CM871 poor power and fuel econ

[Grounded Pilot]

Sorry I haven’t updated in a while. Had things take me away from the truck for a bit. I addressed the egr equip and corrected the plates. And still having issues.

First and what I am focused on at the moment is the TPS.it will only go to 97% throttle (on my scanguageD) and the truck acts like it is underpowered or getting derated (I haven’t gotten a computer/data system to hook up to it myself yet, it’s in my list of things to buy). I have 5v input to the sensor and 3.9volts leaving to the APS circuit which is within spec of 77%+/-2% according to the Williams data sheets. But I’m only getting 2volts out of the IVS circuit under full throttle and I believe it is supposed to be above 3.8v to act correctly???? Both of these reading are at the sensor and also confirmed at the OEM port on the ECM.

I have ohmed the ground wires and all the wires checked out with little resistance. Does it sound like the new TPS is bad?? Or am I not reading something right on the schematic???

[Rawze]

you need to see what it says in Insite... not your scangauge. those things can often be mis-leading.

as far as the ecm not giving it full fuel, etc.. then someone needs to monitor the 'fuel_control_state" and other settings in calterm and see what .. if anything might be holding it away from full power if it is indeed not commanding full power/torque.

Also, what have you done so far about getting the the de-mandate programming copied out of that engine and having it e-mailed to me for a proper review to see if it is any good?. Ensuring 100% that the program in it is safe and will operate it properly as important as using the right kind of oil.. it is that important.

[Grounded Pilot]

The 974 code that pops up as the “cab side TPS low voltage” code was read off the mechanics insite program. Both with the old TPS and new one. And the power issue started showing up when that code started first appearing erratically. The mechanic just kind of blew it off when I asked to get a copy of the Ecm programming. So I haven’t gotten that yet. If I can get met up with another guy I’ve been talking with, he said he would copy it. But we’ve been in different states constantly lately. Or if I can just get the system ordered I’ll do it myself, but I’ve got some bank crap I’m waiting on to go through before I can free up cash. And I gotta buy one of the systems that can do multiple engine makes because I think I’ll be sitting behind a Cat soon.

My other concern is can this be an ECM problem since my voltages match at the TPS sensor and at the OEM port on the ECM? The ECM was replaced 15 months ago but with a used ECM out of a 2007 truck that the previous owner had sitting out back due to a rod poking through the block. That’s all the history I know on the ECM.

It also has another bad metering actuator (under 10,000 miles since replaced with Cummins reman) according to the cylinder cutout test. I’m going to test the wiring to that today before I replace it.

[Grounded Pilot]

This is the schematic from the Williams TPS I have been looking at.

   


This is the IVS output equation I’m unsure of

   

[Rawze]

(04-08-2022 )Grounded Pilot Wrote:  ...
It also has another bad metering actuator (under 10,000 miles since replaced with Cummins reman) according to the cylinder cutout test. I’m going to test the wiring to that today before I replace it.

has anyone bothered to do an injector leak test on it>?...
I doubt it... and that would be exactly why it keeps showing bad actuators.
ref: http://rawze.com/forums/showthread.php?t...8#pid67948

also, on Pete's and KW's.. they are notorious for the cab plugs to show problems with the TPS .. it is a known issue especially if someone is letting their truck get washed by those truck-wash places and letting them open the hood and spray inside around the engine area...

Here is a fine example of someone having the exact problems you are describing, even going as far as wanting to replace their ecm after going thru several TPS sensors, etc... .. just like your saying...
http://rawze.com/forums/showthread.php?t...1#pid12551

[Grounded Pilot]

Yes, replaced #1 and 4 injectors but that was after the actuators were replaced the first time. The #4 injector was bad enough that it was causing the motor to continue running after the fuel was cut off. I can’t speak for previous drivers, but I don’t let them wash the motor/electronics. I’ll look at the link. I’ve taken the plugs apart and cleaned and dried them out and made the connections as good as I can but that didn’t change anything. I did find that the cab 50amp breaker was pretty corroded. Going to change that out and wire brush the cable ends good.

[Grounded Pilot]

I have actually read that post, that’s why/how I cleaned up my connectors. I’m getting ready to take the foot box off the truck to get at the back side of the fuse box and check for any more wiring issues. I have ohmed the ground and power wires as well as taken the grounds loose and cleaned the cable ends and ground lugs. That’s what led me back to the TPS or ECM. But only getting 2v output on my Idle circuit is what has me thinking the TPS may still be the problem. I read on quickserve that it was supposed to be at ~5v when the throttle was depressed to deactivate the idle circuit. However, I can’t get quickserve to give me the solution sets to the symptom search options at the moment in order to get back to that page and look again. It just returns “page not found” when I click on any of the symptoms. Tried it on both my iPad and phone which both worked fine when I used them last time on Monday/Tuesday.

[Rawze]

(04-08-2022 )Grounded Pilot Wrote:  Yes, replaced #1 and 4 injectors but that was after the actuators were replaced the first time. The #4 injector was bad enough that it was causing the motor to continue running after the fuel was cut off.
...

you say "yup" but that does not describe at all if someone actually did a proper injector leak test, as shown in the videos I posted the links to. Most repair shops do not have the proper test block, nor have even ever knew this tests existed on CM871's. This includes most OEM repair shops.

BTW: .. A leaky injector on a CM871 will not cause one to keep idling past when the key is off. - Only a leaking actuator will cause that.

You say injectors were replaced... did anyone bother to do a proper injector leak test on it a second time after the replacements were installed?... to ensure there are no more issues with injectors? / problems?. Timing/metering Actuators do not typically fail over and over unless someone is doing something wrong, they are being abused, or there are contaminants in the fuel system. Having a defective one by the OEM is rare on the CM870/871's. - WHAT exactly failed on/inside the actuator (and subsequent ones)?. Has anyone even bothered to determine that at all?.

You also say it was replaced again due to issues during a subsequent cut-out test.. what was the issue exactly?... How or what was seen to determine that during the test?...

Did someone do something really stupid like unplugging them to test them?.. I see a lot of mechanics make that mistake.. they unplug them to troubleshoot them instead of using Insite to switch them on/off properly, etc. - Unplugging them almost always results in a false positive, as the ecm will not fire them properly after one has been unplugged then plugged back in until the key-switch has been cycled properly.

Did anyone bother at all to disassemble the suspect actuator to see what failed inside it before just calling it bad?. For all anyone knows, it might not have even been bad.. or maybe some trash from the fuel system got in it and it needed cleaning + any fuel system trash problem resolved? .. It is pretty straight forward to find out why an actuator is not performing like it should...
ref: http://rawze.com/forums/showthread.php?t...619#pid619

[Grounded Pilot]

Accident post that I didn’t realize till the next post was posted. Whoops!