Question about EGR

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dlucky894runner

dlucky894runner

10 Year
Joined
Jan 6, 2011
Threads
11
Messages
76
Location
Springville, UT
Hey guys, I know this sounds stupid, but this the only thing I can figure out. Ok, so my truck sat for who knows how long with the previous owner. When I bought it the head gasket was blown. I replaced the head Gasket, Head Job, etc. and got it up and running again. Anyhow, I have a re-occurring CEL of the EGR, but only when my Fuel tank is 1/2 tank or less. I have ran about 2-3 tank fulls of gas through it. Anyone ever heard of this? Once I fill it up the code goes away. I can't tell any difference with the way it runs and it did just pass Emission/Smog testing here in Utah, so it must be running at least ok?

Just thought I'd ask if anyone has heard of this...

Thanks,
 
Check that you ran the vacuum lines correctly. Pay close attention to which ports the lines go to on the manifold.

Another test that is easy and low cost. When the light goes on, take off the fuel filler cap. Does the light go out like when you fill the tank? Also note if air vents out or is sucked into the gas tank. Might be useful for further diagnostics.
 
So, Update....Sorry for so long. Thanks for all of the ideas. I did check all of the vacuum lines and they look correct. Once the CEL came on tonight. I stopped and took off my gas cap and continued driving. After one stop at the store and getting back in the CEL was cleared. So....Does that mean I need a new gas cap? And why does this throw the EGR code?
Thanks,
 
dlucky894runner said:
So, Update....Sorry for so long. Thanks for all of the ideas. I did check all of the vacuum lines and they look correct. Once the CEL came on tonight. I stopped and took off my gas cap and continued driving. After one stop at the store and getting back in the CEL was cleared. So....Does that mean I need a new gas cap? And why does this throw the EGR code?
Thanks,
Click to expand...
I'm not 100% sure. Maybe the lack of air coming in through the fuel system is causing the vacuum level to be lower than designed for and that is tripping something that makes it look like there is an EGR fault. Another idea I have is the fuel pump can only create X amount of pressure difference between the tank and fuel supply rail. That causes a fuel starvation which may be noticed by a secondary effect and thought to be a fault of the EGR system. I haven't studied it enough to tell yet. I've not seen enough details yet to tease out a specific fault.

As for the vacuum in the fuel tank, there are two check valves that allow air into the tank. One is in the gas cap, the other is in the charcoal canister. To get a vacuum in the tank both must get stuck closed.
 
How do I clean the Charcoal Canister? Is there a way to clean it? or do I have to replace it. Thanks for your help Bogo
 
It is a replace only item.
 
So, Anyone have any experience with the little sensor on the EGR pipe? I believe it is the EGR temp sensor? The CEL for the EGR kept coming on more frequently, so I replaced the EGR with another one, not new, but seemed to function properly. The light stayed off for about a day and then it came back on. The FSM states the code could be all different kinds of problems with the EGR system including this sensor.
 
charcoal canister and gas cap came to mind first like stated above :()
 
Cool. Changed gas cap....no change. Gotta talk myself into paying $300+ for the charcoal canister.
 
dlucky894runner said:
Cool. Changed gas cap....no change. Gotta talk myself into paying $300+ for the charcoal canister.
Click to expand...
Have you checked out the charcoal cannister's operation with the FSM checks?
 
You mentioned having the engine topside torn apart for the head gasket repair. There could be an electrical issue with the EGR gas temperature sensor, or the control of the VSV valve. There maybe is a broken wire, or bad connection at a connector.
 
Thanks Bogo, I haven't checked the operation of the Canister per the FSM. That was on my list of things to do tonight after work. I just printed the info off. I will have to double check all my wires, also. It is weird, because it is still kinda sporadic as to when the CEL comes on. Once it is on it stays on, but if I reset it with the negative battery terminal, then it will go for awhile before it comes back on. Sometimes 50 miles, other times 200+ miles.
 
Well, After testing my Vapor Canister, per the FSM, it was bad. I replaced it and the light is now off. Hopefully it will stay off. Thank you for all of your help and suggestions...Once again you guys have helped me solve my problems.
 
Well.....I was happy too early. The CEL 71 code came back up. Dang. I thought I had fixed it finally. Now where to look? FRUSTRATING!!!
 
Do you have an EGR temp sensor? I had a problem with a bad sensor on a truck I had last year... After looking at the diagrams it seems that only CA emissions trucks had the sensor, and the Federal trucks just had a jumper between the contacts... So I just jumped it, code went away...
 
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