Volvo MD22L-B fuel dripping from air intake

[Rich Stidger]

So this issue started in the fall of 2022. I discovered a small amount of diesel that was absorbed into the pads under my engine. The pads were uniformly pink. I searched the entire engine for leaks with no results. I cleaned up the spill and put in new pads. A week or later I discovered that the pads were damp again with diesel. I wasn't surprised since I did not discover the source and hence had not fixed anything.
Every fuel joint was tight and dry. The fuel supply and return lines were dry. I did find that the drips were collecting on the bottom of the bell housing , but I could not find the source.
Until now......
I have found that a small pool of diesel (maybe 1/8-1/4 oz) is first collecting under the air intake. The edge of the bell housing is directly under the this air intake. Of course then it migrates to other spots under the engine. There is a hose that connects to what looks like a crankcase PVC device to the air intake.
So my question to all you gearheads here-
Why would fuel be dripping out of the air intake? And if the source is the PVC connection, why would there be fuel vapor in the crankcase? And even if there was fuel coming out of the crankcase, why wouldn't it be sucked into the engine intake and be burned?
This leak under the engine only seems to occur after the engine has been stopped.
Here are pictures of the air intake and the hose that connects to the PVC device.

 

[Rich Stidger]

I just had a thought- The fuel pump is driven from the camshaft and if there was a leak in the fuel diaphragm, that could let fuel into the crankcase. The oil level is not increasing but perhaps if the leak were small enough any fuel leak would be pulled off as a vapor to the air intake.
So if this were the case, and I am just conjecturing, why would fuel drip after the engine is stopped?

 

[JamesG161]

What kind of shaft seal to you have?

PYI or Stuffing?

Please stay with me , I may have your answer.

Jim...

 

[Rich Stidger]

Stuffing.

 

[JamesG161]

Stuffing.

My Bad, I missed the issue. I was thinking you got Diesel fuel in your oil sump.

But I am tracing the fuel flow now on my MD22 now.

Suspected spots.
1) The hand priming pump to bleed fuel to each injector.
2) No way to get diesel out of your Air intake.[that miss lead me]
3) If you have removed an injector, the brass washer may leak

Jim...

 

[JamesG161]

Here is my MD22L-A trouble shooting guide that may help.

Jim...

 

[Rich Stidger]

OK, Jim, I will ignore all of your posts on this thread.

I just had an idea on how to prove that the diesel fuel is coming from the air intake. I will take a small piece of absorption pad and tape it tightly to the bottom edge of the air intake. If any fuel is coming out of the intake it should be absorbed before it drips to the area under the engine. After the next run, I will check the pad for the answer.

 

[Ralph Johnstone]

I will take a small piece of absorption pad and tape it tightly to the bottom edge of the air intake. If any fuel is coming out of the intake it should be absorbed before it drips to the area under the engine.

My thoughts as I was first reading your description. Buuuuuuuuut, HOW is it coming from the air intake. That's the $64.00 question.

Please don't let it be coming from the air inlet. Please let it be coming from someplace easier.

 

[Rich Stidger]

UPDATE:
After a 4 hour run yesterday, there was a small pool of fuel under the bottom edge of the bell housing. This is where the fuel is obviously dripping from. The absorb pad that I had taped to the bottom of the air intake was dry. The upper area of the bell housing was dry, so I don't understand how the bottom edge can be wet and dripping without some evidence of the fuel leak located higher. I cleaned up everything.
This morning after sitting for 18 hours, there was the slightest amount of fuel (just enough to dampen a half sheet of a paper towel) on the opposite side of the engine from the air intake. This spot is located under the secondary fuel filter, but the filter, joints, and surrounding area are dry. The pad on the intake was still dry. So it looks like the source is not from the air intake.
CONCLUSION: The fuel isn't coming from the air intake, but I still can't identify the source. This is very frustrating. I'm stuck for as to what to do next.

 

[Ralph Johnstone]

This spot is located under the secondary fuel filter, but the filter, joints, and surrounding area are dry. The pad on the intake was still dry.

Experienced the same thing many, many tours ago. Wrap the secondary filter in paper towel and tape it up well. Then see if the bottom edge of the bell housing is wet again after a long run.

 

[JamesG161]

CONCLUSION: The fuel isn't coming from the air intake

Almost all diesel lines and connections are on that side of the engine.
_____

This spot is located under the secondary fuel filter

As you know, there are drain and bleed screws on that filter.

If you did not run your Engine, then it must be that filter.




Jim...

 

[Rich Stidger]

Almost all diesel lines and connections are on that side of the engine.
_____



As you know, there are drain and bleed screws on that filter.

If you did not run your Engine, then it must be that filter.

View attachment 217281


Jim...

The secondary filter is bone dry. I have run my hands over every inch of it and there is not even so much as an oily film on it. The bottom drain is tight and again no fuel is detected. Directly below the filter is the starter and it is dry as well. I just ran for 5 hours and the area under the secondary filter is dry, but there was a small amount under the bell housing and it ran forward into two small areas. It really appears that the drip point into the under-engine sump is from the bell housing.
But the actual source is still elusive.
I am going to wrap the secondary filter as @Ralph Johnstone suggests, but I'm not expecting to observe a different result.
Perhaps another clue:
When I first observed the fuel leak last year, the fuel tank was full. The top of the fuel tank is higher than the engine, so there would be some fuel pressure from the tank thru the supply hose to the lift pump. Then through the lift pump to the secondary filter and from the sec filter to the injection pump. At this point I am seeing a very small amount of fuel after running or overnight but my fuel tank is now just half full. Maybe the seepage only occures when the tank is near full? But I still haven't found the leak or a path to the bell housing.

 

[JamesG161]

This is from the Workshop manual.

My wild Azz guess, from your last description, is in Red Oval.

Jim...

PS: The bottom 2 injection tubes might work on your Fuel Tank level clue.

 

[Rich Stidger]

After an overnight, there were the slightest spots of fuel. In fact if I had my absorb sheets under the engine I would not have even noticed. The bottom of the bell housing was dry, and the towel wrapping the secondary fuel filter as suggested by @Ralph Johnstone was also dry. So i dried up all the spots and left the towel wrapped on the secondary filter.

@JamesG161 - as for your suggested leaking spots, all are completely dry- there is not even an oily film on any of the fittings.

I will be getting fuel soon, so we will see if a full tank changes what I see.

 

[Rich Stidger]

Latest update:
Last night I checked the return lines from the injectors based upon info I found on the web. The Banjo bolt was wet on 1,2,3 cylinders. #4 is hard to get to so I'm not sure of that one. So I pushed tissues around each of the return connections after drying off the banjos as best I could.

This morning I found the tissues on #1-3 to be damp and #4 damp too, but less so. I also found a small pool under the bell housing and a pool under the air intake. I think that the original source is the bell housing and the other spots are just where the fuel runs and settles after dripping off the bell housing.
So I am now thinking that the source are the return lines. Others on the net have found that to be the source of their leak. I still can't figure out how fuel gets to the bell housing, regardless of the original source. I can't find a path.
I have no spare copper washers for the return lines and I don't want to try softening the originals on my stove since I am on a cruise vacation to Maine. So I think I will just live with the situation and deal with it upon my return to my home port.

 

[JamesG161]

This morning I found the tissues on #1-3 to be damp

I keep this on my boat for quick fixes.



You can wrap the Banjo bolt with this. It is removable too.

Enjoy your cruise!
Jim...

 

[kappykaplan]

Rescue Tape, what a wonderful thing! I also keep several rolls on my boat.

 

[Rich Stidger]

UPDATE AGAIN:
After sitting on a mooring for 3 days with no engine running, I found a pool of fuel under the front of the engine (I will guess about 1/2 oz) and smaller pools at the aft end. The oil filter at the front felt like it was damp with fuel. The injector return lines banjo were damp, and the bottom of the bell housing was very wet with fuel. Still I cannot find a source or a path.

I am ordering a set of copper washers from Parts4Engines in the UK and I may order a fuel pump just for the hell of it.
I guess I will just keep mopping up the fuel until somehow the source of the leak is revealed to me.

 

[Ralph Johnstone]

In terms of size for a fuel leak, that's huge !

Maybe wrap every possible leak source with TP and check frequently to see who gets damp first ? Desperate times call for desperate measures.

 

[Rich Stidger]

In terms of size for a fuel leak, that's huge !

The leak appears to be continuous. The picture is after 3 days. Its much less after 1 day.

Maybe wrap every possible leak source with TP and check frequently to see who gets damp first ? Desperate times call for desperate measures.

I have wrapped the secondary filter and found it bone dry after a couple days. I have touched every pipe and hose connection and have detected no dampness except the fuel return lines on the injectors. I have put TP around the fuel return connections and found the tissue just barely damp- not dripping and not saturated.
The only spot where there are actual drips and a great deal of wetness is at the bottom edge of the bell housing. But I can't find a path.....

My current nightmare is that I will check one time and find 5 gallons of fuel sloshing.