I bought a 2004.5 Ram Cummins truck one year ago, my first ever diesel vehicle. Saturday I took it to emission test it for the first time. They checked the emissions equipment, fuel cap, etc. Then for the run test, the emissions guy asked me to floor it while in Park on his signal, then release the accelerator on his follow up signal. I was kind of taken back by his request, so I didn't floor it, just tried to bring it up to the 3200 rpm redline and hold it there. That resulted in an unsteady rpm, so they told me that the readings will be all over the board if I don't floor it. I told him this engine has a 3200 rpm redline. He said the engine's governor will protect my engine. I was required to get the truck emission tested to renew the plates, so I reluctantly did as asked. I had to do the procedure for a few seconds each of three successive times. The governor did kick in, but the engine still exceeded the redline by several hundred rpm. This experience was in Maricopa County, Arizona. My questions are: Even though the procedure caused the engine to exceed its redline, is the governor truly protecting the engine? Are the governors reliable? I'm thinking if the governor failed during one of these tests, the result could be disastrous. Is this typically how the diesel emissions test procedure is done in every state or metro area that has a diesel emissions test? Or is it unique?

In PA, diesel trucks are exempt from this nonsense. They are kept busy destroying the gas powered vehicles.No way would I allow some jerk to abuse my property.

I have read many similar stories, so it seems normal. The ECM is programmed and will protect from overspeed, there is no external governor. If the truck runs normal it should limit rpms. That model ISB is rated to 4200 rpms for 15 seconds.

On Long Island, they follow the same procedure.

I just give it about 3/4 throttle and get it up to about 3k. If it doesn't work we do it over.It will exceed the red line and while the Cummins wont suffer any catastrophic damage until it gets to about 5K, I figure cylinder scarring from revving an unloaded engine is always a possibility.The 3200 RPM red line is just the top of the useful power band and not an indicator of where valves float or any other damage.

Our area also uses the "punch test" to test diesels for gaseous and opacity output. My 6.0 V8 Powerstroke had no problem revving since peak horsepower was developed at 3300 RPM. The I6 Cummins a has lower redline and peak horsepower RPM, so I would expect the test to take account for the differences. I do not have to take my Cummins in for testing until 2017, so I don't know what kind of testing will used. Monitoring was done through the ODBII port with a sensor at the tailpipe with my last Powerstroke test.

Diesel Emissions Test Question | Good Sam Community

20 Replies

crcr
Explorer
Mar 23, 2015
ScottG wrote:
Hank85713 wrote:
Need to check with the manager of the place. Down in tucson its just push it and let go no need to hold so a quick throttle blip is basically it.

All they are looking for is SMOKE and nothing else. They get all the readings they need off the computer and from the tail pipe probe. Mine has 11% or less on the test but it does not get run a lot either so I have to take it out on a run 1st. R floor it and then let it off. Ask to see the procedure they are to follow, but since you ar eup in east LA there is no telling what is going on.

Actually they are looking for heat as well. If you don't push it hard enough to make enough heat it wont even go on to check the opacity. After a certain number of failed attempts, it fails the test.

I will estimate that they probably only had me hold hard throttle no more than a second or second and a half each of the three times in succession. I only did 3/4 throttle, not 100% as they asked, but that was quite enough for the governor to kick in.

Per my emissions result read-out, my Cummins tested with 8% opacity.
rhagfo
Explorer III
Mar 23, 2015
Lynnmor wrote:
In PA, diesel trucks are exempt from this nonsense. They are kept busy destroying the gas powered vehicles.

No way would I allow some jerk to abuse my property.

In Oregon if over 8,500# GVWR also exempt! :)
ScottG
Nomad
Mar 23, 2015
Hank85713 wrote:
Need to check with the manager of the place. Down in tucson its just push it and let go no need to hold so a quick throttle blip is basically it.

All they are looking for is SMOKE and nothing else. They get all the readings they need off the computer and from the tail pipe probe. Mine has 11% or less on the test but it does not get run a lot either so I have to take it out on a run 1st. R floor it and then let it off. Ask to see the procedure they are to follow, but since you ar eup in east LA there is no telling what is going on.

Actually they are looking for heat as well. If you don't push it hard enough to make enough heat it wont even go on to check the opacity. After a certain number of failed attempts, it fails the test.
Hank85713
Explorer
Mar 23, 2015
Need to check with the manager of the place. Down in tucson its just push it and let go no need to hold so a quick throttle blip is basically it.

All they are looking for is SMOKE and nothing else. They get all the readings they need off the computer and from the tail pipe probe. Mine has 11% or less on the test but it does not get run a lot either so I have to take it out on a run 1st. R floor it and then let it off. Ask to see the procedure they are to follow, but since you ar eup in east LA there is no telling what is going on.
Community Alumni
Mar 23, 2015
In Colorado along the front range where testing is required all diesel light duty vehicles are run on a dyno to test emissions. All heavy duty diesel trucks are also tested on a dyno unless the fleet is certified to test. Then we would run them the same way you described. It is called a snap test, quick acceleration up to the governor and then release. We use a meter to read the smoke level. Never had an engine fail while doing this test.
Bedlam
Moderator
Mar 23, 2015
Our area also uses the "punch test" to test diesels for gaseous and opacity output. My 6.0 V8 Powerstroke had no problem revving since peak horsepower was developed at 3300 RPM. The I6 Cummins a has lower redline and peak horsepower RPM, so I would expect the test to take account for the differences. I do not have to take my Cummins in for testing until 2017, so I don't know what kind of testing will used. Monitoring was done through the ODBII port with a sensor at the tailpipe with my last Powerstroke test.
ScottG
Nomad
Mar 23, 2015
I just give it about 3/4 throttle and get it up to about 3k. If it doesn't work we do it over.
It will exceed the red line and while the Cummins wont suffer any catastrophic damage until it gets to about 5K, I figure cylinder scarring from revving an unloaded engine is always a possibility.
The 3200 RPM red line is just the top of the useful power band and not an indicator of where valves float or any other damage.
tmmar
Explorer
Mar 23, 2015
On Long Island, they follow the same procedure.
AH64ID
Explorer
Mar 23, 2015
I have read many similar stories, so it seems normal.

The ECM is programmed and will protect from overspeed, there is no external governor. If the truck runs normal it should limit rpms.

That model ISB is rated to 4200 rpms for 15 seconds.
Lynnmor
Explorer II
Mar 23, 2015
In PA, diesel trucks are exempt from this nonsense. They are kept busy destroying the gas powered vehicles.

No way would I allow some jerk to abuse my property.

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Diesel Emissions Test Question

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