Off color question
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=139991
Printed Date: 28 Sep 2025 at 5:03pm
Software Version: Web Wiz Forums 11.10 - http://www.webwizforums.com
Topic: Off color question
Posted By: Ranse
Subject: Off color question
Date Posted: 01 Jul 2017 at 6:27pm
| I have a 7740 Ford/New Holland tractor. Earlier this spring the fuel injector pump started leaking and it would lose power from time to time and only run about half the rpm's it usually does. I took the fuel injector pump off and had it rebuilt. I also replaced the filter head because the primer pump didn't seem to be working, so I got a new one at Napa. That solved my power loss issues, but it hasn't run right since. For starters, it idles erratically. It idles at 700 rpms and will jump to about 8 or 850 for a few seconds and drop back down over and over without touching the throttle. Then if you shut it off for a few minutes and try to restart it, it will start for a second and quit. Try to start it again and it acts like it's out of fuel. You will not start it again until you pump the primer back up. I told a friend about it, and he said the Napa filter head isn't holding prime. I would have to eat it and get another one form New Holland. I would just do this, but here's what's confusing me. When the tractor has a full tank of fuel it runs perfect, no starting problems, on idling problems, until it gets down to about half a tank then the symptoms start again. I thought it was a fluke or my imagination at first, but I filled the tank three times and run it down and it happened every time. If it was a gravity flow system this might make sense. In my mind it either has fuel and it should run or it don't. Maybe it's a vacuum leak, I don't know, any advice appreciated. Ranse |
Replies:
Posted By: LeonR2013
Date Posted: 01 Jul 2017 at 6:37pm
| Rance, check and see if you have a stand pipe in your tank. If you do there is a good possibility there is a hole in the pipe at the level where it starts acting up. If it's a steel tube just solder it up and away you go. |
Posted By: Gerald J.
Date Posted: 01 Jul 2017 at 7:07pm
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When the lift pump on my gas 4020 stopped pumping my 4020 ran only with the tank at least half full because at that level the fuel got to the carburetor by gravity. Sounds to me like the new lift pump and the filter aren't getting along. Gerald J. |
Posted By: DiyDave
Date Posted: 01 Jul 2017 at 7:08pm
Might also be a bumble bee or clover head floating in the tank, when it gets low enough, it sucks down and blocks the drain hole, limiting fuel... Take a bore scope, if you can beg borrow or steal one, and get a camera image of what's in the tank...
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