Standard practice, but I thought with an engine firing on so few cylinders it might run so rough it would be difficult to tell pulling a spark plug wire would make much difference.
Injectors are not designed to run on 12V. The ECU applies a 12V pulse to open them rapidly, then switches a resistor in series to drop the voltage. 12V is probably OK for a few seconds. A small 9V battery is OK, can’t supply enough current to cook the injector but will open it.
My 1979 coupe I bought in 1984 and ran it with all the OEM systems for 10 years. The Opus ignition amp is not reliable. One time you could buy a U.S. made amp + V12 kit with a 12 slot disc for the dizzy. Not sure it is still around.
Very odd that the engine fires on about half the cylinders. I would check the dizzy inside, the plugs and plug leads.
Also check if the engine has cold start injectors in the middle of the manifold. They were fitted on early cars. If they are open you will get an extra dose of fuel
Faulty Coolant temp sensors are also a weak spot, that can cause overfuelling.
Getting new spares for such an old ignition and fuel injection system might be tricky.
One possible source is www.justxjs.com near Derby, they break a lot of XJ-Ss.
Hi Richard, Sorry for delay in replying.Have had hospital treatments which have left me a bit fragile plus my son and his wife and 4 year old son are here on a visit. They live in australia where my son is a police officer. So nice to see them again.Now back to my v12 problems. I rigged up a test bulb to act like a noid and every injector plug was pulsing. Next I checked every injector with a battery and all were clicking so I am now thing this is not a fueling problem so off with the dizzy cap for the first time. I took off the Rotor arm and the ferrite rod rotor and straight away saw the pickup trigger was cracked with a piece missing which I was able to retrieve. Despair set in with me wondering where I could find a replacement . A few of my petrol head buddies go to scrapyards quite often and I started to ring them and third one I rang said yes he had seen a xjs in a nearby scrapyard a few months ago and gave me the number to ring to see if they still had it. I rang the yard and they said they still had it but there was not much left on it and it was about ready for the crusher I asked him if the dizzy was still on it and he thought it was so I was on my way in no time. The dizzy was still on the engine and was the same as mine withe 3 wires. and I told him I needed a part from inside it to which he replied he could not let me have a part out of it that would leave him a dizzy he could no longer sell but I could buy the whole dizzy for £10 ( about 17 dollars ) needless to say I could`t pay him fast enough. That was yesterday (sat) and I thought I had done enough for the day as I was in quite a bit of pain. Today I stripped down the new dizzy and found every thing looked fine so I swapped the trigger boards over and my engine started immediately on 12 pots and rang as sweet as a nut. I Still have a problem though with the engine idling at about 2000 revs ( tacho no working ). I screwed out the throttle stop bolts on the butterflies but it did not make any difference. Is there something else that controls the idle speed.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
23
Yes, and it’s not the throttle stop bolts! You have now f#%$^d up the throttle linkage adjustment and will need to go through the correct adjustment process. And when done, you’ll need to properly adjust the idle with the screw on the AAV.
As Kirbert said you will have to go though throttle linkage adjustment procedure if you tampered throttle linkage adjustment. but high idle is very often caused by stuck or otherwise faulty auxiliary air valve (AAV) I have developed a rebuild kit for the valve with all new stainless steel internal parts and new oem spec. thermal bulb.
Hi Kirbert, I have seen articles on the net about adjusting the idle by the aav but I have searched my engine and surrounding bodywork but could not find the aav so I thought my engine may not have one being an early car. Does anyone know the location of the aav? I am now going to try and uoload some pics.
Hi, I have sorted the tickover problem, nothing wrong with the AAV. Two bolts were removed by my No 2 son that hold the fuel rails on to the front of each manifold to enable enough give on the rails to remove No 1A and 2A injectors. I remember thinking at the time that they were very long and sure enough a small screwdriver put into the bolt hole confirmed they went right into the manifold and the engine was sucking air through the two bolt holes. My engine is now ticking over nicely and I have set the throttle stops according to site from the net. My AAV is not very easy to access compared to the pics that John sent to me with mine being r/h drive but luckily I had only loosened 1 clip when it dawned on me the bolts may be the problem. I can now get on with other work the car needs before going on the road. Many thanks to all that have helped me. I really appreciate it.Best regards, Chris.
