HerbS 6 #1 Posted November 1, 2022 I'm working on a 518-H. There's no fuel getting to the engine, or to the fuel filter for that matter. I can siphon gas to the entry of the fuel pump, so there's no blockage. I bought a new fuel filter, and that didn't help. I traded the fuel pump with another 518 that works, and that didn't help. The oil level is right and the fuel cap is loose. What's left? Thanks. 1 Share this post Link to post Share on other sites
gwest_ca-(File Mod) 11,246 #2 Posted November 1, 2022 If the fuel lines have hardened they will leak air into them at the hose barbs under vacuum but not leak fuel out. Soft rubber will grip the barbs and not leak. When an air bubble enters the fuel all the pump does is increase the size of the bubble and each pulse does not last long enough to bring fuel with it. 4 1 Share this post Link to post Share on other sites
953 nut 57,963 #3 Posted November 1, 2022 I would suggest you replace all of the fuel system components from tank outlet to the fuel pump inlet. The grommet in the tank and tank valve can be found on as a kit with hose, clamps and filter. https://www.ebay.com/itm/234744976897?hash=item36a7e41601:g:8uIAAOSwWWRjUZSY&amdata=enc%3AAQAHAAAA8AlI1x0ZdA25%2F2WvHebRE8eyEy%2BYY8MHpfY1Taq8HgYWFD5Nu3OhcXCUULsAx%2BFzGSe2%2BsFoz59CFYNBfKe2C0wIJoy3tprdg%2FRhjATrVTovUT35pnK1TjJ%2BLXmaoexo9D0hZyVxfGrE2BSgnMV%2B4MIW%2FQgatVnifGUKvfQzbk80cqTb%2FI3ffRQMgEVNm8e8BHVdgRqX2T6nGDqr2H0wBO%2FV4%2BlHSbUr9YbmFIZxr1IQWgGGSpqwBep%2Fmi5%2BtkN5jhTwKRClpghogrwqK8SM2KYo5ty2zjuZ0%2Fz0dAOdCCzsTmlD2Klv5mMc%2BDpDx%2F%2B7Ow%3D%3D|tkp%3ABk9SR6jt2NWGYQ 2 Share this post Link to post Share on other sites
peter lena 9,092 #4 Posted November 1, 2022 @HerbS agree with others on the fuel issue repair , suggest you use a dielectric grease on the fuel tank grommet , made for dissimilar material , make the grommet a much easier fit into tank and also in the insert of the fuel valve . also regularly add STA BIL fuel treatment to all my fuels . also have 2 fuel filters on my tank to engine , large one close to tank in trans tunnel , smaller one closer to carb . none of my carb bowls have any debris in them . pete 1 Share this post Link to post Share on other sites
rmaynard 15,927 #5 Posted November 2, 2022 Since you said that the known working pump didn't fix it, and since Onan pumps operate via pulse vacuum from the crankcase, my thought is that you may be connected to the back of the pump, but not connected to the crankcase. No offense to those who like to use snake-oil in their gas, but if you have read any of my posts on that subject you will know that I do not use any additives. All I run is ethanol-free gas and that solves gas issues. 1 Share this post Link to post Share on other sites
HerbS 6 #6 Posted November 3, 2022 I've replaced everything from the tank to the carb, so I'm inclined to go with Bob's theory that I'm not connected to the pump vacuum at the crankcase. How do I get to the connection at the crankcase? Big job? Thanks. Herb. 1 Share this post Link to post Share on other sites
rmaynard 15,927 #7 Posted November 3, 2022 The dreaded engine cover removal is necessary. Not that difficult. Share this post Link to post Share on other sites
RED-Z06 2,479 #8 Posted November 6, 2022 (edited) Easiest way is to pull the pump, then pull the rear cylinder cover...its tedious but not impossible, then use long pliers to put the hose back into the pump....then attach the pump. Here's what you're dealing with under it all.. Edited November 6, 2022 by RED-Z06 1 Share this post Link to post Share on other sites
