Bleeding Atomic M-15 fuel system

sapadeni · #1 (**permalink**) 03-31-2009

I am getting up the courage to finally change the fuel filters on my Universal Atomic M-15 diesel and was hoping someone on Sailnet had experience with this engine. I do all my own work and am pretty capable mechanically, I just can't find the procedure for my particular engine. I've read Nigel Calders Diesel manual and Mechanical and Electrical guide, but I'm still not clear on my engine's decompression lever (?). Any help would be greatly apprciated.

JimsCAL · #2 (**permalink**) 03-31-2009

I have a Universal 5411 which is essentially the same engine. I have changed the fuel filters many times and never had to bleed the fuel system afterwards. Just make sure you fill the filter (spin-on type) or filter housing with fuel before installation. The Universal manual does have the bleeding procedure in it should it be necessary. You can download the manual from the Catalina 30 owners website if you need it.

sapadeni · #3 (**permalink**) 04-01-2009

Thanks for taking the time to reply. I'll be changing out the filters this week.

SteveInMD · #4 (**permalink**) 04-01-2009

I think you should take the time to get a manual or that describes how to bleed the low pressure side and the high pressure side of the fuel system. If you introduce air into the low pressure side (for example by changing the filters) and you don't bleed the air out, there is a very good chance you will force air into the high pressure side of the system. Once you do that you will have to bleed the air out of that system as well. These are basic diesel skills and they are not hard to master. Practice in your slip. You will be glad you did someday when you have to bleed the system at sea. If you are unsure hire a mechanic to change the filters and show you how to bleed the system. It can be an enjoyable process to get to know your engine better.

The low pressure system is everything up to the inlet on the high pressure fuel pump. That is your final bleed point for the low pressure system. The high pressure system is the high pressure pump, the high pressure lines, and the injectors.

In very simple terms you will need to open the vent on top of the filter bracket, hold a cup or a rag to catch the excess fuel, then have someone turn to key to "on" (but don't crank the engine over) which should energize the electric fuel pump. They may have to cycle the key more than once. Turn the key off when you get clear fuel. Then close the vent screw. That's usually about it for a filter change. In some cases you need to bleed the air all the way at the last point mentioned above, the high pressure pump inlet.

Bleeding the high pressure system goes like this....

Bleed the low pressure system first. Then open the connection at each injector 1 full turn (open all of them). Turn the key on and crank the engine over until fuel spits from the loosened connectors. The engine cannot start like this so don't worry. Then firmly (these things run at 2,000 - 3,000 psi) re-tighten each connection. Then start it up!

BarryL · #5 (**permalink**) 04-01-2009

Hello,

Does your engine have an electrical or mechanical fuel pump?
Bleeding the fuel lines with an electric fuel pump is very easy.
Bleeding the fuel with a mechanical pump is not so easy.

My engine (Universal M25) has an electric pump. To bleed the
lines I energize the pump by turning the key to 'on' then I
open the fuel return line. The pump then circulates fuel (and
any air) from the fuel lines to the fuel tank. Any air gets
flushed out. After a minute or so I close the fuel return line
and the job is done.

With a mechanical fuel pump you need to crank the engine
to bleed the air.

BTW, I always have to bleed the air on my engine after I change the RACOR filter. If I don't, the engine will start, but then it dies after a few minutes and won't restart until the lines are bled.

Good luck,
Barry

SteveInMD · #6 (**permalink**) 04-01-2009

As BarryL said it's easy with en electric pump, as your motor should have. With an mechanical pump there is usually a lever on the pump which you move back and forth with a finger. So, you don't actually have to crank the engine.

Also as BarryL said, if you skip bleeding they low side after the filter change, you will often have to bleed the high pressure side too.