om602 Priming Fuel System - PeachParts Mercedes-Benz Forum

mcaro · #1 10-24-2011, 02:09 PM

I just replaced the injection pump on my om602 1991 300D 2.5 and wanted a way to streamline the fuel priming process to save the starter and battery.

I'm thinking of two methods.

1.) An in-line fuel primer bulb on the fuel feed before the primary/clear filter. I imagine this is like the primer on the om617 IPs. Will this work on the om602? Has anyone tried this?

2.) Turn the engine over by hand. Since the intake is off it wouldn't be that much work to remove the glow plugs to allow for easy rotations. Would this method work? Will it take an excessive amount of time being not high speed? Has anyone tried this?

Any other suggestions?

Thanks, MarkC.

NJ300sdl · #2 10-24-2011, 06:04 PM

I have used a outboard engine fuel line with primer bulb on a 300SDL (OM603). Works great.

compress ignite · #3 10-24-2011, 06:37 PM

A "Bulb" type squeeze primer in between the Hard Fuel line from the Tank and the Primary Fuel filter will fill the Primary and the Secondary Filter(Along with the Lift Pump and I.P.).
You could Crack Open all the Injector Hard Metal Lines At the Injectors,and SEE if the Bulb can Push Diesel to the Injectors.
Then all you'd have to do would be tighten the Hard line nuts @ the Injectors
Glow and Go.

(mine says Moeller on it.)
Moeller Marine Online - Primer Bulbs

Generally,people fill the Secondary with Uber-Clean Diesel,Crack the Injector line Nuts and spin the starter until fuel flows at the Injectors,Re-torque the Injector cap nuts.Glow and Go.

Biodiesel300TD · #4 10-24-2011, 06:50 PM

I don't think turning the engine over by hand will prime the IP. If it did it would take for ever.

You can try a mity-vac or other vac pump connected to the fuel return and pull fuel through. You'll need a vessel connected to your vac pump to catch the fuel as it comes out with the air.

layback40 · #5 10-24-2011, 06:55 PM

I often use low pressure compressed air.
Pull the fuel return line off the secondary pump. Put a container under the return outlet on the filter to catch any spilled diesel. Apply low pressure compressed air to the return line. You should hear air coming out the fuel tank breather. It will build a slight pressure in the tank. You will start to see bubbles come out the return outlet on the filter. When you have a stream of fuel. Quickly put the return line back on the outlet. Do not use a lot of pressure!! Dont worry if it takes a minute or 2 to purge.

mcaro · #6 10-26-2011, 08:04 PM

To close the loop on this thread I went with the primer bulb method as confirmed by CI and NJ300 because it made the most sense. West Marine was close to work and pulling the glow plugs really was reaching. I must say this is a great little trick for the om602 and om603 engines!! I put the primer bulb in-line starting at the metal fuel inlet in the engine bay and plugged the free end of fuel hose, with the primary filter, to the primer outlet and pumped away. I left the hard injector lines off the injectors but didn't get fuel there. After filling the lift pump and IP, I could see the bubbles disappear in the clear IP fuel lines while pumping, I didn't seem to be pushing fuel any longer using the primer bulb so I removed. I was okay with this, because again I had just replaced the injection pump, which was dry, and was dreading the constant crank, dead battery, crank cycle. Using this method, it took only 2 short cranking cycles and she fired up.

Thanks to all for the feedback!!

MarkC.