Diesel doesn’t start after injectors maintenance

[bobs]

I overhauled the injectors of my 50hp diesel , 4 cylinders , simple engine , no fancy electronics .
After mounting them back and connecting all couplings I tried to start the engine to no avail . Bleeding the supply lines from pump to injectors seemed the right course of action . After the second injector was done the engine started to show sign of life and when all 4 were done it ran smooth .
After 15 minutes and some throttle up now and then I stopped to try a re-start after 10 minutes , immediate respond so Job well done . I would think the 15 minutes run would be enough to get all the air out of the system .
2 days later an oil change was scheduled for which I use a 12 volt extraction pump. These handy gadgets seem to have some problems with cold oil so a short engine run helps to warm up the oil and bring the viscosity down .
I cranked the engine but it wouldn’t start .
Again after bleeding the injectors ( from discharge diesel pump to inlet injectors) it came online .

What am I doing wrong , what am I missing ?
Does anyone recognise these symptoms ?
Thanks for the feedback

Regards

[boatnerd]

Did you service your own injectors? On our perkins pintle injectors the top portion(return cap) were pressure adjustment is has a copper crush washer. When reassembling if you arent careful while tightening you can disturb pressure setting. Did you have them pressure tested?
Sounds like you still have air getting into fuel lines . .

[bobs]

Hi boatnerd , after upgrading the shims a bit I pressure tested the injectors , I have the designated tool for that .
All 4 were within specs and the spray pattern was perfect , if I say so myself .
Indeed , air seems to be drizzling into the system , but I never touched any other couplings than the injector input and output (return) .

Regards

[AA3JY]

Replace the crush washers with new..torque to spec.

[Hesti]

I'd guess there is still air in the system. It can take a while until the last little bubbles are gone. When the pressure in the lines drops, these little bubbles become big bubbas again ... Once you have used (not just idled) the boat for a few hours, all should be fine.

[captstu]

I had an air leak in my Racor that caused intermittent starting problems.

[01kiwijohn]

Originally Posted by bobs

I overhauled the injectors of my 50hp diesel , 4 cylinders , simple engine , no fancy electronics .

I cranked the engine but it wouldn’t start .
Again after bleeding the injectors ( from discharge diesel pump to inlet injectors) it came online .

What am I doing wrong , what am I missing ?
Does anyone recognise these symptoms ?
Thanks for the feedback

Regards

CAV pump? That can happen. You may have to bleed it several times. (ask me about a perkins 6-354 sometime)

[Capt Y Knot]

Could be air in the system. It will prime and probably start with the secondary filter bowl full of fuel.

The engine will run until the secondary filter bowl is empty.

[bobs]

Thank you all for the suggestions , I made sure to replace all crush washers with new , no visible leaks anywhere . The diesel pump is Bosch rotary .

Maybe the supply line has been compromised during the fiddling with the couplings to get the injectors out . I had to replace this line 8 years ago due to cracks and consequently air getting in that stalled the engine on occasions .
Half a meter of line that runs over the engine , it gets very warm and hard over time . No way of telling when that happens because of the metal protection on the fuel line .

Regards

[bobs]

If a washer connection of the diesel return of one of the injectors is not tight enough could air get into the diesel pump or system that way ?
I had to struggle with one of the injectors to get it out of the engine , by using a wrench I slightly damaged the seat of the washer .
All 4 returns run in a single line to to the diesel pump from where a rubber hose ( with metal mantle ) runs back to the tank.
I not really familiar with that part of the pump , but could air get into the pump & system that way ?
Please check photo with explanation underneath .



The red arrow is the collective diesel return from injectors
The yellow arrow is the return hose/line to tank .
The black arrow is kind of a mystery for me , would air bubbles be able to get into the pump ?

Thanks