JK CRD fast cranking not starting, then starts OK after turning key on and off 3x

[rob8888]

Hi All

My JK CRD will periodically not start - the engine will crank fine and fast (in fact slightly faster than normal so I know this problem as soon as I hear the speed) but not start. I'll turn it off and on and it will generally start immediately (with the normal crank speed). If I turn the ignition on and off 3 times then it will definitely start as per normal (in the first second or two).

It's done it for years (since near new) perhaps once every two months, but is now every second day. Does it when warm/cold/summer/winter - any time really.

Everything sounds normal but slightly faster cranking like there's a lower compression in the cylinders perhaps?

Any intel on this issue? I can't find anything with searches here, or via Google. Worried its heading for a total failure of something.

Many thanks

[Classic Boy]

The following more general common rail info, rather than specifics of the JK engine.
The faster starter speed is probably lower compression due to any reason other than no fuel, being injected, as the injection of fuel adds to the compressed volume and the combustion resistance particularly when pre-injection or sometimes called pilot injection occurs.
It maybe an issue with a sticky shutoff solenoid valve/ pressure regulating valve not initially opening fully or maybe the high press pump is not building pressure rapidly.

[rob8888]

Originally Posted by Classic Boy

The following more general common rail info, rather than specifics of the JK engine.
The faster starter speed is probably lower compression due to any reason other than no fuel, being injected, as the injection of fuel adds to the compressed volume and the combustion resistance particularly when pre-injection or sometimes called pilot injection occurs.
It maybe an issue with a sticky shutoff solenoid valve/ pressure regulating valve not initially opening fully or maybe the high press pump is not building pressure rapidly.

Thanks. I find it interesting that the easily identifiable cranking speed difference is due to addition, or lack of, fuel, but I guess that under compression the air volume is relatively small and oil non-compressable.

[MidnightMods]

Common problem for the PCM not to trigger the intake fuel pump, cycle the key and make sure you can hear the pump priming before starting.

some replace the module or just wire a relay power feed to the pump.

its talked about every few weeks on the crd facebook page

[EugeJK]

Mine is 10 years since new and been doing it once or twice a year, mostly in cold and wet. As if the fuel pump relay clicked, but didn't engage the contacts. Cycled power and it cheerfully started no probs. When it happens, no white smoke coming out during cranking that means no fuel compressed.