Recent XJS-C 3.6 5 speed purchase

(alabbasi) #1

All, I recently bought an 85 XJS-C 3.6 with a 5 speed manual. Car has sat for sometime and the fuel tank was removed. I’d like to put the thing back together asap and see if it runs. The PO says that he had the fuel tank and the expansion tank repaired which ‘might’ be good.

I’d like to know the following as the 3.6 was not an official import so there is little info on parts website:

Is the tank the same on the 3.6 cabrio as it is on a the v12 coupe?
Does the tank sender interchange? If jot, what is the correct part # for this sender
Does the fuel pump interchange with a 3.6 sedan? If not, what is the correct part # for this pump?
Same for filter?
Same for expansion tank

Any advice would be gratefully appreciated.


(PeterCrespin) #2

Nice cars. In the rest of the world they were sprung a little sportier than the V12s and a manual loses little in speed to a V12. I had a convertible and a coupe, not the cabrio. Try the Coventry Foundation for spares books - you’re going to need them.


(Kirbert - author of the Book, former owner of an '83 XJ-S H.E.) #3

When all is said and done, you’re going to be the guy to tell us!

Just logically, I wouldn’t expect the tank to be any different. Making it different would have required Jaguar to come up with a different design and tooling, so if the tank used in the V12 would work as is I’d expect them to just use it.

(Jimandhelen) #4

The cabriolet has a smaller tank than the coupe or convertible. The parts manual covers it well.

Jim 1984 XJSC 3.6 manual

(alabbasi) #5

Thanks all. I was wondering if the fuel tank sender is the same. It’s pretty crusty looking. I bought a cheap fuel pump that’s compatible with the bosch fuel pump. In checking the part # , it appears to be the same fuel pump that was used in the SIII XJ6. The main difference between the new one and the old one is that the old one has spade connectors wheras all the new versions use ring terminals.

I’ll buy ring terminal to spade adapters from the local electronic shop which should fix this problem.

(PeterCrespin) #6

If you want factory info that dealers got, (and access to dealer tools & instruments) the charity outfit probably have it. I personally donated a 3.6 manual set (incomplete IIRC) and I know they have s tool loan plan.

The new thing I recently found was that they are selling duplicate or surplus donations via eBay.
. The Foundation now has an EBAY store: . It has stuff added every day or two and lots more coming it seems. The profit all goes towards things like their scholarship program for students doing a car restoration course (to keep the old skills alive).

Worth keeping an eye on or presumably writing them with a specific requests?.

(Mark Lee (Pay Pal Patron)) #7

The short answer is no. the Coupe and the Cabrolet do not share the same fuel holding bits, or at least my '87 XJ-SC doesn’t share the same bits with my '88 XJ-S Coupe. the fuel pump is the same between the two. I don’t think it will matter about the 3.6 and the V12 fuel pumps because it’s not a closed fuel circuit - meaning once the pump gets up to pressure it stops pumping. Jaguar XJ’s Saloon, Coupe, and Cabriolets all share the "looped fuel system - what fuel that isn’t used gets returned to the fuel tank.

However some of the same bits are shared with the (my) '89 convertible.
The fuel tank is the same on the convertible, the fuel neck is the same as well.
The fuel filler cap assembly is shared with the Series III XJ saloons.

I don’t know about the tank sender.

Parts and part numbers if you don’t have manual can be found at is also a source for the manual. is another source for a manual. The XJ-S’s OE is a 4 volume set. the online / electronic version IS the full meal deal. The $100 green service manual is an abridged variant; and I personally find it better than nothing, but just barely.
Kirby Palms ebook which is on the old site; is a fantastic resource for stuff not in the Jaguar Manual as well as tips and tricks and “upgrades” that have been performed on the XJ’s over the last 40 years.


(alabbasi) #8

All, I bought a new fuel pump and sending unit and did a little testing today. I hooked the fuel pump to the existing rubber lines and ran it into a small jerry can full of gas. I also plumbed a hose from the return to the jerry can so that any unused fuel would be collected there.

I was able to get the pump running after a few false starts due to perished hoses; the pump was able to build pressure. I was not able to get the car to start using fuel, but was able to confirm that the car had spark as it would start with ether.
My suspicion Is either of the following:

  1. Injectors are not firing – This is either due to an electrical problem with the ECU or just gummed up. I need a second person to help me test by cranking on the car while I listen to the injectors to see if they’re clicking. If they’re not. I’ll put 12v to them directly to see if they fire. This will tell me if it’s the injectors or upstream of the wiring. If they still don’t click, then the most likely issue is that the injectors are gummed up and I need to get them cleaned
  2. If the injectors fire - I suspect that the fuel pressure regulator is bad because there is fuel going back to the return
    I’m including a video of the car and would be grateful for your opinion. There’s a lot to do.

(Jimandhelen) #9

The AJ6 uses a vacuum sensing fuel control system with an engine ECU in the boot connected by a rubber tube to the manifold. This ECU can fail (mine did) & the other important part is the water temperature sensor. So if you have spark & the fuel pressure regulator is working, then check the WTS. I have the resistor values in the manual.

Jim Brighton, UK 1984 XJSC 3.6 manual

(JimD in Alabama) #10

Al - I believe the injectors will click if you jumper each of them one at a time to a 9 volt transistor battery. I had mine cleaned and then per Dave Faircloth’s recommendation tested them prior to re-installing them and fuel rail back in car.
But I also think as a matter of bucket list items, you probably want those old injectors cleaned. Unless you are getting very strong clicks and great performance.

(alabbasi) #11


Thanks. Injector cleaning is on the card. When I bought my XJ12C, it was converted to propane and I converted it back using parts cobbled from 3 parts cars. Part of the process was to clean the injectors and due to the #'s. It paid for me to buy my own. So I got this. It’s paid for itself a couple of times over.

(alabbasi) #12

I was able to do a little more testing today.

  1. using the battery from my 20v drill, i connected two wires directly to the injectors and using a stethoscope, i was able to hear the injectors clicking.
  2. Using a noid light , i was able to see that the computer was sending an electrical signal to the injectors
  3. On pulling the fuel rail, the rail empties all the gas thus proving that the regulator was maintaining pressure

I removed the injectors and took them home. I’ll get them cleaned this weekend and see if it will free them up.

Here’s a video of the progress.

(Robin O'Connor) #13

Hi no help with the no start but down the track if you want the engine to breathe you can replace the throttle body with one from a 4 litre, it should be a direct fit

(alabbasi) #14

from what’s written on the cam cover, this engine appears to have been swapped for a 4.0 already.

(Robin O'Connor) #15

Good point, just looked again and noticed that there is an oil cap on the cover as well as into the sump.

(alabbasi) #16

I put the injectors on the ultra sonic cleaner today and flow tested them. At first i thought that one of the injectors was out of balance so i ran it through a couple of times and the test tube will always come up low when I get back to check it. Later I realized that the problem might be with my ultrasonic cleaning machine and that particular tube leaking back down into the tank as I had walked away for an hour or so while I took care of some other stuff and it had almost completely drained down.

Good progress!! Tomorrow I’ll paint the injectors as the cleaner strips the paint down and in some cases, the metal casings can cause grounding issues. Then I’ll try to assemble the fuel rail sometime this weekend.

Here’s another video with the progress

(alabbasi) #17

Some more progress. Over the past couple of days, I painted the fuel injectors and took them up to the shop to get them re-installed. The job was not too difficult and after a couple of false starts. I was able to get the car started. It was a big smoky from sitting but it ran well.

Shifter is really sloppy and I was not able to find reverse (any ideas? Anyone???).

Next on the agenda:

New bonnet struts

New air filter

New fuel hoses

New Vacuum hoses

New sender gasket and ring

New fuel injection hose clamps

New fuel filter

Here’s a video for any who are interested:

(Gourgen) #18

this engine does not look original to that car , i know it is still an aj6 but not the original one

(alabbasi) #19

Correct and I mentioned this in one of the videos. The engine appears to be a 4.0 or at least the cam cover indicates that it’s a 4.0.

(alabbasi) #20

Good progress on the XJ-SC, got the tank installed and the new pump wired up properly. I still need to do some tidying but it now runs from fuel inside the tank.