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I Need Help with L-Jet / AFC Fuel Injection Topic FAQ
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busdaddy
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PostPosted: Thu Aug 29, 2013 8:30 pm    Post subject: Reply with quote

So tell us what your fuel pressure is, what that spare TS2 you keep in the glove box did when you swapped it in and if you've ever had the injectors cleaned and flow tested, also are you running points or Pertonix?
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tootype2crazy
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PostPosted: Thu Aug 29, 2013 8:49 pm    Post subject: Reply with quote

It has a brand new TSII. My fuel pressure gauge on the rail is busted, I need a new one. I can test it at work tomorrow though. I have Pertronix. The injectors were sent off to witchhunter about a year ago and tested out ok. I was thinking some fuel might be leaking or pressure might be too high, but I thought I would get more minds on the subject to help me think clearer.

It was a hard day at work today. I had to replace an early bay fuel filler hose through the pie plate with the engine in. The bus tried to eat my arm.

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busdaddy
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PostPosted: Thu Aug 29, 2013 9:15 pm    Post subject: Reply with quote

Owwwww.......busbites!
SGK has mentioned something about the wave or pulse length a P'tronix sets up for the ECU and messes with its head, not saying that's your issue but it's worth exploring, I assume you've replaced the air filter? Very Happy
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tootype2crazy
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PostPosted: Thu Aug 29, 2013 9:20 pm    Post subject: Reply with quote

Yeah filter is kosher. That is interesting about the Pertronix, that had not crossed my mind. Hmmm.
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SGKent Premium Member
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PostPosted: Thu Aug 29, 2013 10:04 pm    Post subject: Reply with quote

to adjust the AFM you must have an air to fuel meter. Do you have one?

IF YOU HAVE NON-STOCK INJECTORS THIS MAY GET YOU CLOSE BUT IT IS DESIGNED FOR STOCK INJECTORS.

Also - someone asked me about the idle mixture screw. Let me explain again. When the screw is turned in (CW) it closes the bypass passage down. This causes more air to be pulled thru the flap opening it. When the screw is turned further out the passage opens which bypasses more air and closes the flap. The idle mixture screw is a air bypass screw but it is bypassing air around the flap. The flap position is such that the more it is open the more time the ECU adds to the injector pulse.


If you do follow my NOS setup thread on AFM's. You set the spring tension using a weight on the flap and leave it. Then you adjust the slider to get the fuel mixture. You also adjust the mixture screw as well. When you get done you will be close enough to fine tune it. It is the best I can give someone on how to do it. The spring is important because it also controls how fast the door opens which in turn affects how much extra fuel is added when accelerating. All I can tell you is that I took measurments from a NOS AFM and passed smog as well on three AFM's so I know it will get you close on an AFM that has been tampered with. I prefer that people leave an AFM alone if the bus has a history of running Ok because they do not change with time and there is a real danger of ruining them or getting them out of tune. Be aware that when an AFM fails it can be because the baseplate seperates from the top and bypasses air in which case the adjustment screw gets goofy.

SGKent wrote:
I think I have the specs needed to dial in a 018 or 020 AFM and if so it will pass smog and test like the NOS one. We will pre-smog it today to confirm this and post back but it is testing with a LM-1 just like the NOS one that passed and is dialed in.

Make sure you have no vacuum leaks and that your fuel pressure and injectors are good. Replace any suspect rubber like injector seals.

With the AFM off the car and the air box open, mark where the spring is set for reference. Set the spring so the flap opens with appx 60 grams (+/-1) weighted on it. Use a postal scale to weight your tool. I did this by setting a rod weighing 60 grams on the edge of the flap. It balances between closed and barely open. Were you to make the rod 55 grams it would be closed and 65 would open some. If the lid is off you can double check with a spring postal scale to push on the edge of the crescent to open it but that is less accurate. It will be about 4.5 oz at the edge of the crescent. Reinstall the AFM.

Warm the engine up to where the oil gets to 180F or thereabouts.

Set the slider (on this AFM it was right there where Bosch left it in 1977) to about 14.9 - 15.0 no load at 2000 - 2500 rpm.

Set the idle mixture to 13.9 - 14.1. It will move a little. You are trying to balance around 14.0.

Check all it again at 2000-2500 and at idle again.

Do a test drive in 2nd flat and level 25 mph and it will be about 15.0:1. Put it in 3rd and speed up to about 35. It will be around 14.8. Put it in 4th and gently give it full gas without lugging it. Mixture will drop to around 12.7 to 12.8 or thereabouts. As the speed comes up the afm will start leaning out to around 13.5. If you ease off the gas to cruise around 40 it will come to 14.7/14.8.

With these numbers any 018 or 020 AFM should be able to be quickly dialed in for both performance and passing smog. If my predictions are correct, this bus will pre-smog about like the other, which is optimal. Hopefully this will make it easier for someone tuning their AFM not only to pass smog but to make sure it performs well. This assumes that all other factors like vacuum leaks, TS-II etc are within spec.

Update:re testing used AFM - passed really well - I richened it 4 spring clicks beyond the above based on the test and an LM1 trace but it was extremely close to the NOS one.

Really can't expect much more out of a used rebuilt AFM without knowing its history. Springs weaken after several million cycles. boards move and get replaced etc. Very happy with the results. I would say 58 to 60 grams on the door and 14.8 at 2500 - 3000 RPM will get you very close and you can tweak from there. Best of all - it only took me maybe five minutes to set it and there was no trial and error getting close to the baseline. So - if you are setting up an AFM and it is way out - use those numbers to get you close.

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tootype2crazy
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PostPosted: Fri Aug 30, 2013 4:27 pm    Post subject: Reply with quote

Ok well I got to test the fuel pressure today while in the midst of fixing a customer's bus (massive vacuum leak at the head where the intake bolts and closed point gap caused it not to run at all, but I got it fixed). At idle the needle oscillates rapidly between 30psi and 45 psi, when I rev it it goes to about 28. I'm going check the CSV and the injectors for leakiness. Without a doubt it is running too rich, but only at idle. I just have to track down why.

SGKent, I appreciate your sage advice, but I have adjusted dozens of customer's buses and beetles AFMs using Colin's method and it works wonderfully. It's actually easier than adjusting a carb in many instances. When I first started adjusting them I checked the adjustment with the shops AFR analyzer and they were all spot on so I stopped because it takes so much longer and time is money. My bus is not responding like all the others do; I don't see chronically rich buses very often in the shop. It's usually the other way around.
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air-cooled or nothing for me
1978 Sunroof Deluxe Bus (daily driver)
1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's)
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busdaddy
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PostPosted: Fri Aug 30, 2013 4:46 pm    Post subject: Reply with quote

tootype2crazy wrote:
Without a doubt it is running too rich, but only at idle. I just have to track down why..

tootype2crazy wrote:
At idle the needle oscillates rapidly between 30psi and 45 psi, when I rev it it goes to about 28.

Seems as if you've answered your own problem, have access to a vacuum gauge?
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PostPosted: Fri Aug 30, 2013 4:49 pm    Post subject: Reply with quote

I have an aluminum mity-vac busdaddy. Should I test the fuel pressure regulator?
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busdaddy
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PostPosted: Fri Aug 30, 2013 4:59 pm    Post subject: Reply with quote

That'll work, what's the manifold vacuum at idle and how does the regulator respond to low and high vacuum?
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PostPosted: Fri Aug 30, 2013 7:22 pm    Post subject: Reply with quote

Quote:
At idle the needle oscillates rapidly between 30psi and 45 psi,


That is not working correctly, at 45 PSI you have 150% the amount of fuel passing thru the injectors than at 30 PSI. The book calls for appx 35 PSI (32-37) with the hose off. The only reason that FPR is there is to keep the fuel pressure constant over manifold vacuum. If the pressure was constant to ambient pressure then more would flow under higher vacuum. If your FPR is good then your manifold vacuum would have to be swinging wildly too or something else causing it like a non-FI tank looped back like an FI tank causing problems.

FWIW Colin uses an air to fuel meter to set AFM's last time I had dinner with him. He spent a whole year testing how hid Bob D AFM's worked using it. The AFM card is a 4 dimensional analog circuit in the sense that it measures five or six different circuits all at the same time and by comparing those can calibrate not only where but how fast and in which direction the door is moving and anticipate the next needed amount of fuel. The spring tension and an air pocket behind the door also protect the door from backfires. The card was tuned at the factory with a laser. Many people think it is a linear circuit but it is not - it is like 5 or 6 graphs working together in addition and subtraction to tell the ECU how much time to add to the injector pulse. Some people recommend moving the card if it is worn but even that will throw it off.
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PostPosted: Sat Aug 31, 2013 8:58 am    Post subject: Reply with quote

Ok well lets back up a little. I went and got a new fuel pressure tester. The shop's tester must be on the fritz. It looks like about 32-34 at idle. When revving it goes to 28 reliably. I used my vacuum pump on the pressure regulator and it shows as follows:

No vacuum = fuel pressure of 40psi
10 vacuum = fuel pressure of 35psi
15 vacuum = fuel pressure of 28psi
20 vacuum = fuel pressure of 20psi (bus idles much better at this range)
Manifold vacuum at idle is about 10 and about 15 at 2500 rpm, and when letting go of the throttle goes up to 20.

Any thoughts on what is causing my rich idle?
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1978 Sunroof Deluxe Bus (daily driver)
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1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
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PostPosted: Sat Aug 31, 2013 9:12 am    Post subject: Reply with quote

tootype2crazy wrote:
Ok well lets back up a little. I went and got a new fuel pressure tester. The shop's tester must be on the fritz. It looks like about 32-34 at idle. When revving it goes to 28 reliably. I used my vacuum pump on the pressure regulator and it shows as follows:

No vacuum = fuel pressure of 40psi
10 vacuum = fuel pressure of 35psi
15 vacuum = fuel pressure of 28psi
20 vacuum = fuel pressure of 20psi (bus idles much better at this range)
Manifold vacuum at idle is about 10 and about 15 at 2500 rpm, and when letting go of the throttle goes up to 20.

Any thoughts on what is causing my rich idle?


Ok - you got those specs - did you compare it to what is published for the test?
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PostPosted: Sat Aug 31, 2013 9:20 am    Post subject: Reply with quote

Yes and it would seem a replacement of the FPR is in order.
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PostPosted: Sat Aug 31, 2013 9:36 am    Post subject: Reply with quote

tootype2crazy wrote:
Yes and it would seem a replacement of the FPR is in order.


Ok. When that is done test the idle vacuum again. 10 is low. 17 - 18 would be more the norm.
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PostPosted: Sat Aug 31, 2013 10:44 am    Post subject: Reply with quote

Well I just put on a spare FPR I have and the gauge now shows 70psi. Ugh. I guess I'll go nab one of my other bus and see if it makes a difference.
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1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
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PostPosted: Sat Aug 31, 2013 11:23 am    Post subject: Reply with quote

Success! The other engine's FPR worked. I successfully tuned the AFM and pressures are where they are supposed to be. Now I guess I'll have to be on the lookout for another FPR for my other bus. And SGKent, just to put your mind at ease I will put it on the AFR analyzer when I return to work next week. Wink Also my vacuum at idle is around 14 now. It's probably different because since the idle is not rich it can actually idle higher now. Thanks for all the brain power you guys.
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PostPosted: Sun Sep 29, 2013 5:40 am    Post subject: Reply with quote

Santaji wrote:
busdaddy wrote:

Sounds good, don't cap the port on the distributor, it needs to breath.

So what changed that's keeping it from running now?, the timing could be off due to the different vacuum but I'd look for a knocked off hose or wire first.


I guessed it was the timing. The engine would quickly slow down and cut off after starting.
We reconnected the hoses as they used to be and Bus started up fine.


A update on this: Today we tried once again connecting the vacuum lines correctly, this time the bus started up and ran fine. Must have been a vacuum leak the last time we tried, although we where sure we had connected everything securely Embarassed

We took a quick test-drive, There where no noises while decelerating so that issue is sorted out!

Only the engine seems to idling faster now, so we'll have get a tachometer and reset it back to 850rpm.

We also borrowed a timing light and checked the timing since we canceled the retard line. At idle the mark on the fan/pulley was around the mark between 4 and 8 BTDC on the scale. At full throttle with the vacuum line disconnected it's at about 32. With the line on around 40. Should we retard the timing slightly to make up for the removed retard line?
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PostPosted: Sun Sep 29, 2013 6:22 am    Post subject: Reply with quote

Yes, 40 is melt your engine zone. Forget timing at idle, it is irrelevant. You want 28 degrees BTDC with the vacuum hose off at 3000rpm. With the hose on it should go to 30-32.
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1978 Transporter (mom's, making into a camper)
1970 Single Cab 2.1 turbo/EFI 6 Rib, 78 front beam, vanagon backing plates on rear (project)
2001 GTI VR6 (wife's)
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PostPosted: Sun Sep 29, 2013 7:58 am    Post subject: Reply with quote

SGKent wrote:
10 is low. 17 - 18 would be more the norm.


10 is low but 17-18 not the norm. norm is closer to 14 or 15. also depends on idle rpm, a hundred either side of 800 can make a big difference in idle vacuum. also, hydraulic lifter engines almost always draw less idle vacuum, not sure if it's cam or what but it's noted empirically by me. just don't want people thinking something is wrong if they don't have 18"Hg at idle, most won't.
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PostPosted: Sun Sep 29, 2013 9:05 am    Post subject: Reply with quote

tootype2crazy wrote:
Yes, 40 is melt your engine zone. Forget timing at idle, it is irrelevant. You want 28 degrees BTDC with the vacuum hose off at 3000rpm. With the hose on it should go to 30-32.

It's not uncommon for a properly timed type 4 to momentarily hit the high 40's with all the hoses connected but that only occurs during conditions where it's OK, as you say the bottom line is the hoses off timing at speed.
The idiot guide and even the big green book are written for engines and distributors that are perfectly matched and have components with young nubile springs and rubber parts, here's the 21'st century idiots guide to timing that makes up for age and wear:

If you only have one hose attached to your distributor pull it off, you don't need to cap it (no need on single hose systems), if you have 2 pull them both off but plug the one facing the distributor (retard). Now connect the timing light to the battery and the #1 plug wire according to the timing light instructions (and set it to zero if it's the type with adjustments). Now start the engine and shoot the timing light at the scale and pulley (hold the light in your right hand), see the mark on the pulley?, good. Now using your left hand slowly open the throttle on the side of the carb or throttle body (move it the same way the cable pulls it) and watch the timing mark VS: the scale, the mark on the pulley should start to move to the left, open the throttle a little more and continue until the mark no longer moves to the left any more (yes it's loud, isn't it?), give it a bit more throttle just to confirm the mark is staying put at wherever it stopped (hopefully 28 degrees) and then release the throttle. If it stopped at 28 move on to carb/FI adjustment, if it went past or didn't make it all the way loosen the distributor clamp a little and turn the distributor a few degrees one way or the other (you pick, if it's worse go the other way), repeat until you find the happy spot and don't forget to tighten the clamp when you are done (make sure the distributor is pushed down all the way into the case too). Avoid loose fitting clothing and long hair near spinning fans and belts too, no need for a trip to emergency. Now put the hose back on, pack up the timing light and move on to carb or FI adjustment.
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