Hi Gents,


Im still working on my basket case of an 87 V12 'Soverign' saloon

And I know, another V12 hot start thread - but having read a lot on the interwebs I cant find a situation like mine

I have managed to vanquish many of the demons bestowed by the previous owners dismal wiring skills - I don't even know what they were aiming to achieve, but we are back to a mostly factory and running state. Safe to say the car had been significantly screwed with, so nothing is off the cards!

The one issue left is the classic 'hard to start when hot' issue

So far I've confirmed:

• CTS is in the right range - (250 ohms when hot from memory - in any case its new as is the plug)
• Spark will jump a good inch from the plug lead in air while cranking - For what its worth the ignition module, pickup, cap and rotor button have been replaced (I regard this as 'maintenance' if you want reliability).
• TPS is renewed and adjusted correctly
• Throttle butterflies, AAV, etc all adjusted correctly
• Fuel pressure is possibly a little low, but at something like 32 psi after the pump primes, and when running.
• Fuel pressure holds reasonable - 32 psi to 28 psi in the half hour after turning the car off (i.e. it leaked down 4psi in 30 minutes after running, had a few PSI left after about 1.5 hours)
• Ive confirmed that both the O2 disable and starter cranking signals reach the ECU in the boot while cranking, and work as expected (0v to pin 25 in P and N, 12 volts in gear, 12 volts at pin 26 while cranking - also tried with both disconnected with no change)
• Not a vapor issue as ive primed the pump numerous times and it doesn't start any easier. pressure is there before cranking
• I did bench test the injectors with the whole setup a few months back, and nothing was dripping / leaking (not to say that it hasn't started since?)
• Holding throttle part open while trying to start doesn't help.

It wont start even with prolonged cranking when hot, unless I follow the below sequence:Even if I stop the engine for an instant when hot, it wont restart unless the above procedure is followed - this leads me to think its not an leaky injector issue?

Any thoughts? - seems like the ECU might be flooding on hot cranking for some reason? I thought it could be related to the O2 sensors, but the inhibit signal is reaching the ECU.

Also:

• no cold start injectors (87)
• there is a random green temp sensor on the 'A' bank that goes nowhere - my understanding is this is for the marelli ignition, which I don't have (maybe someone put a later housing on to replace a corroded one?).
• the ecu fuel mixture adjustment is basically all the way to the lean adjustment - although playing in the shed doesn't make a hell of a lot of difference between the rich and the lean settings - maybe indicative of an issue?

Thanks for your assistance!

Kind Regards,

Jay

 

Welcome back, long time between drinks.

You 100% have a Blonde S3.

That cranking manually with the systems OFF, and then instant start, is a new one on me.

I would be checking the Resistor Pack plug/socket. They are notorious for gunging up, and Hot Start is a PITA. I use Lemon Juice, followed by a rinse off with WD40 or similar.

Sparkers, with all those early issues, they will be in sad shape for sure.
Sparkers gap, just make sure you are at 0.025", the HE is Double Blonde if they are too wide.

I will keep thinking.

 

Glad you chimed in first, Grant. I'm stumped on this one for sure

Cheers
DD

 

The indented paragraph speaks loudly. It is a voltage issue.

Try an independent source of 12v + to the + post on the coil. then crank normaly.
If it fires right up, that is conformation.

Why is the next question. poor connections, including ground.!!!

OR!!!

Your PO screwed things up that you have not yet fixed.
No volts to the coil on the crank position of the key. Issue at the ignition switch



111Long shot. Advanced ignition timing. Starter kick back, no fire...

Carl