Fuel tank filter plug C990 vs C990/1

Does anybody know the difference between the Fuel tank filter plug C.990 as used on the XK 120 and the C.990/1 version as used on the XK 140/150? Can I use the later version on the XK 120?
I cannot see any difference between the two but that may be incorrect.

Bob K.

“A” possibility “MIGHT” be that the C.990 used on the XK120 has a two inch? tall screen filter where the C.990/1 might not?? (the fuel pick-up fits down into the center of the tall screen… helps to keep the rust chunks out of the carbs!)
The Original XK120 Fuel Plug was brass… might be the /1 is a different metal??
Also, the 120 Fuel filter plug being solid brass, I do recall seeing one filter plug that had a “bolt” in the center of the brass plug… like an “alternate method” drain plug…
A few possibilities for you to ponder…
Charles Ch #677556.

Charles,
Could be indeed that the material changed or another similar “minor” modification. Viart used the same drawing for the C.990 and the C.990/1 but that is of course not the final proof. Both Terry (120) nor Roger (140) provided other indications regarding any difference between the two versions.
Most suppliers offer the same unit for both the XK 120 and all the later versions, so I guess the C.990/1 will fit the XK 120 tank as well.
The version with the hex bolt on a square brass boss is apparently a later replacement and now offered by many suppliers.

Bob K.

C.990/1 is listed for the Mark V, which being contemporary with the XK120 and certainly the same drain plug, would suggest the possibility of an error in the 120 parts book (error no. 132 if confirmed) and it should list C.990/1.

My '38 SS came to me with drain plugs which had no screens at all. I attached no importance to it at the time, figuring they had been lost in the distant past. Now that this question has come up, I wonder if they never had them, and C.990 could be the plug without a screen?

Rob,

Thanks for this!
The SPC of the 3½ Litre Saloon & Coupé (1938 - 1947) refers to Filter Assembly C.990. As these versions had two tanks (like the later Mk VII, VIII and IX) the quantity is two. The fact that these are called “Filter Assembly” points in the direction that there actually is a filter.
So it looks like suffix /1 was added with the introduction of the Mk V in 1948. And you’re correct that the XK 120 would/could have had the C.990/1 version from the beginning.
Still don’t know why Jaguar felt the need to add suffix /1…

Bob K.

Hi Bob,

Sorry, but nope, the MKVII was the first and the Ser 3 XJ the last Jaguar saloon to have two fuel tanks.

All SS Jaguars and post-war Jaguar Saloon and DHC (MK IV) and all MKV’s had one single fuel tank, very similar to the XK’s. The whole XK120 chassis is basically a shortened MKV chassis with lower rear springs and slight alterations for the smaller and lighter body and longer (XK) engine.

Cheers!

Sorry to introduce a confusion into this discussion, but I should have said the SS and Mark IV have one tank but two drain plugs, one for the main side and one for the reserve side.
But Bob is correct that the C990 drain plug is called a filter in the '38-'48 SPC, so my guess is probably wrong.

Pekka,

My assumption that two filters meant two tanks was apparently wrong, but Rob cleared everything and the SPC is correct. Still we don;t know why the change in suffix. I understood from Roger P. that Jaguar didn’t change part numbers (even if there were some modifications made) as long as the new part was a 1;1 replacement for the old part.
But all suppliers provide the C.990/1 for the XK 120 as well and apparently no one has complained about it.

Bob K.

Hi Bob,

Yes, I too have a C990/1 in my MKV DHC and it is a perfect fit. True that Jaguar did not even change the part number in 1975-1976 when the shape of the XJ steel wheel hubcap changed, so for the fuel tank sump there had to be a change from plain C990 to add the suffix. It would be interesting if someone could figure this one out.

Cheers!

Ps. Although sometimes if they changed the material (?) or the design, they just added a suffix, or changed the suffix from 1 to 2 etc. I think mine is brass, were there also some made of steel?

I haven’t seen any made of steel.
How about the hex size, to take an ANF wrench rather than a BSF wrench?

Rob,

The original Filter Assembly on my 1954 XK 120 (with broken filter gauze hence my interest in a new one) has a hexagon size of 13/16" or .8125". I guess this is (still) a BSF 1/2" hex head size as the nearest UNF AF size would be correspond with a UNF bolt version between UNF 1/2 and UNF 9/16 bolt (UNF 17/32 perhaps?)

Bob K.

Well, the drain plugs in my '38 take a 1/2 BSF or 13/16" socket, so maybe that guess is another wrong alley.

How about a change in the wire screen mesh size or height?

They do sell 13/16" wrenches and sockets here, and it is for 9/16" diameter bolts, not very commonly used on new equipment but still around.

In any case you will be fine with a C990/1 in yours.
Or if you want to repair yours as I did, McMaster-Carr sells brass wire cloth in a bunch of mesh sizes. I found I had to tin each piece separately, then use clamps to hold them in position together and solder them.

Thanks Rob,

The height of the filter mesh might be another modification why Jaguar added the suffix. If there are too many rust flakes and/or other dirt in the tank, the filter can still get blocked, reason to increase the height. For comparison we cannot use your 1938 SS as it had no screen at all: could that have been removed at some moment in the past?
I had the brass wire mesh already in house but just bought a complete unit via eBay UK for just GBP 10. I can now spend my time on the rest of my car…

Bob K.