r/tractors • u/Professional_Gap4840 • Jun 29 '26
Low compression?
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Tractor has been sitting around 15 years, have been trying a few little things to get it to run but haven’t had any luck yet. Wondering if it’s more likely low fuel pressure or low compression
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u/WinFit9365 Jun 30 '26
Bleed the fuel lines to the injectors. Diesel engines work differently than gasoline engines. Any air trapped in the fuel system can prevent the engine from starting.
Loosen the fuel line fitting (banjo/fuel line nut) at each injector. Crank the engine until you see a steady flow of diesel fuel with no air bubbles coming out. Tighten the fitting, then repeat the process for each injector. Ref: https://www.youtube.com/watch?v=dflMxYDOPns
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u/Deerescrewed Jun 29 '26
As the others have said, it’s most likely not getting enough fuel. You have some smoke, so some is getting through. I don’t remember a lift pump on those old Oliver’s, but it’s been many many moons since I ran one. Change out filters, bleed system, crank on it, then bleed it again, crank and bleed until all injectors have clean streams of fuel while cranking. If it’s still balky, then try a little snort of the upper cylinder lubricant.
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u/mtraven23 Jun 29 '26
you getting fuel to the injectors? my money is on fuel here.
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u/Professional_Gap4840 Jun 29 '26
I know it was getting fuel to the return line but I’m not really sure on how it all works together, just replaced the fuel return line and fittings that were leaking.
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u/mtraven23 Jun 30 '26
so that means you are getting fuel to the injectors, though we dont know if thats at the right injector, or if the injector itself it actuating. They need to be tested. There are probably shops that will test them for you. When I had some injector problems on my old diesel, I ended up making a test rig out of a bottle jack, works really well. cheap easy to build.
I also should have asked, was fuel left in this thing? Even if you added fresh fuel, is it possible thats mixed with other fuel that was in the lines?
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u/Professional_Gap4840 Jul 01 '26
Tank was empty and I added fresh fuel, but it’s definitely likely that the fuel was mixed with whatever was leftover in the system
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u/Wooden-Wishbone-4335 Jun 29 '26
It just firing on ether. Change fuel filters. Have u confirmed fuel @ the pump & fuel up to the injectors?
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u/Professional_Gap4840 Jun 29 '26
I cracked open the fitting that feeds into the injection pump and had some drops come out. I never thought to check actually at the injector
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u/AdFancy1249 Jun 30 '26
If you think there might be air in the injector line, loosen the fitting feeding each injector. You'll know when the air has been bled out, because it will start pushing fuel drops out. Tighten the closest to the fuel pump and then move to the next.
My old Ford sat for a long time like yours. All 4 injectors had air in them. As soon as I bled and closed the second injector, it started. Then, while it was running poorly, I bled the third and fourth and it purred...
After that, I had to bleed the #3 injector if it sat more than a week, but it was reliable.
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u/tihspeed71 Jun 30 '26
Thank you for that bit of info on sitting and repriming..... it's so logical, just never occurred to me i might need to do it again
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u/zol11 Jun 29 '26
Sounds like a fuel issue. As others said crack the lines and bleed out the air. It could also be a supply issue so check to be sure you are getting fuel to the injection pump. Or a lift pump if it has one. If not much fuel blow the line backwards on the tank side of the filter. Could be a plugged sump on the tank.
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u/Hiyou0 Jun 29 '26
First things first, loosen a couple injector lines and and crank it for ~5 seconds. If you don’t a good bit of fuel coming out, then get a container ready, and take off the fuel supply to the injector pump.
You should be having fuel going from the tank, through the filter(s), and then pouring out into your container. Collect at least a half gallon, which shouldn’t take more than 2 or 3 minutes.
If you aren’t getting fuel to the pump, then that’s the next thing to look at. If you are getting fuel, hook it back up, and loosen all the injector lines, set the throttle to max, and crank it in 15 second intervals, letting the starter cool for a bit in between. Once an injector line starts pouring fuel out consistently, tighten it up, and keep going until they are all done. That should do it, unless something is broken or stuck.
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u/Average_k5blazer78 Jun 29 '26
Sounds like fuel, I would change fuel filters, look for sediments in the fuel tank, and bleed the injectors to check for air in the system
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u/Wooden-Wishbone-4335 Jun 30 '26
Drops isn’t going to cut it. Has to be moving fuel. Should have a cam driven lift pump with a hand primer to pressurize the injection pump. Start @ the tank & work ur way to the injection pump. Confirming fuel flow @ each component. If there is fuel up to the injection pump. Then start cracking lines. Loose enough to confirm fuel flow. Should be some pressure @ that point. If not I’d probably pull the injection pump off & have it rebuilt.