That's the one I thought it was. Thanks for the pic. I'm almost tempted to try it, even though I'm still under warranty till next June.

 

That is indeed the very plug I unplugged. Others on here say they haven't had the check engine (orange check mark) come on, but that is exactly what happed after I unplugged the EGR. The truck was cold (hadn't been started in two days) and I had the key in the on position for quite a while before unplugging. I only thing I can't remember at the moment is if I turned the key back off prior to unplugging or not; but after shutting down and restarting a few times, I still have the check engine issue. The truck is still sitting by my shop with the EGR unplugged. Maybe I'll plug it back in, run the truck a while to warm it up and see if the light goes out, let it cool overnight and then try doing this again. If it's going to cause the light to come on, I don't know if this is worth playing with. When I had something really go wrong, I'd never know it.

Thanks, by the way, for the pic you included. I was pretty certain I had the EGR, but as I’ve said 100 times before, I’m a former CAT devotee and therefore a bit of an idiot when it comes to Cummins. At least I know for sure I’m unplugging the correct thing now.

 

Well, I tried plugging the EGR back in and then disconnecting it again, but I still have the check engine light illuminating. As before the truck started and idled fine so I decided to use the old electrical tape on the check engine light trick and go pick up a load in Mattoon, IL (about 150 miles from my house).

The truck ran fine going up, but then again I was empty so there wasn’t much demand being placed on the engine. After picking up, I came back to the house because the load has about three extra days on it and can deliver anytime in Montebello, CA. On the way back (grossing abt. 76k pounds) the engine purred right along. The boost gauge was only putting out 2 – 3 lbs in the flats (normally I’d expect at least 5 – 8 lbs with such a heavy load) and the pyrometer indicated slightly lower exhaust temps than I’d expect as well. On the couple of small hills I encountered on my drive, power seemed to be unaffected in either in a beneficial or detrimental way.

Conclusion: We’ll try running with the EGR disconnected out to SoCal and see what kind of effect it has on fuel over the next 2k miles. After that, I’ll reassess whether we’ll continue with our little experiment.

 

ahmm, I don't know if i would go into CA with a disconnected smog control device. Just saying.

 

What they don't know wont hurt me.

 

All you have to say is if they check it is that "the darn plug keeps coming out of the EGR and I am not a certified Cummins tech, so I'll have to get it in a shop as soon as I can". Or you can tell them that Cummins has put it in "test mode" and doing a running analysis on the engine. Better yet, don't say a thing and I'll bet they wouldn't even know it. Those guys are not firing on all thrusters anyway, and I would bet that a lot of them couldn't find the EGR on the engine if you asked them where it was. You give CARB too much credit.

 

Well, 7k miles driving with my EGR disconnected has yielded the following:

-- there is an improvement in fuel economy, though the biggest increase (perhaps as much as 20%) seems to be with loads under 30k lbs or so. With heavier loads the mpg increase has been about 5 - 10%.

-- the truck runs much cooler

-- boost and pyrometer readings are lower

-- engine noise seems to be reduced

-- my "check engine" light has remained on from day one, but other than that the trucks runs as good as ever

 

1859 miles. Fill up 234 gallons.....

 

14526 Miles 2095.058 Gallons = 6.93345959873188 MPG

We have been running heavier freight than normal recently, so I think the numbers are a little less than they would be if we have been running what we normally do. We had three loads totaling over 5k miles that had us grossing 79k + and running into some pretty nasty winds on I-40 and I-10. Our average loads are more in the neighborhood of 20k – 30k lbs, so looking at the data from those loads, our average mpg goes up to about 7.5, which makes me ecstatic. Over the 225k miles we’ve had this truck, we’ve averaged 6.72 mpg, so even 7 mpg is a welcome increase. I’ll be interested to see our oil analysis when it comes back after our next PM.

 

I was cruising down the boring highway 54 in kansas with 4 trucks and we got to talking about fuel mileage and I asked if anyone had heard of unplugging the EGR on a Cummins.

A driver that hadn't been talking chimed in laughing and said his shop recommended it but he said they went a little further. He said his shop brazed his EGR shut so he didn't have to unplug it.

Is that possible??