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Thu Nov 19, 2009 12:56 am

I am posting this in the Bay forum because most of the Bay FI questions are here.

We need some FI wizard thoughts. This is a long one so get a cup of coffee before you read it. In a nutshell the AFM's that FIC have rebuilt for me are always too rich. They either pass smog barely or flunk and I end up having to tweak them. The one they calibrated but didn't rebuild passed fine. The last one they gave me reads, and I believe them, exactly the same as the new one they use for calibration. - and they said that if it is also too rich then it is something in the engine doing it.

Background - I cleaned up the old AFM that came out of the bus after it failed smog and took it to FIC for testing. They calibrated it and said it was Ok otherwise and didn't need rebuilding. It passed smog with flying colors. With the help of the smog shop we tweaked it to near perfection - passing smog and slightly richer than the center of the test but lean enough not to get nailed on a hot day. It will have to pass smog every two years. Essentially the same test that Richard Atwell went through and same limits. Car goes on a dyno and is driven at 15 in 2nd and 25 in 3rd.

Because California only gives one 30 day extension now to fix it when it fails, we set aside the cat and AFM that passed and put them in an emergency kit in case the bus ever fails. Then we had FIC rebuild 1 of 2 spare AFM's we had collected. The first one they rebuilt grossly failed smog and the second replacement passed but it had a pretty worn board so they cherry picked a 3rd one for me and adjusted it to as close as they could get it to a factory NOS one they use to calibrate their test equipment. But like all the others except my first one, it favors the rich side and barely passed smog by .01% CO - essentially a statistical coin flip. Before I pop the cap off and start tweaking which will piss FIC off because of the work they put into it, I want to be sure I have covered all the bases that might make it run rich at 2000 RPM. Mind you that even the ones that failed under load at 2000 RPM were fine at light loads and 2500 RPM - California is trying to fit a 1977 car into a 2001 smog test but as long as we live here that is our problem.

All the FI components are new or tested. The relays, pump regulator etc are new. I've read all the published L-Jetronic stuff I can get my hands on. All the grounds are cleaned. The ECU has been tested and it has passed smog. The injectors were cleaned by Witchhunter. I matched the best 4 of 8. Compression was set to 7.3. Plugs are NGK and wires are new Bosch. Coil is the good blue one. I don't have the black one and I have read that the coil can affect mixture but I don't have one to see if that is true or an old wives tale.

Here is the issue - the engine favors the rich side, 13.7:1 at 2000 rpm on the 15mph and 25mph loaded dyno tests. Get it out on the freeway or street at 25mph in 3rd gear and it is 14.5:1. But get it on the smog dyno in 3rd under load and it moves to about 13.7:1 and barely passes. If it is 13.6 like the last one it flunks. If it is 13.9 like my other one it flys through. But this one is supposed to read the same as a factory new one at 4 to 6 test points and loads according to FIC. I had a long talk with Tony there and he says that it is so close to the factory one used for calibration that in this case I do not want to touch the spring or wiper - it is set to absolutely the same readings as the NOS unit they use to calibrate. He said no two are exactly alike even from the factory but as it is calibrated it should be perfect except for the idle CO which I set to 1.0% CO per the sticker for CA.

Timing is 7.5 BTDC and advances normally. dist is NOS
Dwell is 49 and rock stable
EGR is adjusted and like new
Idle CO is about 1.0%
Breather is good
Oil is 20/50 Brad Penn
Cam is stock solid (per RIMCO but we can't be certain. WebCam says if they ground it then it is slightly longer duration, 8 degrees or there abouts than stock)
CR is 7.3 on all 4 cylinders
Engine has 350 miles on it
Valves are exact at .006

The test indicates that NOX is 0% (way low) and HC are normal. O2 is 0% and like the low NOX, proof that the mixture is rich. CO at tailpipe is 1.65% (1.67% would have been a fail). My Smog guy tells me that any misfire under load on the dyno would show up as higher HC than I have and some O2 would show left over from the misfire.

I will check the TS II again and the new fuel pressure regulator but other than that is there anything else that I may be missing which can cause a slightly rich condition on the L-Jetronic OTHER than the AFM? Also it seems to me to get richer the hotter the engine is. It is hard to picture anything else that would cause this except the AFM but because FIC spent so much time with it, I really don't want to pop the cap unless that is the only way out. Witchhunter really tested the injectors and the cold start is new. Remember that we had to richen the first AFM to make it right so I know the system can be leaner but like I said - I want to be 100% sure that I've covered all the bases before I pop the top on this AFM because FIC really doesn't think they can do better than this one as it is. Tony does 100% believe that it is as good as a brand new Bosch AFM. It is the correct part number too. His opinion was that any changes to the spring in either direction will throw it off the factory setting he calibrated it to. He didn't say don't do it, he said that he made it perfectly the same as the NOS new one they have so if the results aren't good, I should look elsewhere for the cause which is what this thread is about. Other than the fuel pressure or TSII, is there any base I haven't covered? Example, can new engine blowby cause an engine to run richer under load?

Thu Nov 19, 2009 1:30 am

Don't you just miss the good old carbs?

Thu Nov 19, 2009 1:30 am

Before I have time to read all of this,need I remind your l-jet harness is 35 years old.With out proper continuity everything else is futile.

Thu Nov 19, 2009 1:34 am

Merlin- the dwell and timing have to be exact. Slightly advanced timing will cause rich tailpipe emissions. So can low fuel pressure.

Take the vacuum line off your fuel pressure regulator and see if you can get a whiff of fuel. If you smell fuel on the vac side, the pressure regulator is failing.

You need to get a handheld exhaust analyzer. Worth its weight in gold. I can't tell you how many AFMs I've popped the big plastic cover on and calibrated with mine. Check eBay.

Also- What plugs are you running?

Thu Nov 19, 2009 7:49 am

Quote: Merlin- the dwell and timing have to be exact. Slightly advanced timing will cause rich tailpipe emissions. So can low fuel pressure.

Take the vacuum line off your fuel pressure regulator and see if you can get a whiff of fuel. If you smell fuel on the vac side, the pressure regulator is failing.

You need to get a handheld exhaust analyzer. Worth its weight in gold. I can't tell you how many AFMs I've popped the big plastic cover on and calibrated with mine. Check eBay.

Also- What plugs are you running?
_________________

Good Morning Tram. NGK B6ES

fuel pressure regulator is new and there is vacuum present, No leaks that I can find. All hoses and fittings are new, brake booster tests Ok.

I use the LM-1 and am comfortable using it. The issue is that I've been through 3 rebuilt ones and a new board in another. Other than the first one, they all are on the rich side. Cruzing, the AFM is close to 14.5 but under load it drops to as low as 12.5. That is good from my perspective but I think that the smog dyno is putting enough of a load on it that the a/f is moving to that slightly rich part of the curve. Normally I would just pop the cap and tweak, however Tony at Fuel Injection Corp said that this specific AFM he basically adopted and it is set perfectly the same as the new one they use to calibrate with so if it isn't perfect on the bus something else is wrong. I've set everything to Bentley. Could premium fuel make it richer as it has more octane molecules in it? My smog guy used to own a bus and has been doing pre-tests for free. I hate to go back again and say "this one is with a lower octane fuel..." The dyno time else where would have been hundreds of dollars.

Hoody - we checked each connection on the harness and replaced any questionable connectors where the wire looked like it might have been tweaked or broken.

DMB - yes and I would go that route except for CA smog. I looked for an earlier bus here for 2 years and finally gave up. The ones here surviving 1971 - 1973 are either dogs, not for sale or too much for the money.

Thu Nov 19, 2009 8:25 am

Please explain to me why you would use anything but regular 87 octane gas in a 7.3:1 stock engine. Perhaps I just don't get it.

Also keep in mind that 10% ethanol will burn 5% leaner due to the less energy per unit of ethanol vs gasoline.

Get regular gas in there and play with that LM1 and see what the engine likes to see to make it run well. You can detune it from there.

Thu Nov 19, 2009 8:25 am

I'd say the engine needs more miles on it to set the rings, then test everything. The reading of 13.7 to 14.5 to 1 are correct for your partload runs...Recheck your timing and make sure the vac adv can isnt' sticking..even if its NOS its old and old grease can make it stick..

Thu Nov 19, 2009 10:42 am

Quote: I'd say the engine needs more miles on it to set the rings
Bleyseng - I've been wondering about that. I know my jeep Cj-7 years ago took about 1500 miles to 90% seat the rings. It took almost 3,000 miles to completely seat them but those were TRW moly rings. Once could see temperatures drop and mileage increase as the rings seated in. Do you think this is all it is?

Quote: Please explain to me why you would use anything but regular 87 octane gas in a 7.3:1 stock engine. Perhaps I just don't get it.
Randy - Regarding the fuel - Octane here in California is (R+M)/2 so the 91 RON octane specified for my bus minimum would be about 88 Octane (R+M)/2. Even my Sable which is designed for 87 Octane sees some nasty backfiring issues from the 87 Octane here. We've even discovered that the Chevron gas here in our neighborhood appears to have more alcohol - and it shows leaner on the smog tests than the Shell. We get about 10% better mileage on both the Sable and Acura from the Shell gas so we think the local stations or delivery are spiking the Chevron fuel with excess alcohol and water. We've seen some Chevron tankfuls drop as much as 7 MPG on both cars at the same time so we started buying Shell. If we go into the Central Valley - our mileage from Chevron will go up 3 to 4 MPG in identical driving conditions everytime we buy there and it will drop again once we buy from Chevron stations near home. Until the VW engine is broken in, due to the extra heat we were using 91 Octane which is about 94 by 1977 VW standards. I mixed 50% Shell and 50% Chevron for the smog tests to elminate fuel variables. I guess that our 89 Octane would be the equal of 92 Octane by the 1977 VW standards which specify a MINIMUM of 91 Octane. I didn't think burning 94 octane by those standards would be a problem but we can drop to the 89 and see what happens. It should still be at or over the 91 Octane specified.

Thu Nov 19, 2009 12:22 pm

SGKent wrote: Quote: Merlin- the dwell and timing have to be exact. Slightly advanced timing will cause rich tailpipe emissions. So can low fuel pressure.

Take the vacuum line off your fuel pressure regulator and see if you can get a whiff of fuel. If you smell fuel on the vac side, the pressure regulator is failing.

You need to get a handheld exhaust analyzer. Worth its weight in gold. I can't tell you how many AFMs I've popped the big plastic cover on and calibrated with mine. Check eBay.

Also- What plugs are you running?
_________________

Good Morning Tram. NGK B6ES

fuel pressure regulator is new and there is vacuum present, No leaks that I can find. All hoses and fittings are new, brake booster tests Ok.

I use the LM-1 and am comfortable using it. The issue is that I've been through 3 rebuilt ones and a new board in another. Other than the first one, they all are on the rich side. Cruzing, the AFM is close to 14.5 but under load it drops to as low as 12.5. That is good from my perspective but I think that the smog dyno is putting enough of a load on it that the a/f is moving to that slightly rich part of the curve. Normally I would just pop the cap and tweak, however Tony at Fuel Injection Corp said that this specific AFM he basically adopted and it is set perfectly the same as the new one they use to calibrate with so if it isn't perfect on the bus something else is wrong. I've set everything to Bentley. Could premium fuel make it richer as it has more octane molecules in it? My smog guy used to own a bus and has been doing pre-tests for free. I hate to go back again and say "this one is with a lower octane fuel..." The dyno time else where would have been hundreds of dollars.

Hoody - we checked each connection on the harness and replaced any questionable connectors where the wire looked like it might have been tweaked or broken.

DMB - yes and I would go that route except for CA smog. I looked for an earlier bus here for 2 years and finally gave up. The ones here surviving 1971 - 1973 are either dogs, not for sale or too much for the money.

Try NGK BR5ES or B5ES and see what that does. Slightly hotter plug.

Just because a part is new doesn't mean it can't be defective. I'd run a gauge just to be sure. Proper atomization requires specific fuel pressure. Since the L-Jet regulator adjusts itself with vacuum, and you seem to only approach fail at higher RPMs on the dyno, that's why I asked. Possibly adding a vacuum one- way valve in the line (like a Mercedes pneumatic door lock valve) might correct small variations.
If all that fails, it sounds to me like you need to get another airflow and tweak it just for smog testing, even if it makes the engine run like crap. I wonder if your FI guys are using a federal spec or CA spec AFM for testing/ calibrating.

Also, as was mentioned before: try ethanol.

You'd think that there should be a way to avoid having a 34 year old classic smogged. Do they smog motor homes down there?

Thu Nov 19, 2009 12:50 pm

Actually 87 octane of "new gas" = 91 octane of gas of years ago when you bus was new.

For more information I would suggest the following sites:

http://type2.com/bartnik/octane.htm

These probably go a lot deeper than you are interested in, but here they are anyway....

ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/rec/autos/tech/Gasoline_FAQ_-_Part_1_of_4

ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/rec/autos/tech/Gasoline_FAQ_-_Part_2_of_4

ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/rec/autos/tech/Gasoline_FAQ_-_Part_3_of_4

ftp://rtfm.mit.edu/pub/usenet-by-hierarchy/rec/autos/tech/Gasoline_FAQ_-_Part_4_of_4

Thu Nov 19, 2009 9:56 pm

The manual he quotes says use 87 to 91 octane (R+M)/2. If you want to run the minumum grade gasoline that is your choice but my bus deserves the best protection we can give it. Y'all argue for hours over what kind of oil to put in your bus or the grade of transmission gear lube is best for your baby, then you throw in the cheapest gas you can find? Come on...

Use 89 or 91 and stay away from the bare minimum unless that is all you can afford to put in it.

Thu Nov 19, 2009 10:04 pm

Tram - yes - any gasoline powered vehicle 1976 and later I believe gets smogged. Starting January 1 all diesels get smogged too bi-annually. That includes inspection for non-oem exhausts and air cleaners too. Expect lots of California diesels to be sold in your state.

That you all for the suggestions. I will check the fuel pressure and TSII to see what they are, and try the alternative way of setting timing at RPM on it to see if it is accurate. Ethanol isn't a solution as this is not about tweaking to get by smog once. It is about being a itsy bitsy bit leaner all the time without tweaking the AFM. Like Bleyseng said, maybe it just needs more miles on it for the rings to seat.

Thu Nov 19, 2009 11:03 pm

SGKent wrote: Car goes on a dyno and is driven at 15 in 2nd and 25 in 3rd.

If they are putting a heavy load on the engine at 25mph and 3rd gear with an 091 gearbox, they are going to have to open the throttle, which drops manifold vaccum, which boosts fuel pressure, which makes it run rich, which is what it should do under those conditions.

I would not set the bus to pass CA smog and drive it that way on a daily basis.

You have more than one AFM and an LM-1. I would suggest setting one airflow meter for the best combo of head temp, fuel consumption and performance and use another every two years if neccessary.

I wouldn't lose any sleep over either. After all, I wouldn't be driving within the parameters of the test.
Who drives 25 in third under load?

I'm all for emission controls, but the dyno testing of older cars is stupid.

Thu Nov 19, 2009 11:13 pm

josh wrote: dyno testing of older cars is stupid.

Why would you think that? It's a way to weed out the poluters. I'm surprised that Cali doesn't check older vehicles like we do here. Testing at idle catches some of them but they all drive down the streets loaded.

Thu Nov 19, 2009 11:49 pm

Desertbusman wrote: josh wrote: dyno testing of older cars is stupid.

Why would you think that? It's a way to weed out the poluters. I'm surprised that Cali doesn't check older vehicles like we do here. Testing at idle catches some of them but they all drive down the streets loaded.

Because they test a late bus at 25mph in 3rd gear under load is why. It's not a load that the bus would realistically see on the road. If it is, the driver will toast the engine and it won't be on the road long anyway.

The test isn't designed for the car and the car isn't designed for the test.

I guess I should have been more specific and said that the CA dyno tests for older cars is stupid. But even that being the case, older cars weren't designed to pass an emissions test under load.

How can you expect something to do something it was never designed to do?

It's like judging a model T on how well the air conditioning works, a dog on how well it meows, a tape deck on how well it plays DVDs...

Fri Nov 20, 2009 1:40 am

Without a dyno Mr. Raby would not have been able to clue this community onto thinking out side the box.Your statement is foolish at best.

Fri Nov 20, 2009 4:19 am

Hoody wrote: Without a dyno Mr. Raby would not have been able to clue this community onto thinking out side the box.Your statement is foolish at best.

You are misreading the intent of the CARB dyno test. They have no interest in testing the performance of the engine, it is just the way they test the emissions.

It is likely the least problem the state has right now.

Fri Nov 20, 2009 11:14 am

Quote: You have more than one AFM and an LM-1. I would suggest setting one airflow meter for the best combo of head temp, fuel consumption and performance and use another every two years if neccessary.

That is probably the best advice. 13.7 isn't bad when it jumps up to 14.5 at cruise. I guess the issue for me is I'd like to see it come back at 1.3 or 1.4% CO instead of 1.65% when the cutoff for a fail is 1.67%. I may just drive it another 1000 miles and see if the mixture drops as the rings set in. You may have just given a clue. What I think you told me is that there is a vacuum dance going on between the AFM door and the fuel regulator. A lower vacuum might make the door open less to reduce fuel spray but it also tells the FR to increase the pressure which increases it. Is that correct?

Also - does anyone know which coil works best with the FI? I am running the best version of the blue coil but since the ECU gets its signal from the coil, does the coil type affect mixture? I had to add a diode to my tach, could there be a signal bounce in the blue coil that throws the ECU off too?

Fri Nov 20, 2009 12:32 pm

SGKent wrote: Quote: You have more than one AFM and an LM-1. I would suggest setting one airflow meter for the best combo of head temp, fuel consumption and performance and use another every two years if neccessary.

That is probably the best advice. 13.7 isn't bad when it jumps up to 14.5 at cruise. I guess the issue for me is I'd like to see it come back at 1.3 or 1.4% CO instead of 1.65% when the cutoff for a fail is 1.67%. I may just drive it another 1000 miles and see if the mixture drops as the rings set in. You may have just given a clue. What I think you told me is that there is a vacuum dance going on between the AFM door and the fuel regulator. A lower vacuum might make the door open less to reduce fuel spray but it also tells the FR to increase the pressure which increases it. Is that correct?

That's pretty much it. I was basically agreeing with your instincts when you thought the load was pushing mixture into the rich part of the curve.

Airflow alone isn't a very good indicator of load. That's where the rising rate fuel pressure regulator comes in. The airflow meter determines the pulse rate of the injectors and the FPR adjusts the fuel pressure based on load. The amount of air+pulse width+fuel pressure determines mixture.

Quote: Also - does anyone know which coil works best with the FI? I am running the best version of the blue coil but since the ECU gets its signal from the coil, does the coil type affect mixture? I had to add a diode to my tach, could there be a signal bounce in the blue coil that throws the ECU off too?

I've never heard of the ecu getting thrown off by the coil. There might be some situation I've never heard of where this would be an issue. Probably at least half the L-jet systems I've seen have been running various models of blue coil. The ecu just uses the signal from the ignition for timing. Other things determine the pulse width.

Fri Nov 20, 2009 12:48 pm

Randy in Maine wrote: Hoody wrote: Without a dyno Mr. Raby would not have been able to clue this community onto thinking out side the box.Your statement is foolish at best.

You are misreading the intent of the CARB dyno test. They have no interest in testing the performance of the engine, it is just the way they test the emissions.

It is likely the least problem the state has right now.

It's probably also a money maker. I think that the actual purpose of the test is to fail as many vehicles as possible.