Both engines hunting on idle

[SeaAndSea]

Our pair of Cat 3208s both developed the same issues at the same time. Both are hunting when idling. As soon as load is applied, even if no increase in RPM, the hunting stops.

Further info:
Both engines recently removed from boat, cleaned and repainted
New fuel tanks fitted along with fuel hoses.
New filters
New fuel.

We've taken her out for a good n hard run

We've used a Gerry can to feed different fuel directly to the injector pump

Any ideas?

 

[volvopaul]

I have over the years done two different boats with this problem , basically it is dirt accumulated inside the injection pumps , the fuel turns into a sticky substance not allowing the governor to stabilise , it’s both pumps off and send to a pump shop that knows this product , the only company in the UK that dealt with caterpillar products was Colchester fuel injection , they were very good , this is of course in the uk , by the looks of your info your not far away , I’d also remove the injectors and send them in as well .
As for special tools I had the guidance of the workshop manual which unfortunately I no longer have as I had to part with it when we sold the HIStar 42 we had , same engines . The jobs I carried professionally were both on Broom 44s but same model engine although they were the 442 ho versions .
As for special tools you require very little other than a 3/4 inch long 5/16 unf bolt to insert into the timing gear to lock the crank , a drill bit to set the pump camshaft , and a puller to unlock the taper where the injection pump mates to its gear and that’s it .

 

[vas]

+1 on what volvopaul says (not that I had to confirm what he's saying...)
friend had same engines, same problem, seem to remember at some point mentioning that diesel lubricates the HP pumps in CATs differently to other engines making them more prone to gumming up. I do remember he had to eventually spend a fair amount on CAT spares (some plungers and whatnot). I also remember they recommended to add a bit of 10W sae oil in the fuel tank (but as far as I know he's not doing that, thought it was a bit ott)

V.

 

[Bandit]

As Volvo Paul said could be crud in the system or pulling air through a joint or the prefilter?

 

[Hardmy]

Volvopaul exactly described what to do. My port 3208TA had a similar issue. With vas' help, I sent the pumps to a good workshop for refurbishment and pulled also all injectors for a check. After that, all was good.

 

[volvopaul]

As Volvo Paul said could be crud in the system or pulling air through a joint or the prefilter?

Bit of a different set up on this engine , we have to remember this unit was built and designed for automotive use in the 1950s , you would think at 10.4 litres it would have extracted a lot more power than 442 at the end but unfortunately it wasn’t really that well developed because it has no oil piston cooling system unlike nearly every other marine diesel that’s turbocharged.
The injection pump has an in built gear driven lift pump to pressurise the injection pump body to around 36psi with a bleed valve on the tank return, I’ve had one of these motors down to a bare block over the years , they are very simple units , they also have an advance and retard timing gear so the pump is fixed injection angle on start up only advancing as it’s revs increase , bit of a rubbish design as the early ones like my Late fathers had a design flaw which made it run rough and not perform , this was sorted with a new advance unit and timing gear to match , many hours spent chasing the performance issue I can tell you .