Think I have a fuel injector problem

[stormpetrel]

I loosened one injector fuel line at a time and got this:

Loosen #1 injector line and tractor tries to die at low idle
Loosen #2 injector line and tractor tries to die at low idle

Appears whatever my problem is, it is not the injectors.

The only thing I changed in the fuel system was the bowl filter. I had ran it for a couple of years with the bowl filter bypassed and used an external fuel line filter. The new filter only goes in one way that I could tell by the fit.

Would I be taking a big risk by bypassing the bowl filter to test it with just a line hooked from the tank to the fuel pump?

Not if you filter, or otherwise make darn sure you're using good clean fuel.

On the injector/injector pump thing: just because the injector pump works good doesn't mean you have good injectors. The injector pump pressurizes the fuel, and the injectors atomize it for good combustion. The pop test of the injectors will quickly tell you if they are good or not.

 

[Gary Sweat]

Not if you filter, or otherwise make darn sure you're using good clean fuel.

On the injector/injector pump thing: just because the injector pump works good doesn't mean you have good injectors. The injector pump pressurizes the fuel, and the injectors atomize it for good combustion. The pop test of the injectors will quickly tell you if they are good or not.

I was hoping to not have to pull an injector as I don't have the tool for that and will have to order it. If I go that far would it be advisable to go ahead and replace the injectors? My guess is these are probably the original ones. I saw on Hoye that there are a few other parts below the injector but I don't know if they can cause problems unless they are burnt or cracked.

 

[California]

If loosening each injector line separately slows each cylinder the same, then there doesn't seem to be one good injector and one bad injector. I don't think that's where the problem is.

And the way you describe the throttle response doesn't sound like an engine running on one cylinder, it sounds like both cylinders are impaired equally.

Could there be something choking the air intake or the exhaust? Did a rag or something go down the intake while you were working on it? Or water in the fuel which should be visible in the filter bowl?

I wouldn't run without some sort of filter ahead of the fuel pump. The clearances inside that pump are literally microscopic. (As are the clearances in the injectors). A generic disposable filter from Autozone is cheap and would serve to make a test rig if you decide to bypass the existing filter.

 

[Gary Sweat]

If loosening each injector line separately slows each cylinder the same, then there doesn't seem to be one good injector and one bad injector. I don't think that's where the problem is.

And the way you describe the throttle response doesn't sound like an engine running on one cylinder, it sounds like both cylinders are impaired equally.

Could there be something choking the air intake or the exhaust? Did a rag or something go down the intake while you were working on it? Or water in the fuel which should be visible in the filter bowl?

I wouldn't run without some sort of filter ahead of the fuel pump. The clearances inside that pump are literally microscopic. (As are the clearances in the injectors). A generic disposable filter from Autozone is cheap and would serve to make a test rig if you decide to bypass the existing filter.

Well I just got back to the garage from testing it after I found the problem and fixed it. Running like it used to and pulls fine now.

I hate to even say what it was. Here's a clue, always go back to the last thing you did before you screwed it up:laughing

 

[California]

We want photos!!!!

 

[normde2001]

Reason I asked is that both cylinders exit into one hole at the exhaust pipe. I'm not sure how to tell which cylinder is exhausting when.

That's why you remove the manifold . . . . (2 holes).

 

[Gary Sweat]

We want photos!!!!

I was thinking that maybe the governor had some how fouled up so I did a search on the Yanmar forum and came across a thread about a tractor that had rough idle and couldn't take off in high gear. Same symptoms I had.

The problem was the fuel bowl. Somehow when I changed the filter and put on a new bowl the bowl did not seat all the way. It wasn't leaking any fuel but apparently was sucking just enough air into the fuel to cause the power loss and rough idle. So I really can't take credit for finding the problem.

I took the bowl off and pushed up slightly on the filter and it moved up just a tiny bit. Put the bowl back on and the tractor runs great. The new bowl is slightly different in size at the top and requires a matching "O" ring, so if you ever replace one be sure to make sure it actually seats all the way up. It's a little tighter fit than the original bowl.

 

[Gary Sweat]

That's why you remove the manifold . . . . (2 holes).

That's where I was getting confused. The engine does not have a manifold. Anyway, found the problem. Leaking air at the fuel filter.

 

[stormpetrel]

That's where I was getting confused. The engine does not have a manifold. Anyway, found the problem. Leaking air at the fuel filter.

The dreaded air!!!! Lucky it was so easy (and cheap) to fix.

I was leery of loosening the injector nuts to test the individual cylinders because many engines (including my tractor) will run just fine with the nut loose and leaking fuel. In fact, when bleeding air out of the system, the engine usually starts running the moment fuel gets to the injectors, even though some air must be getting in as well.

I'm glad you're back up and running!!:thumbsup:

 

[clemsonfor]

I realized you fixed it, but reading on Hoyes site in there tech forums. They recently have had 2 people with upside down filters in the bowl. There symptoms were a little different than yours but similar. They said there was no power and had to fully press the throttle to keep it running and it would choke down slowly but then restart. The kicker is this guy said it did it whe he bought it (was recently purchased) but then ran flawlessly for 12 hours, then started to slowly die like a fuel restriction. But would always crank up, and he had very little power, to none. His problem was the filter was in the bowl, upside down.

I thought this little bit of knowlege may help someone trouble shoot a problem in the future who may run across this thread in a search.