David Brown 995 air in the system

[Lian]

Hello everyone.

I have DB 995 for a 2 years now. Recently Im struggling with air in fuel system problem or at least everyone says so. So far tractor is starting and after a minute shut down. We cleaned the fuel tank, restore CAV pump, new filters, new lift pump, injectors checked. No bubbles into lift pump. There is seems to be enough petrol going all the fuel lines. Right now im about to change fuel lines after lift pump all the way to the CAV hoping some fittings are the problem. What is your opinion of the matter.

Best regards

 

[Dieseltech]

MF/Perkins with the CAV DPA pumps have a CONSTANT BLEED orifice fitting on top of the final filter base. When that orifice gets plugged it won't let any trapped air out of the base like it's supposed to, then the air bubble goes into the injection pump inlet and engine WILL stall. The orifice fitting is usually connected with the return line across the injector tops. ALSO, be aware if NAPA/WIX fuel filters are used MAKE SURE there's NO extra O ring seal placed in the filter TOP OUTER INLET GROOVE next to the lip, that groove is the filter INLET PASSAGE and MUST NOT be blocked. I've made lots of service calls to correct that mistake.

 

[Lian]

Everything you said is done properly but still no results. Im wondering if its possible something wrong with the filter aluminium assembly which is not a common problem

 

[showcrop]

Everything you said is done properly but still no results. Im wondering if its possible something wrong with the filter aluminium assembly which is not a common problem

Every now and then someone posts about a problem, and as is the norm, are given advice on how to solve it based on the most common causes. They will insist that they have already checked and eliminated the suggested cure, and state that they "feel" or are convinced that the problem is actually something that is very unusual. Sometimes pages and pages and hundreds of posts by dozens of members, and weeks go by before the original poster is convinced to try the usual solution.

 

[Lian]

Its not like that. Im just looking for suggestions. Thays it. Im not convinced not sure not nothing. Looking to sort my issue and get help by someone more experienced than me. Thanks for the reply. Anyway if i fix it i will post my resolution so if actually someone struggles with same problem can get help.

 

[caterpillar guy]

Dieseltech does injection pump repair and has a very good handle on your problem. Notsaying it can't be something else but if you look at the top of those filters for that tpye of filter you will see the groove around inside that edge lip ad I can see where people can think an o-ring seal should set there and cause the problems associated with that filter. I personally hat to deal with those glass bottom filters like those. Had one break just setting idling after just changing the filters. My brother mad a couple aluminum cups to use instead of those junk glass bottoms and no more problems with them. I would like to convert it over to the spin on filter so they would be the same filter as the 574 . One less thing to inventory here.

 

[used red MN]

Everything you said is done properly but still no results. Im wondering if its possible something wrong with the filter aluminium assembly which is not a common problem

I think you understand this but here is a link to a previous YT post that shows how an “.extra” oring can cause a problem when using the Wix/Napa filters. As has been said the only oring needed to seal it goes up in a groove in the filter base and seals against the rolled outer seam of the filter. YT post on Wix/NAPA fuel filters
You say no bubbles into the lift pump was this confirmed by using a clear section of fuel hose? That is about the only way to be certain of this.

 

[Lian]

Im using fleetguard ff167 which does not have extra O ring. When Ive been able to start it there were no bubbles into lift pump during engine work

 

[used red MN]

Im using fleetguard ff167 which does not have extra O ring. When Ive been able to start it there were no bubbles into lift pump during engine work

The question is how did you determine there are no bubbles? Some how temporarily installing a clear section of line with an hose barb and clamps and seeing NO air is traveling in the sealed lines is the only way to be certain of this. Maybe you did this, you didn’t say you did. It kind of turns back to what showcrop replied. If you don’t heed suggestions here you can go on chasing unicorns.

 

[Lian]

Excuse me maybe im too incompetent. I said it base on no visible bubbles into the visible part of lift pump. Pump looks like that

 

[used red MN]

Excuse me maybe im too incompetent. I said it base on no visible bubbles into the visible part of lift pump. Pump looks like that

My apologies, I didn’t realize that the pump had that glass bowl on it. That would indeed also confirm what you are saying. That’s the thing about a forum, if things are not explained or mentioned by the poster, us guys on the “dumb end” have no clue. You are there looking at it so it is in the mental picture you have of the situation, on this end not so much. I have never worked on a David Brown, I think I maybe have driven one once.

 

[Lian]

Thats why im looking to change lines after that lift pump. I would like to hear some opinions also on the leak off pipe if its stopped after the T turn for the tank. I mean leak off line to the tank is working but down to the filter is shutted. Would it be wrong effects.

 

[Jim.ME]

Excuse me maybe im too incompetent. I said it base on no visible bubbles into the visible part of lift pump. Pump looks like that

If you have bubbles showing in the bowl of the lift pump, the air is getting in between the tank and the lift pump, not after the lift pump. A bad pump is also a possiblity. The pump pulls vacuum on the tank side and gives pressure going out of it towards the injection pump.

 

[Not db4600]

If you have bubbles showing in the bowl of the lift pump, the air is getting in between the tank and the lift pump, not after the lift pump. A bad pump is also a possiblity. The pump pulls vacuum on the tank side and gives pressure going out of it towards the injection pump.

See above

 

[Jim.ME]

See above

If you are replying to me.

In post 8 he posted: "When Ive been able to start it there were no bubbles into lift pump during engine work".

That says to me there are bubbles showing when it won't start. If the line is pressurized after the lift pump, fuel should leak out of any compromised area, not air get pulled into the line.

 

[Lian]

No there no bubbles at all. Maybe i was not clear about it. Excuse me.

 

[JimB2]

Check the passage ways in the banjo bolts. Many years ago on IH B414D with CAV fuel system when engine came under full load it would cutout due to fuel starvation, found a sliver off rubber inside the passage way inside the banjo bolt on the inlet of the lift pump. Suspect the rubber came from inside of the rubber filler hose on the Diesel fuel storage tank.

 

[Jim.ME]

No there no bubbles at all. Maybe i was not clear about it. Excuse me.

Thank you for clarifying. I was going on how I interpreted what you wrote, which indicated to me you have bubbles at times.

When you say the CAV pump was restored, was this done by a qualified pump shop that was able to test and calibrate it after "restoration"?

A rubber hose breaking up and a piece getting caught somewhere in a fitting is a good thing to check for, as has been mentioned.

 

[Lian]

After changing all the fuel lines after lift pump everything seems to work fine so far.