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Car Forum / Driving, Maintenance, Tuning / RVs / February 20081984 onan 4k giving me trouble...
mod 4.0bfa-1r/16004c 1984 onan 4k its been running fine then it started giving me trouble the other day... it runs fine for about 10 seconds then starts throtling itself to corect itself and never quiet recovers... ill shut it down start it back up and same thing.... im thinking the fuel pump is weak...what should the presure be on it? its got a napa pump on it now thats got some patent numbers on it.. no model number as far as i can see.... it pumps fuel if i unhook the out side on it.... i tooks the carb off and sprayed it down... thanks.. >mod 4.0bfa-1r/16004c 1984 onan 4k > >its been running fine then it started giving me trouble the other >day... it runs fine for about 10 seconds then starts throtling itself >to corect itself and never quiet recovers... ill shut it down start it >back up and same thing.... I presume you've checked the oil level, right? GB in NC > >mod 4.0bfa-1r/16004c 1984 onan 4k > [quoted text clipped - 6 lines] > > GB in NC oil level is fine.... st <shane2bt@gmail.com> wrote in news:3cc1e39c-3919-4b02-86dc- d0cc08898ddb@e6g2000prf.googlegroups.com: >> >mod 4.0bfa-1r/16004c 1984 onan 4k >> [quoted text clipped - 8 lines] > > oil level is fine.... How old is the fuel? > st <shane...@gmail.com> wrote in news:3cc1e39c-3919-4b02-86dc- > d0cc08898...@e6g2000prf.googlegroups.com: [quoted text clipped - 13 lines] > > How old is the fuel? fuel is new... fuel lines are good... i took the carb apart and cleaned it out as best possible... > mod 4.0bfa-1r/16004c 1984 onan 4k > [quoted text clipped - 12 lines] > > thanks.. The usual causes of this are an 'idle' mixture that's too lean, or throttle linkage that has play in it. The governor attempts to hold the generator at a constant rpm by positioning the throttle as needed. When the genset is stopped, the throttle is wide open. Once the genset starts and comes up to speed, the governor closes the throttle, then as the genset slows a little, opens the throttle a little. If everything is right, the genset will wind up running at a constant speed with a constant throttle opening, with the engine producing just enough power to maintain speed under whatever load is present. If the load changes, the speed will start to change, and the governor will open or close the throttle to try to maintain that constant speed. If the 'idle' (closed throttle) mixture is lean, when the governor attempts to position the throttle for a light load, the engine keeps losing speed until the throttle gets far enough open for the main jet to come into play - then the genset will gain speed until it passes the desired speed, at which point the governor closes the throttle, the genset loses speed, finally hitting a point where the governor has the throttle far enough open that fuel flows through the main jet, at which time the genset starts to gain speed again....... lather, rinse, and repeat. If the throttle linkage has play in it the same thing can happen, because small movements from the governor are not matched by equal movements at the throttle - the throttle is always either ahead or behind where the governor wants it to be. Checking for play in the linkage should be easy - it should move freely, but -any- play is too much. The easiest way to see if the problem is due to fuel mixture is to hold the throttle in position once the genset is up to speed and has positioned the throttle to the normal no-load (almost closed) position - if mixture is the problem, it will lose speed until it dies. If mixture is the problem, you WILL need to take the carb apart and soak in carb cleaner to get some of the neessary places clean, and although you don't necessarily need a carb rebuild kit, you WILL need to use a new gasket between the carb body and the airhorn - because some of the idle passages go from one to the other, and re-using a 20+ year old gasket is almost certain to leak enough air to these passages to cause problems all on its own. Trust me on this - been there, done that, didn't enjoy it at all. The fuel pressure should be about 3.5 psi (maximum of 4.5 psi). Any more than this, and the float doesn't have enough leverage against the float valve to seat it completely, so you'll wind up flooding the carb at light loads. Actually, I'm surprised that a NAPA fuel pump is doing ok - most automotive fuel pumps are spec'd for 6.5 - 7.5 psi, which is too much. Alan > > mod 4.0bfa-1r/16004c 1984 onan 4k > [quoted text clipped - 63 lines] > > - Show quoted text - loads of great info .. thanks... there is needle valve on the back of the carb... what does it do? where should it be set to? > > "st" <shane...@gmail.com> wrote in message > [quoted text clipped - 74 lines] > > - Show quoted text - BTW ordered a new gasket today.. should be here tomorow.. how should i clean the carb.. just open it up and soak it in carb cleaner overnight???? when i blow on on the main fuel tube should air flow evenly when the floats are moved? > > > "st" <shane...@gmail.com> wrote in message > [quoted text clipped - 81 lines] > > - Show quoted text - here is a video of it acting up.. under no load btw... http://www.youtube.com/watch?v=MtN3xOiCdCY thanks > > > > "st" <shane...@gmail.com> wrote in message > [quoted text clipped - 87 lines] > > - Show quoted text - I talked to napa and its a 4psi napa pump for small engines....i still have yet to put it on a guage cause i have not located one yet.. does the pump stay on all the time the engine is running? if so, how long should a genest run (w/gas in bowl) if the pump is disconnected once it cranks... > > > On Feb 24, 9:51 pm, "Alan Robinson" <a...@bmi.net> wrote: > [quoted text clipped - 126 lines] > > - Show quoted text - I talked to napa and its a 4psi napa pump for small engines....i still have yet to put it on a guage cause i have not located one yet.. does the pump stay on all the time the engine is running? if so, how long should a genest run (w/gas in bowl) if the pump is disconnected once it cranks... Clean the carburetor by taking it apart - take the top (airhorn) off the body, remove the float and float valve from the body, remove the main jet and idle needles from the body, remove the main jet from the body. Soak all parts except the float and the gasket washers for the float valve and main jet in the carb cleaner for the time that your cleaner recommends, then rinse with clean solvent. Blow out all passages with compressed air. Once everything is sparkling clean, re-assemble and re-install the carb. Set the main jet and idle needles to their preliminary settings. The needle valve on the -back- of the carb (meaning opposite the throttle linkage side) is the main jet - preliminary adjustment is turn in until lightly seated, then turn out 1 1/2 turns. The needle valve on the side of the carb towards the point box and generator end is the idle jet - preliminary adjustment is turn in until lightly seated, then turn out 3/4 turn. These are just starting points, but should be close enough for the genset to start and run. Once you have it running and thoroughly warmed up, apply about 2kw load and adjust the main jet for highest speed/best running. Remove the load, allow genset to stabilize, then -slowly- adjust idle mixture for highest speed/best running. If it's hard to tell if adjustments are making any difference, hold throttle linkage closed against idle stop (should be running about 55 hz/1650 rpm) and repeat idle adjustment. Release throttle linkage, let gen recover speed, then apply 3kw load and adjust main jet for highest speed/best running. Now move the linkage to slow the set down a little, then release - genset should pick up speed cleanly, without coughing or hesitation. If needed, adjust main jet out slightly, a little at a time, while repeating this test until gen does recover properly (should take a maximum of 1/4 turn more). Note: do NOT do this procedure while the genset output is hooked to your rv - some things may not be happy with the voltage or frequency produced while you are making adjustments. Use resistive loads for your load test, such as heaters/hair driers/lamps. The voltage produced by your genset depends almost entirely on the speed the genset is running - if it runs too slow, the voltage will be low, if it runs too fast, the voltage will be high ( I've had sets come in with 170v + output after someone 'adjusted' them). Once it seems to be running ok, check your voltage and frequency before you hook it back up to your rv...... The fuel pump on your genset stays on all the time that the genset is running. If you disconnect the 12v to the pump once the genset is running, it should run 15 - 45 secs before starving (can't really be more precise than that). Alan ///snipped for brevity/// > Clean the carburetor by taking it apart - take the top (airhorn) off the > body, remove the float and float valve from the body, remove the main jet [quoted text clipped - 41 lines] > > Alan Alan, That is excellent info. Although I don't have a genset problem presently, there is always the possibility. Your post will be invaluable in working the problem. We should start an archive of posts such as this for reference purposes. Does anyone have an idea how to do this? DaveD > ///snipped for brevity/// > [quoted text clipped - 57 lines] > > - Show quoted text - thatis tre.. alan is the best source ive ever had anywhere on the net ......great stuff!! thanks > Alan, > That is excellent info. Although I don't have a genset problem presently, [quoted text clipped - 3 lines] > > DaveD Dave, There's already an archive for all of Usenet - go to groups.google.com and use the advanced search. If you want threads that have posts by me with generator information, just use the appropriate search terms. I DO plan to one day have a website with troubleshooting information, but keep running into a shortage of roundtuits. Keep a few things in mind, though - what is appropriate for one generator may be either different or entirely wrong for YOUR generator. For instance, just in (relatively) common 4kw Onan rv generators, there are the 4.0CCK, the 4.0BF, the 4.0BFA, the 4.0BGE, and the 4.0KY. Within just the 4.0BGE, there have been two different methods of voltage regulation/generation, 4 different control boards, 3 different carburetors, ...... well, you get the idea. So before you try using advice you find on the internet, make sure that it applies to YOUR generator. I've been (sort of) training people on alt.rv and rec.outdoors.rv-travel to mention the model and spec of their genset in the intial post, and things seem to be getting better in that regard - so I can tailor my advice to the specific situation. And, of course, a more detailed post that gives exact symptoms usually gets things resolved faster than if you were to post 'my genset doesn't want to run. Anyone have any advice?' <g> Alan >here is a video of it acting up.. under no load btw... >http://www.youtube.com/watch?v=MtN3xOiCdCY Hmmm . . . that's the same thing that happens with the governor on my lawn mower when the mixture is too lean. On Feb 26, 1:41 pm, stan.bi...@hotmail.com wrote: > >here is a video of it acting up.. under no load btw... > >http://www.youtube.com/watch?v=MtN3xOiCdCY > > Hmmm . . . that's the same thing that happens with the governor on my > lawn mower when the mixture is too lean. well this sucks.. onan sent the wrong part .. a hose instead of the gasket.... they toldme tampa hada kit for 50$ .. wrong kit after driving 40 miles... then they tell me my carb has no replacement parts and i have to get a new chinese model carb for 160...woopdeedoo... this is gonna be fun.. ;(
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