Hi. I'm a new member as I haven't really done anything mechanical with my car since owning.

The car is a 1982 XJ6 4.2 Daimler Sovereign - circa 90k miles.

Issue - won't idle, won't rev too easily. I think it's running very rich.

Background - about a year ago (500 miles) it did almost exactly the same thing. At that time I decided (for some reason) that the issue was probably fuel injectors and either way thought cleaning 30+ year old items would be money well spent anyhow. I ended up having the car terrocleaned, and following that it ran quite well, as well as it ever has should I say.

For the rest of last season (~500 miles) it drove as it always had done - not brilliant, but quite acceptable.

Today - I've eventually got it taxed and tried to start using it this year, and it's doing the same thing from the word go. Only done 3 miles in it and I daren't take it off the drive again as it struggles up the slight hill out of the garage. It also won't idle.

So this year I've decided that I think it runs very rich (exhaust pipes carbon up very quickly other such reasons) also the symptoms seem to be the same as when the terroclean sorted it. I've been googling for a couple of nights and decided that I might have a passing fuel pressure regulator, and thought I'd change this - anyhow they appear to be hard(ish) to get and aren't sufficiently cheap to replace on a whim.

Last night i decided I'd clean the throttle body, after taking it off I can see that the inlet manifold has a small covering of something in the bottom, probably oil, probably a few millimeter deep. Also the breather pipe has a reasonable amount of gloopy oil in it also. I'm in the middle of rebuilding at the moment but am waiting on a new gasket. The throttle body was a complete mess btw - it's nice and shiny now!!

So the advice I'm after is (1) should I change the fuel pressure regulator? (2) why might I have oil in the manifold? (3) could it be petrol - doesn't smell too much like petrol but it probably mostly old so might not anyhow? (4) do I need to clean the manifold or will it all burn off if and when the car starts running better?

Note - I haven't measured the fuel pressure yet as I thought I'd have the throttle body on and off in the night. I will do this when the car's back together, but would a split membrane in there be shown in a pressure test?

Advice greatly appreciated. I am sure this will be a topic regularly asked, and I've looked through many posts, however I've not seen one which fits perfectly.

 

Oh - I remembered that the first thing I did was remove all the spark plugs and they were all covered in carbon deposit - why I thought the cars running rich. Cleaned them and made no difference. Checked compression whilst I was there and it was good on all cylinders.

 

Here are some thought starters

XJ6 Series - EFI Rich Mixture


Wet gooey glop in the intake is normal


More later


Cheers
DD

 

Many thanks. Thats one of the documents id used to make me think of fuel pressure regulator. Since much of the other stuff on there isn't applicable once the car is running. Mine is wired for single tank operation, can't remember why! I've order all the gaakets to enable a rebuild and also those and the gauze around the breather. I'll
Put it back together and see how I get on. I just wonder where my injectors are all clogged up again. Once rebuilt the cause might be cured but it may still run tough If the injectors are blocked. I'm thinking of getting them cleaned again anyway.

 

How disappointing..........

....so I started working on the car by removing the throttle body and giving it a proper clean. I was really filthy, and the breather line from the front of the head was almost blocked.

I gave everything a good clean and ordered all the new gaskets. This evening I put it all back together and it started and ran lovely. I left it idling whilst I move the other cars, and during that time I was thinking that it sounds better than it ever has, there didn't seem to be much crap coming of the exhausts either. Maneuvered the car around the yard and it was lovely, but then after about 5 mins of running I drove out of the drive for a quick go 'round the block and it all fell apart. Stalled at the first junction and spent the next 5 minutes there trying to get it to run long enough to get it in gear and back home. Worse than ever now!!

Don't get me wrong I'm not too dissappointed that it wasn't cured as this it the first thing I've tried, but it ran so gorgeous for the first 5 mins that I thought it was.

Whether to look at electrics or fuel next? I will try it again tomorrow when it's cold again and see just whether there is a change when it warms up.

 

Bad to worse........came back from work and thought it would start cold at least. Wouldn't even try. Found lots of petrol in the inlet manifold. Took vacuum line of fuel pressure regulator and it didn't appear to be wet. Cleaned and dried all the spark plugs and it just about went eventually.

Leaking injector?

BTW - is there anybody out there?

 

That's good, but it doesn't confirm that that the regulator is actually regulating properly.....only a fuel pressure test can do that. Excessive pressure can certainly flood an engine.






'Tis been known to happen....but the degree of flooding you've described makes me think that all of 'em must be leaky. That's seems a bit of a stretch



If the coolant temp sensor is 'skewed cold' you'll get over-fueling as the engine warms up.....very similar to forgetting to push the choke knob 'off' on an old carbureted car.

Remove the connector and jump the two terminals with a paper clip or small wire. This gives a sixed 'warm up' reading to the ECU. Now go drive. Any change?


Cheers
DD

 

Thanks for the advice. I've ordered a fuel pressure test kit so I'll see what that shows when it comes. We also started the car with the vacuum line off and no fuel came out so its probably not the diaphragm. Very possibly too high pressure though.

Good point that it's probably several injectors and therefore probably the common fuel pressure regulator.

I've been investigating getting the injectors cleaned and checked on a bench also. Only because the terraclean last time seemed to do some good. With no performance tested "in the lab" pre and post though you never know when it has done much!

I'll test the pressure as soon as the kit turns up and go from there.

 

oh and the temp sensor. I did bypass that as suggested yesterday. Not a lot of difference, but already flooded by then. I might leave it like that for the forseeable.

 

It sure sounds like over-fueling... I could be wrong... Good idea to check the fuel pressure, lacking a gauge myself I pressurized it the regulator with a bicycle pump to see what pressure it "broke" at.

Do all the plugs look to be in the same condition? If so then I'd doubt a leaking injector... It's strange that you state that she ran well after cleaning everything...

Having only got a series 3 earlier this year, and the V12 too, my knowledge is limited... But I've had a very similar problem myself... The CTS as Doug said can also cause this type of problem.

Best of luck.

 

So my fuel pressure tester turned up. Connected to car and started it. Gauge showed ~30 psi for about 20 seconds, then suddenly went to ~90 psi. Not slowly but instantly. I assume that means I'm looking for a Lucas 73177A.

Any guesses as to why the sudden change?

 

Quite possibly a blocked return line as well, when I was trying to get my parts car running, one fuel tank was rusted out, which had caused issues in the whole fuel system, so I deleted it from the feed and return lines, but one thing I noticed was that in the return changeover valves, they were both full of rust/dirt/debris restricting them.

Just another thing to look at if the regulator doesn't fix it.

 

Just to complete the thread, a new fuel pressure regulator fixed it. Bought at worldcarparts.co.uk for about £65. Thanks for your advice throughout.

 

I too, had a failure of the pressure regulator when I had a Series 3 in the early 90s. The pressure went up so much I got leaks at all the injector connections !! These things are peculiar, as it seems to me that as the fuel pressure is pressing against a spring-loaded valve, the failure should be low rather than high fuel pressure.