YM1500 Surging/Loping/Smoking

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DPresnell88
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YM1500 Surging/Loping/Smoking

Postby DPresnell88 » Thu Feb 18, 2021 3:20 pm

I recently installed a new injection pump purchased from Hoye on a Yanmar YM1500. 2 cylinder. I performed R&R per the YM1500 shop manual in regards to setting crank position. The old pump did not have any shims underneath.

The new pump did not have the notch in the rack like the old pump. Pre-install the tractor would not run. After installing new pump, I drained and cleaned the tank, changed all soft fuel lines, changed fuel filter.

I blew out the hard lines from pump to injectors. Unit will now start and run but will not hold it's RPM steady, it will only surge up and down from near shutting off to WOT. I performed governor adjustment procedure per shop manual, did not help.

When running, unit produces heavy white smoke throughout RPM range. I performed compression test, and leak down test at both BDC and TDC. No issues there. I'm stumped.

Aaron
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Location: Iowa Park, TX

Re: YM1500 Surging/Loping/Smoking

Postby Aaron » Thu Feb 18, 2021 3:25 pm

The heavy smoke would seem to indicate unburned fuel- maybe a clogged or misfiring injector. You can test that with the instructions below
https://www.hoyetractor.com/support/kno ... article=72

The failure to maintain an RPM is almost always caused by the rack being sticky or the governor linkage binding. The new pumps are coated in a sticky lube and sometimes need to be cleaned with WD40 or similar until the rack slides just by tipping the pump.

What did you have for compression pressure?

DPresnell88
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Joined: Thu Feb 18, 2021 3:13 pm

Re: YM1500 Surging/Loping/Smoking

Postby DPresnell88 » Thu Feb 18, 2021 3:42 pm

320+ PSI on each cylinder. I checked that both injectors were spraying fuel. I know that doesn't mean they aren't causing an issue but preliminary inspection seemed to be ok. Is there a different governor timing setting for the new pump that doesn't have the notch in the rack? I will try the WD40 when I get back to the unit.

Aaron
Site Administrator
Posts: 3413
Joined: Thu Jul 26, 2007 12:39 pm
Location: Iowa Park, TX

Re: YM1500 Surging/Loping/Smoking

Postby Aaron » Fri Feb 19, 2021 8:56 am

320 is very low compression. The fuel timing is just set by the shims under the pump and is normally just the same shims as the original pump. Did you check the fuel timing using the procedure in the manual?

DPresnell88
Volunteer Poster
Posts: 3
Joined: Thu Feb 18, 2021 3:13 pm

Re: YM1500 Surging/Loping/Smoking

Postby DPresnell88 » Sat Feb 20, 2021 2:20 pm

I did the fuel timing procedure per the manual. I have checked and lubricated the rack slide and made sure that it is moving freely. I am unable to attach the video here of the surging. I will send it to you via email.


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