Engine stops after a random time XJ12 V12 1983

Hello . I recently purchased a XJ12 from 1983. I had a problem caused by a foreign object witch dropped in the distribuitor cap, removed it, cleaned,trigger sensor removed and putted back, all’ things in place.

The issue is that now i start the car, run’s very good and smooth for 1 min, or 5 min and it stops for no reason. Start again very good and the defect repeats .

What can i check? For sure i miss something to check and I don’t know what.

Thank you in advance

Random guess? Ignition amp. Inside the ignition amp is delco d1906, so you can replace just insides pretty cheap.

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Put a fuel pressure gauge on the fuel rail and check the fuel pressure as the engine runs and then dies Perhaps you have some old stale or contaminated fuel and the fuel pressure is dropping due to fuel starvation. BTW, some of us have added two inexpensive aftermarket inline fuel filters in the spare tire well between the fuel tanks and the fuel changeover valve to prevent debris from the fuel tanks from clogging up things.
You can also try removing and replacing the fuel filter and draining the old fuel filter to see if it has any debris in it. You can also try switching fuel tanks. If the engine stops running on one tank, and runs OK on the other tank, you may have debris in just one tank.

Paul

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I checked the fuel system and everything is in proper condition. One it stops i can start immediately like nothing is wrong. The symptoms are like you take the ignition off.

Yes. Random…like you take the ignition off. Another thing is that the ignition amplifier is very hot after 1-2 minutes of working. The strange thing is that those symptoms appeared after i removed the entire distribuitor, cleaned it and grease it. Strange coincidence to remove something and to appear a defect into another place.
I don’t have so much experience on this model I really appreciate your support and advice.

Thank you

Not so strange, really.

With age and engine heat the wiring and connectors become fragile. It is very easy to unknowingly damage them while doing other work. Go back over your previous work and carefully inspect for any damage.

Cheers
DD

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[quote=“sandustoica, post:1, topic:426661, full:true”]
The issue is that now i start the car, run’s very good and smooth for 1 min, or 5 min and it stops for no reason. Start again very good and the defect repeats .
[unquote]

If the engine suddenly quits, Sandu, it’s most likely an ignition problem - and the prime suspect is the ign amplifier as mentioned by others.

Run the car while watching the tacho - if it instantly drops to ‘0’ before the engine stops turning; the ign amp has likely failed due to heat. It will then likely restart - to repeat performance. If the tacho gradually drops as the engine winds down other faults cannot be excluded…:slight_smile:

An alternative is to connect a triple gapped spare spark plug to any plug lead to watch sparking - if spark disappears as the engine winds down; again lost ign

Do you have one or two coils - and are there two or three wires between coil and amplifier?

Welcome on board…

Frank
xj6 85 Sov Europe (UK/NZ)

Thank you for warm welcome and for advice. In order to answer to your question I have just one coil.

Greetings to all :wave:

When the distributor pickup module (not the amp) warms up, the windings in the magnet open up. When it cools down, it reconnects.

Thank you. At my car the symptoms are like this…running smoothly for 1 min or 5 min or 20 min and suddenly stops. You turn on the key 1 second later and starts very good like nothing is wrong…and the circles repeat.

Still, Sandu - a verification of your ignition/injection set-up is pertinent…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

Yes, for sure. I already ordered the ignition amp and i will give a feedback after installing it.
Thank you

When it dies, immediately meter the pickup module to see if it is open.

Hello to all,

After weeks of waiting the spare parts ( the transistor witch is inside the ignition amplifier) i have this issue…it starts after 9-10 seconds of cranking and after that it works perfectly. With the old transistor witch cause the engine to stop after 1-2 minutes it starts immediately.

That’s the only conclusion that i have.

Can somebody help me with another advice? From where can I purchase this transistor- the correct one because unfortunately i only find after market ones and it’s very difficult to pick the correct one.

Thank you

It could be that the new amplifier has also a problem or it could be just a coincidence Sandu.
Put the old amplifier back to verify.

An other thing to do is to try priming the fuel pump before you start the engine, either by shorting the fuel relay contacts, either by turning the ignition on and off a few times, so the pump builds up pressure.
This will determine if it’s a fuel issue or something else.

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The ‘old’ module likely failed from the common ‘heat problem’, Sandu, but a properly working amp should not in itself delay starting…

As Aristides suggests; compare the two - including their spark color using a spare spark plug. The delay may be related to an ignition issue related to the ‘new’ module, but may be a coincidence, or a separate, coincidental, issue…

Frank
xj6 85 Sov Europe (UK/NZ)

The ignition amplifier is the obvious candidate. For this sort of problem, I’ve found it’s also worth triple checking every earth line, engine, distributor, …, for the condition of the cable and connectors.

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