I am just getting my 1971 XJ6 4.2 duel Stromberg carbs running. Both fuel cells are bad so I have taken them out for replacement. The Rear fender cavities face some deterioration so for the meantime I am running of of a Gatorade bottle while I sort out these issues. Question is: The motor starts fine on full choke but seems to take a while to be able to ease off the choke. In the meantime it swallows up a pint of fuel very fast! Are there any numbers regarding fuel consumption for these setups?

Also have great oil pressure on start up according to the gauges then drops of to almost nothing. Water temp gauge dies not work either but coolant seems to be flowing(possibly not past the thermostat)

 

I have had S1 and S2 XJ6 cars. Only sold a S2 a few months ago. I had it for 15 years.

I used to get about 15 miles per gallon (mpg) around town and 20 on the open road. However that was imperial gallons (160 oz) versus your US gallons which are 130 oz.
So you would be looking at roughly 12 mpg around town and 16 mpg on the open road.

The only way to be sure about actual oil pressure is to use a mechanical oil pressure gauge. The electrical ones can give you all sort of erroneous readings.
Also just check the oil flow to the camshafts by taking the oil filler cap off while the engine is running. If there is plenty of flow then the engine is fairly "safe".

I suggest the water temperature transmitter has failed. The gauges themselves are fairly reliable.

Bill Mac
MK1
MK 2
S3XJ6
X300
Previous 14 Jags MK5 to X308

 

Thank you Bill Mac. Sound advice. When I get the fuel system back on line I will try. Where do you think I could find a good photo of an original glass bowl filter set up to sort out the bracket I seem to have?

 

Are you trying to go concourse or just have a good runner. Those glass bowl filters were ok for trapping water but did not work as well on solids.
I suggest you substitute a modern online filter rather than chasing up a glass bowl original.
I also suggest you consider putting on line filters between the fuel tank outlets and the fuel pumps.
Unless you are a fanatic for originality I would also recommend getting rid of the SU fuel pumps and substituting Facet pumps.
The Facet pumps are far more reliable.

Bill Mac
MK1
MK 2
S3XJ6
X300
Previous 14 Jags MK5 to X308

 

Many years since I had my XJ6 Series I's and II but I recall the same 15 mpg. I also had a brief fling with an XJ12 Series I. It returned 8 mpg and I went back to XJ6 in six months.

Graham

 

Jaguar made beautiful dashboards but the instruments were more decorative than scientific. I miss the way XJ speedometers used to sway gently between +5 or -5 of the actual speed. Not really the fault of the instruments as other vehicle manufacturers also using Smiths gauges didn't have the same issues.

However, I would be concerned about actual oil pressure. It could well be a faulty sender or relief valve not seating but I'd tap a line and get an external gauge on it to be certain.

Graham

 

I rigged upo a 1 litre fuel bottle to run the engine in my series 1 manual o/d XJ6. It had rotten tanks and no fuel pumps when I got it.
This car is fitted with 2" SU and despite bveing in good condition (all cylinders +150psi) it drank fuel when I fired it up from cold.
However my good car (series 1 auto) can achieve 24mpg on a run if I do not exceed 70 mph, and has averaged over 22mpg for the past 6 months of use. These are imperial gallons and I only take the car out if it going to get properly warmed up on a longer run. Never use the car on short runs to the shops.
I will say that I have tuned this car very lean - so lean that it does not idle smoothly. I put up with that and have never had any engine damage.

 

I don't know how you guys are getting those great MPG numbers with carburetors. I have a 4.2 with 175 CD Strombergs and I'm not a spirited driver (as I have to fix it when it breaks) and I only get 11 MPG in the city (US gallons). Don't know about highway because mine is only driven around town daily. If I have to go on any long trips - like to Orlando or Miami or the Left Coast - I use my Mercedes. Don't want to be stranded with the Jaguar.

 

Bill Mac, you pose a really good question of which I wish I knew the answer. Perhaps you can help me out.
This is my first jaguar and could be a major lift but it feels ok to me, but i have yet to really get into the nitty gritty of the unibody. It appears pretty whole. Regarding the fuel filter question it has a glass bowl setup which
i just went through and have new tanks and am working on the pumps. There is an in line in the engine bay. Being my first and being a bit of a history buff I am inclined to stick with original but the more I read the less I am inclined. That is why I am here!! I will be changing both the exterior and interior colors if it matters and would love your feedback!

 

Since I am so new to this I don't even know the size of the two fuel tanks I am putting in. It was not listed. Do you know what capacity they are?

 

I think they are both 11 1/2 or 12 gallons.

Dave

 

Wow! That's not a lot!! They do look that small, and will that fuel consumption.......

Thank you Dave!

 

Don't forget, there are two tanks which would be 23 to 24 gallons. My '02 Suburban has a 25gal tank, my wife's '05 Yukon has the same, my '04 diesel pickup has about 26-28gal. The Jaguar has a pretty customary load of gas in most "full sized" vehicles.

Dave

 

Dave, this is a good point. I guess pretty important to make sure the sending units, switches, and gauges are working properly. Are they problematic? Does the fuel tank transfer/toggle switch run both the fuel pumps and the sending units?

 

DBaer, I have a 1985 XJ6, I believe the fuel system is a little different on yours. The L/R switch in the cabin would toggle both your internal fuel pump and the gauge sending unit for each side. Mine has a single external pump with a change-over valve to swap tanks. Mine also has two change-over valves in the rear wheel wells that control fuel return on fuel injected cars. The change-over valves can be problematic, especially from non-use. Sending unit issues seem to be hit or miss on the Forum, I replaced both of mine, one didn't work and I was unsure of the other one--not expensive. Gauges seem to be reliable, again from posts on the Forum.

Dave

 

Congratulations on restoring your wonderful car to life! Once well sorted and sensibly maintained, a Series 1 XJ can be an extrememely reliable and endlessly rewarding daily driver (same goes for Series 2 and Series 3 derivatives too!).
Regarding your carburettors, the Zenith-Stromberg 175 CD2 came in both "automatic" (choke controlled by water temperature) and manual (cable-operated) forms. Cn you tell me which you have? Basically, do you operate the chokes yourself by pull/pushing a cable? I ask, because a common eror on these cars is for service centres to only use a 30% glycol concentration as the coolant; when the required is 50% (mixed with distilled and not town supply water to be sure the minerals are removed). If the car has been run with a "lean" coolant mixture and then sat for an extended period, it is highly likely that there is corrosion and correspondent sludging in the narrow "arteries" of the auto-choke water galleries (if you have auto chokes). If this is the case, the chokes will be slow to come "off" or can often be stuck in the "on" position which makes the engine run very rich; consuming lots of fuel and also potentially fouling the spark plugs and even washing the bores (not something you want happening). The cable=operated "manual" choke carbs do not suffer this issue. In the last 3 months, I have had to repair the chokes on four XJ's that were drinking fuel and (as usual) discovered that corrosion was the cause. A quick test for the water temperature gauge is to pull the wire from the sender and ground it out (with key in the "on" position). When grounded, the gauge should move to the extreme right "hot" side. If the gauge moves there, the sender is likely faulty. If it doesn't move, likely a power supply issue (fuse, corroded connections, etc) and if it only moves part-way, then there is likely some form of short circuit to trace. I can only lend my support to the importance of confirming your oil pressure with an analogue gauge, as wisely recommended by others here.

 

DBaer
The fuel tank capacities quoted for Series 1 XJ6 North American delivered cars is 11 imperial gallons/50 litres/13.2 US gallons per tank.
For other markets it is 12 imp. gallons/54.8 litres/14.5 US gallons. Don't ask me why the difference. I don't know!

Might I also suggest that you get a copy of Haynes Owners Workshop Manual for Jaguar XJ6,XJ and Sovereign. I have full Jaguar factory manuals but they are expensive. Haynes manuals are quite good for owners general maintenance and relatively cheap.
Trying to sort out a Jaguar with no manual is like playing blind mans bluff. A real hit and miss affair!
Cheers
Bill Mac
MK1
MK 2
S3XJ6
X300
Previous 14 Jags MK5 to X308

 

That is an excellent response! Thank you. it is a manual choke with a nice little light that works when the choke is on. Although I have not tested the coolant mixture, but will upon your advice, it appears very green and bright. I will try your test on the temp gauge followed by some research on the oil side once I put the fuel system back together. I have cleaned up the glass bowl filter nicely and am wondering about the bracket it had. It does not make much sense to me and am looking for photos of an original set up?

 

Bill Mac, fortunately the car came with both an original manual and parts manual of which I am grateful. I am sure a lot of my questions are answered within those but the knowledge in this forums tells the stories learned between the lines. When merited tell me to go read!!

 

Great job cleaning-up the filter; looks terrific! One more little tip about that glass filter housing... I too prefer originality on my own cars (of course, I defer to my customer's wishes on theirs). That said, what has been said here about the sub-standard performance f these bowl filters I would agree with; they do make a great water trap, but less so as a fuel filter. A solution I have employed often, is to retain the glass bowl, but once the paper element has reached its replacement interval, I instead replace it with a redily available (and much cheaper) debris screen as shown in the photo attached. I then also put a modern "in-line" fuel filter hidden away in the boot (trunk) as a pre-filter for the pump. In this way, you get the best of both worlds, a modern, effective and readily-changed fuel filter and an original and efective "sight glass" that readily captures and displays "at a glance" any water present in your fuel. Just another option