cummins M11 hard start help

Im after some help please. I have a western star with a M11 cummins. The engine will crank a long time before it starts on its first start. After its first start for the day it starts fine. It is like it is repriming itself. Has any body had trouble with this before and what is the fix? I cant see any external leaks. Thanks in advance

Your fuel return line to the tank has a leak or the tube that is internal to the bottom of the has a leak

Rarely will these leaks be visible to the eye but can be found by applying a small amount of pressure to the tank

Plenty of people try changing lift pumps etc or putting no return valves in to try and fix the problem with out ever understanding fully how the fuel system works on diesel and continue to have problems

Hope this is of some help

Paul

I don't know the M11. If it is self bleeding, it has a pressure releaving check valve in the return line. It could be leaking. You can't see the leak coz it is internal.

Hope this helps.
Tony

Is this a mechanical or electronic engine? There are some known issues....

M11's are all electronic.

The L10 could be had in either mechanical or Electronic versions..

@indiana, I reckon TonyD is on the right track. I've had the same problem with N14's

hayseed wrote: M11's are all electronic

Not from where I come from. I have worked on several mechanical M11’s.

dieseldog wrote: I have worked on several mechanical M11’s.

Were they Automotive or Industrial Spec?

When have I ever been on the right track & got there.
Here is my 2 bob's worth. Wow showing my age.

I don't see mechanical or electronic, industrial or automotive making any difference. If there is such a valve and it leaks… well it leaks.
Electronic, to me, means the diesel pressure and flow are controlled electronically but it does not know if there is a small leak. It just raises the volume flow and pressure to accommodate. When the engine is stopped for a long enough period e.g. over night, a small amount of fuel dribbles back to the tank. I cannot understand why it should self bleed coz no air should get into the system. Perhaps it is only building up the pressure to bring the injector pump to correct specs.

If it is electronic, perhaps it says "Nope, not enough pressure - no start".
Because you keep cranking it says "Correct pressure, fire now".

If it is such a leak, it will most likely get worse and one morning it will not start.

Note that valve or cracked line could give similar symptoms, as mentioned by someone else above.

I am not necessarily right so keep digging and you will find it eventually.

Well, that's my 2 bob's worth. I hope it helped.

Tony

Along the same lines .....but if its an electronic engine ... or controlled but any sort of computer ....does it have a sensor that wont let it have fuel until a certain oil pressure is reached? had an N14 redhead that was a pain for long crank times of a cold morning ...guy checked it out and said it wont fire until oil pressure hits a certain level.... older more worn engine takes a bit longer to build pressure .... he then said "just put up with it"

Tony, there are huge differences between an electronic engine and a mechanical one. If a mechanical engine won’t start, it’s usually a fuel problem. An electronic engine might not start because it cant detect a sensor, oil pressure, a low battery voltage, a mismatched injector serial number, the list goes on. Sometimes, if say a sensor is bad, the ecu will let the engine wind over, but not start, in the hopes the sensor may start to read. If after say 15 seconds there is no sensor reading, the ecu will rely on the previous sensor readings in it memory, and allow the engine to start and run on these, in a “come home” mode. So in an electronic engine, you can’t use the no smoke, no fuel theory, because anyone of 100 things could be holding off the fuel delivery.

If it is an electronic M11, the check valve on the ecu cooler, which a mechanical engine doesn’t have, is known to play up. It is internal to one of the connecting elbows.