Q: Tuning Air/Fuel Mixture on 1977 Bus with Fuel Injection

[Hoody]

I sure hope you did not have clamps on the hoses going into your S boot.

[Randy in Maine]

I can't remember if you have your decel valve hooked up or not. Do you?

[equinox]

"I sure hope you did not have clamps on the hoses going into your S boot."

Unsure and which hose is the S-boot. I know there weren't a lot of clamps on the hoses, so I added a couple, but unsure to what. I just think everything needs clamps.

" can't remember if you have your decel valve hooked up or not. Do you?"

I have no idea. Where is it at?? I know previously, my cables were all jacked, so had new ones in and the shop adjusted. Last year had a new transmission/transaxle completely rebuilt.

[Randy in Maine]

The S boot is the big black one shaped like an "S" between the AFM and the throttle body. No real clamps on any of the smaller hoses that connect to it, zip ties may be used if needed to make a nice vacuum tight connection.

The decel valve is what D, E, and T are plugged into. If you don't have that your engine will back fire as you are headed down a hill with your foot off the gas.

Usually (in my experience) when you have a backfire, B will come off the air plenum.

[equinox]

Ok Randy, thanks. I will check after work today and take a photo for you also to show the current condition.

As as far as your comment about backfire DOWNhill...my backfire(s) were UPhill under load, just to clarify.

I should mention the gas milage from that ~100 mile run is calculated at 14.19MPG. Previously as follows:

19.50mpg - Originally
13.12mpg - 8/2/15
12.50mpg - 6/8/16 (after many things and drivetrain rebuilt)
14.19mpg - 4/16/17

[equinox]

Ok. Here is some pics in the engine cabin for reference.

Any suggestions?? I need to get a better electrical connection than clamps for the LM-2 as it resets while recording, so not getting a solid recording. Let me get it fixed and do a nice run up a hill underload once warmed up and I'll post it and get your thoughts.

I'll also pull the plugs and we'll take a look at them. The most recent and nechanic I had it at also noted he did not pull them and check. I don't think this will solve the issue I'm having, but will be an indicator how the engine is running and current condition.

I'll likewise, pull the S-hose off and check it out 100% for any cracks or anything.

http://i934.photobucket.com/albums/ad185/rroza/VW%20Bus/IMG_6615.jpg

http://i934.photobucket.com/albums/ad185/rroza/VW%20Bus/IMG_6618.jpg

http://i934.photobucket.com/albums/ad185/rroza/VW%20Bus/IMG_6619.jpg

http://i934.photobucket.com/albums/ad185/rroza/VW%20Bus/IMG_6620.jpg

[equinox]

Circling back around....I know it's been a while, but we left off with the bus getting crap for gas mileage and just not running well.

Earlier in the year, I had it in to the new shop and the fuel pump/regulator were taking a crap and on their way out! I replaced both and getting 35psi and all cool, but still was not acting right.

I never could let it just idle at a light without it dying...sometimes and went on a 60 mile trip each way to my sisters and running rough, as I said could die while idling in gear at a light, could not put gas all the way down or would act like dumping too much and up a steeper hill, could not put to the ground or make it worse so would have to find a spot but could still loose speed until top and other side!

Recently would not start and just crank intermittently start at times, but run rough or die on idle.

The plugs looked good, but replaced the coil and plug wires as original, but unfortunately still did not solve the issue.

I took to my new mechanic and he's had it about 2.5 weeks (I told him no rush), but he's a little baffled. Hes not ruling out anything and saying, yep gas pressure good at 35psi, no vacuum leaks. Did a compression check and fine, tried double relay and new computer, but still nothing better!

Next, he is going to check sensors and voltage at coil and fuel pump. It't almost like timing is off, but it's right were should be and 6-8 deg-ish.

He spoke about swapping out the distrbutors (though I had a new one with EI installed and it has FI and hydraulic lifters so should be maintenance free)! What would make it SEEM or act like this and like a timing issue? Oh he also sais something about checking the timing belt/chain, no issues there. Nothing is suggesting what the problem is!!

In parallel, I ordered a new (rebuilt) AFM 018 from Bus Depot and will swap it out just for giggles. If no issues, I'll send it back or resale it off, the price will only go up, but I have to eliminate this. Other things that come to mind is like wiring issues and like not supplying full voltage at coil or something?!?

Any suggestions?? Thanks in advance. Another season of camping down the crapper because the bus was not reliable! Hopefully next spring and year will be it. Good grief, Charlie Brown.

[SGKent]

generally speaking a shotgun approach to troubleshooting does not work well on these buses. In fact, it can get you into more trouble. The fuel injection manual includes how to test each component. It is here:

https://www.thesamba.com/vw/archives/manuals/afc_f...Manual.pdf





.
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[equinox]

Thanks Kent. I will ensure we go thru and test every component systematically.

I have a second AFM coming today as a backup if need be to try and see if it's that also! DAMN, these things are expensive!!! :O

[equinox]

New AFM came. It's a 020 instead of 018, but I understand it's the next revision and replacement and so betterment!

I can't get down to my mechanic until Wednesday, but looking forward to it.

[williamM]

I just read thru this whole post One thing did stand out and need some input about the shortening of the push rods on an hydraulic lifter motor??

Bueller? Bueller?--
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[equinox]

Sure...the engine was rebuilt a while back before I bought it. There was an issues with the pushrods not hitting the valves correctly...probably block or heads cut down or something.

The original mechanic (Munks) brought in a specialist in VW racing and measured everything and determined the geometry was off, so a set of pushrods had to be cut down.

Everything has been checked...compression, bleed-down, vacuum test, smoke test. The current mechanic is leaving no stone unturned and rechecking everything including lash on the lifters/pushrod which he was hoping was overtightened leaving the valves open but said a couple were actually loose, so he tightened them to spec, so unfortuntely that didn't solve it!

I know he re-checked the fuel pump. filter, regulator just to make sure didnt get a lemon, but it registered 35psi and no issue.

A couple things I'm concerned about is 1. the AFM. Has always left me feeling like there may be a problem since Munks fudged with it. The original problem bck them my have been compounts, but one was a backfire which took out the "fuse plug" in the flap of the AFM in the original. Now that I have the 020 and it doesn't have that fuse plug or whatever on the flap and supposed to be a later, better version, I'm hip to putting it in either way as a betterment. 2. When I read the voltage to the coil (recently replaced with spark plug wires) before it went to the machanic, my cheap Harbor Freight meter only read like 9.75V! I want the mechanic to check it. Easy check and could/would cuse a problem and may be a wiring issue. 3. Funny looking at the notes from all of the times in the shop over the last couple of year, the verbage used in some of the same issues I seem to have now!...idle will die, etc. and previously due at lest in part to breather tubes coming undone, etc.

Going to have to check the AFM and voltage at coil with key in run position first.

I think if we know the failure modes that can cause the effect(s): hard starting, can die when idling, start losing power and have to back off the throttle going up hill or hard excelleration (like too much gas being dumped or something), possibly backfires thru the muffler under load up hill, it can help solve the issue faster. AFM I think is one of them. What else would cause this??

[williamM]

for your mileage drop- I'm looking at other stuff they (M) touched- about the only thing you haven't re-placed/ rebuilt or fixed- list is getting small- also would consider putting points back in and hooking a jumper directly to the coil to act as a "key switch" . That back fire could be an ignition dropping out because of low voltage.

I once had a 3 cyl- 4 stroke boat motor acting up and ended up putting 3 timing lights with the triggers taped down -one on each cylinder- then running it to find ignition problems.

might try that during backfire and see if at least that part of the problem can be eliminated.

sounds like you have some gremlins having a party in there.


Hoody had a good point- VW got rid of the pressure valve in the AFM and decided to put some hose with out clamps in there so they would "blow out" during a back fire- with that in mind- if it backfires and then runs like shit- it probably blew a vacummn line out of the S .
_________________
some days I get up and just sit and think. Some days I just sit.

opinion untempered by fact is ignorance.

Don't step in any!

[equinox]

"also would consider putting points back in and hooking a jumper directly to the coil to act as a "key switch" . That back fire could be an ignition dropping out because of low voltage. "

Yes, gonna try that any run leads directly off battery to coil and fuel pump to eliminate some poor/intermittent old wire issue.

Yes, Gremlins and it's really frustrating. I've been trying to get this bus 100% reliable to camp with and enjoy and as you said, I really replaced everything on the bus! lol...even remote starter and wiring 2 and 4AWG wires, but if there is something with say the power lead to coil or something, it looks like may cause similar situation(s). If so and just a wire or AFM, which I have both and can replace, I pray and am thinking positive it will be fixed soon.

Yes, I currently have all hoses clamped trying to eliminate issues. I may want to ensure one's that I should not and remove those clamps just in case of backfire.

I appreciate soo much the advice here. You guys are top-notch. Thank you.

[equinox]

Uh. Unfortunate, my VW mechanic contacted me earlier in the week and said that pulling on the new rebuilt 020 air fuel meter and battery poweer directly to the new coil and fuel pump did not solve the problem!

Next steps: I will keep the 020 as it's an improvement over the 018 and readings fell more within nominal than the 018, but he will have to do a more hieristic search.

I looked over the past repairs and comments over the last couple of years and there seemed to be similarities to current situation...dies at idle (intermittently), hard starting, etc. Some of these items should be reinvestigated

Any more advice and direction would be greatly appreciated.

Thanks in advance.

Robb

[equinox]

Ok, i got the bus back from the machanic the other day and although works and start up every time...he could not specifically identify the root cause! Now, I'm glad it works, but scary "root cause" was not identified. He did say from the wiring document(s) I gave him the double-relay ground should go back to the battery, but it did not and to the body and the connection he foudn was loose!

In any event, I put in the 020 unit, replaced the old worn out spark plug wires, added a new set of gapped plug, and new coil.

However, the bus does pulse on acceleration at times and when decellerating can die, which means I need to completely stop the vehicle as will not start in neutral and I have to put in park and restart.

1. Any suggestion what in the hell is STILL going on?

2. Is there a neutral lockout or something?? The manual says should start in Park AND neutral, but does not and I flipping HATE this. It's dangerous stopping in the middle of the road or highway. If it does have something, I want it removed for next season.

All support is greatly appreciated.

[aeromech]

I worked on an automatic Vanagon once. There was a switch in the base of the shifter. I’d start by looking at that switch
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[aerosurfer]

I have no input on the automatic transmission issues you may have, but I have heard, like Aeromech said, to look at the switch at the base of the shifter.

Have you done a simple vacuum test and smoke test recently? Hook up a vacuum gauge off the nipple on the right side of the plenum and see what your getting at idle.

A smoke test works opposite when the motor is off, pump in smoke and see where it’s leaking from.

BTW, clamping can also lead to kinking the hoses if you secure them down too tight, creating vacuum leaks. Another overlooked source of leaks is the plastic gasket between the throttle body and the plenum. It fits snug, but gets warped over the years or the screws holding it on loosen.

As far as the AFM, rebuilt does not necessarily mean tuned. Have you or your mechanic put a tailpipe sniffer (o2 sensor) on it to see what your exhaust mixture is? Plenty of things to test more of before you would want to mess with the internals of the AFM, but rebuilt doesn’t mean it’s ready out of the box for your vehicle.

Sgkent and Colin have some great writeups, as well as warnings, on tuning with the AFM.

The best description about tuning the AFM
http://itinerant-air-cooled.com/viewtopic.php?f=50&t=7761

Information overload, but very in-depth discussions with results here

https://www.thesamba.com/vw/forum/viewtopic.php?t=442112&highlight=afm

I also have a 77, I put in permanent mount O2 sensor and have tuned (both) my AFMs, after all other mechanical and in your case electrical faults are looked at, the AFM can be adjusted and with the right tools and eye, results can be seen.

Good luck
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[SGKent]

yes - the automatic has to be in neutral or park to start. You best look for a spare of that lockout switch because they are getting harder and harder to find.

As others have suggested - check the TSII to be sure it is properly installed and not corroded or loose. Get a smoke generator off e-bay and check the vacuum system. Also have someone test the mixture at idle and running once that is done to be sure the mixture is within spec. Last - ignition switches go bad sometimes too. Best to have a strategy to test that.
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[equinox]

SGKent - Hmm, if it should be able to start in Park AND Neutral, why does it only work when in Park?!? Could be a sign of something wrong. If it was supposed to start in Neutral, would a going bad neutral safety cause it NOT to work??

Well, I have had multiple mechanics say there are no leaks and "did" do a smoke test...but why they can't figure out the problem, I have no idea and I don't believe anyone at this point and double check everything. I will check the vacuum and report back. I just needed to know where to check it at.

What is a "TSII" to check?!??

Being I have two completely different AFMs now, I think I can honestly say they are not the problem. Being that my gas milage is shit, I have to wonder, what is reason(s) for a "rich" mixture or engine dumping fuel?? Could computer cause this or sensors? What about faulty injectors? What about vacuum leaks??