Struggling to find the problem - air within fuel system?

[patrscoe]

Like to get some input on any possible issues. I have read through past threads but did not find a path to my problem.

History:
- Last Year Late Summer / Early Fall; out of the blue, my engine would not start with no sign of issues. I ended up bleeding the fuel and notice air bubbles so I kept trying to track down the leak. Eventually I could get it running but the air bleed curling knob had to be partially open but when motoring, it would loose power and stall out; mainly due to that I was starving the engine with fuel as the curling knob was directing fuel back to the tank, as designed. After several days over a few weeks, I notice when I slightly pushed on a fuel line from the secondary filter to the injector pump, diesel would spray out within a finest pin hole. I replaced the small fuel line and it ran for a few weeks until I winterized / hauled out.
- Last week during my spring launch, my engine would not start. long and short, I tracked down a leak at the tank copper connection tube to the tank, as it was crinkled and was dripping fuel. Looked like the hole that was put in the plywood bulkhead near the tank was too small and the line pushed on the small opening and developed a leak. I removed the copper line and associated fittings and replaced with a rubber fuel line running from the tank to the Racor fuel filter. Bleed the system at the secondary filter, at the curling knob by removing the nut and ultimately, I had to also crack one of the injector nuts. got it to start and motored to my marina, 3 hours away and ran fine.
- Now. This past weekend, I attempted to start the engine and did not start nor did it even tried. Just turned over. So I went back through the fuel system and notice that the hose clamps that I put on the day I splashed and worked on it into the night, was just slightly too large (solid band type clamps) and did not create a tight fitting. I said... ok, so I installed new hose clamps and checked all other connections and all seem good.
I bled the air from the fuel system. First bleed bolt at the secondary filter came out like a shot - did not see air bubbles.
Second bleed bolt at the curling knob, removed the nut where it connects as the curling knob does not work great for bleeding, fuel came out.
Did not start.
Loosen the top and first injector nut, fuel was dripping out (with the fuel pump on).
Did not start.

Because the first bleed bolt at the secondary fuel filter came out with no bubbles and came out like a shot, I am ruling out leak in the first fuel filter, pump and anything behind this point.
When turning the engine over this last time, it would just turn over without any firing attempt.

Any thoughts, input, ideas....? Perhaps I hit something, could there be something else going on here...

 

[patrscoe]

I have the stock Universal M25 XP.

 

[Dave G.]

Obviously still have air somewhere, hard to speculate from afar other than recheck everything and bleed it all again. If that doesn't work may need to check the high pressure injector pump output.

 

[Frank Langer]

This is puzzling, but you've done a pretty good job finding the various leaks, and problem solving. You seem to know how to fix any leaks / air entry in your fuel system, so if you've really checked them carefully, Save may be right that its a problem with the injectors or injection pump.
The only other thing that comes to mind is whether your glow plugs, or whatever you use to preheat the engine when starting, are faulty. It's a long shot, as most likely it's still air somewhere in the system.
Frank

 

[gabriel]

have you checked the condition of your fuel\tank and replaced fuel filters first?

 

[patrscoe]

yes... Very puzzling and frustrating. A lot of time invested into troubleshooting this and feel like I am back to square one.
When I was troubleshooting this in the late fall, I also thought it was potentially the glow plugs and replaced them with after-market gp and it didn't make a difference. I also tested them to make sure they were working.

I was thinking that only thing left is the injectors or injector pump, but when the engine ran just last week, it did not skip and ran quite strong in a terrible head wind all the way to the marina for 3 hours. So it was a surprise this past weekend when I was unable to just start the engine right up.
Besides skipping and running poorly, I am not sure what else would be the symptoms of a clogged or bad injector. If it was one clogged or bad injector (seems unlikely that all 3 would be bad) I would think that it would still start and run, just run rough and skip but that is not the case.

Fuel was left over from the winter and fuel filters were changed during the troubleshooting in the fall so they are still fairly good.
I also cleaned the tank through a access port I made earlier last year. I was thinking that too, old fuel but the engine ran really well in the 3 hours of motoring.

I spoke to the marina's mechanic and he basically ran down the same things I did. Perhaps I am missing something or missed a glaring issue. My conversation with the mechanic was me attempting to give up and ask for some services and input but they are slammed right now.

 

[gabriel]

and how many hours on the engine?

 

[Dave G.]

I would do an extended bleed session on both bleeder valves just to make sure there isn't any air pockets.

 

[Jerry VB]

Did you verify (at the engine) that your fuel shutoff for stopping the engine is not activated? The last thing you did before the engine stopped running was pull the fuel shutoff.

Long shot: verify the decompression lever is not activated.

 

[Dave G.]

On the knurled knob bleeder I think there is also a retaining nut for that knob ? If so make sure it is seated and tight.

 

[patrscoe]

Knurled knob bleeder is where I bled the air but I will check to see if the nut and where the fuel line comes in is seated correctly.

jerry; good points and I was thinking of this on the way home from work that I have been all over the engine and my body or arm could have hit the depression lever. I believe it is towards the back of the engine and clicks up and down. Also I am going to look at the engine stop lever to see if I hit that too.
Yup, I was thinking of bleeding the air out for a extended amount of time. My thought there is that the last line replaced was the main fuel line that comes from the tank to the primary filter. Long run and would have a good distance of air if the fuel went back down to the tank.
I am making a list of tasks and will check them off so I can keep track of what I have done. At some point, after going through all these and still is sucking in air, I will start creating bypasses i.e. bypass the primary and secondary filter to help isolate the problem.

 

[Kenneth K]

Somewhat related: I have a temporary plastic diesel tank installed while my aluminum tank is out. I too have a small leak somewhere in the temporary system that I tolerate until the main tank goes back in. Here's the way I see it.

A "vacuum" leak (air entering the fuel system) can likely only occur in two ways:

1) A loose fitting or small hole in the "suction" side of the system (between the pickup in the tank and the inlet of the fuel pump). This type "vacuum" leak only occurs when the pump is running and creating suction.

Or, 2) a loose fitting or small hole in the "pressure" side of the system (between the fuel pump outlet and the injector pump AND only when the pump is not running and pressurizing the fuel lines. This type "vacuum" leak will only show up after the engine has been sitting shutdown for a long period and the force of gravity on the fuel in the lines causes it to recede and draw air into the hoses as it does.

The fix for the second type leak is to open the bleed "curling" knob fully for 3-5 minutes before engine start (to purge air from the lines). You should be able to hear and/or see fuel from the return line dribbling back into the tank. After purging, any leak in the "pressure" side will result in fuel spraying outward, not air seeping inward, so the bleed curling knob can be closed after the engine is started.

The fix for the first type leak is again, to leave the curling knob fully open 3-5 min before start (to purge the lines), but then to leave it open just a crack (1/16th of a turn maybe) while the engine is running. The valve must be kept open a crack because a leak in the "suction" side will continue the whole time the fuel pump is running. If you open the knob too far, the engine will idle ok but will begin to stall out at higher rpms.

I have the first type leak, and the above has been working for me.

 

[patrscoe]

That all makes sense. Now I just need to track it down without replacing the entire fuel system and components, which is getting to that point.

 

[Christian Williams]

It's easy to bleed each individual injector. There was a marvelous video on how-to by SErvice Department Vic of Orange Tractors, but for some (no doubt complicated) reason all his videos have been removed from YouTube. Here is the Kubota technique he demonstrated:

Apparently air can get trapped between the injector pump and the injectors. To bleed that, loosen the nut that holds the steel fuel pipe atop each injector, one injector at a time. You don't have to remove the nut, just loosen enough to be able to pull the pipe flange up a little, so it will leak.

Have somebody crank the engine for 10 seconds with the raw water turned off. The starter motor is required to prime the injectors, an electric fuel pump can't do it. That is, the injector pump only works if the engine is turning over.

Fuel will spurt out under the loosened nut--along with any air trapped in the injector pipes. Loosen and bleed each injector pipe. Then tighten back down. Wipe up the small amount of diesel with a rag.

The engine may start as you're doing this, which is fine (but now open the raw water intake you closed).

I later discovered I could bleed the injectors without help: Loosen the fuel lines, go to the cockpit and turn over the engine for the count of 10, then return below, re-tighten the connections, wipe up the bled diesel on top of the engine.

This technique is mostly for bleeding after replacing injectors. But Service Department Vic said it often solves any air-in-system problem.

 

[Kevin A Wright]

Real suspicious that it won't even try to start. The first 2 things I'd check is if the fuel shut off is fully in the proper position (check it on the engine and not just at the toggle). Second I believe your engine also has a decompression lever. You might have knocked that open while you were working in there?

The last suggestion if you are looking for an air leak is the one I just found after months of searching. The fuel pickup tube inside the fuel tank on my '86 E35-3 had a plastic drop leg to the bottom of the tank just press fit onto the fitting at the top of the tank. The plastic had gotten hard and lost its seal Was sucking air in above the level of the fuel in the tank. It was pretty easy to just remove the screws and pull out the fuel pickup tube, but to find it had started to use a 5 gal jerry can of diesel to isolate each filter, etc. Hint, also run the fuel return line back into the jug, it will last a lot longer that way.

Good luck!

Kevin Wright
E35 Hydro Therapy

 

[supersailor]

Have you checked to be sure your glow plugs are working?

 

[patrscoe]

Yea, I know. Running great and then does not even try to start. Just turns over.
I was also wondering if I potentially hit the decompression lever but I have not idea what position it should be in. It seems like that the arm could be turned to the left (facing the engine) and it clicks while almost horiz. It could also turn / rotate to the right where the small arm unclicks and can almost be upright 90 degrees. No clue what position is decompression or not. I try finding it in the manual but does not show you what position it should be in.
My body and arms was all the side and back of the engine, changing the main fuel line, etc...but I did not touch it from the time I splashed and motored over to the marina.

I am not sure if the engine stop lever is in the right position. I would think so as I never had a issue with it but I am going to check this weekend.

Yes, glow plugs work and I replaced them last fall when this all started. I saw a post from Christian and how easy and economical it was.
Ordered them online and easy to install. Tested them and they all work.

This weekend I am going to start from the beginning and run through the entire fuel system. Check hoses, connections, re-tighten clamps, replace two older clamps that might be in question, etc... and then bleed the system again but as suggested in this thread, take my time on bleeding each area to ensure that is not a air pocket. Also cracking each injector.
Then see if it starts. If it does, I will let it run and take it out and bring it back. Restart it later in the day to see if it held it's prime.
If it does not start, I will start to bypass certain areas and potentially run new fuel through a jerry-rig system. I guess keep trying and cross off any potential issue. Seems like it should be simpler than this but what can you do.

 

[Kenneth K]

M-25 decompression lever should be spring- loaded to the counterclockwise position (as you face the stern, looking at the front of the engine) for normal operation. To keep mine in the de-compression (clockwise) position, I have to hold it by hand or by a piece of wire to hold it open against the spring tension. I do this every once in a while to turn the engine over a few rotations if it hasn't been started in a while.

 

[patrscoe]

ok. my spring is not a in a position where it holds it in either position. I do believe the though it is in the position you have shown in your image.
Because of that, perhaps it lifted up. I will check.
Thanks Ken, image and notes was very helpful.

 

[patrscoe]

Update:
Today, I made a check list and checked every connection and hose within my fuel system, bled the air at multiple locations, checked the decompression lever and engine stop fuel lever position and fuction.
I checked the decompression lever (which I noted below) and engine stop lever. When bleeding the air out, I did not see any noticeable air but I ran the process extra long and also ran the bleeder valve open prior to this for 5 minutes.
Once I finish with everything, I attempted to start the engine and it took a about 10 seconds and two attempts but the engine started and ran. I restarted 30 minutes later and multiple times after that and on the restarts, engine started immediately. Also let it run and motored out and in my dock slip.

Not sure if I pin point the problem but it seemed run well and on my restarts, it started immediately. The noted the following items:
- Decompression lever was over near the 'normal' position per Ken's image (thanks Ken, that was helpful). My spring does not push the lever all the way in the normal position and you need to push the arm so it 'clicks' once it is all the way in this position. I found the arm just above that 'normal' position (about an 1") but not all the way over in the decompression position (which I don't think it could get to that 90 degree angle with the spring). I pushed it down so the arm 'clicked' into place.
- Although I found no air bubbles or at least nothing noticeable, I did not find a flat type hose clamp maxed out on the main fuel from the tank. Another words, it would not tighten up anymore and the hose was not super loose but I could twist the hose by hand. This was on one of the new fuel lines I changed just before I motored over to the marina last week. I replaced the hose clamp with the correct size and re-tighten.
That's all I found.

So I am thinking it was partially the decompression lever, too large of a hose clamp that maybe put air in on the suck side of the system, potentially old fuel from mid last year which probably makes things start a little harder, and a more complete and longer air bleeding process. Maybe all of the above contributed.
I am going to swing by the sailboat mid-week and see if it still starts up. Hopefully it is resolved.

Thanks for everyone's input and suggestions!