Low Boost

[TomJohnston]

I used drive pressure readings by hooking up my boost gauge to the pyro hole using copper tubing. I figured if my drive pressure was high and boost was low then that could mean some obstruction through the IC. But my readings where within the 1:1. 2 range which is normal. So as much as I would like a shiny new IC I don't think it is the problem. There is something I am going to look at in addition to the APPS and alternator, the electronic wastegate fooler(not boostfooler) that came with my new turbo. I have been told that they are supposed to be 100 ohms and mine reads 150. Probably not the problem but if 100 ohms means shut and the ecm sees 150 maybe it won't fuel properly. Anyways just grasping at straws. Good Luck, Tom J.



BTW, I have been playing with the APPS and by doing the calibration of turning the ignition to run and depressing and releasing the pedal then starting truck I have picked up a few psi. Now I can get to 41 pretty easy instead of 38 but I can't use more than 2/3rds pedal or truck starts to lose power. So maybe the APPs is the problem but I can't find an 06 APPS for sale anywhere, it's like they don't exist. They run off of two potentiometers, one starts at zero with pedal up and goes to 5v at full pedal, the other starts a 5v and decreases as pedal is depressed. It most be a safety precaution to have the dual system. I need to get a special tip for my multimeter so I can get a reading through the insulation on the wires and actually watch the APPS return voltages while the truck is running. This will let me know if there is some dead spots on the potentiometer that could be causing these problems.

 

[SShafranko]

Tom, i switched my APPS with my friend's and i got no change. Our APPS is self calibrating and i don't think calibrating it would make any difference but i could be wrong.



I also don't think that my IC is the cause of my problem but i will switch it out with my buddies just to be sure. I think my problem is more of an electrical/fuel issue.



My EGt's at idle hover around 400 degrees almost like fuel is being dumped in and the combustion outcome at idle is too hot do to too much fuel at idle. once in a while if i let it idle for a long time it will come down to 350 but its very rare. Also at WOT my EGT's will pin around 1250 to 1300 and it seems to be the same all the time. If my IC was bad i would think that my EGT's would be slightly higher at WOT than they should be do to not enough air getting to the mixture.



I wonder if my problem could be do to a bad battery? Where can i get them load tested? Napa?

 

[SShafranko]

Tom, Todd from T&C Diesel recommended getting on the highway and setting the cruise control on. Accelerate with the cruise control as far asyou can and then stomp on the throttle. I got a few psi more doing this i don't know why? when i did this i figured i bypassed the APPS in cruise control and maybe it was bad. But when i switched it out i got the same result. Weird



I also have to look at my fuel pump wiring. When i installed my AD 2 i broke the factory fuel pump plug. I took out the four wires and directed the red wire to the new pump and the other remaining three to the factory pump canister and plugged them in individualy. I know one is for the fuel gauge which works fine, another probably ground and the third i'm not sure. Maybe i switched the two wires, or maybe they are touching some how? I have to get a new plug from somewhere and install it to make sure it is OK. Just thinking out loud here

 

[TomJohnston]

I just had my batteries tested at a local auto parts shop and they were fine. Make sure you disconnect the big red wire that connects the drivers side battery which runs all the electronics that goes to the passenger side battery that is used mainly to run the starter. This will isolate the batteries so they can be tested individually. BTW, Todd at TCWest told me that when you swapped your ECM it worked for a while. Did it stop working after you loaded the smarty back on? Also have you checked the resistance on the wastegate fooler? I also wonder if with a aftermarket fuel system if the ECM doesn't see a current draw from the stock pump it may not fully fuel. Just some ideas. Good Luck, Tom J.

 

[SShafranko]

I just had my batteries tested at a local auto parts shop and they were fine. Make sure you disconnect the big red wire that connects the drivers side battery which runs all the electronics that goes to the passenger side battery that is used mainly to run the starter. This will isolate the batteries so they can be tested individually. BTW, Todd at TCWest told me that when you swapped your ECM it worked for a while. Did it stop working after you loaded the smarty back on? Also have you checked the resistance on the wastegate fooler? I also wonder if with a aftermarket fuel system if the ECM doesn't see a current draw from the stock pump it may not fully fuel. Just some ideas. Good Luck, Tom J.

No i didn't check the resistance on the fooler. Not sure how to do it? Do i use the multimeter on the ohm setting?



I connected the hot wire from the harness to the new pump so it should see a current draw from the new pump. The old Air Dogs had a new harness and you had to run a hot wire. On my buddies truck we cut the hot wire going to the factory pump and just left it there in case he needed the stock pump again and his runs fine.



When i installed the new ECM it seemed like it was OK for ten minutes, i got all the low and mid end back but then it went into the default mode after a few minutes again. I don't know if the problem is burning out my ECM or if it is just causing it to go into the default fueling mode.



i belive all of this started happening right when i installed the ADII. I have to get the right plug and re-do all of it to eliminate it.



Thanks for the help Tom.

 

[SShafranko]

Tom did you load test the batteries? There is a recent post on here where the guy tested the batteries and they came out OK. He wasn't happy with it so he took them out and had them load tested. One came back bad. I believe it fixed his issue once he replaced it.

 

[TCDiesel]

SS. . I have the Harness... ... its plug and Play for extra lift Pumps. The Green Wire is hot the Blue Wire is ground. Hmmmmm... the AD W/O plug and play?

 

[SShafranko]

You're the man Todd. Did you get those valves? I'm in OC Maryland on vacation. Coming home tomorrow, i'll call you and purchase one of those harnesses if you sell them seperate that is.



I took my truck for a ride earlier(i was bored) and i found a nice stretch of open highway.



I got into it in fourth gear topped out at 30psi and 1100egt



fifth gear 32psi and 1200egt



sixth gear 34 psi and the egt kept climbing i let off around 1400



Could it be the IC? But wouldn't my EGT keep climbing in every gear all the time if there is no issue with the fuel end of it and the ECM keeps fueling but the turbo air is not passing through the IC enough? Does the IAT or the MAP sensor stop fueling if not enough boost or vise versa?

 

[SShafranko]

Ohhh i failed to mention that i loaded SW 5 on Smarty. Truck seems to pull pretty good it does not cut out any more like it used to when loaded down and at max psi. I don't know why it is not cutting out any more. It could be do to the several sensors i have replaced or maybe the new ECM.



The one thing i did notice is that my idle seems to be hanging up in between shifts and also if i rev it in neutral. This is very annoying as it bucks hard when shifting gears because instead of the rpm dropping quickly it hovers and i go into gear somewhere in the 1500 range.



Help

 

[SShafranko]

Just got done reading an old post on Cummins forum. A guy had a simiolar boost problem to mine and it turned out to be his sending unit. He replaced it and boom everything was back to normal.



I'm starting to lean towards the fuel pump wiring i rigged on my tank. Have to fix it sooner than later.

 

[SShafranko]

Switched out the IC today absolutely no difference in boost. Definitely a fuel issue i think.



Next step is to pick up the new fuel pump plug from T&C Diesel and a new fuel pump/canister assembly.



Will post outcome once complete.

 

[cerberusiam]

Sorry bud, hoped that would work for ya.

 

[RankRam]

I have nothing constructive to add, other than... ... . hang in there and good luck!

 

[SShafranko]

Thanks for the ideas guys. We'll get it. Happy Fourth and be safe!

 

[TomJohnston]

I have been thinking about our mutual problem quite a bit lately. What I have come up with is that the ECM is pretty sofisticated and if it is seeing something that it doesn't like or is out of the norm it should set a code. So if you are not getting any codes and the ECM is good then it has to be either a mechanical problem or something like a high temp reading that causes the ECM to defuel. I changed my IAT sensor but if it has a short then maybe that can explain the defueling. I have also explored just about anything mechanical that can be the cause and found nothing out of the ordinary. My wastegate is set at 50 psi and I can verify that by crimping the wastegate hose and in fourth gear if I ease into the pedal on a hill I can hit it pretty easy. If I floor it I will only get 40psi. I am not sure if it is more related to rpm or pedal position but at a certain point the truck defuels (rail pressure is 25,000+ so fuel pres is not the problem). If I crank up my pressure box I can get a little more boost so I am sure that the duration is what is being effected. For some reason no matter what performance level I program the truck for, at a certain rpm or pedal position the duration will decrease limiting me to 38-40psi of boost. I am going to disconnect the plugs on the ECM and remove the IAT sensor, I will then ohm out all the wires going to the IAT to see if there is a short. If I find anything I will let you know.

 

[SShafranko]

Ty very much. Please keep me posted because we are on the same exact brain wave. I have been thinking exactly as you for a while now. It sounds to me like you know what you are doing when it comes to looking for shorts and testing sensor parameters. I am glad you are here. It also sounds like we have the same exact issue exept you are able to boost a couple more lbs than me. Please let me know your outcome on the IAT cuircit test. Good luck



Sasha

 

[TomJohnston]

If my theory is correct the reason I can boost more than you is because of my injectors. Given that everything is fairly similar between our trucks I can move more fuel at the same duration or pulse width to the cylinder. So you may want to get some injectors if we can't figure this out(soon). 120's would work great with your truck and probably get you to 50psi of boost. I am not not going to give up and we will eventually find the issue. Happy Independence Day, Tom J.

 

[TomJohnston]

Checked out IAT and found one of the wires was the wrong color according to the maintenance manual but went from the right pin in the IAT plug to right pin in the ECM so not a problem. I did find out that the IAT also measures pressure so I don't know if my aftermarket intake system can be producing some weird values or not. I am going to put my stock intake system back in and see. After looking at all the inputs to the ECM it has to be either the intake pressure, LP fuel system or transmission that is causing the problem. Those are the only other things the ECM monitors that wouldn't set an immediate code. The can bus brings additional info but it would come as an error and set a CEL.

 

[AH64ID]

The IAT sensor is used to compare ambient pressure to MAP pressure to determine overall boost. A free flowing intake just shows a higher pressure under heavy draw, which means you actually should be able to get more boost out of it, not less. But that shouldn't matter anyhow with the BF.

 

[TomJohnston]

I am so frustrated. I work on electronics that are so much more complicated than this and can troubleshoot and fix some of the most unexpected problems in just a few hours. But I don't know all the modules and exactly what they do. All inputs to the ECM seem good and within limits. Can something coming in from the Can bus cause the ECM to change the injector pulse duration? It seems like the ECM has all the inputs necessary to control the fuel to the injectors and control the transmission on an Auto. It also seems to directly monitor all the sensors needed for engine management. So if the sensors are good, ECM is good, No codes then WTF. The truck is not going into what I would consider a limp mode but it is not following the programmed map from the Smarty or Bullydog. It is going into something like a safety or fall back map but not limp mode, plus I am sure limp mode would throw a code. What kind of signal could be missing, wrong value or shorted and not throw a code but put truck in a fall back mode. I have a 225 page wiring diagram from Todd @ TCWest (thanks Todd) I have been through the whole thing checking and ohming out wiring and checking voltages but without the knowledge of what every module does exactly I am just chasing ghosts. Is ther any way to get a schematic of the entire engine control system showing data flow and providing descriptions of every module with voltage correlations? Thanks, Tom J.