1975 XJ12C Repair Operations Manual needed

I just purchased a 1975 XJ12C in really nice shape. I drove it at the seller’s home and now it quit. I suspect a fuel system fault. Need a Repair Operations Manual for this model. Anyone have one they want to sell?

**
You do, Judd - but in the meantime; why do you suspect a fuel issue?

Frank
xj6 85 Sov Europe (UK/NZ)
**

Felt like it was running out of gas. Slowly stopped running smoothly and started sputtering then quit.

David A. Judd
951-640-6188

David,
Did you try switching over to the other fuel tank? If your car came with the owners manual, that will show you how.
Phillip

Duh. This is my fourth Jag and my second double six. I have only owned this coupe a few days. I called the previous owner this morning and he said he had never switched tanks, he only used the right tank. I did switch the tank to see how much fuel was in the left tank and that was when the trouble started. I suspect the left tank is full of crud and I have fouled the fuel system. I just need some trouble shooting tips. I have found a ROM on eBay and it is on the way to me.

Thanks for your input.

David A. Judd
951-640-6188

David,
Duh? This is how you respond to someone that takes the time to respond to your request for advice?
In defense of my “basic” suggestions regarding the fuel tank switch, from your original posts, it appeared to me that you were new to jaguars and thus ignorant of the operation of fuel system switches etc. Based on your rude “duh” response, it’s obvious that your ignorance is much more generalized.
Phillip

Listen Mic,
Since I have been a member for more than 6 months, I was not aware you were under the impression I did not know anything about Jags. Sorry if my attempt at humor offended you. I apologize if I seemed rude. Now that you know I switched tanks do you have any helpful suggestions? Like for instance how do I check the function of the fuel at the injector fuel rail? What is the correct fuel pressure for the 1975 Fuel Injection system and where can I access the fuel rail to check pressure?

From the Haynes XJ12 1970-1980 manual.
jag fuel pressure check pg1.pdf (211.9 KB)
jag fuel pressure check pg2.pdf (107.7 KB)
jag fuel pressure check pg3.pdf (614.7 KB)

Thanks very much. Now that is helpful.

David A. Judd
951-640-6188

**
Indeed, David - full of crud, or simply empty…:slight_smile:

In principle, crud may foul the filter, the changeover valve, pump and or the tank lines - but will not normally interfere with the injectors; they are protected by the main filter.

An easy preliminary test is to open the fuel filler lid and listen for fuel returning with the pump running. If there is no return; the cause is blocked ‘arteries’ and the cleaning the mentioned items should be considered first…

If there is fuel return, checked at both filler lids with alternate tank selection - should give return only(!) to the selected tank. If so, and there is still a ‘no-start’ situation; it gets more complicated. Nominally, with adequate fuel pressure and volume; fuel will return as described.

However, it is prudent to verify ‘raw’ pump pressure first; connecting the pressure gauge to fuel rail inlet hose. A ‘perfect’ pump should deliver 100+ psi, and a fair one some 70 psi - below 40 psi the pump is inadequate to the task. Checking rail, ‘regulated’, pressures without verifying pump performance is insufficient…

You have of course checked starting with ‘right’, previously used, tank. A shortcut to detect pre-pump clogging is to feed the pump from an external source of fresh fuel…

Not forgetting that the non-start after changing tanks may be a coincidence - however remote…:slight_smile:
Frank
xj6 85 Sov Europe (UK/NZ)
**

Frank,

Thanks for the input. Actually the car was running and quit after a considerable amount of stumbling and dying. Finally it would not restart. I will perform the diagnostic tests you suggested. And report back my findings.

David A. Judd
951-640-6188

**
Did the seller tell you why he used only the ‘right’ tank, David…?

Obviously engine didn’t like the ‘left’ feed - and sucking grit may have clogged the changeover valve. Which may then be stuck on the ‘left’ tank - which may be empty. One of many fault possibilities - like both tanks being empty…:slight_smile:

Verify that you have sparking while cranking - and that you can hear the injectors clicking while cranking. Just to verify absolutely that lack of fuel is the likely cause…?

Frank
xj6 85 Sov Europe (UK/NZ)
**