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E7 with intermittent boost.


Curtis78
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We have a 2001 Mack CH613 E-7 460 XT that I'm working on. Will not build consistent boost. Engine will suddenly build boost for 20 or 30 seconds and run great then it stops and goes back to no power. Truck doesn't have a wastegated turbo or a vgt turbo.

Checks I have made or performed.  No lighting bolt, has only came on momentarily once in three weeks.  Had some stored codes. Saved codes and then cleared.  Went through the test procedures on the codes and came up with nothing.  Fuel pressure at idle 68psi, at 1400+ rpm's 76psi. Base engine oil pressure at idle cold 60+ psi, hot at idle 22+ psi. Pressure checked air cooler and hoses, ok. Visually checked engine wiring harness and also wiggle tested some of the dash harness while the truck was driven by another driver. Also did a complete service on the engine.

Previous owner threw a bunch of parts on this truck (we just bought the truck last month)....new throttle pedal, numerous new fuel lines, new crossover valve, new turbo, etc, etc.

We took the truck to the local Mack dealer last week and they kept it all week. They swapped turbos just to check, swapped a known good ECU and ECM just to check. They replaced both timing sensors, fuel temp sensor, intake air temperature sensor, both coolant temp sensors and the boost pressure sensor. They checked, removed and cleaned the engine ground and frame ground.

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13 hours ago, Curtis78 said:

We have a 2001 Mack CH613 E-7 460 XT that I'm working on. Will not build consistent boost. Engine will suddenly build boost for 20 or 30 seconds and run great then it stops and goes back to no power. Truck doesn't have a wastegated turbo or a vgt turbo.

Checks I have made or performed.  No lighting bolt, has only came on momentarily once in three weeks.  Had some stored codes. Saved codes and then cleared.  Went through the test procedures on the codes and came up with nothing.  Fuel pressure at idle 68psi, at 1400+ rpm's 76psi. Base engine oil pressure at idle cold 60+ psi, hot at idle 22+ psi. Pressure checked air cooler and hoses, ok. Visually checked engine wiring harness and also wiggle tested some of the dash harness while the truck was driven by another driver. Also did a complete service on the engine.

Previous owner threw a bunch of parts on this truck (we just bought the truck last month)....new throttle pedal, numerous new fuel lines, new crossover valve, new turbo, etc, etc.

We took the truck to the local Mack dealer last week and they kept it all week. They swapped turbos just to check, swapped a known good ECU and ECM just to check. They replaced both timing sensors, fuel temp sensor, intake air temperature sensor, both coolant temp sensors and the boost pressure sensor. They checked, removed and cleaned the engine ground and frame ground.

It’s Halloween and this truck needs an exorcist. You’ve covered all bases...except Fred’s out-on-a-limb idea, which is where I’d go next. Stranger things have happened.

Twice this year I’ve been amazed at crackpipe fixes on our equipment. I had a little transformer on an LED light go out (with light never failing to illuminate) and back-feed high voltage to an ECM making it go crazy. This week I had a stereo shorting out causing a CAN line communication fault on a Volvo. Had the stereo not finally burned I may have never figured it out. 

Edited by Mack Technician
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13 minutes ago, Mack Technician said:

It’s Halloween and this truck needs an exorcist. You’ve covered all bases...except Fred’s out-on-a-limb idea, which is where I’d go next. Stranger things have happened.

Twice this year I’ve been amazed at crackpipe fixes on our equipment. I had a little transformer on an LED light go out (with light never failing to illuminate) and back-feed high voltage to an ECM making it go crazy. This week I had a stereo shorting out causing a CAN line communication fault on a Volvo. Had the stereo not finally burned I may have never figured it out. 

Is it possible for the torque limiting switch on the transmission to cause this symptom? It has a Maxitorque T2130 transmission. When I asked the dealer about this they told me they turned that function off in the ECM.

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7 minutes ago, Curtis78 said:

Is it possible for the torque limiting switch on the transmission to cause this symptom? It has a Maxitorque T2130 transmission. When I asked the dealer about this they told me they turned that function off in the ECM.

 

7 minutes ago, Curtis78 said:

Is it possible for the torque limiting switch on the transmission to cause this symptom? It has a Maxitorque T2130 transmission. When I asked the dealer about this they told me they turned that function off in the ECM.

Your symptom Would only happen in low range if that were the case ! unless you had the wires were rubbed together ! If its turned off in the ECU the wires SHOULDN'T be being monitored! The torque switch Engaged Limits boost to approx 15 psI ! You Got nothing to loose I have also seen what you are thinking about happen !If your suspicious of this trace back and disable the torque wires at the VECU! 

Edited by fjh
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1 hour ago, Curtis78 said:

If it is a wiring problem somewhere would it set a code?

So long as the wiring issue is creating an open circuit, short or taking the return signal out of normal range.

Its possible for a sensor or wire to cause a failure while staying inside normal range parameters. Not so often.

Edited by Mack Technician
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We still have a few ETECH trucks running at my work. Last week we had a random low power complaint with no codes or malfunction light coming on . Pulled the kick panel down in front on the passenger seat where the VECU and ABS ECM are located. Found wire rubbed on the ABS  ecm and kick panel and the cab it’s self. I took lots of pics of this issue but out of data to post them here. Repaired the wires and problems went away. If you had access to the older VMAC 3 diag program ( not Tech Tool) you could test drive while watching the “Active Code” screen as sometimes a code will pop up on the screen and go out before it logs the code or turns the malfunction light on . Also there’s shims on the timing sensor on the camshaft. Too deep or to shallow and you will have issues. 

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9 hours ago, Mackpro said:

We still have a few ETECH trucks running at my work. Last week we had a random low power complaint with no codes or malfunction light coming on . Pulled the kick panel down in front on the passenger seat where the VECU and ABS ECM are located. Found wire rubbed on the ABS  ecm and kick panel and the cab it’s self. I took lots of pics of this issue but out of data to post them here. Repaired the wires and problems went away. If you had access to the older VMAC 3 diag program ( not Tech Tool) you could test drive while watching the “Active Code” screen as sometimes a code will pop up on the screen and go out before it logs the code or turns the malfunction light on . Also there’s shims on the timing sensor on the camshaft. Too deep or to shallow and you will have issues. 

I do have abs codes. Didn't realize they could effect the engine.

SID 151 FMI 14

SID 2 FMI 14

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15726152949195424765894890880525.jpg

Edited by Curtis78
Added information.dn't
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10 hours ago, Mackpro said:

E8E5DE36-F178-4E68-B7BE-B2A6EE36326B.jpeg

 Good Find Pro !  How ever Curtis  not necessarily  ABS wires that rubbed on the box there  Curtis ! The wheel code would not likely dial back power However the other code you have may ?? Best thing to do is go where people are sending you here ! All of these fixes Are Real life Experiences ! Not written down in a book  anywhere Just shit people have come across over time Pro and Tech  and All the guys here  Are  awesome  At passing on experiences!  All ya got to do is give each experiance a try till ya find the one that works!

Just saying !😂

Edited by fjh
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I completely bypassed the compressor system. Removed the air supply hose from the intake and left it naturally asperated. Put a pipe plug in place of the fitting in the intake manifold. Just test drove the truck and it didn't change anything. So that rules out the compressor and or the dryer. Since the boost comes and goes very suddenly and intermittently, with no pattern to the chaos, is it possible something is wrong with the uni-pumps? Maybe injectors?

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Real crap shoot party, love it!

Time to get it on a dyno and stand inside the hood as it's doing it under load with all gauges present...…...Chassis twist opening up a blow hole?...….Wiggle test harness wires while it's freaking to see if it corrects?...……. live read each EUP's with a fluke meter?......….Exhaust sound changing because a baffle collapsed?....... etc. See and hear a lot, in real time, on a dyno. 

Make sure you list the solution to this one.  

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8 hours ago, Mackpro said:

The wires that rubbed the ABS ecm were wires coming out of the VECU. No telling what wires were shorting out . Seen this issue on more ETECH trucks than I can count. 

May have something to do with ATC.I have seen this with 60 series two times in freightliners.

glenn akers

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6 hours ago, Mack Technician said:

Real crap shoot party, love it!

Time to get it on a dyno and stand inside the hood as it's doing it under load with all gauges present...…...Chassis twist opening up a blow hole?...….Wiggle test harness wires while it's freaking to see if it corrects?...……. live read each EUP's with a fluke meter?......….Exhaust sound changing because a baffle collapsed?....... etc. See and hear a lot, in real time, on a dyno. 

Make sure you list the solution to this one.  

Yup definitely post your fix.

another easy check/ thought Check your engine Ecu plug for corrosion!

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On 11/1/2019 at 2:25 PM, Mack Technician said:

Real crap shoot party, love it!

Time to get it on a dyno and stand inside the hood as it's doing it under load with all gauges present...…...Chassis twist opening up a blow hole?...….Wiggle test harness wires while it's freaking to see if it corrects?...……. live read each EUP's with a fluke meter?......….Exhaust sound changing because a baffle collapsed?....... etc. See and hear a lot, in real time, on a dyno. 

Make sure you list the solution to this one.  

Just a question...I checked the fuel pressure under a load and it was 76 psi which is supposedly good. What about fuel volume?? When I look in the tank while the engine is running there is a fair amount of fuel being returned.

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40 minutes ago, Curtis78 said:

Just a question...I checked the fuel pressure under a load and it was 76 psi which is supposedly good. What about fuel volume?? When I look in the tank while the engine is running there is a fair amount of fuel being returned.

Pressure and flow(volume) will act as the sum of one. As long as pressure maintains the flow is sufficient. As long as flow is sufficient pressure will remain inside spec. If rate of consumption exceeds available flow........pressure will drop off. If you have pressure maintaining under load, your flow is sufficient.

Edited by Mack Technician
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