Emissions Issues and Accelerator Pedal Stop

[rtadams89]

I took my M35A2 to be emissions tested today for my registration renewal. This was first time I personally drove it through emissions testing, and the second time it has been tested in Arizona. The first time the previous out of state owner came with it and drove it through before we transferred the out of state title to me and registered it under my name.

Both times, getting it through was a real pain. The test consists of holding some sort of optical sensor on the smoke stack and having the driver floor it (ugh, hate that part) three times. The issue I've run into both times is that the initial burst of smoke ends up clogging up the sensor, and therefore the calibrated zero value for the sensor drifts too much over the three successive tests (or this was my take away from what I could see/was told by the employees). This isn't a "failure", but because the test can never be completed successfully, it isn't a pass either.

I don't remember exactly, but the first time we went through testing, I remember the station manager coming out after trying 4 or so tests, taking over the testing, and then waiting for the initial burst of smoke to go by before putting the sensor up into the smoke stream. That worked right away and I got a "pass." This most recent time I went through, the employees tried 8 times to get a test, then told me to take a lap to warm up the engine (which I think is just their catchall excuse; the engine was already warm) and then come back. When I came back, the test again didn't work, so they told me not to floor it all the way. The test then worked and I again got a "pass". I don't know anything about the testing standard, but it seems odd they had to modify the testing process both times; not sure if that is going to happen the next time I go through.

Let me preface this next part by saying, I am not asking how to cheat the emissions test. I do not want to do anything that would even be a "gray area". I don't really know what the testing standard (is there a "standard"?) calls for, but in talking with the employee this last time through, it seems you are just supposed to step on the accelerator pedal and push it as far down as it physically will go. The limiting factor in my truck is a bolt that sticks up under the accelerator pedal, the head of which contacts the underside of the pedal and prevents it from going further down. It seems if I extended this bolt out, it would prevent the pedal from going down as far, and perhaps reduce the issues I have with that first burst of smoke.

Here are my questions:

1. Here are videos of both my RPMs and the smoke coming out of my stack under the "floor it" test. Does either look unusual/problematic?
2. Since I never floor it under normal conditions, is there any reason I can't just extend the bolt mentioned to reduce/prevent that initial burst of smoke?
3. Where is this travel stop bolt mentioned in the TMs? I expected there to be an adjustment section, but I looked in the -10, -20, and -34 and the closest thing I find (3-33. ACCELERATOR PEDAL, BRACKETS, AND ROD MAINTENANCE) doesn't even show that stop bolt.

https://youtu.be/eqp1HS84F3Y
https://youtu.be/Sz1vU_BXLvY

 

[rustystud]

First off your video doesn't load up. You need to post it here on this site. Second I'm pretty sure the "testers" don't know what their doing on a large older truck. We have to test our busses every year. It's called an "Opacity" test. It measures the amount of carbon and "soot" in the exhaust . On older diesels your suppose to rev the engine then put the meter into the exhaust stream. Not just stick it up the exhaust and rev it. You will always get a fail if you do that. On any big diesel with a mechanical injection pump, the first amount of exhaust flow will have some unburned fuel. That is just the nature of diesels. Turbos cannot spool up immediately, and the injection pump being a mechanical unit will always put out more fuel then can be used when you floor it. Now the newer electronic diesels can "cut back" the fuel when reving up the engine like that. Like I said, these testers do not know how to test older diesels. You might ask them what is the "proper" procedure for "older" diesels with mechanical injection pumps. I'm sure there is a procedure written specifically for them.

 

[rtadams89]

First off your video doesn't load up. You need to post it here on this site.

Tried that. First video (RPM) worked. Other one wouldn't (but oddly got nor error, just wouldn't show up). I'll throw them up on YouTube and replace the links.[/QUOTE]

Second I'm pretty sure the "testers" don't know what their doing on a large older truck. We have to test our busses every year. It's called an "Opacity" test. It measures the amount of carbon and "soot" in the exhaust . On older diesels your suppose to rev the engine then put the meter into the exhaust stream. Not just stick it up the exhaust and rev it. You will always get a fail if you do that. On any big diesel with a mechanical injection pump, the first amount of exhaust flow will have some unburned fuel. That is just the nature of diesels. Turbos cannot spool up immediately, and the injection pump being a mechanical unit will always put out more fuel then can be used when you floor it. Now the newer electronic diesels can "cut back" the fuel when reving up the engine like that. Like I said, these testers do not know how to test older diesels. You might ask them what is the "proper" procedure for "older" diesels with mechanical injection pumps. I'm sure there is a procedure written specifically for them.

I know nothing about the testing procedures, and what I know about diesels in general, I've learned from this site and the TMs over the last 18 months. Everything you said makes sense and I know you have the experience to back it up. If the proper procedure is to put the meter into the stream after the rev, that sounds like the station manager the first time around knew and did that, which finally worked. No the problem is spinning my lottery wheel each year until I get a (likely rarer each year) employee who knows what they are doing. Is there a federal law that actually describes the proper procedure, or are their usually state laws, or is this one of those things in the MVD procedures books us regulars never get to see? It would be super handy to have a reference I can point to the next time I have to test to get them to actually do the test the right way.

PS: I don't know how you manage to spend so much time on here posting your knowledge AND spend enough time in the field to actually gain that knowledge. Thanks again for this response and all the other threads you've helped in.

 

[frank8003]

questions 2 + 3.
data + picture, part 32

View attachment engine multifuel stop and go controls.pdf

from http://www.myazcar.com/why-and-how-we-test
In metro Phoenix, heavy duty diesel vehicles are tested using a procedure called "snap acceleration".

and from http://www.tercenter.org/pages/tailpipe.cfm
Are these tests required only in Metropolitan Phoenix and
Metropolitan Tucson?

 

[rtadams89]

questions 2 + 3.
data + picture, part 32

View attachment 708683

Thanks, I found that previously in the -20P TM, but the -20 TM doesn't mention that bolt. It may not exist, but I had assumed there would be a TM section on adjusting that bolt so that it extended out the correct distance.

 

[frank8003]

Hey, if they would want to play silly with my truck I would play too. Adjust the sitting idle to 1100 rpm and adjust the pedal stop bolt up. Under an engine no load situation why would I ever "snap it" above the 1800rpm torque peak.
Someplace back in the past times some were known to fill exhaust pipes with steel wool and bananas,
I heard about that once.

 

[wheelspinner]

Do they ACTUALLY emissions test a vehicle that NEVER had emissions considered inits design? That's insane.

 

[Floridianson]

Is you FDC bypassed or has your fuel been turned up? If the FDC was bypassed the droop might not have been turned down. Turning down the main fuel also might help a bit.

 

[M35A2-AZ]

If you have it reg. as Historic it does not need emissions, just an fyi.

 

[Katahdin]

Do they ACTUALLY emissions test a vehicle that NEVER had emissions considered inits design? That's insane.

Since the late 1960s these engines have been subjected to smoke and emissions tests, that's what got us the turbos on the LD-465s. Also, if you read the injection pump TMs, the fuel calibration on the LDT-465-Cs are very specific, most likely to comply with EPA smoke regulations at the time.

 

[winfred]

find the size spacer for under the pedal that gets the desired effect, make wood block and paint green and dirty it up a little, install good magnet on back side then stick to floor when exiting truck at arrival to testing station. once complete stick block to back side of dash till next time

 

[Floridianson]

Lets see if you can lower the fuel by the droop or smoke cam. Then one thing that might help is don't let the engine cool down before the test. Don't let her idle for a long time before the test and maybe just maybe if you remove the air filter just before you drive it in to the shop. PM if you need to talk about lowering the fuel.

 

[rtadams89]

The FDC is not bypassed. I do not know if the fuel has been turned up or not, but as the truck came to me with a EGT gauge installed, I suspect so.

I tried what winfred suggested as a test, using sockets and socket adapters to reduce how far the pedal can go. To get it to a point where there isn't a large puff a smoke when flooring it, I also had a truck that wouldn't get up over 30 miles an hour.

With the input from rustystud, and the fact that I never get a plume of smoke under normal driving conditions, I don't think my truck has a problem. I think the testing method applied to a 50 year old truck is the issue. If anyone watched my vids and thinks my truck is performing abnormally, please do let me know. What I would also still like to know is if there is some officially recognized document on how these trucks should be tested -- using the floor it, then stick the opacity sensor into the exhaust stream method.

 

[Floridianson]

The FDC is not bypassed. I do not know if the fuel has been turned up or not, but as the truck came to me with a EGT gauge installed, I suspect so.

Till the turbo kicks in more fuel less air. As I said most people who bypass the FDC or turn up the fuel don't reduce the fuel at the low side. Turn down the fuel at both ends.

 

[dmetalmiki]

Rusty said it all.
(And) In the U.K. testers do not 'smash' the pedal to the floor, and rev the nuts out of an engine. and especially on diesel cars. As this has been known to snap cam belts!.
Old and historic Vehicles (All types) are exempt testing.

 

[Floridianson]

No one read Franks post how they do it in Az.
If I remember right the Cummins turbo PT has a A/F screw that can be used to control some of the lower end fuel. Same as the Deuce but it's the smoke cam /droop screw. If you don't think you can do it then I bet there is member close to you that could help turn down the fuel to see if it helps.
When we adjust the fuel we do the main first then the droop. In this case lowering the main will also lower the droop or fuel at the lower end.
The states I believe are cracking down on big and little diesel trucks. You see it all the time in the smaller trucks rolling coal on take off.

 

[rustystud]

Tried that. First video (RPM) worked. Other one wouldn't (but oddly got nor error, just wouldn't show up). I'll throw them up on YouTube and replace the links.

I know nothing about the testing procedures, and what I know about diesels in general, I've learned from this site and the TMs over the last 18 months. Everything you said makes sense and I know you have the experience to back it up. If the proper procedure is to put the meter into the stream after the rev, that sounds like the station manager the first time around knew and did that, which finally worked. No the problem is spinning my lottery wheel each year until I get a (likely rarer each year) employee who knows what they are doing. Is there a federal law that actually describes the proper procedure, or are their usually state laws, or is this one of those things in the MVD procedures books us regulars never get to see? It would be super handy to have a reference I can point to the next time I have to test to get them to actually do the test the right way.

PS: I don't know how you manage to spend so much time on here posting your knowledge AND spend enough time in the field to actually gain that knowledge. Thanks again for this response and all the other threads you've helped in.[/QUOTE]

I used to post when I got home from work at midnight. It gave me some time to decompress before going to bed. Now I'm retired (going on three years now) and have more time to play here !

 

[rustystud]

No one read Franks post how they do it in Az.
If I remember right the Cummins turbo PT has a A/F screw that can be used to control some of the lower end fuel. Same as the Deuce but it's the smoke cam /droop screw. If you don't think you can do it then I bet there is member close to you that could help turn down the fuel to see if it helps.
When we adjust the fuel we do the main first then the droop. In this case lowering the main will also lower the droop or fuel at the lower end.
The states I believe are cracking down on big and little diesel trucks. You see it all the time in the smaller trucks rolling coal on take off.

Most all diesel trucks in the commercial world have modern diesel engines. They are just more fuel efficient which means more money saved. You might see a small owner operator still using an older diesel but in all honesty I haven't seen one in years now. As for the little diesel trucks, if they cannot pass the emissions test they get sidelined until the problem is fixed or the truck is taken off the road. That is what Washington state has done at least.

 

[cattlerepairman]

Also, do not forget that your multifuel can run on fuels other than diesel. I went to my emissions test (long story) with a tank full of regular gasoline. Much less smoke.
Note that it is YOU who tells the DMV that this truck is a Diesel powered vehicle. Says who? It could equally be a gas powered truck. Runs fine on gas.
In my case, they could only test diesel trucks, not gasoline ones, so....

 

[Floridianson]

Most all diesel trucks in the commercial world have modern diesel engines. They are just more fuel efficient which means more money saved. You might see a small owner operator still using an older diesel but in all honesty I haven't seen one in years now. As for the little diesel trucks, if they cannot pass the emissions test they get sidelined until the problem is fixed or the truck is taken off the road. That is what Washington state has done at least.

My GMC 3500 has EFI live and I can roll coal or dial it down when I want. Mechanical or computer controlled we have control.
All rtadams89 has to do is get a black marker. If he has a heater he will have to leave it hooked up just lay it over the motor. If no heater then it will take five mins. to turn down the fuel. Loosen jam nut two turns. Mark inner nut with marker and loosen one complete turn counter clock wise. Fire up the motor and see how the exhaust looks. If there is still to much back off 1/4 turn counter clock wise till you get the exhaust to clear on throttle snap. Tighten up jam nut go get it inspected. When you get the truck home bypass the FDC and retune the motor to you liking with pyro.