Quote:
Originally Posted by JimSmith
This is an interesting question. For the most part visible bubbles are in the low pressure side of the fuel system as the plastic lines are not high pressure lines, and are not an indication of any potential trouble for the injection pump. In the high pressure side of the fuel system, those atmospheric bubbles will be collapsed and not noticed by either the pump or the injectors. If the engine starts fine, and runs fine, that is an indication that the high pressure side of the system is solid, at pressure. With enough air in the system at pressure to cause a problem for the longevity of the injection pump, I doubt the engine would run at all.
In my experience there is always a series of bubbles in the clear lines, they just don't fill the entire cross section of the insides of the lines at any particular point. When you say you have a leak, are you seeing Diesel leak out, or are you just concerned about these bubbles?
The flow rates of Diesel through the fuel lines is pretty slow in terms of feet per second or meters per second. Which means it is a task for the system to drag bubbles anywhere. If you want to try to eliminate the bubbles it might be good to take it out for an "Italian tune-up" and drive WOT up a hill for a few minutes to try to up the fuel flow rates. Someone more familiar with the routing of the lines may be able to provide a sequence to close them up or specific instructions for venting.
The owner's manual typically instructs you to crank the starter on these later models to clear the air in the lines after running out of fuel or opening the system and letting air inside. That is typically all I do, and once she fires up and runs smoothly, I ignore the little bubbles. Jim
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My concern is air in the fuel. There's definitely more air in the lines since I replaced the fuel shut-off valve, fuel filters, and fuel line o-rings. I now see the downside of replacing so many things at once.
I tried the "Italian turn-up" yesterday and all air was purged after that. But this morning, the air was back.
I found the following information from a manufacturer of centrifugal pumps (like a water pump) but I don't know what type of pump the IP or lift pump is...
"Both vaporization and air ingestion have an affect on the pump. The bubbles collapse as they pass from the eye of the pump to the higher pressure side of the impeller. Air ingestion seldom causes damage to the impeller or casing. The main effect of air ingestion is loss of capacity.
Although air ingestion and vaporization both occur they have separate solutions. Air ingestion is not as severe as vaporization and seldom causes damage, but it does lower the capacity of the pump"...
Based on your reply, I'm thinking I can safely wait for the fuel leak to appear (if it ever does). If the fuel leak appears, then it should identify the location of the air leak.