OhioGuy89 4 #1 Posted December 24, 2014 Hi folks, in piecing back together my 520-H with the Onan P220-G engine, I was looking at the fuel pump and lines that run to it. There is the line from the fuel tank to the pump, and then the line from the pump to the carburetor. What I'm curious is a smaller diameter line that also connects to the fuel pump. I noticed on the fuel pump that there is smaller diameter hose that connects to the top of the fuel pump. I was wondering what this hose may be for, as the little plastic tip on the pump broke, and I'd like to avoid replacing the pump if I have to. Merry Christmas Everyone! Matt Share this post Link to post Share on other sites
bitten 134 #2 Posted December 24, 2014 Is it a vacuum operated fuel pump? I am not familler with the Onen's. Share this post Link to post Share on other sites
OhioGuy89 4 #3 Posted December 24, 2014 I believe it is, Share this post Link to post Share on other sites
ericj 1,578 #4 Posted December 24, 2014 the onan fuel pumps are vacuum operated fuel pumps there is a port on what i call the back side were the engine supplies the vacuum. then on the front cover they have 2 inlets and 2 outlets and they are marked as to in and out. it is stamped in the cover. with this being said not all of the ports are actually open and are closed off inside the pump. you have to take the pump apart and see if you have another port open that you can use for the broken port. I have j. b. welded a broken port closed and reused another port and ended up with a working fuel pump, but i have seen some pumps like i said that the other inlet or outlet was not open to do this, it varies for one reason or another. if i remember correctly each end of the pump has an inlet and a outlet so what you end up with is the fuel coming in either the top or the bottom and going back out the same side unlike oem were it comes in bottom and goes out the top. hope this helps and good luck eric j Share this post Link to post Share on other sites
OhioGuy89 4 #5 Posted December 24, 2014 So I took some photos to better illustrate my situation. One of the pump, one of all the hoses that go into the pump, and one of the smaller diameter hose that seems to come off the carb. That hose is the one that is throwing me off. Share this post Link to post Share on other sites
ericj 1,578 #6 Posted December 24, 2014 trace it back i believe that is the hose that goes to either the intake manifold or the air cleaner base the intake manifold is for you vacuum gauge and the air cleaner base is for a light for dirty filter, that almost always break off. i'm sure somebody on here can chime in and post pictures of the sensor along side of the battery eric j Share this post Link to post Share on other sites
OhioGuy89 4 #7 Posted December 31, 2014 Ok, so I got a new fuel pump, which is supposed to be the replacement for the old one, but I got a problem. The line for what I think is the vacuum will not,fit on the fitting on the pump because it is smaller diameter than the pump fitting. Any way I can get around this? Share this post Link to post Share on other sites
Geno 1,929 #8 Posted December 31, 2014 Do you think it will fit if you put a little lube on it? Share this post Link to post Share on other sites
OhioGuy89 4 #9 Posted December 31, 2014 I could try that, but the old fitting was smaller, and I don't think they make that fitting on the pumps anymore. What should I use for lubrication? Share this post Link to post Share on other sites
Geno 1,929 #10 Posted December 31, 2014 Any penetrating fluid would work, I use white lithium grease a lot. If it's real close and the older line is hard a new softer line may make the difference. Share this post Link to post Share on other sites
OhioGuy89 4 #11 Posted December 31, 2014 Hmm. I'll see if that works. If not, I'll just get a new line Share this post Link to post Share on other sites
boovuc 1,090 #12 Posted December 31, 2014 That vacuum hose can be a royal PIA to get back on a new pump and that is most likely what the issue is. Even a very small amount of dish detergent will work. Put it on the outside diameter of the fitting off the pump only. Make sure you have your hose clamp ready to slide it up and secure. Share this post Link to post Share on other sites
OhioGuy89 4 #13 Posted December 31, 2014 Looks like I'll be having some fun today lol. I just don't get why the fitting on the New pump isn't the same diameter as the hose like it was on the old pump. Mumble grumble. 1 Share this post Link to post Share on other sites
Geno 1,929 #14 Posted December 31, 2014 If your not worried about looks you can use a vacuum adapter to go to a bigger line, local parts houses will have those. Share this post Link to post Share on other sites
OhioGuy89 4 #15 Posted December 31, 2014 Nice. I'll have to look them up. Any idea what one would look like? Share this post Link to post Share on other sites
boomers_influence 106 #16 Posted December 31, 2014 matt the nikki fuel pumps all use 1/4" hose for in. out, and PULSE. the pulse line hooks to a port in the timing cover or a port in the side of the block, above the oil filter adapter. NOTICE i said pulse, NOT VACUUM. thank you. boomer ( the used onan engine parts guy ) Share this post Link to post Share on other sites
OhioGuy89 4 #17 Posted December 31, 2014 I figured that out, but do you know what diameter the vacuum line would be? Thanks, Matt Share this post Link to post Share on other sites
OhioGuy89 4 #18 Posted December 31, 2014 Actually, looking at diagrams now, the hose I have been referring to,is the breather hose! What does it do, and does it need to Connect to,the fuel pump? Share this post Link to post Share on other sites
OhioGuy89 4 #19 Posted December 31, 2014 Pictured is the hose in question, that I am holding,in my hand. It runs until the air filter cover and somewhere near the carb. Share this post Link to post Share on other sites
varosd 1,185 #20 Posted December 31, 2014 like Ericj stated. that should be the line from the air filter to the sensor along the "firewall" area of the tractor, the left side as you sit on the tractor. bad picture of the sensor Share this post Link to post Share on other sites
OhioGuy89 4 #21 Posted December 31, 2014 Hmm. Ok. Now,I gotta find where that plugs in on the firewall Share this post Link to post Share on other sites
varosd 1,185 #22 Posted December 31, 2014 not a real firewall like a car but look at the picture and note that right next to the battery, there should be the air sensor with 2 wires coming off of it back into the wire harness. supposed to like a idiot light if the air filter gets all dirty and clogged up not a requirement to run the tractor. Share this post Link to post Share on other sites
OhioGuy89 4 #23 Posted January 1, 2015 Ok, so I looked at that lineagai,, and Turns out it's a 5/32 fuel line. Now I have to find an adapter of some sort so I can connect it to the pump Share this post Link to post Share on other sites
ericj 1,578 #24 Posted January 1, 2015 sorry i'm late to the party but the vacuum line you are looking for is under the old fuel pump , take the 2 screws out and pull the pump out a little and you'll see the vacuum line. it runs down close to the oil filter to the side of the block. lately i'v been replacing that line when i have the engine tin off on all of my motors, hopefully save a problem down the road. with out rereading and refreshing my memory a bad vacum hoe from the block to the pump could be the problem why your pump is not working ? good luck eric j Share this post Link to post Share on other sites
OhioGuy89 4 #25 Posted January 1, 2015 Well, I had to replace the pump because the fitting on it broke off ( actually got stuck In the hoses) so now I have a new pump. I notice there is the pulse, a line from the tank to t be pump, a line from the pump to the fuel filter, and a line from somewhere around,the carb to the pump,that is 5/32, which right now does not fit on the new pump Share this post Link to post Share on other sites
