Air Leaking Into Fuel System
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Construction and other equipment
Forum Description: everything else with orange (or yellow) paint
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=176706
Printed Date: 01 Dec 2024 at 6:28am
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Air Leaking Into Fuel System
Posted By: DKB552
Subject: Air Leaking Into Fuel System
Date Posted: 12 Dec 2020 at 6:18pm
| I have a John Deere loader with the 3179 diesel engine. With the engine running rough I noticed there are air bubbles entering the fuel filter. I checked all lines and found nothing wrong. Could it possibly be a bad fuel pump or bad injector pump allowing air to seep into the system?? |
Replies:
Posted By: NomoreJohnDeere
Date Posted: 12 Dec 2020 at 6:54pm
|
how do you know air bubbles are entering the fuel filter? ------------- HD3 |
Posted By: Dnoym N. S. Can.
Date Posted: 13 Dec 2020 at 6:37am
 some John Deere used glass filter could possibly be a bad fuel pump sucking ail HTH B:-) Dnoym |
Posted By: DougG
Date Posted: 13 Dec 2020 at 11:39am
| Clear fuel filters alow you to see air bubbles, had an AC 200 do this and it was a rubber grommet in bad shape letting air in on a metal fuel line - new rubber grommet no more problems |
Posted By: NomoreJohnDeere
Date Posted: 13 Dec 2020 at 12:28pm
|
If it has a transfer pump with a rubber bladder that is breached it can feed air ------------- HD3 |
Posted By: DMiller
Date Posted: 13 Dec 2020 at 12:41pm
| Even if Gear pump and seals are failing can suck air. |
Posted By: injpumpEd
Date Posted: 13 Dec 2020 at 12:55pm
|
The filter base for those Roosa Master square filters have a bleeder screw that is supposed to have a rubber seal, and it gets old and torn off, allowing air in. ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |
Posted By: DKB552
Date Posted: 14 Dec 2020 at 1:35pm
| From the fuel tank there's a clear automotive type filter that runs to the inlet side of the mechanical fuel pump. Then from the fuel pump a line connects to the big square glass filter mounted on the engine. The air bubbles (a lot) are seen in both filters. Both filters are not that old and are clear. The flow of fuel is restricted due to air entering the system. So could it possibly be the mechanical fuel that's bad?? I'm hoping it's not the fuel injection pump itself because that thing is around $1,200 dollars. |
Posted By: NomoreJohnDeere
Date Posted: 14 Dec 2020 at 2:01pm
|
I would think it would be between your first filter and the tank...... What kind of line/fittings? Low on fuel in the tank and sucking air? Find a suitable temporary fuel tank and run a line from it to your mechanical pump, gravity feed and see if the same thing happens ------------- HD3 |
Posted By: DKB552
Date Posted: 14 Dec 2020 at 8:00pm
| I has a mechanical fuel pump and a fuel injection pump. Where is a "fuel transport" pump located? As far as I can tell it doesn't have one |
Posted By: DKB552
Date Posted: 14 Dec 2020 at 8:04pm
| Good idea. I'll try using a separate fuel tank and see what happens. |
Posted By: NomoreJohnDeere
Date Posted: 14 Dec 2020 at 8:07pm
|
mechanical fuel pump = transfer pump = fuel transport pump = lift pump it feeds (sucks) fuel usually from a tank below the injection pump and keeps injector pump fed at low pressure I suppose there might be an injector pump with a lift pump built in that I am not knowledgeable enough to know about some may use a 12 volt pump in place of an engine driven one ------------- HD3 |
Posted By: Jim.ME
Date Posted: 15 Dec 2020 at 7:04am
| If there are air bubbles entering that clear, automotive filter which is between the mechanical transfer pump and tank the problem is pretty much certainly between the inlet of that filter and the tank. That filter is something someone cut the line and added in for some reason, likely trying to save money by not having to replace the designed fuel filter, because the tank has/had a problem with crap in it. It does not need to be there, by design. You may need to drain the tank and remove the filter, line, and fitting/valve in the tank to clean them. Check the fittings when reassembling to be sure they are not damaged on the seats. Check the shut off valve at the tank to be sure it is tight around the valve stem. Restriction in the valve body could cause air to be drawn in around the valve stem. What model is this loader tractor? |
Posted By: injpumpEd
Date Posted: 15 Dec 2020 at 8:02am
|
Your injection pump should not be causing air in the filters that are ahead of it. And not sure where you're going, but a Roosa/Stanadyne DB is not typically 1200$ unless you have one seize. Did you check the bleed screw on the filter base itself? It is supposed to have a thin rubber sealing washer that is usually torn. Air ingress can damage the injection pump though, it causes the cam pin to break. The poor running may not be because of the air, it may be other pump issues, which cause the return to plug. That makes them run poor by not allowing the timing advance to work properly. ------------- 210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers! |
Posted By: DKB552
Date Posted: 15 Dec 2020 at 8:39pm
| Yes, someone added that clear filter because they were too lazy to clean the tank out. (which I did clean last year and replaced the filter). The filter did allow me to see the air bubbles BEFORE the fuel enters the mechanical fuel pump so I'm assuming the problem may have something to do with the line going into the tank itself. I will try all these suggestions this weekend and I purchased a new fuel pump anyway because it looks as old as the machine. I will update when I discover the problem. This is a super rare 1980 Prime Mover LD50 articulating loader. They were only made a few years before the company went out of business. Very few of these can be found in running condition. I plan on posting pictures of it and the work I've done to it as time permits. Luckily I have a huge catalog that contains the owners manual, shop manuals and detailed parts diagrams with part numbers for every part installed on the machine. Finding parts is no problem. |
Posted By: DKB552
Date Posted: 15 Dec 2020 at 9:05pm
| Thanks for the info. I plan to tackle the problem this weekend if the weather is good. It has the older model Roosa Stanadyne pump and the only ones I looked at so far were on E-bay for around $1,200 dollars. I'm sure I can get one rebuilt for half that price though. Right now I'm thinking the injection pump isn't the problem. |
Posted By: Jim.ME
Date Posted: 15 Dec 2020 at 9:32pm
| Does that pull fuel out the top of the fuel tank or the bottom of the tank? The bottom pull would be flooded. The top pull likely uses a suction pipe inside the tank that is run down close to the bottom of the tank. If that pipe has developed a crack inside the tank it could be a source of air bubbles if the crack is above the fuel level. Depending how it is built that pipe might come out of the tank with the fitting the line to the transfer pump hooks to. As has been suggested, use a temporary tank and fuel line hooked to the inlet of the added filter to see if the bubbles go away. If they do, you know the source of the air entering is somewhere from the inlet of that filter back to the tank. (Which it would seem to me it is, since you say the bubbles show in the added on filter which is ahead of the transfer pump and OEM filter.) |
Posted By: DKB552
Date Posted: 16 Dec 2020 at 9:45am
| Yes, that makes sense. I plan on doing that first before changing the fuel pump. Using a separate fuel tank is a great idea. |
Posted By: DKB552
Date Posted: 06 Jan 2021 at 2:23pm
| PROBLEM SOLVED. As someone suggested, the fuel pick up tube in the tank had developed a leak at the top of the tube. It now runs great!! Thanks for all the replies!!! |