Hello everyone, I've got this machine, was running well, then not, and after some history, now won't start at all. Cummins 6cylinder engine, Injection pump is a Bosch, placard says 3929404RX (model I think) and SN M0325990058. Doesn't say which is which so not 100% sure. Said History: - it was starting and running pretty good for a while. I use it often but certainly not constantly. - developed a no-start issue. It eventually would start after various fussing. - determined that the fuel/water separator was clogged with slime. Cleaned/replaced all the fuel filtration. - still had intermittent no start, but usually could get it to go, until recently - fuel solenoid is relatively new and definitively moves the fuel shutoff lever and shaft on the injection pump (IP). It remains engaged while cranking. - fuel is definitively going into and out of the IP as per cracking both the input line coming from the lift pump, and the return line. - with ether, the engine turns over for short duration, so it's getting air. Air filters relatively clean. - no fuel is coming out of the IP's fuel line ports going to the injectors. I would expect that there would be squirts every 2 rotations on the crankshaft. This is obviously why it won't start, but the cause? -took off the access plate on the side if the IP, and when cranking, the metering pistons are all moving as one would expect. I'm not sure how to further diagnose. Any suggestions before end up having to pull the pump and rebuild it? Is there something in the fuel shutoff mechanism to look at? Thanks in advance.
I would make 100% sure your lines are not clogged and run it off a different fuel source like a fuel can. I have an electric pump set up with a filter head and fuel can to quickly rule out clogged fuel system before going after injection pump
I suppose I can rig up a fuel can above it and gravity feed, but it does spit out plenty of fuel out of the return line when I open it and crank, and also if I loosen the fuel intake port it also seems to have plenty of pressure. ZERO is coming out of the individual injector lines. I haven't found any info on this IP. Can anyone point me to some doc's? Questions for instance, does the fuel shutoff lever disable the metering pistons, or does it cut off fuel to the rail? My observation was that the metering pistons move when cranking, regardless of the shutoff lever position. Anyway, I'd like to understand how that thing operates.
Your best bet is to remove the shut off solenoid..from the lever. Now watch the “pistons” thru the side cover as your cranking.. Granted they’ll go up and down BUT are they going left and right when u reach around and work the shut off lever.?? If it won’t pump at all, that usually means the control rack is stuck and not moving left and right.. ANOTHER THING.. the overflow valve (return banjo bolt) can b broken to the point that it won’t hold fuel in the gallery.. NO FUEL in the gallery means no fuel to the injectors.. Easiest way to check is, remove it and shake it.. if u hear it rattle it’s broken.. Here’s hoping for the best..
There should be a transfer pump on the same side of the block as the injection pump. The transfer pump may have failed. Cummins used two types of transfer pumps one looks like a diaphragm pump from a carburated gas engine the other is a plunger style which is the better of the two. The diaphragm pump has a lever on it to prime the fuel system, the crankshaft may have to be rolled if the lobe on the cam is up to use the priming lever. The plunger pump has a plunger on the end with a rubber cover for priming the fuel system. Near the front of the injection pump there is a banjo bolt holding the return line on. That banjo bolt has a spring and plunger in it to regulate the fuel pressure. If the spring failed or ther was something holding the valve off the seat it will not start or may start but have no power. Loosen the banjo bolt and pump the priming pump, you should have fuel squirting out around the banjo bolt. If there is no fuel remove the banjo bolt and try again.
To close this thread, indeed after some additional fussing I finally got 'er running again. Here's what I did: - Opened metering piston cover again and inspected, while moving the fuel shutoff lever pretty aggressively stop to stop--no motion observed but I haven't found any documentation on this IP so I don't know exactly what's supposed to happen. - took off a small access cover under the pistons and turns out that's the oil sump and probably some cams or such, looked okay, wiggled anything I could but not much really. - loosened the IP return line and pumped the lift pump a couple dozen times. 1 squirt per pump stroke. Tightened and pumped ~150 more times. Squirting sound very evident in return line. - loosened an injector line at the IP and cranked. Noticed a very small amount of metered "squirts" finally, so optimism ensued. - cracked all the injector lines at the IP and cranked--basically all of them finally emitted some fuel. - retightened and then cracked the easy to reach lines at the injectors, cranked again until getting fuel. - retightened and she started. It's a mystery what actually went wring here. It's possible there was some sort of vapor lock. It's possible that somehow the fuel shutoff mechanism was stuck, and massaging it loosened it up. Maybe the check valve in the return line was gummed up or had a leak that cleared. Who knows. Anyway, thanks to all who gave advice.