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Old 03-07-2020, 02:21 PM   #1
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Need to bleed dumb mistake

I was replacing my FL 80 CAV secondary filters with new adapters for spin on filters yesterday and did a dumb thing. I went down to the boat and did other things while my new diesel heater got things warm. I got all the tools and parts ready (except for the NAPA 3361 filters that I didn't have) and removal and replacement of the old stuff went fine. Off to the local NAPA for filters. They had one. I needed two and there was one in the neighboring town. Off I went.

When at NAPA, I bought an old school oil can, filled it with clean diesel, and used that to top off the filters because my trigger pump is in an awkward position behind the oil filter. Filled the filters and the oil can quickly topped them off once spun on. I did trigger it a few times at the end just because I'd never used it. I thought it was strange that it seemed to make a sucking noise, like there was air clear down in the line at the pump. That should have been my warning.

Engine started, ran a bit, then died. I tried a couple more times and then figured that I had to bleed the lines at the injectors and was afraid to pull too much water in without shutting off the raw water intake. And I was getting cold. I noticed the diesel heater had shut down when I returned with my filters, but didn't think much about it. Then it dawned on me.

I had shut the fuel off at the tanks, but the diesel heater was on and was pulling all of the fuel out of the line to it and to the engine (because the line was open at the filter housing). When the 6 feet of line was empty after the heater had run about 4 hours, it shut off like it is supposed to. When I installed the filters and turned the tank back on, I had a 6 foot long bubble in the fuel line(s). Priming the heater was easy. Looks like I get a messy lesson in completely bleeding the engine system.

I just watched a YouTube video where the diesel fuel line and injectors where bled by using a vacuum pump on the return line. I have a big "sucking oil changer" that I have used on other boats and cars. Is it possible to simply suck the air/fuel out of the injector system this way? Bleeding the injector lines is messy, especially if working solo. Sucking on the return line sounds too easy.
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Old 03-07-2020, 02:58 PM   #2
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Possible but I think the high points like in the injection pump and secondary filters will still trap air. When bleeding the air out it will be mostly air and some fuel until its full. Put some oil sorbent sheets under the bleed points and have at it. And expect for it to stop at least once when the air bubbles shift around a bit.
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Old 03-08-2020, 08:02 AM   #3
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I have used the small hand pump built to pull fluid to service auto brakes to prime lines , or pressurize them to find a block or a leak.

Handy tool to have on board.

For rare use a simple outboard rubber fuel bulb is also handy.
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Old 03-08-2020, 08:17 AM   #4
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Check with a parts supplier like American Diesel to see the best way your engine is bled.

On Lehman 120s, one or two bleed screws on the injection pump are all that need to be loosened.
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Old 03-08-2020, 11:25 AM   #5
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Mighty vac 8500.
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Old 03-08-2020, 11:41 AM   #6
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Never tried to vacuum the air out of the line but although I guess it might work I really don't like the idea.pumping fluid IN to replace the air seems like the best option, tried and true.

Give it a try and let us know how it works. Just seems like a lot of work when pumping the lift pump a couple hundred times will give you results you can SEE.

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Old 03-08-2020, 07:53 PM   #7
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I came up with another Rube Goldberg scheme. My "new to me" boat has a rat's nest of fuel lines that includes a polishing system that uses a little fuel pump with a pressure sensor (no idea what pressure cut off is). I adjusted the various valves so that, instead of filtering from tank to tank, the fuel line to the engine was under pressure and ran my giant bubble out of the line without too much of a mess. It seemed like the little trigger pump might have been holding up the bubble, but not when under pressure from the pump.

I then bled everything by just cracking the top off bolts and fittings. Pulled the injector lines out and turned the engine over. Got fuel on two out of four and that was enough to get it running rough for 10-15 seconds and then settled down. Turned the raw water back on and ran for 15 minutes without a hiccup.

So my 20 minute project only took 4 hours. That's about right. Didn't get to try the suction idea. I noticed that my return line actually has a small section of clear tubing (not very clear anymore). No idea what the prior owner used it for, but maybe had I looked I would have seen bubbles going by.
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Old 03-09-2020, 04:53 AM   #8
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Apologies for being critical.
1st you did a good job converting your fuel filters to 'spin on' type, unfortunately you made a mistake in not fitting a 'push button pump' to the filter head. It makes child's play out of changing fuel filters and with practice you don't even need to bleed the engine after.
Go to www.asapsupplies.co.uk and look at their spin on conversions, you will see one filter head that incorporates the push button priming pump and see that you can buy the button priming pump separate, you will need the longer banjo bolt.
Once you fitted it, bleed the engine by pushing on the button pump with the heel of your hand as you try to start it. You may the first time have to loosen 2 injectors.
Thereafter when you wish to change the fuel filters start the engine and run until warm. Stop the engine and remove the filters, fill the new filters to the brim and refit carefully, start the engine and at the same time push the button pump vigorously with the heel of your hand. The engine may run lumpy for a 5 seconds but that's the job done. No more hassle.
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Old 03-09-2020, 05:04 AM   #9
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Again I urge.... make sure you need to loosen injectors for your type injection pump before making it a habit.

From some pictures of Lehman FL-80s, it looks like it has a similar injector pump to the FL-120s and might not need anything more than a screw or 2 loosened.

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Old 03-09-2020, 07:07 AM   #10
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"No idea what the prior owner used it for, but maybe had I looked I would have seen bubbles going by."


For a good installation a refrigeration shop will have an armored sight glass metal with a metal cover . not expensive.
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Old 03-09-2020, 09:59 AM   #11
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Quote:
Originally Posted by Irish Rambler View Post
you will see one filter head that incorporates the push button priming pump
I couldn't find the part, but I already have a little manual priming pump in the system. The problem was that I had a giant air lock from having emptied out the fuel line. I could push a little bubble of air/fuel with each manual pump stroke. It might have taken several hours of pumping. The electric pump still had its prime and did it in seconds.

Now that I think about it, I'm not sure that I could have pushed any bubbles out through the return line. I haven't chased where the return line actually returns, but maybe it is back to the fuel line and not to the tank? If so, there is no place for the bubbles to escape and they would return to cause problems again.

On a prior boat, the excess was returned to the fuel tank and I had to be careful not to return it to a tank that I wasn't using or it could over fill while the tank in use dropped quicker than expected.

Time for more sleuthing on my new boat. Another week and I may feel comfortable enough to leave the dock.
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