Your best Aiir leak Detection Techniques

[Rebol]

Hello. As a couple of you already know, I've been at my '67 MF 150 for now 4 months off and on trying to fix it for good - Fortunately I don't have to rely on her for my livelihood.

The Problem:
In December I discovered I had air in my diesel.
Since then I've got it to run but anytime I put a load on it it sucks in air.
I've replaced the fuel lift pump
I just recently replaced the O rings on the injector as I had a leak on the throttle side.
I'm looking and looking but I can't figure out where the air is coming from.

The Request:
I'd appreciate any experience you might have in air leak detection.

Thanks so much.

 

[DEWFPO]

Is the tank venting properly? I have to assume you've checked every single fuel line, fitting, O-ring, gasket, washer, connection and filter in the fuel system.

DEWFPO

 

[banjodunn]

G'day Rebol anything on the tank side of the lift pump can cause you prob if you are drawing air whilst it is running, this does make it a little easier than if id draws in air after sitting for a while. I would start with the lift pump and check the rubber seal on the inlet pipe ( if fitted some do not have a seal but a brass olive) from there i would work my way back to the tank i.e seals on water trap ( if fitted ) and i would prob replace all the rubber hose if it has not been done already also check the outlet pipe of the tank, if it is removable pull it out and check for cracks also blow it out as the bend in the line is a good place for crud to accumulate and make it hard to draw fuel. Just a few things to check hope you find your prob.
P.S If you have got a water trap and want to replace the seals don't go to massey as they will charge you an arm and or leg buy a fuel filter ( baldwin bf 825 the only one i know that gives you the three large 'o' rings ) and that will give you all the seals for a couple of $$ plus if you are running the same fuel filter ( would say so ) you can get away with turning your rings upside down when you change the filter



Jon

 

[Rebol]

Thank you both. Actually the tank is something I haven't inspected as much as the other parts.

 

[Mur386]

Just wondering and am not familiar with your tractor, does your lift pump have a glass bowl, and does it have air in it? Anything on the exit side of the lift pump should be under pressure and should leak out. I agree with others about checking tank and line from tank. Some tanks may have a filter inside and it may be clogged. could it be possible for you to build some pressure in tank to possibly show a leak somewhere. Maybe you need to build some type temporary setup on the exit side of liftpump and make sure its building pressure. Once I forgot to open tank outlet valve and the injector pump pulled enough vacuum through its leaking gaskets to kill engine. That all I have for now, hope it helps
Bill

 

[oldnslo]

What I have used on hydraulic pump inlets to find a leak is coat the connections with grease. Kind of messy but you know when the leak is plugged and most people have grease available.

Also agree with Mur386 on if the lift pump is working everything between it and the main pump should be under pressure.

 

[Rebol]

Thank you for your input. I've read each one

I'll be the first to say I have no idea how to check if my tank is venting properly so any advice there would be welcome.

I also don't know what or if I have a water trap unless it is part of the fuel filter system. From what I can see there's the tank, the sending unit, cap, drain control valve and a return line.

When I changed out the fuel lift pump, I replaced portions of the metal fuel line with rubber hose suitable for pressure and diesel. These are clamped down well and this installation allowed me to really get the short metal metal tubes I used for the in and out ports of the pump very snug as opposed to wrestling with the metal pipes to get a good and straight fit.

Today I noticed that droplets would form from fuel drain control valve (tank shut-off valve). I had it really unscrewed so I simply tightened it a bit and the drops stopped forming.

I also cracked the nut of the line going into fuel filter. By the way, my fuel filter is not the kind that is right next to the fuel lift pump but closer to the fuel injector. Anyway, I do see air bubbles there when I turn it over or use the manual level on the pump. Would you not agree that this would indicate that the air is coming in PRIOR to this point?

I'm going to try the grease method offered by Oldnslo starting with the fuel drain control and see what happens. I'll let you all know.

Regarding my glass sediment bowl. That's a great question and I wish I really know what it's supposed to look like inside. Quite frankly, the top part is opaque and the bottom half looks like there is liquid in it. It's just not clear. Perhaps that's the problem but what would I do about it? I've hesitated to take it apart. What do you think?

Thanks in advance.

 

[boomer1025]

Thank you for your input. I've read each one

I'll be the first to say I have no idea how to check if my tank is venting properly so any advice there would be welcome.

I also don't know what or if I have a water trap unless it is part of the fuel filter system. From what I can see there's the tank, the sending unit, cap, drain control valve and a return line.

When I changed out the fuel lift pump, I replaced portions of the metal fuel line with rubber hose suitable for pressure and diesel. These are clamped down well and this installation allowed me to really get the short metal metal tubes I used for the in and out ports of the pump very snug as opposed to wrestling with the metal pipes to get a good and straight fit.

Today I noticed that droplets would form from fuel drain control valve (tank shut-off valve). I had it really unscrewed so I simply tightened it a bit and the drops stopped forming.

I also cracked the nut of the line going into fuel filter. By the way, my fuel filter is not the kind that is right next to the fuel lift pump but closer to the fuel injector. Anyway, I do see air bubbles there when I turn it over or use the manual level on the pump. Would you not agree that this would indicate that the air is coming in PRIOR to this point?

I'm going to try the grease method offered by Oldnslo starting with the fuel drain control and see what happens. I'll let you all know.

Regarding my glass sediment bowl. That's a great question and I wish I really know what it's supposed to look like inside. Quite frankly, the top part is opaque and the bottom half looks like there is liquid in it. It's just not clear. Perhaps that's the problem but what would I do about it? I've hesitated to take it apart. What do you think?

Thanks in advance.

You could use clear plastic line (suction side) between the primer pump & tank to see if there is air coming into the system. You might want to take a good look at the hand primer pump, that could be a place where it's sucking in the air.

 

[Rebol]

OK, so I got curious about the fuel filter and the way the glass bowl was looking like inside. Obviously something was in there since it wasn't the same color. I drained it and there was quite a bit of junk in it.

I just returned from the Napa store with my new filter complete with new seals and O rings. Whether or not that was part of the problem remains to be seen but at least it needed to be drained and probably replaced. Now I know what it is supposed to look like. I guess I never mentioned that this old tractor is new to me and so I don't know what things are supposed to look like when there in tip-top shape.

I'll have to visit another store to get some clear tubing. That's a great idea, boomer1025, and with my new set-up will be an easy way to check.

Thanks for the continuing advice. Keep it coming and I will let you all know what progress I am having.

 

[whistlepig]

If your diesel fuel system is leaking air it is also leaking fuel from the same place. Give the engine a good cleaning and drying and you will find the leak. I have done this many times.