Genset is slow to crank

[rwells36]

I have a 15 yo Onan 17kw genset. It used to crank 1st try now it takes several attempts ( start button depressed 3 seconds) to get her to fire up. Looking for direction on what to check.

[Lepke]

Diesel, I assume... Is the starter turning the engine over as fast as original? A diesel creates ignition heat by compressing air before injection. Turning slower allows more air to escape. Or, as the engine ages, the rings and valves are not as tight, letting some compression leak by. Also running on light loads will glaze the cylinder walls causing more compression leak. 17 kw is a lot for an average yacht. I have 14 kw and since disposing of the electric stove, rarely use 3 kw.
As the engine is now, cranking several seconds warms the cylinders enough, building higher temps from compression to ignite the fuel. Block heaters, glow plugs, #1 diesel, etc., will help starting.

[boatbod]

If cranking speed it's good, next suspect is burned out or inoperable glow plugs. Check the current draw - should be about 10A per plug. There is also a solenoid somewhere nearby that can fail and disable the pre heat

[rwells36]

The weather has changed by 20 degrees since my 1st crank fire.

[Octopus]

I have a 7yo 16.5 kw Onan gender. I had to replace the starter recently. It failed after a period of slow cranking. Other possibilities are poor/ dirty connections at battery or engine. Corroded contacts on isolator. Isolator on the way out.

[rwells36]

Originally Posted by Octopus

I have a 7yo 16.5 kw Onan gender. I had to replace the starter recently. It failed after a period of slow cranking. Other possibilities are poor/ dirty connections at battery or engine. Corroded contacts on isolator. Isolator on the way out.

Did you replace the starter before it failed? How would I diagnose a bad starter?

[keepondancin]

You might check the linkage for the solenoid activated fuel shut off, that it is working properly and not hanging up.

[Cadence]

Originally Posted by Lepke

Diesel, I assume... Is the starter turning the engine over as fast as original? A diesel creates ignition heat by compressing air before injection. Turning slower allows more air to escape. Or, as the engine ages, the rings and valves are not as tight, letting some compression leak by. Also running on light loads will glaze the cylinder walls causing more compression leak. 17 kw is a lot for an average yacht. I have 14 kw and since disposing of the electric stove, rarely use 3 kw.
As the engine is now, cranking several seconds warms the cylinders enough, building higher temps from compression to ignite the fuel. Block heaters, glow plugs, #1 diesel, etc., will help starting.

Lepke pretty much covered it. If she runs good and your start revs are up, fuel is good. The old girl may be getting old. Diesels don't like light loads 17KW is huge.

[Brewgyver]

It would be helpful if you could provide some more info. What kind of loads are you powering with the genset? Any idea of runt time? Age alone doesn't mean all that much, I have a 14 year old portable genny at home, but it has less than 50 hours on it.

As others have mentioned running with a light load is really bad for any diesel. The closest to fully loaded, the longer they'll last.

[Jesse]

Check the starter to ground cable, give it a good tug, mine pulled out of the terminal when I tried this. After replacing it with a quality cable the starter turned the engine faster and it returned to starting quickly again.

[Scrimshaw4]

Had similar problem with 6 KW unit. Diagnosed it as air getting into the fuel line. Check all your filters, lines and connections under positive pressure starting at the fuel tank going forward to the engine. I used my dinghy pump JHMO.

[boatbod]

I see many good suggestions, but for a variety of potential ailments. I think the OP needs to be clearer about the symptoms. Is the issue that the genset turns over slowly while cranking, or it cranks for a long time before firing?

[DeepCut]

From the above comments, (I have new boat with 13 KW Genset), I should run all 5 a/c units when genes is on in effort to prevent this .

[boatbod]

Originally Posted by DeepCut

From the above comments, (I have new boat with 13 KW Genset), I should run all 5 a/c units when genes is on in effort to prevent this .

You do want the genset nicely loaded - running it unloaded (i.e. battery charging) is not going to do it any good in the long run.

A/C, water heater, water maker,... Whatever you can turn on at the same time all helps.

[charliehows]

slow cranking can be caused by poor connections in the power feed system or internal wear and tear of the starter from age - i recently went through my whole starter system in episodes from batteries/earth to the starter connections - not unusual for there to be more than 1 problem.