ericj 1,578 #26 Posted January 1, 2015 in post # 5 were the fuel pump mounts to the engine shroud you can see the vacuum line coming out from under the fly wheel cover shroud. it might have been pushed back inside the engine tin and that's why you can't find it. there should be a nipple sticking out the back flat side of the pump and goes through the hole in the tin. i'll see if i can get pictures later today and post tonight unless somebody already has pictures that they can post eric j Share this post Link to post Share on other sites
boovuc 1,090 #27 Posted January 1, 2015 Hi Ohio Guy, I have three lines that run to my fuel pump on the P series Onans I own. They are all 1/4" hoses. The "what I call vacuum" (pulse) hose that comes in behind the flywheel shroud and attaches to the back plate of the fuel pump and of course the inlet and outlet fuel lines. I checked the service manuals I have for the Onans. One from John Deere and one from the gensets they were used on and both state the pulse line is quarter inch in diameter. The 5/32" line you have doesn't attach to the fuel pump in my opinion. (And we all know what opinions are like and every human has one)! That small hose is most likely a line for the vacuum gauge or sensor. In the picture above that shows the flywheel shroud, I can see very clearly the 1/4" pulse line in the hole and mounting area of the pump. They are the three lines you need on that pump. If the 1/4" hose is no longer visible in that hole through the shroud, it fell in behind the shroud. Does this make sense? Share this post Link to post Share on other sites
OhioGuy89 4 #28 Posted January 1, 2015 Hmm. Ok, someone mentioned that vacuum gauge earlier. Any idea where I would find it? And yes, that makes sense. Share this post Link to post Share on other sites
boovuc 1,090 #29 Posted January 1, 2015 (edited) Only guessing that it may be the gauge. I have a 520 but I haven't had any issues with my gauges. On your 520-H dash, there is a gauge on the upper left side that "may" say HORSEPOWER, it may show a team of horses at the bottom of the gauge or something similar. (Doing this by memory). This is the "percent" Horsepower gauge and it runs off a vacuum line. I just can't remember where that line connects to. Since it is vacuum, I would "assume" it comes off the intake manifold but I do not know for sure since I never had issues with mine. When your engine requires more power, it draws more vacuum and the more vacuum it draws, the gauge swings more toward the 100% side of the scale. At idle, no load on the motor so there is less vacuum and the gauge reads more toward the 0% end of the scale. You can look at the back of the gauge and try to follow it but your best bet is to get manuals for your tractor and a file called "Toro Demystification Guide" that is also on our forum in the manuals section. The quarter inch pulse line that runs the pump and attaches to the back plate of the fuel pump is behind the shroud and you may have to take the flywheel shroud off to get to it "if" you can't see it through the mounting hole. Good Luck and I hope this has helped. Edited January 1, 2015 by boovuc Share this post Link to post Share on other sites
ericj 1,578 #30 Posted January 1, 2015 (edited) the 5/32 hose is for the air filter light on the dash. don varos posted a picture of his in post # 20 it's right along side the battery on the left side of the tractor the plastic nub in the center of the line suggest that it's broken off witch is very common for them the other 1/4 vacuum line goes from the intake manifold to the vacuum gauge on the dash like boovuc described above. maybe you need to take your air cleaner of the tractor then you can understand and follow the hoses were they go. you have been given lots of good advice in this thread you just need to reread and try to understand and listen to what is being said eric j Edited January 1, 2015 by ericj Share this post Link to post Share on other sites
boovuc 1,090 #31 Posted January 2, 2015 And there is the end of the mystery. (Though a little on the harsh side)! Inlet, outlet and pulse hose which fell behind the flywheel cowling are 1/4" hoses. The smaller mystery hose is for the air filter idiot light and has nothing to do with the fuel pump. I understand all the overwhelming responses, OhioGuy! Especially when this chore you were working on is probably a back burner issue to your family, house, cars, etc. We work on these tractors a lot and for someone who is new to it and especially with a 520 that has all those electrical connections, gauges, hoses and safety BS on it, it's easy to not follow all the responses you were given. Don't sweat it! Just hope you get your horse up and running again soon and I hope this new year is a good one for you! Share this post Link to post Share on other sites
OhioGuy89 4 #32 Posted January 3, 2015 Thanks Boovuc! I do truly thank everyone for the responses. WIth that, where does the small hose connect to to connect to its idiot light? Or does it just hang there. I looked at the dash and didn't notice anything ( I could also be blind) I do love my wheelhorse. My dad got it from his cousin years ago, and after my dad passed, I've seen it as my job to maintain it, since I have fond memeories of it, and still use it. Share this post Link to post Share on other sites
boovuc 1,090 #33 Posted January 3, 2015 There "should" be a small nipple on the bottom pan of the air cleaner assembly that the hose fits on. It may be broken off but that is where it should go. Share this post Link to post Share on other sites
OhioGuy89 4 #34 Posted January 3, 2015 Ah. Ok. Is it a big deal if that nipple broke off? Share this post Link to post Share on other sites
Callen 64 #35 Posted January 3, 2015 Post 20 is what you're looking for....by the battery. The nipple is probably broke off inside the hose. That is why you can't find it. On things like this the factory didn't use a lot of excess hose. you can pull the hose to its length and look for some where to hook it just short of the end of the hose. The really long 1/4 hose from the engine will go to the vacuum gauge on the dash behind the battery. Share this post Link to post Share on other sites
OhioGuy89 4 #36 Posted January 3, 2015 Ok. You are right about the nipple breaking off in the hose. I had to yank it out with a piece of needle nose pliers. I'll just find some place to stick it Share this post Link to post Share on other sites
