Pacar MX Engine fuel mileage

Billy17980 · Sep 14, 2018

Sako3006 said: ↑

fland, I'm sorry but that is not possible for the truck to show a stop engine light derating the motor and there be no history on it. Everytime there is any type of light or code come on in that engine, there is a logged event in the ECM hands down. Now, it is possible to have an electrical issue showing that you have an engine light coming on and off, but it would not derate and affect the performance of the truck as you are stating. It's also very possible for the mechanic to have told you that there was no trace of a code or event as there are some unscrupulous ones out there, but it probably due more to the fact that he doesn't know exactly how to fix the problem. Good luck, and maybe ask for a different technician to look at the truck if you don't feel good about the one on the truck now.
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Billy17980 · Sep 14, 2018

Sako3006 said: ↑

fland, I'm sorry but that is not possible for the truck to show a stop engine light derating the motor and there be no history on it. Everytime there is any type of light or code come on in that engine, there is a logged event in the ECM hands down. Now, it is possible to have an electrical issue showing that you have an engine light coming on and off, but it would not derate and affect the performance of the truck as you are stating. It's also very possible for the mechanic to have told you that there was no trace of a code or event as there are some unscrupulous ones out there, but it probably due more to the fact that he doesn't know exactly how to fix the problem. Good luck, and maybe ask for a different technician to look at the truck if you don't feel good about the one on the truck now.
Click to expand...

This happens to me, I get a low fuel pressure code, then it goes away, then the red stop lamp comes on and derates truck, then disappears, it does not show red stop lamp on computer, just the fuel pressure code,

Billy17980 · Sep 14, 2018

fland said: ↑

Hi Sako,

At my dealer there are two mechanics that work on the MX. I have full confidence in both of them, they know what they're doing. It's an oldfashioned shop, the driver can stay with his truck, talk to the mecanics and it's no problem when I'm reading the computer results over there shoulder and discuss it with them...

My truck shows two problems. When driving on a flat road, engine idling along, not having to work at all, the yellow check engine light comes on. It doesn't effect the driving, it's just there. It shows up in the history of inactive fault codes when they read out the computer. It was there for about 15 - 20 times. It reads out as low fuel pressure, but that's all the information it's giving.

The second problem occurs when the engine has to work. Driving with a loaded trailer and the road is going up a bit, turboboost comes up and the red stop engine light comes on (most of the time there's no yellow check engine light on). Light comes on, buzzer comes on, boost drops down 10 - 15 psi. Truck slows down and lots of times has to shift back. Same happens going up hill. Shift back, engine speed exceeds 1300 rpm and red light and buzzer come on, boost drops... There's no code showing on the dash, just the red light. There's nothing to be found in the history of the truck between active and inactive codes.

We've been testdriving, with the computer hooked on. First thing that surprised the mechanic was the fuel pressure jumping up and down, something he had never seen before. A little fluctuation is okay but not the way it worked in my truck. We didn't get the yellow light on while driving with a loaded trailer but several times the stop engine light came on, engine got derated. Nothing was showing in the computer, also it wasn't on a moment that there was no pressure at all.

Probablytoday the other mechnic will work on my truck on his day off. He is the one who has been working on my truck since the day I got it. My truck has never worked good, not enough power, slow respond to the throttle, bad fuel mileage. He has been working close with Paccar engineers to get the problem solved but they never could find anything wrong with the engine. Now, since two weeks the truck is working fine. Pulls better, more turboboost, quicker respond to the throttle and most important of all, 10 - 20 % better fuel mileage. Nothing has been changed to the truck, it just happened. Only at the same time this yellow and red light problem showed up.

BTW, both mechanics would agree with you for 100%. There should be something in the computer but there isn't...

Thanks for the respond..!!
Click to expand...

So what was the problem, and what was the fix

Billy17980 · Sep 14, 2018

fland said: ↑

Hi Sako,

At my dealer there are two mechanics that work on the MX. I have full confidence in both of them, they know what they're doing. It's an oldfashioned shop, the driver can stay with his truck, talk to the mecanics and it's no problem when I'm reading the computer results over there shoulder and discuss it with them...

My truck shows two problems. When driving on a flat road, engine idling along, not having to work at all, the yellow check engine light comes on. It doesn't effect the driving, it's just there. It shows up in the history of inactive fault codes when they read out the computer. It was there for about 15 - 20 times. It reads out as low fuel pressure, but that's all the information it's giving.

The second problem occurs when the engine has to work. Driving with a loaded trailer and the road is going up a bit, turboboost comes up and the red stop engine light comes on (most of the time there's no yellow check engine light on). Light comes on, buzzer comes on, boost drops down 10 - 15 psi. Truck slows down and lots of times has to shift back. Same happens going up hill. Shift back, engine speed exceeds 1300 rpm and red light and buzzer come on, boost drops... There's no code showing on the dash, just the red light. There's nothing to be found in the history of the truck between active and inactive codes.

We've been testdriving, with the computer hooked on. First thing that surprised the mechanic was the fuel pressure jumping up and down, something he had never seen before. A little fluctuation is okay but not the way it worked in my truck. We didn't get the yellow light on while driving with a loaded trailer but several times the stop engine light came on, engine got derated. Nothing was showing in the computer, also it wasn't on a moment that there was no pressure at all.

Probablytoday the other mechnic will work on my truck on his day off. He is the one who has been working on my truck since the day I got it. My truck has never worked good, not enough power, slow respond to the throttle, bad fuel mileage. He has been working close with Paccar engineers to get the problem solved but they never could find anything wrong with the engine. Now, since two weeks the truck is working fine. Pulls better, more turboboost, quicker respond to the throttle and most important of all, 10 - 20 % better fuel mileage. Nothing has been changed to the truck, it just happened. Only at the same time this yellow and red light problem showed up.

BTW, both mechanics would agree with you for 100%. There should be something in the computer but there isn't...

Thanks for the respond..!!
Click to expand...

What was the problem, and the fix

Amandsonshaulage · Oct 22, 2018

fland said: ↑

Nope..!!

Mechanic working with Paccar engine support noticed some similarities in the data log after test driving. Seemed that bthe fuel lift pump had some difficulties in the 1300 - 1400 rpm area, same area where red light comes on and engine gets derated. After adjusting or changing things fuel pressure was good on all rpms. No lights during test drive so i picked up my truck yesterday evening.

Today i did a testrun with a loaded trailer and nothing seemed to have changed. I do realize though that the truck is driveable if grossweight is 80,000 lbs. You can drive it without going over 1300 rpm. That's hardly possible in my regular triaxle 100,000 gross work. I might need to jump to tandemwork for a while, cannot afford to have my truck in the shop for a couple of weeks.

I'll be in the shop again tomorrow, hope they can come up with something to solve the problem...

Thanks..!! more info in the weekend I hope...
Click to expand...

I have the same exact problem my friend same exact motor please call me 973 296 6877 thanks mike

Amandsonshaulage · Oct 22, 2018

Amandsonshaulage said: ↑

I have the same exact problem my friend same exact motor please call me 973 296 6877 thanks mike
Click to expand...

fland said: ↑

Nope..!!

Mechanic working with Paccar engine support noticed some similarities in the data log after test driving. Seemed that bthe fuel lift pump had some difficulties in the 1300 - 1400 rpm area, same area where red light comes on and engine gets derated. After adjusting or changing things fuel pressure was good on all rpms. No lights during test drive so i picked up my truck yesterday evening.

Today i did a testrun with a loaded trailer and nothing seemed to have changed. I do realize though that the truck is driveable if grossweight is 80,000 lbs. You can drive it without going over 1300 rpm. That's hardly possible in my regular triaxle 100,000 gross work. I might need to jump to tandemwork for a while, cannot afford to have my truck in the shop for a couple of weeks.

I'll be in the shop again tomorrow, hope they can come up with something to solve the problem...

Thanks..!! more info in the weekend I hope...
Click to expand...

steve092 · Jan 9, 2019

ProudTrucker said: ↑

Update regarding my 5 MX powered T-660's.
Mileage: Five units ranging from 70,000 miles to 80,000 miles.
The fuel mileage and performance of these units showed substantial improvement after the 50,000 mile mark. The fuel mileage is ranging from 6.6 to 6.9 mpg driving economy. This is close to a full mpg gain over the initial break in numbers. Mechanical issues after software updates have gone away. I am having zero problems with these engines now and the T-660 chassis is very good. These engines don't use any oil. I have never seen an engine go so far without adding any between changes. Oil analysis look very good.
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What software update is this? Where can I get it? 2013 Pete MX13 EPA10 18 SPEED 455

steve092 · Feb 15, 2019

RiskyBusiness said: ↑

I have a 2012 KW T660 with a Paccar MX 13 455hp engine. Other than routine maintenance and the manual cleaning of the DEF system I haven't had any issues with mine. I just turned 751k still getting 7-8 mph with an Eaton Fuller Ultrashift transmission.
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How do you touch 7! I struggle to hold 6

Lightning McQueen · Feb 22, 2020

Hardlyevr said: ↑

One thing I did find interesting in the literature about this engine is that they want you to do a valve train adjustment every 160,000 miles! I wonder what that will cost and work out to on a per mile basis?
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Valve adjustment cost about 300 at kw

Lightning McQueen · Feb 22, 2020

RiskyBusiness said: ↑

I have a 2012 KW T660 with a Paccar MX 13 455hp engine. Other than routine maintenance and the manual cleaning of the DEF system I haven't had any issues with mine. I just turned 751k still getting 7-8 mph with an Eaton Fuller Ultrashift transmission.
Click to expand...

Whose leg are you trying to pull mines got the big d on it twice if you know what I mean and it still keeps in the 6s ..if I'm bobtailing lol granted I'm hauling a van with a flat top truck so I don't have too high hopes but I would like to see 7s I'll have to get the overhead done then check back

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