My 86 V12 HE suddenly developed a cold starting issue and I
am a bit at a loss here.
Have been troubleshooting for a week with no result.
She will fire and idle very roughly.
The idle will hunt between 200 and 500 rpm, and after about
15 sec, or as soon as I touch the gas pedal, she dies…
After the 19th or so consecutive attempt she will fire and
all is fine, will restart with no problem and engine idles
and runs flawlessly.
Next morning the same story all over again…
Noticed that an injector hose would leak just by touching
it, so I replaced all engine fuel hoses.
I took the opportunity to change the injector seals and the
same time rerouted some cables.
Coolant Temp Sensor reads 2.6 K ohms @ 10�C
Placed a 4.2 K ohms resistance and there was a mild improvement.
When disconnected the idle improves even more but still hunts.
Air Temp Sensor reads 3.3 K ohms @ 10�C
FPR is not leaking.
I think the Ignition is doing it’s job, all 12 pistons
ignite, and all 12 injectors click.
Auxiliary Air Valve works and have extra boost from the
Supplementary Air Valve through a switch.
There is some popping at the intakes.
I disconnected the FPR vacuum line, no improvement.
Fiddled with the ECU’s idle fuel mixture, no improvement.
After the 19th or so attempt it will progressively get
better but it’s the 20th or so attempt that will make the
difference, she will fire and all is forgotten.
It worked enough for the temperature to rise and cure the
I know, I also need a fuel Pressure gauge, but I don’t have
one, and we are in the country here.
Have pre-pump fuel filters, pump is slightly noisy but
When I disconnect the fuel line and run the pump there is
plenty of fuel coming out.
When I block the hose the pump slows down to zero.
As if I am low in fuel pressure though, and therefore the
hunting idle, but combined with injectors that don’t stay
open long enough, and can’t explain why.
And yet again it can run as good as it does after it climbs
What am I missing ?
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