DSHequipment Posted September 22, 2014 Share Posted September 22, 2014 I had a broken manifold stud on the exhaust, so i took everything off to get to them. Turbo, fuel rails and injectors and the exhaust manifold. I put everything back together and went to go start it and it runs like crap. It sounds like its missing. So we tired bleeding the air from the injectors, and then we pulled power from each injector one by one. Only number 1 and 3 injectors would kill the engine. I replaced the other 4 injectors and nothing changed. I changed the fuel filters, changed the oil and filter, changed o-rings, and everything else small i could think of. The only code on the computer is 4-1 and that is just a speed sensor. Any help or info would be great, thanks Quote Link to comment https://www.bigmacktrucks.com/topic/37164-mack-400-poor-idle-and-high-rev/ Share on other sites More sharing options...
wheeler73 Posted September 24, 2014 Share Posted September 24, 2014 I have had them get air bound. What you are calling an injector sounds like a unit pump and not the actual injectors. Did you plug off the unit pumps and the heads? Debris can get in them easily. If they are air bound I find that a nice hard run will bleed the air out of them. Quote Link to comment https://www.bigmacktrucks.com/topic/37164-mack-400-poor-idle-and-high-rev/#findComment-260950 Share on other sites More sharing options...
DSHequipment Posted September 29, 2014 Author Share Posted September 29, 2014 yeah we bled the air out of the system and nothing changed. and yes i meant the unit pumps. I dont have the tool to take out the nozzles to see if they were junked up but it just seems too coincidental to me that only the back three would not be working. Is there something that controls the two heads separately? Also, the sensor right below the #3 unit pump does not have power going to it. Could not identify which sensor it was though. We also traced wires from unit pumps to ECU and everything looked fine. Im at a loss.... Quote Link to comment https://www.bigmacktrucks.com/topic/37164-mack-400-poor-idle-and-high-rev/#findComment-261501 Share on other sites More sharing options...
wheeler73 Posted September 30, 2014 Share Posted September 30, 2014 Make sure to check the wires for continuity. The unit pumps are ground controlled. Each one separately. Does the sensor go into the fuel delivery galley or where the fuel line goes? If so then it is a fuel temp sensor. Unfortunately debris getting into the injector from the fuel line holes usually is not able to be seen. Quote Link to comment https://www.bigmacktrucks.com/topic/37164-mack-400-poor-idle-and-high-rev/#findComment-261586 Share on other sites More sharing options...
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