I have just completed an inframe rebuild of my 3306 PC. All went well and the engine is running well. After the expected fuel bleeding the engine fired up and appears normal.

The fuel pump was not touched but of course the injector lines were removed during the process. Also the fuel line and return line were taken off. A new 3 metre section of hose was installed from the pump to the Racor filter. The engine is in a boat.

After the engine hasnt been run for a few days it is hard to start and appears to be lacking fuel. I have to crank it for about 30 seconds or longer. Plenty of battery and when it does start to fire it struggles for a few seconds just like when it was started for the first time. The temperature here is about 20 C, 70 F.

After I have been boating and the engine has been stopped for about two hours it starts immediately, as it should and did prior to the rebuild.

I have been over the injectors, fuel lines etc and cant find any leaks and I'm not sure how to proceed. Any thouhts?

Thanks Ian

Sounds like you have a new air leak. They can be hard to find, but I would try by getting an air pump of some kind and pumping air into the fuel system when the boat has sat unused long enough that you expect the problem to arise.
It won’t build up much pressure unless you can somehow shut off the supply and return to tank and you don’t want more than a few psi anyway, just enough to get bubbles from the leak when you spray all the lines and connections with soapy water solution.

Make sure you don’t over pressurize the tank if you’re using an air compressor. I think a bicycle pump or air mattress inflator would do the job.

I have no idea what the boat fuel system really looks like but Ive chased similar leaks on a couple machines where the fuel level in the tank is always below the engine and I believe the principals are the same. You can pressurize the fuel tank and try to find a fuel seep or you can admit air and use leak detector solution to see the bubbles. For tiny leaks, the air will be much more easily detectable.

There is a bolt to loosen on the governor housing to bleed it also.

Are you sure your glow plugs are working?

Thanks ccjersey, I think you are right and I will try using air. I think it is on the supply side otherwise it would leak fuel when going. The fuel in the tank is the lowest its ever been so that could be exasperating the situation. I will re check or re do all my new connections. The water separator could be the culprit now the tank is so low.


Rome K/G thanks for the diagram. My serial no is 66D01651 and I think I have a scroll fuel pump but I'm not sure. I will be at the boat later in the week and I will look for that bolt. I do have a fuel return line which I believe comes with a scroll pump. Is it possible for the hand pump to let in air?


Hi Glum I don't use the glow plugs. I realise they may help but I don't think that is the problem. And the manual reckons they are not required above 15 c (60 f?) and if its colder than that I will be staying home!

Yes the valves in the priming pumps can do bad too.

"waltini" wrote:

Thanks ccjersey, I think you are right and I will try using air. I think it is on the supply side otherwise it would leak fuel when going. The fuel in the tank is the lowest its ever been so that could be exasperating the situation. I will re check or re do all my new connections. The water separator could be the culprit now the tank is so low.


Rome K/G thanks for the diagram. My serial no is 66D01651 and I think I have a scroll fuel pump but I'm not sure. I will be at the boat later in the week and I will look for that bolt. I do have a fuel return line which I believe comes with a scroll pump. Is it possible for the hand pump to let in air?


Hi Glum I don't use the glow plugs. I realise they may help but I don't think that is the problem. And the manual reckons they are not required above 15 c (60 f?) and if its colder than that I will be staying home!

-i wouldn't rule out an air leak or air entering the system....but i agree with Glum

-my 3306pc is not what i would call a good starter for a diesel...i think the compression ratio is 15:1, on the lower end of the spectrum...
-on a 70F day, it cranks a LOT without glow plugs....and may not even start..
-20 seconds on glow plugs....it starts instantly...so in my books that's a pretty fair trade-off....

I wouldn't write off those glow plugs.
My climate is similar to yours, and unlike the DI 3304 and 3306's, those PC motors seem to like a bit of heat on their first start of the day. Not saying it is your problem, but is the quickest and easiest place to start.
Also, did you replace or have your injector capsules tested when you did the rebuild?

Thanks guys, I will try starting with the glow plugs to see if that helps.

And I will try introducing air into the system to check for leaks. Could be the primer pump as I used it for the first time in years.

Can you tell me whether I have a scroll pump or a sleeve pump? Serial no. 66d01651.

Hi waltini,
you have a scroll pump shown in your picture.

Been a while since I worked on one of these in situ-- also I suggest to check the spring and plunger in behind the the big nut to the top right of the filter housing, the plunger has a flat rubber seat that can deteriorate and can also get crud stuck in the rubber so preventing it from seating--the seat area can pit from rust too or fretting from rubbing by dirt embedded in the plunger seat rubber.
From memory, and I stand to be corrected, that it also acts as a non-return valve on the supply side of the system, if it leaks it can allow air into the system via a faulty bleed screw on top of the filter Hsg.
Cheers,
Eddie B.