OVERFLOW VALVE
 

The connections at the overflow valve are quite tight and I have both aluminum washers visible. I am going to put the new overflow valve back on as that will eliminate one source of possible leakage (one piece bolt).


I revved the engine to almost 3M revs, and the only place I am seeing air is overflow valve to secondary filter. When you mention the line from filter to IP, I am assuming that you are referring to the clear line that goes to the side-front-near top of the IP. Does that line flow to the filter from the IP?


When I rev it, the flow rate from the overflow valve to the filter seems to slow or almost stop (even though the bubbles keep coming from the valve). That would seem normal, as the rate of fuel being used by the IP has increased. Does that seem right to you?


I also assume that the clear line that goes from secondary filter to lift pump flows to the lift pump. Does that seem correct? In that case, when I check everything yesterday, I loosened that joint, pulled on the clear line to keep it straight up and tightened at the same time. If that is letting air in, you would not see it until the overflow, also.


As stated, I am only seeing air from overflow to secondary. Also, new primer with new copper crush washer, about as tight as I could get it with crow foot wrench.

That doesn't seem normal to me. The lift pump will supply well in excess of what the IP needs, even for full-load, full-RPM operation. Revving the engine in your driveway is far from either.

Air will not be entering your fuel system in the pressure lines (anything on the discharge side of the lift pump) during operation. It may leak down when the engine stops and sits, but it will burp out when it runs. Any air ingress (and you still have air ingress problems) will be on the SUCTION side of the lift pump.

You continuously ignore suggestions from people here, the only way for air to get int the system is to be at HIGHER pressure than the fuel supply pressure, that means the SUCTION side of the pump (on it's suction stroke, the pump is easily capable of pulling a vacuum). You have a leak in the rubber lines, a weak clamp, pinholes in the fuel lines, or a clogged tank strainer. You've already replaced the primer handle.

Important question: Have you installed 2 new o-rings on the 24 mm filter housing center bolt? It is well known those 2 o-rings will let air into the system if not sealing well.

A suggestion: Do not start the first few words of your first sentence in the subject title then continue the rest of the sentence in the body of the post. It is confusing if one did not read the title. Why do you consistently do that? To be cute or to be more confusing?

Funola, I put two new "O" rings on the filter bolt. It improved things but I am still getting air from the overflow to secondary filter. Sorry about the title to body stuff. I looked more closely, and see that most leave the title blank. I am relatively new to this.


Diesel300, finally someone agrees with me that the air is coming from the SUCTION side of things. I have made several posts where I thought this problem is at the lift pump or earlier. I suspect the connection on the left side of the lift pump. I also took the fitting (valve) off that the clear line was connected to with the flare fitting. I found no washer under this brass fitting (valve, and not the flare connection), and when I put the valve back on, right now I cannot remember whether I added a washer or not. Will check.


You an Funola have both suggested my lines from the tank may have pin-hole leaks that let the air in, but no one has addressed my question; If air was coming from back there, I would naturally assume that you would see bubbles entering the primary filter. I am not seeing bubbles coming in the filter. So, I ask both of you, if air was entering the lines from the tank, would I not see bubbles entering the primary filter?


http://www.peachparts.com/shopforum/...lwhitey_e0.gifHe just keeps dancin' dancin' dancin'

Diesel300, you should also know that I do not ignore suggestions, but if you read this thread and others, not everyone makes good suggestions. Maybe, you can give me advice (my not being a certified mechanic and all), how to sort out folks that tell you something wrong vs. those that know what they are talking about. I see no qualifications are necessary for posting here.

Another possible source of an air leak is an actual crack in one or more of the three clear hard lines connected to the fuel filter head.

They are especially prone to cracking at the junction where the barbed fittings end.
If the clear hard lines are old and discolored they turn brittle and can develop hairline cracks at any time.
Visually inspect your clear hard lines closely.

On a cold engine, clean all your clear fuel lines and their associated fittings with brake fluid.
Ten to 15 minutes after all the brake cleaner has dissipated, run the engine for a few minutes, and then shut off the engine.
Check the clear hard lines and their associated fittings for leaking fuel with dry tissues.
Every fitting and line should normally be bone dry.

If you find a wet fitting or line you will have found your air leak.

Thanks Alec300SD, however, I replaced all three of these clear lines and have no sign of fuel leakage.

No sign of fuel leakage?
 

This does not preclude air entry.

A steam boiler is under pressure. How is additional water added to that boiler when it has a full head of steam? A venturi. It is possible for air to enter and fuel to remain in the flow without fuel leaking.
If there are loose or damaged components, you can be entraining air where you don't want it. At one time I had air entering, yet there was no wetness of a leak.
That was cured by tightening a rubber hose fitting that for all intents and purposes was quite tight; tightened it further, the minute air bubble stream stopped.
Unlikely? Yes. Impossible? No. The steam locomotive just used it's own steam pressure to inject the water. A "venturi" formed by accident can do the same thing. Fuel out-no; air in-yes. Not common. Possible.


snapped_bolt

snapped_bolt, I am not sure this applies. You mention tightening a clamp on a rubber hose, and all rubber hoses are on the suction side of things until you reach the cigar hose. I have done boiler work, and I am not sure I fully understand what you are saying.


At this point, it seems the main suspect connection that I have is the flare fitting on the left entry point of the lift pump.


Don't know what to say.

So you want to have your cake and eat it too? You want to sort out folks who are trying to help you whether they know what they are talking about? Short answer: You can't. Don't forget, members here tell you things to try based on what you tell them. **** in **** out applies. Maybe you should take your car to the dealer? They are qualified on paper.

Sorting air in fuel in a diesel can be difficult. Here's an old post from Brian Carlton http://www.peachparts.com/shopforum/diesel-discussion/254261-sdl-fuel-issues-trip-hell.html , an ex. mod who is not on this forum anymore. He is very knowledgeable with diesels and had a long and expensive ordeal looking for air in his SDL. In the end, turns out it was a clogged pre-filter that was letting air through the fuel clamp.

Didn't anyone tell you if you don't have anything nice to say don't say it at all? Insulting to a lot of people on this board. Maybe you should take this car to the dealer. They are qualified as Funola said.

You have ignored several suggestions on this very thread, many of them good ones. Instead, you took up several replies questioning them over and over until the person(s) suggesting them to you gave up and went to help other people.

Most of the folks on this forum are hobbyists of varying degrees of mechanical aptitude. Most of the suggestions and advice you're going to get are based on personal experience, other people's experience, and knowledge gained from the FSM or other credible sources. Asking to see everyone's pedigree all the time does nothing but cause the person offering advice to withhold further advice that could have been useful to you.

When you start thinking you're smarter than everyone else in the room it's time to re-examine your opinion of yourself.

To echo what others have already said, if you want someone who has the credentials to work on your car or offer advice, go visit the dealership and pay their $200/hr labor rate. So far you've paid $0.00 for the advice you've gotten, most of which is more educated than what you'd get for that $200/hr at the dealership. Your time, your money...

Funola has gone out of his way to help you and gotten nothing but pushback. I stepped in to attempt to offer some support and back up and explain what he was trying to help you do, but that doesn't seem to be appreciated either. I don't normally give up on someone I'm trying to help, but it seems in this case you clearly don't want my or anyone else's help or suggestions. I wish you luck. :)

Suction of fuel by lift pump and injection pump
 

can entrain air if there any possible leak points.

I used to modify aquarium water filters by drilling a small hole in the top of the discharge tube. Trillions of tiny bubbles would enter the aquarium by that tube- but it didn't leak water to the outside!

I would carefully cut new rubber hoses, make sure you have good, non-cutting clamps, and tighten them good!


Cheers,

snapped_bolt

Here's maybe one of the best suggestions of all: Just replace everything with new. I seriously doubt everything new will cost more than $40.00. New Cigar Hose, new clear lines (the ones you make yourself), new O-rings, new crush washers ... It's a royal pain looking up each individual part, but you know you will fix it. All those parts are 30+ years old most likely and once you start tinkering with it, who knows. Why selectively replace this or that once you open that can of worms ?

I'm with greazzer!
 

I have been thinking the same!
Time for doing a change-out of the plastic parts, double check, or change crush washers.

Cheers,

snapped_bolt