Diesel engine bleeding

martinriches

martinriches

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I changed the secondry filter and cleaned the primary filter today.I followed the instructions in the manuel about bleeding but I cant get any fuel into the secondry filter despite pressing the lift lever about 100 times.Fuel is going into the lift pump I just cant get it to go out the other side.I am sure it is something simple that I haven't done.

any help would be great.
 
Is there a vent bolt near the filter that you have to undo to allow the air out of the system? My yanmar has one. After the filter is full then you will have to crack the injector lines one at a time and keep pumping till all the air is out of them as well. If your filter doesn't have the vent then you may need to go directly to cracking the injectors loose.
 
You haven't said what engine, so guessing at priming lever on the lift pump?? If so cam may be in wrong position not allowing full stroke. Turn the crank 1 complete revolution and try again.
 
I have never has to crack the injector lines on a Yanmar to bleed it. If the injector lines haven't been disturbed, fuel should reamin in them and the lift pump should pass any air through the injector spill line back to the tank.

It can be difficult to get a primary filter to fill using the lift pump manually aloneif it is in a high position above the tank . Some Racor filter units have a manual lift pump built in to get over this. However, I have found the best solution is to replace the primary filter element/bowl as full of clean diesel as possible without spillage. Then remove the bleed bolt at the top and top up the filter unit as full as possible. I also put the engine filter element on filled with diesel and as a result very few lift pump strokes are required to get pure fuel coming out of the filter bleed screws. Once this is achieved and the bleed screws tightened I hand pump more to expell any air down the injector spill line and then engine fires immediately.
 
Duh! which engine? which make of filters etc. A little basic info might help the erudite authorities to diagnose your problem and offer practical advise on a cure!
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I have never has to crack the injector lines on a Yanmar to bleed it.

[/ QUOTE ]

So be it. We have, however, had air enter our system through the external Raycor when servicing it and followed the detailed intructions in our factory manual resulting in the motor starting instantly. Previous attempts omitting bleeding the injector lines resulted in a hot starter, dead battery and frustration from cranking the air out without much success.

I trust my manual, besides, you can't argue with results.
 
I agree with Oldhand regarding Racor Filters. Only its not just the Racor ones that are difficult to fill with fuel using the lift pump either.

I have had several boats where it was quicker to put a clamp on the fuel tank breather pipe to seal it and blow (or pump with the dinghy pump) into the tank filler to force the fuel round and into the primary filter, than sit there all day pumping away on the fuel pump on the engine. Some fuel pumps seem to be very poor at 'pumping air' to draw the fuel through from the tank to the primary filter and ultimately to the pump itself.

My experience is that once the fuel is through to the lift pump, you are 90% there.

Furthermore IMHO you can almost certainly disregard bleeding the injectors. I can only remember one engine in the last 25 year which needed the fuel bled up to the injectors and that was a Perkins. All the Yanmars and Volvos and others that I have had to bleed have started as soon as you bled the fuel up to the injector pump.

The three basic places that you need to bleed fuel through to are:

1. Primary filter
2. Secondary filter
3. Fuel injection pump.

A little inspection should find bleed screws (or bolts) on all of these places.

Think logically and follow the fuel through and you will get there...
 
Hi, not suggesting this is the first time you've bled it, but the first time i bled our volvo 2003, I was using the lift pump wrong, you have to press the lever a long way till it really bottoms out, and can then use a shorter stroke by not letting it fully come back into position to continue... not sure how clear this will sound, but make sure you were bottoming out the lever. Good luck.
 
If it's a Volvo 2001 or maybe one of the other 200 series engines, then you may have the same problem as me - a knackered lift pump that sucks as much fuel back on the release stroke as it pumps on the pump stroke.
 
might be a silly one - did you turn the fuel tap back on after changing the first filter ??
also make sure the bleed bolts are well loose on the engine filter(s). some lift pumps are not very clever - had to pump one for twenty minutes to get all the filters running properly. once the engine filter bleed hole is running clear fuel with no bubbles, nip it up and open the bleed screw on the injection pump itself (if it has one). you shouldn't need to bleed individual injectors unless you have teken the pipes off the injectors - the pressure generated by the injection pump itself will clear them out after a few revs on the starter
 
Undoing a couple of injector pipes will bleed the whole system. It's very quick, especially on a rolling boat. Better if fuel fillters are filled first. But it will start eventually. Even better with twin engines to ensure you dont flatten batteries. It might not be the recomended way, but quick and simple, with no crawling about hot and inaccessable places.
 
On my previous boat which had a Beta , the primary filter, a fairly standard Cav type, was fairly low down. I had a situation which had several of the chaps at the sailing club bewildered. The filter wouldn't fill, and the fuel just bypassed it and the engine kept running !! Everything was connected correctly. The only way to get it to fill in the end was to crack the fuel out line till it filled then reconnect it.
 
LeonF
If it's doing that, I don't see how it can be filtering the fuel. It hasn't got 4 entry/exit ports on top has it? You may have chosen 2 entry or 2 exit ports thus bypassing the filter itself...
 
Is this a wind up? IMHO you are just plain wrong! Undoing a couple of injectors and spinning the engine over will NOT bleed the fuel system. In fact, unltimately, spinning the engine over without fuel through to the injector pump will damage it. The injector pump relies on the fuel to lubricate its extremely high tolerence clearances.

Why post things that people without any engineering or mechanical knowledge might believe?
 
Would not post it if it was not the only method I've used for years and many other folk do to. Especially mechanics.Not saying it's the most politically corect method, just very effective.

Now, you were saying about engineering???
 
Pay your money and take your choice. There are many yacht engines I have bled that would have destroyed the starter motor and got through several batteries before they bled successfully that way if ever!

And I will stand by the engineering principles. Diesel injector pumps rely on the fuel to lubricate them.

And starters are not designed to be run for lengthy periods and yes I used to build them!
 
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