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2007 MP7 No Power


Kentucky Joe
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Just purchased a 2007 Granite dump truck. MP7 with 270k miles. Truck has no power. Changed fuel filters and replaced the Boost pressure sensor. No change. Only time I really hear the turbo spool is around 1600-1800 RPM. I’m coming from a Cummins, so I’m used to my truck sound like a jet engine idling. I’m assuming it’s a problem with the VGT, wondering if any of y’all have ever pulled one apart to check the actuator and what that might entail. Thanks and looking forward to learning these Mack engines. 

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When you say no power, are you saying it doesn't pull on the hills and flats? This MP7 is an 11 liter engine compared to your cummins where it was a 15L (I am assuming it was an ISX?). I would not chase the turbo as of yet. Check the basics CAC, intake, fuel pressure and fault codes. Lots of issues with older MP series engines that caused low power.

V

 

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1 hour ago, Vmac3 said:

When you say no power, are you saying it doesn't pull on the hills and flats? This MP7 is an 11 liter engine compared to your cummins where it was a 15L (I am assuming it was an ISX?). I would not chase the turbo as of yet. Check the basics CAC, intake, fuel pressure and fault codes. Lots of issues with older MP series engines that caused low power.

V

 

When I was test driving the truck before I bought it I chalked it up to me being use to 600 HP and it only having 370, but once I put a load in the bed it became apparent that I had issues. It can’t accelerate on flat ground, coming out of a local gravel pit that similar trucks pull in 1st I’m in deep reduction and struggling. 
 

I’ve been over the whole intake, no obvious leaks. Haven’t checked fuel pressure, but I’m assuming it would throw a code. Only active code is EGR Mass flow sensor, local Mack dealer told me I could replace the $1000 pipe with the two sensors and it would probably fault out in a week or too, so just to ignore it cause it ain’t hurting anything. Not sure how true that is. 
 

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The truck is telling you what's wrong (lol)  mass air assembly probably is coding cause your EGR cooler is leaking. That's the first thing needs to be addressed. Then look close also at the EGR plumbing. If you're not familiar with the engine it's easy enough to miss a leaky hose on the EGR plumbing.  Same effect as a leaky charge air hose.  Someone probably knew this before the for sale sign went on.

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54 minutes ago, Mark T said:

The truck is telling you what's wrong (lol)  mass air assembly probably is coding cause your EGR cooler is leaking. That's the first thing needs to be addressed. Then look close also at the EGR plumbing. If you're not familiar with the engine it's easy enough to miss a leaky hose on the EGR plumbing.  Same effect as a leaky charge air hose.  Someone probably knew this before the for sale sign went on.

How about blocking off the whole EGR system?

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I guess there's some ways to delete it ??? IDK  believe it or not, an MP7  '04 emission engine is actually pretty strong compared to their displacement .  It'll never run like a big bore or even a good running 13 liter , but they are a reliable engine with very good drivability when they run as they should. 

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It should be possible I was successful in blocking off the egr on a Detroit 60 series it had a coolant leak internal it was being sucked into the intake and being burned creating a similar problem I did have to buy a modified barometric pressure sensor to make the ecm work

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the EECU would need to be re-programmed...too bad we cant just add a little exhaust pipe to the EGR pipe and let it leave like the big exhaust pipe...   Crazy thinking by me.... jojo

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  • 3 months later...
On 8/27/2021 at 3:27 PM, Kentucky Joe said:

Just an update. Pulled the turbo and took it to a guy, the vanes were completely seized. He’s cleaning it up and I should have it back on the truck this weekend.

On another note… does anyone have in info on blocking off the egr? 

you need to be checking the EGR differential pressure sensor on the intake manifold! If it or the tubes to it are plugged the EGR valve will be commanded right open by the ECU! thus polluting the system with soot!  Just a whole can of worms! no power VGT STICKING  plugged  EGR cooler Its a BIG Viscous circle! you need to really start at the source of the problem there or you'll be back at it in a week! blocking the EGR with send the truck into DErate!

Just saying!

 

Edited by fjh
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