Hi all, My 120 won't start and it has what I think is a fuel issue. I have done a bunch of things to diagnose it but to no avail. Hoping someone can show me what's staring me in the face. - Ran fine the last time I used it, didn't notice anything unusual. - Sat for about two weeks, came back and it just cranked with no smoke. - Figured the fuel system lost prime, tried to bleed and got lots of bubbles that didn't seem to end. - Installed a new rubber fuel line from the tank to the water separator. - Took the water separator off and pressure tested the seals, also checked the screens in the banjo bolts going in and out of the separator, they were clear. - Re-assembled and now it seems to prime up fine, bubbles are gone and I can hear the return fuel splashing back into the tank. (was bled at the return line banjo bolt on top of the fuel filter as per the manual) - Now when I crank it I get blue/white smoke with the occasional puff of brown/black smoke but no start. - Also tried bleeding at the injectors and fuel does squirt out when the lines are cracked. - Pulled 3 and 4 injector out, flipped upside down, then re-connected, cranked the engine and both injectors were spraying a mist of fuel out of the nozzle holes. - Pointed a heat gun into the intake, didn't help. - Disconnected the glow plugs and sprayed brake clean into the intake, seems to want to run on that. - Fuel shut off lever is free so it's not like the engine stop motor is seized from the last time the engine was shut down holding the fuel shut off lever in the off position. Right now I'm leaning towards some kind of timing issue but I don't know how something like that would happen while it's parked. It has a Zexel fuel injection pump, same as a Bosch A-size pump I think. The engine is an Isuzu 4BD1T. Any and all wild guesses are appreciated.
Try spraying WD40 into the air intake while cranking over ( 2 people required ). If it fires right up you have a fuel issue or a cylinder condition issue. If it pops right away, does it run afterwards on its own. Does it have a positive air shutoff, just a few cheap things to try before firing the parts cannon. Cylinders need good head gaskets, some need glow plugs or ribbon heaters, and air plus fuel to run. Just a few things to check. Simon C
On the side of the inj pump is the supply pump.. the inlet line coming in from the bottom has a filter screen in the banjo bolt, they clog up with debris.. Give it a look..
I had my brother spray brake clean into the intake and it did want to run on that. I will not run afterward on its own. There is no positive air shutoff. It has glow plugs, temperature was around 0 deg C. I usually use the glow plugs when it gets around freezing. When I do forget to use the glow plugs its still starts fine until its gets colder like -5 and below, then it really like glow plugs. I think the compression is fine, before it stopped working it ran just like normal. Would be weird if it just lost compression while it sat right? So you're telling me that there are 3 filter screens before the supply pump?! My machine has a brass screen in the inlet to the water separator and a plastic one on the outlet that leads to the supply pump. Both are clean. This third screen would be at the bottom where the hard line coming from the water separator enters the supply pump? Seems kinda overkill to have that many screens in the system. Never would have thought there would be 3. I will have to check this out, hopefully during the week or on the weekend at the latest.
Ok, I got the banjo bolt off at the bottom of the supply pump. There is no filter screen to be found, just an empty banjo bolt. Looked with a mirror, doesn't look like the filter is stuck up inside the supply pump. I also took off the line exiting the supply pump that goes to the fuel filter. No screens in there either.
Could try putting 2 psi into the fuel tank with a ball of rags stopping the air from exiting too much. If there is any fuel leak in the lines to the transfer pump, could be sucking air when cranking over. Did you try disconnecting the line coming out of the transfer pump to see how much fuel there is coming out with it cranking. Could check with it cranking and with air on fuel tank. Also not sure how dry Brakleen makes the cylinders versus WD40. Just a thought. Simon C
I replaced the line from the tank to the water separator and just had all the hard lines off that go from the separator to the supply pump and then from the supply pump top the fuel filter while I was looking for that screen. Put it all back together and primed up good with the hand pump. No bubbles coming out of the return line on top of the fuel filter housing. I might give wd40 a try. I understand what your saying about brakleen being too dry. If I disconnect the line coming out of the supply pump at the fuel filter, how much fuel should I be looking for? Obviously it shouldn't be a dribble but it shouldn't be squirting out either should it? How much pressure does the supply pump make? A new thought I had is that the engine stop motor could be stuck holding the fuel shut off lever in a slightly closed position. Since the machine was running perfectly fine the last time I used it, it might make sense because the stop motor is the last thing to operate when the engine is shut off. I should add that a few times the machine has kept on running when I turned the key off. It hasn't happened in months but I have had it happen probably 3-4 times. I had to the cycle the key a few times to get it to shut off. Maybe that was a sign that the stop motor was having troubles. Also according to my workshop manual only the 6 cylinder engines had the screen in the banjo bolt at the inlet to the supply pump. The water separator was an option, so maybe 4 and 6 cylinder excavators that were sold without the water separator got the screen in the inlet of the supply pump. Mine has the water separator so it makes sense now why I was not able to find a screen in the inlet of the supply pump.
Disconnect the stop motor control cable from the injection pump shut off lever and see if the engine will start and run at full power. Also check when in “P” engine speed on the monitor that the injection pump throttle lever is against the high idle stop.
Good point Dave.. I don’t think in my 40 years, I’ve ever seen one that actually touched the hi idle stop screw.!! The “break-back lever” was ALWAYS worn out.. THAT wouldn’t have anything to do with his fuel flow problem but it’s a good point.. Remove the solenoid arm from the shut off lever and move the lever to the run position.. as Dave mentioned.. Sorry I sent u on a wild goose chase looking for the filter..
It runs now! I loosened the jam nut on the stop motor cable and pulled it out of the bracket. As I pulled it out, the spring on the stop lever pulled the lever forward about half an inch into the run position. Gave it some glow plug action, turned the key and it fired right up. I have since pulled the stop motor out and took it out of the bag. After a little disassembly the cable seems to move freely, there is plenty of grease in the gear case and the brushes don't look all that worn in the motor. When I turned the key to shut it down the stop motor didn't even try to move the cable, so now I probably have to look for an electrical problem in the stop motor control circuit. I did not check that today when I got it running but I can in the future. The I,L,E,P buttons have not lost their programming and the arrow keys move the throttle up and down incrementally like they are supposed to. No worries, now I don't have to wonder if there is a filter down there that could cause future problems. Which one is the "break-back-lever" and how could I fix it if it is worn out? I have not had any trouble reaching any of the circuit relief pressures when in "P" mode so I don't think its lacking power.
How about posting a picture of the throttle assembly..
After further inspection... the stop motor has some serious issues! It must have gotten really hot at some point, I'm thinking before I owned the machine. That problem where it intermittently wouldn't shut the engine down, well that's probably because one of the magnets inside the motor casing has a large crack in it. This last time it must have pulled the stop lever enough for it to shut the engine off and then got stuck on the cracked magnet. Gonna need a new stop motor even if there are other electrical issues I don't know about yet. I will try and get a picture of it tomorrow after work.
Ok, here are a couple of pics of the pump. The stop motor cable is not in the pictures, I had already removed it before taking them.
I was wrong AGAIN.. U have a Zexel pump, I ASSUMED it would be a Bosch pump.. & those are the ones that wear out the B/B levers.. I better cut my loss’s and bow out of this conversation.. lol
It's all good! I appreciate your willingness to help.