I have a 1995 EX 120-3 with about 8000 hrs. Recently when it gets warmed up it starts to bog down & then start missing under a load. The more I use it the worse it gets until it misses to the point of quitting. It will run ok at an idle or max rpm without a load. If I leave it off for 10-15 minutes, it will work ok until hot (10min) where it starts again. I've replaced all the filters, checked for H20 in fuel, & check lines. The fuel pump seems to pump ok but I haven't put a pressure gauge on it yet. No visible leaks and I don't think it is getting air in the lines but I haven't cracked the bleed line when it's missing yet. Clean air filter. Good vent on fuel tank. The throttle linkage stays at the max setting while it begins to bog down. I haven't owned the machine long enough to know it's history or care. Any ideas? Is there anything electric that affects the fuel delivery through the pump when a load is placed on the system? I'd appreciate help or a trouble shoot process to find the problem. Is this typical of a wore out injection pump? Obviously the most expensive fix. Thanks - Bill
Start at the first connection for the fuel suction line coming from the tank, usually at the transfer pump, pull the bolt out of the banjo fitting, look at the hollow center see if there's a tiny screen screwed into it. Might want to check them all right on up the line, I have seen more than one, sometimes none, depends on the engine make and model. Fuel priming pump can suck air sometimes and also the fuel transfer pump can get weak or the check valves hung up, etc. Here's a generic picture, #4 is the screen inside the banjo bolt:
I've checked the lines. There is no inline screen filter. Fuel flows freely at the output of the cartridge filter. Is there a port to install a gauge to measure the pressure into the injection pump while running? What should that pressure be? Generally feed pumps fail. In this case everything works until the engine gets hot and surprisingly it doesn't have to be shutdown very long before it acts ok again for awhile. If it sucking air, should I see the bubbles coming out of the bleeder screw at the top of the filter while running poorly? I'd like to check as much as I can before I begin the difficult task of tearing thing apart in tight quarters. Thanks for the pump schematic.
There should be a small plastic screen screwed into the line that feeds the filter before the pump, if it's not there then someone has removed it and there is more of a chance that rust/debris from the tank will get places it should not. If I get a chance I'll try to remember to take a pic next time I'm greasing ours. might be a few days....
Is there any smoke from the exhaust while it's bogging and missing? (there should be if it's running that poorly) If so what color is the smoke? What is the make/model of the engine??
Bdward did you ever get this figured out? Mine is doing the exact same thing. I’ve changed filter, cleaned thank. Changed filter again. Guess I’ve gotta check banjo screen next. But seems if that was stopped up that it would run bad form the start. It usually runs good for 10-15 mins.
It can run great for a while then poof!!! the banjo screen is a bottleneck when it comes to rust granules and such, they are a bit fragile but easy to clean... don't tighten it too much when screwing the plastic part back in... it WILL crack and separate at the threads. It's a very common issue with these things, best action would be to put a bigger remote filter inline(before the banjo) and remove the banjo as these machines get older the rust will be more prevalent. When you say you 'cleaned the tank' what does that mean exactly? there is a fuel tank sump drain on these do you drain it periodically?
Ronsii- I have thought about adding another strainer on the line. One that’s easier to access. WS thinking I’d mount it above the water separator. When I bought this machine a year ago I had fuel issues. So I pulled the tank and pressure washed inside and used shop vac to completely clean it. When it started acting up again, I drained almost all the fuel out. I looked inside tank with a light and could see the bottom of tank. It looks fairly clean, no noticeable sediment laying in bottom of tank.
I pulled banjo fitting at pump and it wasn’t bad. Found another banjo with strainer at water separator. It was really nasty. Cleaned it up and that seems to have fixed my problem.
I gave ours a good cleaning several years ago including a good shopvaccing at the end to get anything loose but the rust will keep appearing so now anytime ours starts to sputter first thing is pull the first banjo screen and clean it... it's always full o' rust... about a dozen times a year or so... it's just the nature of older macines designed like this unfortunately...
Sounds like my issues which turned out to be bad fuel lines. Mine would run great once started and then at some point id notice the RPMs start to drop and eventually stall. A restart would require all the cylinders to be primed. I wasnt smart enough to realize the problem. After a little inspection, the fuel line from the tank to the lift pump was cracked at the fitting. I replaced all those and its been running great for a few days now. Oh, dont forget to turn the fuel back on before trying to prime your cylinders. It doesnt work with the valve shut!