D15 Loosing RPMs and "surging"

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   Hey new to the forum and not much of a mechanic.  Bought a D15 Series 1 last fall.  Did service on it - lubrication, verifying fluid levels, etc, tightened up the fan belt, replaced the starter, and it was running pretty good doing pulling hay rakes, racks and digging food plots.
Having an intermittent issue where the tractor will start to lose RPMs, and then, on it's own, regain the RPMs and continue to "surge" alternating between expected RPMs and nearly dying.  When it's in this state, it keeps getting worse - eventually you have to start pulling the choke to keep it running till it revs back up - then it will run OK for a minute, and start "surging" again.

First time I did it was right after refueling.  It was at the end of the day, so I added sea foam to the fuel and let it sit. Next time we used it, it ran fine for many hours.  Then the 2nd time was after running several hours digging food plots with a 6 tine cultivator.  Again, it would lose RPMs, nearly die, but then "surge" back to normal for a few seconds until losing RPMs again and nearly dying.  Continued to get worse so we let it sit for about 45 minutes during lunch.  After lunch, symptoms continued and we needed to use the choke intermittently to keep it running while we drove it back to the shop.

We added an in-line clear plastic fuel filter between the carb and the sediment bowl as the tank is pretty rusty inside, and we can see the sediment bowl doesn't catch everything - you can see the sediment in the filter.  Tractor has run OK since then, but we've only used to tool around the farm doing easy jobs.

Anyhoo - could these symptoms be caused by sediment getting into the carburetor?  If this happens again - what would be the next logical step to look at?

Any ideas appreciated!

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mnjoe2025 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 28 Jun 2024 Location: 55321 Points: 4	Post Options Post Reply Quote mnjoe2025 Report Post Thanks(0) Quote Reply Topic: D15 Loosing RPMs and "surging" Posted: 28 Jun 2024 at 6:53pm
	Hey new to the forum and not much of a mechanic. Bought a D15 Series 1 last fall. Did service on it - lubrication, verifying fluid levels, etc, tightened up the fan belt, replaced the starter, and it was running pretty good doing pulling hay rakes, racks and digging food plots. Having an intermittent issue where the tractor will start to lose RPMs, and then, on it's own, regain the RPMs and continue to "surge" alternating between expected RPMs and nearly dying. When it's in this state, it keeps getting worse - eventually you have to start pulling the choke to keep it running till it revs back up - then it will run OK for a minute, and start "surging" again. First time I did it was right after refueling. It was at the end of the day, so I added sea foam to the fuel and let it sit. Next time we used it, it ran fine for many hours. Then the 2nd time was after running several hours digging food plots with a 6 tine cultivator. Again, it would lose RPMs, nearly die, but then "surge" back to normal for a few seconds until losing RPMs again and nearly dying. Continued to get worse so we let it sit for about 45 minutes during lunch. After lunch, symptoms continued and we needed to use the choke intermittently to keep it running while we drove it back to the shop. We added an in-line clear plastic fuel filter between the carb and the sediment bowl as the tank is pretty rusty inside, and we can see the sediment bowl doesn't catch everything - you can see the sediment in the filter. Tractor has run OK since then, but we've only used to tool around the farm doing easy jobs. Anyhoo - could these symptoms be caused by sediment getting into the carburetor? If this happens again - what would be the next logical step to look at? Any ideas appreciated!

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BillinAlberta Members Profile Send Private Message Find Members Posts Add to Buddy List Silver Level Joined: 12 Sep 2009 Location: Saskatchewan Points: 342	Post Options Post Reply Quote BillinAlberta Report Post Thanks(0) Quote Reply Posted: 28 Jun 2024 at 7:18pm
	I run into this from time to time. 1)Thoroughly clean the whole fuel system from tank to carb 2)change plugs and wires plus points and condensor or go to electronic ignition.I did this on all 6 of mine. 3)cross your fingers.

AC720Man Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 10 Oct 2016 Location: Shenandoah, Va Points: 4926	Post Options Post Reply Quote AC720Man Report Post Thanks(0) Quote Reply Posted: 28 Jun 2024 at 8:55pm
	I would start by removing the fuel tank to clean it. Muriatic acid will get rid of the rust and get it sparkling clean. But you need to be careful with the fumes it produces, remove the fuel strainer and put a plug in its place. Add a few gallons of water then the acid per the instructions on the container leaving fuel cap off. Allow it to work for 15 minutes. Do not allow it to get on the outside of the tank as it may damage the paint. Drain the tank by removing the plug, use a power washer to throughly clean the tank through the fuel filler. Until you have a clean tank your problems will continue.
	1968 B-208, 1976 720 (2 of them)Danco brush hog, single bottom plow,52" snow thrower, belly mower,rear tine tiller, rear blade, front blade, 57"sickle bar,1983 917 hydro, 1968 7hp sno-bee, 1968 190XTD

DSeries4 Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 12 Sep 2009 Location: Ontario, Canada Points: 7338	Post Options Post Reply Quote DSeries4 Report Post Thanks(0) Quote Reply Posted: 28 Jun 2024 at 9:10pm
	A couple of things: you added an in-line filter between the sediment bowl and carb. They can add restriction to fuel flow and cause fuel starvation issues. Hence, your need to use the choke some times. Secondly, if the engine is surging, check to see that there is an anti-surge spring on the rod going from the governor to the carb. It connects a hole in the rod and up to one of the manifold studs. It sounds like you definitely have crud in your gas tank. Get your tank properly cleaned out and then you will have a better idea on how your tractor runs afterwards.
	'49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '61 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080

steve(ill) Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 11 Sep 2009 Location: illinois Points: 81334	Post Options Post Reply Quote steve(ill) Report Post Thanks(0) Quote Reply Posted: 28 Jun 2024 at 11:06pm
	probably crap in the carburetor.. needs removed, bowl pulled off cleaned and blow out passes......... inline filter is a good idea for a rusty tank.. Make sure it is a full flow gravity feed type.. you can blow thru it EASY... should not have check valve or restriction...Pull the old one off and blow thru it... when they get "restricted", throw away and install new.. Eventually the tank will get clean, but drain and flushing NOW is always a good idea.. i bet crap is in the carb floating around at this time.. ... if you have a DRAIN PLUG , pull that and let a cup full flush out into a can ... see what you get... that might be GOOD ENOUGH with a new FILTER. Edited by steve(ill) - 28 Jun 2024 at 11:07pm
	Like them all, but love the "B"s.

mnjoe2025 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 28 Jun 2024 Location: 55321 Points: 4	Post Options Post Reply Quote mnjoe2025 Report Post Thanks(0) Quote Reply Posted: 30 Jun 2024 at 7:19am
	BillinAlberta - Thanks for the tips - consensus seems to indicate a fuel tank cleaning may help - but at least it can't hurt! Electronic ignition conversion is something I would have never thought of - I'll have to look into that. Fingers crossed, indeed!

mnjoe2025 Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 28 Jun 2024 Location: 55321 Points: 4	Post Options Post Reply Quote mnjoe2025 Report Post Thanks(0) Quote Reply Posted: 30 Jun 2024 at 7:33am
	AC720Man - thanks for the advice and the specifics on cleaning a tank. We did just restore an old above-ground fuel storage tank, so we have experience there. It'll probably be a lot easier to clean the ~15gal tank on this AC vs. the ~315gal storage tank! (And would require much less acid!). DSeries4 - thanks for the tip about looking for the spring - I'll be sure to look at that. FYI - we added the filter AFTER these problems, and we havent had the issue since (but we also havent used the tractor much). But point taken that a filter could add unwelcome restriction. steve(iii) - the inline filter we got was a full flow, no check valve. It's actually sized for a larger diameter fuel line than the old fuel line, so we replaced some of the fuel line and made it bigger, so that should help with flow. It's on the list to drain that carb and look what comes out, along with a tank cleaning. Thanks to all who replied - I believe I have some good direction to work on the issue - now hopefully I can find the time!