Volvo EC160BLC air in the fuel.....?

I have posted on here before about my Volvo 160 and FwF (along with others) helped me a lot with a swing motor issue and setting pressures on my new thumb.
My machine has been running great but now I have developed an issue that is related to fuel delivery. The machine starts right up and runs well but after several hours on Saturday the RPMs noticeably declined and it finally coughed to a stop after about 15 seconds. We thought for sure that the fuel filter was clogged (not completely clear on the maintenance the previous owner performed) but after draining some fuel out of the bottom of the fuel/water separator and then taking the fuel filter off and pouring all of the fuel out of it......there was not a bit of debris in the clear container we poured it into. We put things back together and she wouldn't start so I bled the injectors and she fired right up and ran the rest of the afternoon. On Sunday it did the identical thing after running for several hours but as it was coughing to a stop I turn the throttle to maximum. It coughed for about 30 seconds and then took off and ran fine the rest of the day.
My theory is that I have a very small leak in the vacuum part of the fuel system (from the tank through the separator to the injection pump). For whatever reason the air slowly leaks in and then when it gets a certain amount that air pocket is released to the injectors causing enough of an issue that it can stall the machine. Once bled out (or pushed through in the second situation) it runs fine for another 3 or 4 hours. If I had to guess I would think the small leak is in the separator or the rubber plunger on the top of the separator. Why it gathers the air then sends it though all at once - I'm not sure. Maybe the tilt of the machine....?
I'm looking for some encouragement with my theory or alternate theories/ideas on what this could be. Because it only happened twice I really don't know if it is more prevalent with a full tank of fuel or only after it gets low. The first time it happened on Saturday I was slightly below half a tank and on Sunday I was at about 1/4 tank.
BTW - this is the first tank of fuel that I have put through my machine (I just bought it last year and worked this winter on fixing all the small things).

Thanks, Scott

Good day U M
This machine was originally equiped with the Separ pre filter & water trap due to issues was later replaced by the same unit fitted to the other Volvo products. In extrem case's the common rail releif valve can open early you can easily check it out by nipping the return line. Attached some more information that may help.
Kind regards
Uffex

Fuel pump will deliver between 45-70 psi. Not the 700 shown.
Look at your fuel supply line, many of the earlier production machines had lines that were very susceptible to dry rot cracking. Some as little as 2 years. I always recommend replacing these rubber lines with parker push lok. When it comes to hoses with the banjo ends, I just carefully cut the crimp band and put the end into my new hose.
The diaphragm pump on top of the filter, if you can prime with it, odds are it isn't leaking.
Another thing to consider is a piece of trash in the tank blocking your sump strainer. Inside the tank at the bottom, is a stainless standpipe with a strainer. That should keep large debris from ever hitting your fuel separator.
Lastly is the overflow valve. They are known to get weak over time. The excavator fuel pump is really strong and reliable. Unless you see/smell fuel leaking at/around the pump, odds are, it's not your problem.
One last thing that comes to mind, is your fuel turning dark? This could be an indicator of combustion gases escaping into the fuel system.
Good luck

If you have this pre filter I recommend replaceing with a later type.
Kind regards
Uffex

Uffex / FwF -

Thanks for your help (again).

Combining your posts - does the following make sense? First I use my remote Bluetooth camera I have that comes up on the display of my cell phone to inspect the inside of the tank and look for debris - most likely a rag that may cause my issues if it wraps around the intake screen. Assuming I do not find anything next I replace the vacuum lines from the fuel pump back to the separator and then from the separator to the fuel tank looking for areas of dry cracking. If I am still experiencing the issue I replace the fuel/water separator assembly with the newer model.

I'm assuming the new model separator model is available at Volvo or is it aftermarket? Also - does it come with a primer? It is hard to tell from the image above.


Thanks,

Scott

FwF -

I do not believe my off-road fuel is any darker than normal. When I drained the fuel filter and looked at the fuel thru a clear plastic container it was the normal (dyed) shade of red just slightly lighter than cranberry juice. I believe it is very close to the color of other diesel fuel that I have seen in the past.

Thanks,

Scott

Uffex -

I am hoping I did not misunderstand your recommendation but from reading through your post and the attachment it almost looked like you were describing an issue that caused a starting issue rather than an issue that happens when in normal operation. My machine starts right up every time no problem. The issue I am having is when it is running for several hours it just seems to develop an air pocket and, for whatever reason, sends it to the injectors all at once stalling (or nearly stalling) the machine. Then once I get it going again it is good for the rest of the day and into the next day.

Did I misunderstand your post?


Thanks,

Scott

Only the very earliest made it to America with those slurry bowls attached. You have a serviceable cartridge. Beyond that, if you swing the house 90* to the tracks, you should be able to drain your fuel into storage, and remove the lower manhole cover. From there , you can see and clean everything.
One thing I forgot to mention. The fit of the bowl to the cartridge filter is very critical. Volvos really don't like to play well with others. Stick with factory filters. Can't explain it, just know it for fact. And the camera idea is pretty solid.
Hope this helps .

I believe the cartridge currently installed on my separator is a WIX filter. I will look to order an original Volvo separator cartridge.

Do you still recommend replacing the vacuum fuel lines or take one thing at a time?

Thanks,

Scott

One thing at a time. ,but BUT you should still physically inspect your hoses for damage and cracking.

FWF is spot on with his recommendations. I would look first at draining and cleaning the tank given your complaint. And as he said as long as you are there replace the hoses from the tank to the feed pump.
This is not a high pressure common rail system but one with six individual unit pumps. If the machine had been run with contaminated fuel for an extended length of time it could also have contamination in the unit injectors. there are small screens behind the plate on on the back side of the unit pumps that can be carefully removed and cleaned if found dirty. But this is only after you have cleaned the entire system, verified fuel pressure and checked for air intrusion.

Good day this may clear up any questions.
Kind regards
Uffex

Errors corrected appoliges for any inconvienence.
Uffex

Hey guys -

Sorry for the delay on this response. Here is what I found (and hope this was the problem):
The fuel and the tank look fine - I don't believe I had any issues there. The lines actually look decent with little to no cracking.....HOWEVER....when I was inspecting the lines at the fuel/water separator connections and at the fuel pump connection in all cases I could easily spin the fuel lines with just two fingers at the connections. This being the case IMO they could have easily been sucking air especially with lower fuel levels in the tank (which is when my issue acted up). I think the hose wall of the rubber lines shrunk over time. I simply tightened the hose clamps by several turns and they feel good now. Along with this I also found that the vent plug on the top of the fuel/water separator was "metal on metal"....meaning there was no type of gasket to seal that plug. I found a good fitting O-ring in my kit and put it on which gave it a great seal.
I have run the machine but not a lot so I cannot say for sure if I got the issue but so far so good.
Thanks for the help on this. I will add more comments to this post if the issue comes back.
I do have another issue now with the machine but will start a new post as it is a hydraulic issue not related to the fuel system. Hopefully you guys will be up to offering me some advice (again) to point me in the right direction on that issue.
Thanks, Scott