Code 311 has me stumped!

[Wanabee FTer]

I am having a difficult time diagnosing a code 311 on my '97 F53. I actually found 2 codes after I installed the Banks Powerpack system. The first code was 332 (insufficient EGR flow detected) an easy fix, I repaired a broken plastic vacuum line that I somehow snapped during the install. That solved the problem that was causing the ce light to come on. But this pesky code 311 is driving me crazy. The code definition is "Thermactor air system fault during engine run self test" also on the internet another definition is "AIR system not working – Single, Right or Rear HO2S – Air Injection"
First thing I did was replace the AIR pump because I thought there was not enough air pressure coming out of it (and it was noisy) Now quieter but no change still code 311, next I found an AIR delivery hose that was crimped, replaced it, still the same problem. Then I found a post on the internet that said the o2 sensor might cause this code to set because it will send a lean signal to the PCM, but the PCM determines a fault in the AIR system due to excessive o2 in the exhaust. I replaced the o2 sensor, still same problem.
Fortunately this code does not set the check engine light, but I guess I am a bit fanatical when it comes to fixing things that are not working properly. I read a post today on one of the many Ford forums that said to remove the vacuum connections from the TAD solenoids and check for vacuum at the source line. I did that and started the engine, no vacuum from source. OK now we're getting somewhere. I traced the black source line best I could to the vacuum canister, but not 100% sure if I have the correct line. They're all multi colored and shrouded inside plastic wire protectors, so hard to tell for sure. All the lines appeared ok, so I applied vacuum to the black source line and to my surprise it holds vacuum. So this means there is no vacuum leaks on the source line to the TAD solenoids.
Next I started to remove what I think is the source line from the vacuum canister, but I put it back on because I could hear the vacuum escaping from the vacuum tank and I was afraid of breaking something.
So here I am, perplexed by a problem I probably don't even need to worry about. I am starting to think this is a factory defect in the vacuum source line that has gone unnoticed for 12 years. Im afraid to go any further for fear of breaking brittle plastic lines and opening a bigger can of worms.
Anybody that wants to put in their 2 cents worth, please do!

[mpaton]

Originally Posted by Wanabee FTer

I am having a difficult time diagnosing a code 311 on my '97 F53. But this pesky code 311 is driving me crazy. The code definition is "Thermactor air system fault during engine run self test" also on the internet another definition is "AIR system not working – Single, Right or Rear HO2S – Air Injection"
First thing I did was replace the AIR pump because I thought there was not enough air pressure coming out of it (and it was noisy) Now quieter but no change still code 311, next I found an AIR delivery hose that was crimped, replaced it, still the same problem. Then I found a post on the internet that said the o2 sensor might cause this code to set because it will send a lean signal to the PCM, but the PCM determines a fault in the AIR system due to excessive o2 in the exhaust. I replaced the o2 sensor, still same problem.
Fortunately this code does not set the check engine light, but I guess I am a bit fanatical when it comes to fixing things that are not working properly. I read a post today on one of the many Ford forums that said to remove the vacuum connections from the TAD solenoids and check for vacuum at the source line. I did that and started the engine, no vacuum from source. OK now we're getting somewhere. I traced the black source line best I could to the vacuum canister, but not 100% sure if I have the correct line. They're all multi colored and shrouded inside plastic wire protectors, so hard to tell for sure. All the lines appeared ok, so I applied vacuum to the black source line and to my surprise it holds vacuum. So this means there is no vacuum leaks on the source line to the TAD solenoids.
Next I started to remove what I think is the source line from the vacuum canister, but I put it back on because I could hear the vacuum escaping from the vacuum tank and I was afraid of breaking something.
So here I am, perplexed by a problem I probably don't even need to worry about. I am starting to think this is a factory defect in the vacuum source line that has gone unnoticed for 12 years. Im afraid to go any further for fear of breaking brittle plastic lines and opening a bigger can of worms.
Anybody that wants to put in their 2 cents worth, please do!

The F53 Thermactor air system is designed to send air in one of 3 directions, called Upstream, Downstream or Bypass. In the case of the F53 with no catalytic converter, Upstream and Downstream refer to upstream or downstream of the O2 sensor. Bypass means no air is pumped into the exhaust, but it goes to a muffler mounted just in front of the top of the radiator. When air is bypassed you may hear noise from the pump.

The 3 directions are controller by 2 valves, one called the Bypass valve which sends air either to Bypass or to the other valve, the Diverter valve. The Diverted valve sends air either Upstream or downstream.

The ECU sends an electrical signal to a solenoid for each valve which sends vacuum to actuate the valve.

The ECU has a set of tests to check that the solenoids draw the expected current when operated, and you seem to be passing these.

There are further tests to check that air is being pumped to the correct place. the first check is for upstream air. If this check is failed, then Code 311 is set, and the other 2 tests aren't run.

What this test does is to make the fuel mixture richer than usual, and then direct Thermactor air upstream. The Thermactor air should overwhelm the effect of the richer mixture and make the O2 sensor register a Lean mixture.

Other tests to check that the O2 sensor is working will have been run before this test. So when you fail this test, there is an insufficient amount of air being sent upstream, which on this engine means to the exhaust header of the left (Driver's side) cylinder bank.

As you've checked vacuum to that solenoid, you should next check that air is being pumped out of the Diverter valve towards the left side header with the engine running, and with vacuum applied to both valves.

You could also remove the check valve for upstream air and see if it is working properly.

[Wanabee FTer]

That's allot more info than I could find on the internet about the AIR system.
That should keep me busy for a while.
Thank you mpaton.

[Topflite51]

Have you called Banks and asked them? I seem to remember that there was some kind of issue but alas my memory ain't what it used to be.

[Wanabee FTer]

Thanks for the suggestion David,
Just got off the phone from Banks tech support, nice people, they sure tried, but thanks to mpaton's post, I knew more about the trouble code then they did.
Since the check engine light is not coming on, I am going to put this on a low priority list.
When I get a chance I will rerun the scan test while applying vacuum to the diverter and bypass valves and see what happens.

[mpaton]

Originally Posted by Wanabee FTer

Thanks for the suggestion David,
Just got off the phone from Banks tech support, nice people, they sure tried, but thanks to mpaton's post, I knew more about the trouble code then they did.
Since the check engine light is not coming on, I am going to put this on a low priority list.
When I get a chance I will rerun the scan test while applying vacuum to the diverter and bypass valves and see what happens.

While in theory, running that test with vacuum applied manually could work, in practice, I think you'd be very skillful if you timed the vacuum application exactly when the ECU expected it. So you risk anomalous results.

The last 2 tests I suggested are straight out of Ford's PC/ED diagnostic manual. They shouldn't be very hard to run.

With OBD-1, not many of the codes cause Check engine lights. I couldn't say if that means it's not important. If your new pump were always pumping against a closed valve, then that would probably shorten it's life. Your noisy pump could also be a clue, but nothing is definitive until you test the air coming out of the diverter valve and also the check valve. Have you also checked that each solenoid applies vacuum to the correct valve?

[Wanabee FTer]

Originally Posted by mpaton

As you've checked vacuum to that solenoid, you should next check that air is being pumped out of the Diverter valve towards the left side header with the engine running, and with vacuum applied to both valves.

You could also remove the check valve for upstream air and see if it is working properly.

OK, I misunderstood how to check the valves. I know there is air pumping to the first valve (bypass valve I think) because I can feel it pulsating through the rubber hose when I squeeze it, but not sure where it's going from there. I will apply vacuum to both valves with the engine running to see what direction the air goes.
If I remember properly it's easy to test the check valves by removing the AIR hose and running the engine to see if exhaust comes out.

[mpaton]

Originally Posted by Wanabee FTer

OK, I misunderstood how to check the valves. I know there is air pumping to the first valve (bypass valve I think) because I can feel it pulsating through the rubber hose when I squeeze it, but not sure where it's going from there. I will apply vacuum to both valves with the engine running to see what direction the air goes.
If I remember properly it's easy to test the check valves by removing the AIR hose and running the engine to see if exhaust comes out.

From the bypass valve, it should go either to Bypass (the muffler in front of the radiator) in which case I'm not certain you'd feel it pulsating, or to the other valve, the Diverter.

You should also be able to check the vacuum line routing by looking at the VECI label. If it hasn't fallen off, you should find it on the outside rear of the driver's side rocker cover, viewable through the wheel well. If it's gone, you can find a copy on Ford's web site, at http://www.motorcraftservice.com/vdi...E=F-SUPER+DUTY

[Wanabee FTer]

I have never seen the website link you posted.
Mororcraftservice.com looks like a wealth of info. Definitely worth the price of admission.

[mpaton]

Originally Posted by Wanabee FTer

I have never seen the website link you posted.
Mororcraftservice.com looks like a wealth of info. Definitely worth the price of admission.

I hope you got in OK. I just tried the link and didn't get anywhere. But if you go to http://www.motorcraftservice.com and then click on Quick Guides, and then VECI Labels you can then select your chassis and year and get a choice of 2 VECI labels, and get to decide which could be the right one. VECI Labels are free.

[Wanabee FTer]

I got the VECI label downloaded for Ford super duty CA emissions. Studying the vacuum diagram it shows the vacuum reservoir is called a vent reservoir. The vent reservoir is connected to two solenoids that control the bypass/diverter valves. The vent line shows unrestricted vent (vacuum) source to the solenoids. I have checked for vacuum at the solenoids from the vent (vacuum) line with the engine running and there is none, and I also applied vacuum to the solenoid side of the vent lines and it holds vacuum which leads me to suspect there is a blockage in the vacuum source vent line. I still need to perform the diverter valve tests, but with no vacuum source to those valves I suspect this to be the problem.

[Wanabee FTer]

I am so excited right now I can hardly stand it. I found the cause of the problem and it is now repaired!
I traced 2 black vacuum source lines. One for the EGR the other for the bypass/diverter solenoids. Most of the lines are shrouded in protective wire wrap so I checked the visible lines first. All looked good at the solenoid end, then I checked the vacuum reservoir end, all appear ok. I found two vacuum connectors about 10 inches away from the reservoir. I pulled them both apart, one at a time I blew air through the solenoid side. The line for the EGR was wide open, but the line for the diverter solenoids was still blocked. Great, that narrowed it down to about 4 feet of hard plastic vacuum tubing. I was almost ready to entirely bypass the blocked section but I started feeling the line as far back towards the engine as I could. Then I felt something that didn't feel right, a flat spot that was not visible. I cut about a one inch piece of tubing out to examine it. What I found amazed me. At some point the line had gotten too hot and collapsed on itself. I tried to blow through this small section, but it was 100% blocked. I then put a short piece of vacuum hose onto the existing line to repair it.
That was it! I started it up and found the AIR system pumping air where it was not doing anything before. I ran a scan test on the ECU and the only code I got was 111, meaning all systems passed the scan test.

Thanks to all for your help in resolving my problem

[mpaton]

Congratulations!

Was this vacuum line supplying both Thermactor solenoids, or just the diverter valve. I'm wondering if any of this may have caused wear on your pump, but I can't work out a mechanism for that yet.

The CA emissions 1997 model year lighter duty trucks, F250 and F350 are Mass Air and Sequential Injection, and OBD-2, unlike the F450 and motorhome chassis, and the OBD-2 systems managed to delete the Thermactor altogether; there's just an idler pulley there.

I don't know if you get given gas percentages in CA, but look for them to be even lower with the Thermactor system working. You may also notice a little more popping from the exhaust on overrun with it working.

Michael

Originally Posted by Wanabee FTer

I am so excited right now I can hardly stand it. I found the cause of the problem and it is now repaired!
I traced 2 black vacuum source lines. One for the EGR the other for the bypass/diverter solenoids. Most of the lines are shrouded in protective wire wrap so I checked the visible lines first. All looked good at the solenoid end, then I checked the vacuum reservoir end, all appear ok. I found two vacuum connectors about 10 inches away from the reservoir. I pulled them both apart, one at a time I blew air through the solenoid side. The line for the EGR was wide open, but the line for the diverter solenoids was still blocked. Great, that narrowed it down to about 4 feet of hard plastic vacuum tubing. I was almost ready to entirely bypass the blocked section but I started feeling the line as far back towards the engine as I could. Then I felt something that didn't feel right, a flat spot that was not visible. I cut about a one inch piece of tubing out to examine it. What I found amazed me. At some point the line had gotten too hot and collapsed on itself. I tried to blow through this small section, but it was 100% blocked. I then put a short piece of vacuum hose onto the existing line to repair it.
That was it! I started it up and found the AIR system pumping air where it was not doing anything before. I ran a scan test on the ECU and the only code I got was 111, meaning all systems passed the scan test.

Thanks to all for your help in resolving my problem

[Wanabee FTer]

Originally Posted by mpaton

Congratulations!

Was this vacuum line supplying both Thermactor solenoids, or just the diverter valve. I'm wondering if any of this may have caused wear on your pump, but I can't work out a mechanism for that yet.

It supplied both solenoids, then went to the right and left side diverter valves.
I'm not really worried about wear to the pump, I have less then 100 miles on it since it was replaced and the air pulse seemed strong when squeezing the supply AIR hose.

Originally Posted by mpaton

I don't know if you get given gas percentages in CA, but look for them to be even lower with the Thermactor system working.

Here in Cali we have 3 emission types to pass, Hydrocarbons (HC), carbon monoxide (CO) and nitrous oxides (NOx). I would expect the next smog test will look better then the last. Probably wishful thinking to get a little more MPG.

Originally Posted by mpaton

You may also notice a little more popping from the exhaust on overrun with it working.

Michael

Michael,
Thanks for all your help, the link to motorcraftservice.com gave me the ability to get the VECI label vacuum diagram. My label was painted with undercoating and was un-legible.
I did notice a little more popping on decell while revving in neutral. Good to know it's nothing to worry about. I have owned this MH for about 4 months and I bet the AIR system has not worked properly in a long time.