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Big Dog
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Posts posted by steeler

  1. 10 hours ago, fjh said:

    Easier  stuff first rad cap ,  egr cooler !  Is it throwing up any  codes?

    No codes. What I do with these is put a pressure tester on the coolant tank, fire it up and watch to see if the pressure builds. This one instantly started climbing, normally I don't see much pressure building until the coolant temp starts to come up.

    At an idle the pressure steadily climbed to 10 psi in about 3 minutes. If I ran the rpms up it would build pressure even faster.

    I've only seen this on an mp7 one other time which ended up being pitting in the head where the injector cup seats, letting compression into the cooling system. 

    As far as the egr cooler, am I correct that there wouldn't even be 10 psi of pressure there at an idle? I know that it isn't leaking coolant anyway.


  2. On 12/3/2019 at 10:58 AM, Rogerhays said:

    I have a 07 Mack mp7 it will do this daily it starts and runs fine as the day goes on it will start missing I stop and shut the truck off and let it set for 2 minutes start it back up and will run fine the rest of the day. Just had an overhead done and it didn’t do it before then

    All of the above advise applies here also. Very well could be that the harness is pinched between valve cover and oil valve, or bad terminals at injector.

    Figure out which cylinder is the culprit first.

    As far as the new harnesses having the high tension terminals, I've ran into both 04 and 07 emission new harnesses that do not have the new terminals. The last harness I changed out, I replaced the terminals before I put it on the engine. (After I confirmed it didn't have the good ones)

  3. 2009 mp7, what are you guys seeing as the most likely culprit for building pressure in the cooling system? This one is building quickly, literally spraying out of the overflow cap.

    I know I'm probably looking at either head/gasket, injector cup or air compressor. Trying to decide which row to take here.



  4. 2 hours ago, c-mac said:

    I've pulled the differential pressure sensor and used a small drill bit by hand to remove the carbon buildup in the two ports in the mounting bracket , when I figured I have cleared the mounting bracket I took a spray nozzle straw and pushed it into the venture

    That's what I normally do on other applications, but this one has the ports making a 90 degree turn down inside the hole so I can't get anything to eat thru it.

    I tried carb cleaner which I've had luck with in the past, but it didn't help. I just put it back together and told the customer that he will have to deal with the yellow light until the part comes in. We ordered it as unit down, which usually speeds up the process. Hopefully it won't take a month.

  5. On 9/3/2019 at 3:11 PM, c-mac said:

    Yes it has a/c the new fan clutch is on at all times with the harness to the clutch disconnected. I’d really like to see the diagram if it shows wire number and numerical pin placement 

    Sorry for the delay, crazy busy lately. I'll get that for you tomorrow!

    Hopefully I can find it.

  6. 8 minutes ago, Steve 97 said:

    Ya we have one kit here just wasn’t sure if adding the oil lines would solve the problem 

    I don't think I've ever successfully fixed one with just the kit, but have fixed many with kit and lines. Do both. Make sure you have the new style oil feed screws, and remove the little ball and spring from the bottom.

    The kits usually had instructions in there.

  7. Be careful messing with the gov. 

    The rule of thumb I always used when bumping them up was to screw the star wheel as far forward as it will go, then slide the plate forward about the thickness of a dime. That will make them pull stronger and dump more fuel sooner, without waiting for the boost to build.

    I've never messed with the springs though.

  8. Well I found the problem. Pin 16 on the control panel is a ground, I was getting just enough of a ground to operate everything but the compressor. So after running a new ground I have good power to the compressor, but the clutch is toast. Oh well at least it'll be working tomorrow!

  9. 10 hours ago, 41chevy said:

    Eliminates alot with that info. Does you diagram show the compressor circut tied in with powering the engine fan?

    It shows that as separate. It has a separate pressure switch that sends is signal to the ecu for the fan. Didn't have a chance to work on It today, probably in the morning.

  10. 8 minutes ago, 41chevy said:

    One of the fuse /relay panels has an AC compressor relay that supplies power.  Also the low pressure switch the prevents the compressor from kicking in with less than 50 PSI in the system so I would also put a set of gauges on and check the pressure in the system for starters. 

    Should have mentioned that I replaced the condenser due to a leak. I've also tried a new control panel and new temp sensor as well.

    I don't have any fuses or relays that are labeled specifically for the compressor. There are a couple others that are marked HVAC, but they are powered and good. 

    I did find a different diagram than the one I was using, it's showing power to the compressor coming directly from the control panel, unfused. I'll check for continuity on that circuit in the morning.

  11. 2014 GU713, I've got no power to the ac compressor. My wiring diagram is a bit outdated so I'm not sure I'm going in the right direction.

    My diagram says fuse 53 is for the compressor, but the sheet in the fuse panel shows 53 as a spare. There was no fuse in it, and three is no power to it, even though it is pinned.

    So does anyone know where the power comes from? I know it goes to the pressure switch, I have continuity from switch to compressor, but no power.

    Thanks for any help guys.

  12. On 6/25/2019 at 3:35 PM, CCMtruck said:

    Update: Just like steeler said. I found aluminum pieces in the inlet side of the ecm cooler plate. Its the simple stuff we forget sometimes.

    Good deal. Glad you found the problem!

  13. Kinda off topic here but we do quite a bit of work on paccar engines. You wanna talk about an SCR nightmare, wow.

    I had one with a def quality fault that just would not clear. I threw everything under the sun at it, nox sensors, def doser, new def fluid, dpf filter, catalyst, 7th injector, countless hours of troubleshooting and test driving all to no avail.

    Ended up opening a case with paccar engineers and after several regens and 2 40 mile test drives that had to be recorded and send to them, they simply gave me 24 hour special access to a feature in the software that allowed me to clear the code out.

    I mean really? After all that, it was that easy? I wish they'd give me that special button permanently!

    The truck worked fine after that for about a year, then the same crap started again. The customer said screw it and had it deleted, and I don't blame em.

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