We have a Deere 444E wheel loader with about 5000 hours or so, it is primarily a yard machine so it does not see a lot of use these days. For a while if it was parked with less than 3/4 of a full tank of fuel it would lose prime, so we always keep it topped off. Well now even full it loses fuel prime in a day or less. We have no lines that are leaking or even damp for that matter, to get her going we bleed at the filter and crack lines all the way to the injector pump till we get fuel by pumping the primer. We replaced the fuel priming pump a couple of years ago but Im wondering if that could be the problem? Any help would be greatly appreciated.
Tags This can be a real pain to trouble shoot at times and before you start changing parts, you need to find the source of the problem. Remove the fuel line that connects to the fuel pump. Need to do two things. 1. If you have a priming pump, pump it very slowly to see if you have any air bubbles mixed with the fuel. If you only have fuel, you don't have any air leaks. If there is any air at all, need to find out if it is the pump or the fuel line connections. 2. To see if the pump is developing pressure, place your thumb tightly over the fuel line on the output side of the pump and stroke the fuel pump. You shoul have 6-16 PSI even with air in the line. If you have no pressure at all you may have a crack or pin hole in the diaphram. Before you replace the pump, most pumps have a fine screen internally that becomes clogged when the debris moves around. Good pressure one moment and then slowly starves the engine as the debris clogs the screen. One way to check if it is the pump that is causing the air leak, use a jar or can filled with clean fuel. Drop the inlet side of the fuel hose from the pump into the jar or can and stroke the pump. Output side should be open. If air continues to flow with the fuel, the pump is bad as in #2 above. If the fuel is clean and no air is present, the air source has to be in your fuel line from the tank to the pump. I prefer to use a steel line with fittings on both ends. Rubber can develop pin holes that will not seep fuel as well as cracks around hose clamps. For the sake of argument, let's say your fuel line and and pump check out and are good. Now you need to verify that the fuel system is tight between the pump output, filter and injection pump. If you have the cube type fuel filter, they are known leakers-- be cautious. Disconnect the fuel line that feeds the injection pump from the filter. Stroke the priming pump. Again ensure that there is no air with the fuel. If you have air, the problem has to be the filter or hoses/tubes betweem the priming pump and the injection pump. If you have no air mixed with the fuel at the injection pump inlet, it's time to check the injection pump. You didn't state what pump you have, however this troubleshooting technique should work. Most injection pumps have a pressure relief at the return line to the fuel tank. If it is the ball & spring type, the ball can become pitted and cause air to renter the pump from the tank because the seal is broken. If the retun line is broken you should be able to stroke the injection pump and purge the air from the low pressure side of the pump. Once the air is purged, tighten the return line. Bleed the injectors until they are clear and run the engine for a few minutes and turn it off. Allow the engine to sit for a while. If your pump is air tight, you should have only fuel flowing when you open the return line. If any air is present, then the pump is your source of the air leak. If the pump/engine run fine, then it's just a matter of resealing the pump. Hope this helps you troubleshoot this elusive issue. Paul
Paul, thanks for the very detailed steps on trying to solve this, I will get back to it Monday and see where I get. Nice job on the Trojan re power, really enjoyed following you through it.
Thanks It takes time to find the poblem-don't give up. Paul