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  #1  
Old 04-29-2008
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Universal M21, long story and fuel line question

Hello,

A few weeks ago I test ran the engine when the boat was on the hard. She started right up after sitting all winter. I noticed a fuel leak at the Racor water separator / fuel filter. As I wrote previously, a trip to West Marine solved the O - ring problem. After bleeding the air out, the engine started and ran fine.

This past weekend my boat was launched. I went down Saturday to move the boat from the marina to my mooring. I got on the boat and started the engine. Again, she started right up. I let the engine warm up while I checked the transmission (forward AND reverse), made sure the stuffing box didn't leak, checked the bilge pump, etc. After 5 minutes I felt confident the engine was running OK. So I cast off and motored about 1/4 mile to the town dock, so I could load sails and other gear.

The engine ran run and my wife met me at the dock and helped me tie up. As I was connecting a spring line, the engine, which was idling, just died. I was not able to restart it. It was very lucky that the boat was on the dock. It would not have been fun to have engine die when I was in the harbor, with no sails on the boat, etc.

Anyway, we forgot about the engine for the next two hours as we loaded gear, ran lines, etc. Then I tried to restart the engine. No go. It seemed like a fuel problem. I bled the lines at the fuel filter on the engine and got a steady stream of diesel. However, the engine would not run, it would get close to starting, and sputter a little, but would not stay running. The fuel pump was making a funny sound, not the usual ticking I expected to hear. I removed the output fuel line, and with the pump energized, only a trickle of fuel came out.

At this time I suspected the pump had died. Fortunately, the PO left a brand new spare pump on board, so I spent 20 minutes installing it. I bled the air from the fuel pump mounted on the engine, but the engine did not start, this time it wasn't even close.

That's when I gave up and went home.

That evening I read the factory service manual, which refers to bleeding air at the fuel filter and on the fuel injection pump. Unfortunately, the manual doesn't have any pictures. Sunday I went down to the boat. No air at the fuel filter. I could not find a bleed bolt on the injection pump. Then, reading the service manual more carefully, it mentions that the injection pump may have a 'self bleed return valve'. Ah ha, that's what I have. I energized the pump, opened the valve and then heard the pump tick as it moved fuel. I let it run for 30 seconds then closed the valve. After cranking for 15 seconds the engine roared to life.

I was now very happy. I let the engine run for 10 minutes, ran it up and down the rev range, in gear and out of gear. I stopped it and restarted it, no problem.

So I went up the beach, got my dingy, and rowed to the dock. I got back on the boat, and started the engine, which ran for 5 seconds and then died.

CRAP CRAP CRAP CRAP.

I repeated the 'self bleed return valve' trick, and the engine started right up.

So, after that long winded story, I get to my question:

It seems like I have an air leak somewhere. When I installed the new fuel pump I did not use any thread sealant. No fuel is leaking when the pump is running, but could air be getting into the lines when the pump is off?
Is it likely or possible that the o Ring on the racor water separator is bad? I don't see any signs of air in the bowl.

Any other ideas? I have ordered a replacement fuel pump and some new fuel lines b/c mine are very old. If I should use thread sealant, what do you recommend? I don't want to use teflon tape because I don't know how it would hold up to diesel fuel.

Lastly, there is a big bolt on the bottom of the fuel pump. Just to see what was inside, took the bottom off. I saw a small screen in there. Ah ha! That's what the filter in my maintenance kit is for! BTW, the screen was very clean, which is what I would expect because it is after the Racor with a 2micron filter. Still, I will change it as part of my normal maintenance.

Thanks for any suggestions.
Barry
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Old 04-29-2008
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Barry,
Geez... this sounds exactly like what I've been dealing with since last July. Every time I shut down the engine I need to bleed the fuel at the injecter before it will start. Once done it runs fine. I have been changing all my clamps trying to find where air might be getting in. I am about ready to buy a new fuel pump because everything else checked out. I have also considered putting a check-valve into the fuel line. I am as stumped as you are.
Mike
Sea Cliff

Last edited by mikeg516; 04-29-2008 at 12:21 PM.
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Old 04-29-2008
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The good news is you are becoming an expert on your fuel system, the bad news is, well, you had to do it the hard way and the engine is not working.

You appear to have air leaking in and going with the most likely cause I'd say a fractured hose or loose connection. I arrive at that point by using Peter Compton's (Trouble shooting Marine Diesel Engines) methodology (a good simple book by the way, I recommend it).

The first question, did you change anything, answer 'yes' - the filter and the now the pump. I assume you KNOW the pump is the right model to replace it with.

Second question 'did the change work' (fuel pump) answer 'yes' apparently and at first and 'no' not long term.

Third, what is in common - answer the hoses, and connections leads to his most likely 'answer' of a air leak in the hoses or the connections.

Nigel Calder would have you remove the diesel fuel overflow return line from where it enters the tank, put the now loose end into a bowl of fuel and run the pump, no air bubbles should show in the bowl/bucket. If you can get to the return line that is a valid check of the entire system. You can then move from there to the next connection and rig a method of checking it and so on back to the source.
Lastly, most automotive stores sell sealant specifically for diesel hose connections, save a few bucks and get what you need there.

Mike's check valve idea seems good, fuel would not be able to flow backwards sucking air into the system when the pump shuts down. I would suggest instead finding the source of air and eliminating it. Back flow should not happen as the pump is a suction pump, creating a vacuum.

My system (a westerbeke 30b) is self priming and self bleeding; it uses a solid state fuel pump that runs just like yours. I'm actually surprized you have to bleed at all, I never do. Assuming your pump comes on when you hit your preheater (glow plug) any air in the system caused by back flow should be pushed out and down the return line by on coming fuel - which comes back to what I think is the cause of your problems (both of you) - you have a air source in your system that is injecting air in while the pump is running.
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Old 04-29-2008
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Hello,

Thanks for the info / advice / sympathy.

Chuckles wrote:
My system (a westerbeke 30b) is self priming and self bleeding; it uses a solid state fuel pump that runs just like yours. I'm actually surprized you have to bleed at all, I never do. Assuming your pump comes on when you hit your preheater (glow plug) any air in the system caused by back flow should be pushed out and down the return line by on coming fuel - which comes back to what I think is the cause of your problems (both of you) - you have a air source in your system that is injecting air in while the pump is running.

The reason the fuel system needs to be bled is that
the pump is an 'on demand' type. When the pump is energized it pressurizes the fuel line to 5-6 psi (for the Facet pump I have) and then shuts down. When the injector pump runs it sucks fuel in, the pressure in the fuel lines drops, and the facet pump turns back on.

So when the engine is not running (or turning over) the fuel pump does not run and can't pump the air out. When you open the 'self bleed return valve' the fuel pump sends fuel back to the tank and the air gets bled.

I wonder what would happen if I left the return valve open a little?

Anway, my next course of action will be to change the fuel lines I messed with, and apply thread sealant to the hose to pump connections.

Barry
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Old 04-29-2008
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Quote:
Originally Posted by BarryL View Post
Hello,



The reason the fuel system needs to be bled is that
the pump is an 'on demand' type. When the pump is energized it pressurizes the fuel line to 5-6 psi (for the Facet pump I have) and then shuts down. When the injector pump runs it sucks fuel in, the pressure in the fuel lines drops, and the facet pump turns back on.

So when the engine is not running (or turning over) the fuel pump does not run and can't pump the air out. When you open the 'self bleed return valve' the fuel pump sends fuel back to the tank and the air gets bled.

I wonder what would happen if I left the return valve open a little?

Anway, my next course of action will be to change the fuel lines I messed with, and apply thread sealant to the hose to pump connections.

Barry
Barry,
my pump runs all the time at the same PSI as yours, or about 25 -30 gals a hour. My WB30 uses 1.2 gals at full RPM, the extra is ALWAYS returned to the tank - what you are describing as the 'self bleed return valve' being open is my normal operating position.
For a secondary benefit, my fuel tank is essentially polished every hour.
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Old 04-29-2008
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I don't recall any return line on my fuel pump. There is simply a lead in from the fuel tank and lead out to the engine. There is a racor fuel/water serperator and filter between the tank and the the pump. There is also a spin on fuel filter at the engine. I have some clear tubing I can use temporarily to check for air. I think that is what I will try next. I am really hesitant to replace what seems to be a working pump until I've exhausted all other possibilities.
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Old 04-29-2008
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Too weird.

I have the exact same symptoms on my Universal M4-30. SAME SAME SAME symptoms. Reading posts above is like I having deja-vu . I had already ordered replacement fuel lines prior to reading this. I was about to take apart my 'lift pump' this evening to see if anything was amiss there. One point of interest, when my engine died underway, I was able to bleed visible air bubbles out of the fuel line at the engine's injector pump. On the M4-30 there's a bleeder bold that showed signs of air when the ignition was on (with pump running continuously) and the engine not running.

I too was assuming the cause was 'air in the line' either being sucked in anew or left over from doing a thorough cleaning of the primary racor filter/separator back at the tank. But the engine died a few more times on the way in, and required a few more 'bleed the bolt' efforts to get to the dock - not a very enjoyable ride in.

Furthermore, the M4-30 is supposed to be a 'no bleed needed' engine, but I've found that any time I interrupt the feed, bleeding get's me going fasting than cranking.

I will post my results after complete fuel line replacement and lift-pump diagnostics.

Good luck you guys.

Final thought: Could there be a common cause? Diesel additives have had a lot of press lately. Thoughts?
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Old 04-29-2008
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Maybe a air leak between the tank and pump/filter, very hard to find. Fuel goes into the tank when shut off and then the pump sucks air at start up.
Check the inlet hose fitting at the intake side of the pump after that it should be all pressure and you can detect a leak.
Permatex #2 is good to seal most every thing but alchol and there is no waiting.
DO NOT USE #1 IF YOU EVER WANT TO TAKE IT APART.
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Old 04-29-2008
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A reason you do not want to use teflon tape on anything that has small valves or orfices is that it tends to leave strings that may clog them.
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Barry,

I've had on two different occasions, very similar symptoms you discribe, on two different boats. If I understand correctly, you found that you have no evidence of air at the main fuel filter (after bleeding)and when the system is free of air, the injector pump does it's job well. At least until air is again injected into the system. So...it sounds as if air is being introduced somewhere between the main filter and before or at the intake of the injector pump.

I think if the fuel lines are as old as you say, new ones are not a bad decision. While waiting for their arrival, I would break out the wrenches and check all line fittings between the main filter to, and including the inlet line fitting of the injector pump. It doesn't take much for air to be introduced into these fittings, so a physical check is needed to insure proper torque. If you find any of these fittings even slightly loose, back off the torque and retighten. This usually will insure any debris or maybe a small burr will be eliminated and no air can bypass. An old aircraft high pressure line trick.

After that procedure and if the same symptoms still ocur, another problem I've found, is the bleed pump. With age, sometimes the diaphram inside will develope a small pinhole and introduce air into the system. A good check is to get the air out as you have done, shut the engine down and check for good resistance when operating the bleed pump. If little resistance is felt, you may very well have a bad pump. Another easy way to find out is to pump this finger torturing device for about 30 seconds (quick pumps) and then try to start the engine. If the pump has a hole in the diaphram, the engine will start and then die in a few seconds.

The loose fitting scenario was a Yanmar 30gmf and the latter was a Perkins 4-108. Different engines, same principles and probably worth a try. Hope this helps and good luck.

Bob

Last edited by fullkeel7; 04-29-2008 at 10:28 PM.
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