuel pump SEEMS to have an affect on whether or not it will start at all, but no matter what I do, it doesn't seem to want to sustain itself and dies out. But the symptoms of dying out are the same whether or not the fuel pump is jumped--the car always dies. I think this might rule out the Air Flow Meter, but anything could be wrong at this point.

I just want it to run like it did in the video... all the time! I feel like this is that movie "Awakenings" where the patients come out of their comas for just a few short weeks and then return to their comatose states!

 

With the fuel pump relay connected normally, (and if the contacts in the MAF are not making proper contact when the engine starts), the car will start because starting uses Position 3 of the ignition switch which bypasses these contacts and activates the relay, then, when you relax the switch on engine start, the MAF box contacts should have closed and hence keep the the fuel pump relay activated.
If you have jumpered the fuel pump, then the car should start and run because the pump will be pressurising the fuel rail regardless of whether the engine is running or not. However, I am not clear if this is what you have done, as you refer to putting the fuel pump relay back into the circuit.

I have also looked and listened carefully to your video, (it brings back some memories, I can tell you !!), and first off it seems to me the starter is very lazy, and is not turning the engine over quickly enough. Only towards the end of the video does the starter seem to wake up at all, and turn the engine over vigorously, at which point it starts and then the engine sounds perfectly OK to me. So there is a starting problem.

Now here's a thing......

Late on in my ownership of the car, (Year 12 probably !!), I got a starting problem which seemed to gradually creep up on me, (this was after I had got the MAF fuel relay contacts fixed. The starter would ocasionally be reluctant to turn the engine over, then it got commonplace. Thinking it was the battery, I replaced this, but although things marginally improved, it then deteriorated again. Anyway, I took the car to a Jaguar specialist well known in the Jaguar Enthusiasts Club, who mainly works on the older Jaguars. He advised it was a worn-out starter, put a used but good one on and hey presto, end of starting problem. I think that was the last faultI had with the car !!
I think what happens with worn-out starters is they take too much current and the car's electric system voltage drops so much other components cannot function correctly, like ignition, EFI and fuel pump, so it is a key component.

Anyway that is my pennyworth, (or cents worth, lol)

 

Read my other thread. I'm almost 100% sure that a malfunctioning of the fuel changeover valve and the return valves has caused the fuel to run empty in one tank and filled the other tank. I'm trying to bypass the changeover valve tonight.

 

https://www.jaguarforums.com/forum/x...at-back-66836/

Following up.