Fuel Pump PSI

[Greg K]

Hi - I have a 1983 Ericson 35-3 with a Universal M30 marine diesel engine. The engine died while motoring to Catalina Island 2 weeks ago. After tracing the fuel delivery path from the fuel tank to the injectors, the failure point seemed to be the fuel pump because it was making a lot of unusual clanking noise.

So I replaced the old pump with a new one - Facet 476087N Fuel Pump 4-5.5 psi Maximum Pressure. That solved the problem and the engine runs well. But I noticed that while the engine is running, if I loosen the fuel line bleed screw (between the fuel filter and the injectors) just a little, the engine will die. I don't know if that is normal, and I wonder if I should have installed a fuel pump with a higher psi spec such as this one - Facet 476459N, Fuel Pump 6-8 psi Maximum Pressure.

Questions:
1) Do you know the proper fuel pump psi specification for a Universal M30 engine?
2) Would a 4-5.5 psi fuel pump or a 6-8 psi fuel pump be better for the Universal M30?

Thanks for your input on this.

 

[Loren Beach]

An admittedly quick look at this model on the web from a trusted vendor shows a flow rate up to 40 GPH. (Gasp!)
As for noise, our old OEM facet lift pump always made a clicking sound when operating, and this would start fast in tempo, and slow way down once pressure was reached.
Our mechanic once commented, when asked about lift pumps for our little diesels, that most any of them would provide more pressure than our engine would ever need.
One thing not mentioned in your trouble shooting efforts was the rest of the route from tank to high pressure pump on your engine. Have you replaced the OEM fuel lines from tank to filter to pump? All it takes is one little teeny invisible vacuum leak in the system to stop the engine. If, and I am just guessing, your engine was built out with a Racor three-part design series ( https://www.parker.com/static_content/parkerimages/Racor/7238 Rev D (200 Series).pdf )
Those earlier Racor's will often develop microscopic cracks in the housing, attachments, or just maddeningly-small leaks in either of their O rings.
I replaced ours with a **Racor 500 series to proactively solve this problem.

Keep us informed as you work thru this. I have had my (previous) engine quit once in the middle of a vacation, and it took me part of a day to narrow down the problem, and then plumb around the Racor and get the engine running again. (I ran the fuel supply directly to the spin-on filter on the Universal M25XP.)

**If interested, I have a blog entry detailing the changeover. https://ericsonyachts.org/ie/ubs/new-location-racor-lift-pump.682/

Welcome to the Viking ranks!

 

[Greg K]

Thank you very much for the thoughtful response!

In my troubleshooting of the fuel route from tank to high pressure pump to engine, what I did -
1) With the bad fuel pumped energized, I checked the bleed screw at the fuel injection pump. There was no air bubble or fuel when loosened.
2) Also checked the bleed screw at the secondary fuel filter (between fuel pump and engine). Same thing - no air bubble or fuel when loosened.
3) Checked the primary fuel filter ( I have a Racor 500 series filter), looked clean
4) Checked the secondary fuel filter, looked clean
5) Replaced the suspect old fuel pump with a new one (Facet 476087N Fuel Pump)
6) After replacing the fuel pump, the engine still could not turn over and stay on.
7) Checked the secondary fuel filter bleed screw again - no fuel and no air bubble still with new fuel pump running, suggesting the new pump was not delivering enough fuel.
5) I then decided to changed the primary filter just to see if it made a difference. It did! The secondary filter bleed screw now showed air bubble and then fuel when fuel pump was on. I was able to bleed all the air out.
6) The engine now started and stayed on.
7) I thought to myself - When I first replaced the fuel pump, I probably let too much fuel drain from the primary filter. So, the filter was not properly primed. When I replaced the filter later, I properly primed it in the process. The fuel pump was then able to deliver enough fuel pressure.

But.... after reading your response, I now question whether there was a tiny vacuum leak in the primary filter gasket that was the cause of the problem. When I replaced the filter, the gasket was also replaced. Thus, the problem was fixed. So whether it was a faulty fuel pump or a leak in the primary filter gasket, I may never know unless I put the old parts back in and test it. At least the problem seems to be resolved and the engine is running fine now.

 

[jtsai]

If your Racor primary filter is unknown of age, you may consider rebuilding the unit with their seal service kit for around $50. The check valve on my 500 series, which consisted of a SS ball resting on top of a cone-shaped seal developed a leak. The service kit solved my engine problem.

 

[Greg K]

If your Racor primary filter is unknown of age, you may consider rebuilding the unit with their seal service kit for around $50. The check valve on my 500 series, which consisted of a SS ball resting on top of a cone-shaped seal developed a leak. The service kit solved my engine problem.

Good to know. Thanks!

 

[Dave G.]

But I noticed that while the engine is running, if I loosen the fuel line bleed screw (between the fuel filter and the injectors) just a little, the engine will die.

That should/will happen no matter how much pressure you have. Any air/fuel leak in the system will cause failure. And as your troubleshooting process showed filter seals are a known culprit.

 

[Christian Williams]

I think we have all learned that if the diesel engine dies, it is in most cases a fuel supply issue. Clogged primary filter or, especially if recent work has been done, air in the line.

The devilish part is that the fuel pump creates suction to draw fuel from the filter, so upstream air leaks are invisible. Fanatical suspicion is the best tool--reseating of gaskets, lids, connections and so on, and bleeding. Racor 200 series especially develop hairline cracks in the casting after many years in a vibrating engine compartment, and have to be replaced.



The culprit on an M25.