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1977 fuel injected bay window fuel pump and timing issues
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SGKent Premium Member
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PostPosted: Thu Nov 20, 2014 11:06 am    Post subject: Reply with quote

Wasted youth wrote:
I did not have any problems with mine. And, I am not knowledgeable about working through failed smog checks on these, so I cannot really help. Mine passed the very first time, but I am sure I was lucky. Anyway, here is my smog check sheet. This was based on all stock set-up, tuned normally. Only difference is it had an Accufire electronic ignition in a new distributor and a new exhaust system, including an Emico CARB 2 compliant catalytic converter.

Don't know if this really helps, but maybe you can use some of the info to help you figure it out.

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excellent
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guanella74
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PostPosted: Thu Nov 20, 2014 12:59 pm    Post subject: Reply with quote

Thank you both for your help thus far.

I've also replaced the temp sensor with a new unit, and I'll follow your advice and clamp down/double check all vacuum connections.

Is there a consensus on NGK vs OEM Bosch plugs? I've got new, gapped Bosch units in there. I haven't looked into the aux air regulator; any directions on what to do there, and are those units fairly robust or do they go out often? They look like they're hard to come by and expensive!

Also, I've got my mixture screw turned 'out' 4 turns at this point; it was out 2.75 turns when I started. If everything else checks out, should I just keep leaning out on the mixture screw until it starts to miss, turn it back a bit, then go for a hard drive on the way to the emissions station?
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Randy in Maine
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PostPosted: Thu Nov 20, 2014 1:06 pm    Post subject: Reply with quote

When you say "mixture screw" are you referring to the idle by-pass screw on the left side of the AFM unit? that is how the idle gets adjusted for CO. Put that bad boy in the middle of the range.

Been here?

http://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=7834

If it were meI would take this to a shop that has a exhaust gas sniffer before I went back to the test place. If they did some work on a VW bus before that would be a plus.
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guanella74
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PostPosted: Thu Nov 20, 2014 1:12 pm    Post subject: Reply with quote

Yes - that's what I was referring to, and thus far I had it adjusted as per the smog recommendations by Colin in that link (which is great, btw).

The middle, from what I understand, is ~3.5 turns, but I already have it at 4.

I may just have to bring it somewhere; I don't want to just shoot from the hip either for passing emissions or daily driving. It's always a bummer though having to educate the mechanic at the shop as to what to do as most these days haven't looked at this FI system and don't know about the fine adjustments...
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SGKent Premium Member
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PostPosted: Thu Nov 20, 2014 1:43 pm    Post subject: Reply with quote

guanella74 wrote:
Yes - that's what I was referring to, and thus far I had it adjusted as per the smog recommendations by Colin in that link (which is great, btw).

The middle, from what I understand, is ~3.5 turns, but I already have it at 4.

I may just have to bring it somewhere; I don't want to just shoot from the hip either for passing emissions or daily driving. It's always a bummer though having to educate the mechanic at the shop as to what to do as most these days haven't looked at this FI system and don't know about the fine adjustments...


just request a pretest first then go home and fix it if it fails.
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guanella74
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PostPosted: Tue Nov 25, 2014 10:38 pm    Post subject: Reply with quote

OK, I took the bus in today to Verner's VW in Boulder since they've always treated me right. With a warm engine, they put the sniffer in the exhaust and let it idle, and to get down to <1.5 on the CO, we had to a)adjust the idle bypass almost all the way out, and b)turn the tensioned spring in the AFM 6 clicks CW. We ended up at ~1.3 on the CO at idle, with all tuning parameters in spec. I'll go to get emissions tomorrow, but...

It seems like everything I've read to this point means that with our adjustments, the bus would now be running WAY lean. We're at the far end of the range on the idle bypass screw and not 1, not 2, but 6 clicks CW on the tensioner spring. Should I be concerned about baking my heads and being too lean, or am I just being paranoid?
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Randy in Maine
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PostPosted: Wed Nov 26, 2014 6:07 am    Post subject: Reply with quote

After you pass, take it back to them and have them adjust it back to where it runs the best.

Take notes on the changes so that you can put it back yourself when needed.
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guanella74
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PostPosted: Wed Nov 26, 2014 1:55 pm    Post subject: Reply with quote

This seems like another case of there being no one left working at any mechanic shops who REALLY know these old beasts. I didn't have confidence in their tuning it when I left, and I don't have the confidence to take it back to them that they really know how to fine-tune it. I had the Itinerant Air Cooled article with me, and at one point when the mech didn't know what to do about it not leaning out enough when at the max of the range, I took out the article and we used it to get the rest of the way...

Anyhow, I passed, and am now looking into getting my own LM1 and doing it right. Glad to be registerd and legally driving the bus now!

That reminds me, I need to update my build thread...
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SGKent Premium Member
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PostPosted: Wed Nov 26, 2014 6:03 pm    Post subject: Reply with quote

turning the screw out lets air bypass the flap so you are correct, you are now leaner.

The real issue is that you do not know what was done to it before. I gave a weight that two NOS flaps just started to open at, so contrary to other's opinions I am confident it is a good place to start adjusting a flap spring. I would check it the next time it is out but don't waste your time unless it is out. I would not change anything without really thinking why. The numbers I posted were solely to help someone find a starting point when their AFM had been tampered with. Yours has passed so you have to be in the window close or it would not have passed.

One thing I would recommend - if the fuel pressure regulator is old, consider a new one before they become totally obsolete. If yours allows a little higher pressure then you will run a tad richer. Other things that can vary the mixture is if the injectors are tired and dirty. They can stick open longer, spray in a pattern that is larger droplets than a fine mist - making it harder to burn it all - which can throw the mixture off. So a new FPR and having the injectors cleaned if you haven't already are two good places to go next if you are looking to improve things.

A LM1 or equal will let you do a lot. The down side is that once you are happy with the performance it is really rock solid and rarely changes, so other than an occasional check you won't use it much.
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