I have a Caterpillar 3126 crank no start once in a while it will try to run for a few seconds and dies out. At times it has smoke then at other times you can crank and get no smoke at all. I have fuel coming back from return line with no bubbles. Anything else common on these? I also tried connecting a high pressure electric pump to feed the fuel system but does the same thing. Engine family number is 5CPXL07.2HSL ARRANGE 198-3456 SERIAL BEJ14497
Sounds like injectors are worn out I have the tooling to set up and replace injectors on MUI Engines, Im located in Mn
I have all the tooling to do the injecters 507 244 0769 Al
How do I confirm the injectors are faulty?
Put thin pair of vvice grips on rack bar ans while cranking move to fuel on and see if it starts, if it does the injectors have to much. Leakage at idel dlont put vce grips next to rack mount ,any adjustment screws , have u checked fuel preszure, how abt shut off solenoid ?
Attached is psi while cranking over. But this will not run.
Did you get this thing figured out. Just curious. Simon C
Just getting back to working on it. It almost fires and but not quite. How do I determine if the injector coils are bad or if it's mechanically something wrong with an injector or injectors?
Could try pulling the air filters out after first cleaning the housing with air, then try blasting quite a lot of WD40 into it to see if it starts up any better. If the fuel pressure is too low it probably won't make any difference, if it does it would indicate an sudden increase in compression helping to start. Not sure how much fuel pressure you are suppose to have. Is the cranking speed around 250 RPM is another thing to consider. Not sure what is exactly controlling the fuel pressure as the desired is 10.5 psi low. It might just be too much for it to go. How many hours on the unit, is it just worn out or have all the fuel filters and banjo fitting screens been changed if it has any. If forcing air into the tank while cranking helps it to start, it would indicate either bockage of the fuel or wear on the fuel system charging circuit. Simon C
Since you already verified fuel return and no air bubbles, I'd start looking at the HEUI side. On the 3126, low injection actuation pressure is a pretty common no-start cause. The fact that it sometimes smokes and sometimes doesn't makes me think ICP sensor, IAPCV/IPR valve, high-pressure oil leak, or even a weak HEUI pump. I'd also hook up Cat ET and watch cranking RPM and injection pressure while it's acting up. Fuel supply sounds less likely if you've already tried an electric feed pump. If you don't already have the service manual for that arrangement/serial number, the troubleshooting section can save a lot of guessing. You can usually find Caterpillar manuals at ManualsKart .
Working on this again finally while cranking it has 1150 psi injection actuation pressure engine oil pressure 50 psi fuel pressure 63 psi. Could it be the injector or injector coils? I'm thinking of trying a stethoscope while cranking to see if I'm can hear each injector could click. I tried a noid light and the injectors are getting power.
Nothing wrong with the actuation pressure looking at your picture above. 24% current, along with desired versus actual injection actuation pressure within 100 psi, means no high pressure oil leaks. I'd expect fault codes if the injector coils have failed. Also those coils run on about 100 volts so keep that in mind when you're poking around with a stethoscope. With your scan tool, there should be a parameter in there for 'injection disabled', verify that's reading 'OFF' while cranking. Going back to your very first two sentences, if at times you crank it and get no smoke, injectors aren't injecting. Likelihood of all 6 failing at once is extremely unlikely unless your fuel is not fuel. Tried alternate fuel source yet? While cranking, is your RPM reading stable, or does it fluctuate and do silly things? That'll stop injectors injecting. Before you start cranking with just key on, do you see any strange readings on your sensors? Eg, all pressure sensors should read zero, all temp sensors reading ambient. Fairly sure injection actuation will read about 250 psi with zero pressure, that's normal. Any loose ground cables? What's the engine powering, any E-stops or shutdown switches playing up?
There are no fault codes showing. I connected a high pressure fuel pump and it's feeding at 65 psi. Engine rpm is 0 while sitting and about 180 while cranking. I do not see any loose grounds. There are no shutdowns that are telling it to not run. The engine powers a air compressor.
Can you confirm that sensors are reading correctly and your fuel is good? Will it run on some starting aid spay?
Yes all sensors seem to move as they should. Yes it will fire off ether. Fuel is new and fed from a bucket of new diesel
If it runs on ether that's promising. Regarding that fuel return line at the back of the head, there's a fuel pressure regulator in there. Later ones had a metal screen to catch debris. If you find metal shavings either in the screen or stuck in the regulator it's open up your wallet time. Not sure what scan tool you're using but I think you're going to need ET from here. That will probably be the cheap part of the repair. I'd be checking the injectors are still programmed (ECMs can lose their memory), all logged/active codes & events, and anything else that's obvious. I'd also want to see an ET Product Status Report and a screenshot of parameters required to start engine. In addition to your screenshot above, while cranking: Desired engine speed Atmospheric pres Shutdown switch status Battery voltage Injection disabled status Unlikely but the turbo hasn't seized has it? Edit: Is there a backstory to this engine, ie been sitting for years, recent repairs, etc?
The screen on return is clean. Fuel returns with no bubbles while cranking. I'll get the other info Monday. How do I know if injector is possibly stuck closed? Engine has say for several years I purchased it not running.
We've had surplus 3126's that sat for a long time before auction need all new injectors before. Sitting combined with probably poor maintenance on both the fuel and oil side led to issues.