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ndvaughn

Mack CH613 no top end power

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Wondering if you guys can help me out. My 2000 Mack CH613 has no top end power. When I first got it it had plenty of power at all speeds. It would got 70 fully loaded into a wind. Now all of a sudden it won't go at highway speed. It's like it's not even trying, it's not blowin smoke, it's not even trying. It just goes about 60 and if I go behind some trees where the wind is shielded it will go up to 65 and then when I get back in the wind drop back down to 60. I've had it in the dealer and they checked it over and couldn't find anything. Of course with not trailer it's not recognizable, but with even an empty trailer it doesn't wAnna get up and go. I'm stumped and it's frustrating, losing money by not getting more loads in a day. I'm running it on a side dump. It has an E7 motor. Any ideas? Could the foot pedal throttle sensor be off or something? Like I said it's not it's not even trying to go faster....

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When you had it at the dealer they should have checked the fuel pressure at the lift pump,  that is always a good place to start. Also check fuel lines and connections for places it could suck air.

What are your exhaust temps like when you are having this problem? You could have a boost leak at a silicone boot or at the air to air itself. 

My experience with the pedal sensor is that it either work or it doesn't. 

 

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Would the truck run fine if the lift pump was weak? The truck seems to run excellent, no smoking or missing, just no power. I'm not sure on exhaust gas temps cause i don't have a guage for that. Engine temp is normal, and all filters have been changed. Is there an easy way to check for a boost leak? 

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18 hours ago, ndvaughn said:

Would the truck run fine if the lift pump was weak? The truck seems to run excellent, no smoking or missing, just no power. I'm not sure on exhaust gas temps cause i don't have a guage for that. Engine temp is normal, and all filters have been changed. Is there an easy way to check for a boost leak? 

 

yes!  you would not notice  a miss it would just be doggy with low fuel pressure I Check the fuel pressure  change out the fuel filters It can be the pedal how ever not often ( to check that use the cruise buttons!) The other hold out can be the torque limit switch on the trans the wires may be rubbed and shorted together or a faulty switch this will cut the boost in Half so the ECU will not see anything as a problem! If you have no boost gauge GET one! it will tell you allot!

Edited by fjh

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Where would I install a boost gauge sensor on a 2000 E7 350? Is there already a hole with a plug in it somehow were? Any suggestions on where to get a gauge? Order from dealer? 

 

Thanks for for the help 

Edited by ndvaughn

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Where would I install a boost gauge sensor on a 2000 E7 350? Is there already a hole with a plug in it somehow were? Any suggestions on where to get a gauge? Order from dealer? 
 
Thanks for for the help 

The engine hardware is probably already there. The gauge is electronic, just need to purchase the gauge at Mack and have them turn it on in the ECM.

Sent from my XT1254 using Tapatalk

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So is this plug on the intake where I can put in a boost sensor? Any reccomendations for an aftermarket gauge? I'd rather put it in myself rather than take it to the dealer if possible. I'd also like an actual dial gauge rather than something that reads off an ECM. Thanks for the help.

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Also, to add to my dilemma, my MPG is down to about 4.3. Could that give any more idea on what my problem could be? If it is low fuel pressure would my MPG go down as well? 

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OR install and after market gauge and plumb in directly to the intake manifold !

Yup that will work gauge will be hose not sensor!

You likly have a boost leak/ lack of air most times causes poor fuel milage and low power

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Been a long time since I posted on this but I hope it brings it back to the top. Well it’s been like a year and a half and I still have the same problem, lack of power. Could the fuel lift pump last the long and still be weak? Truck runs well just gutless at speed, drove today and 60 was tops. Have a body gauge and it shows 20+ pounds. Filters are all good, since the original post have had injectors cleaned and valves set and still same problem. How would I go about checking fuel pressure if it were that? My closest dealer is over an hr away and I’m tired of spending money and not getting the problem fixed. This dog used to growl, now it whimpers.....

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My guess would still be an intake/boost leak.  I believe you should be making high 20 to mid 30 pounds of boost.

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We used to check for air leaks by spraying starting fluid on the hoses and charge air cooler while the engine at idle..

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Challenger: what should my fuel pressure be at idle and under full throttle? That sounds pretty easy to rig up, I’ll try that once it warms up a bit. Don’t use the truck a lot in the winter and it’s been damn cold lately. 

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11 hours ago, ndvaughn said:

Challenger: what should my fuel pressure be at idle and under full throttle? That sounds pretty easy to rig up, I’ll try that once it warms up a bit. Don’t use the truck a lot in the winter and it’s been damn cold lately. 

Your fuel pressure should be above 60 preferably 70 and should not drop below that under load ! Make sure your tank vents are clear its easy to be fooled by simple shit! 

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