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

[equinox]

Ok, had a little bit of time to check part numbers, but that's it (did not check fuel pump function yet - need time and someone else available during that time and live solo).

In any event, here are the part numbers I could find:

ECU - tbd

AFM - 0 280 200 018
Distributor - 0 230 168 005
Dual Relay - 0 332 514 120
ThrottleBody - 022 133 067

I still don't get what knowing the part numbers is going to do for me thou.

[equinox]

Ok, so because after the AFM rebuild from Fuel Injection Corporation and no time to diagnose the issue, I went the rest of the season without using the bus and it has sat!

It's the first day of sprinf and I'm looking forward to finally getting it running again and use for a complete season without being at the mechanic. I found a new mechanic close by and will be taking it to him/them if I can't diagnose or fix the issue myself.

I found this FANTASTIC diagnosis manual - AFC_FI_Training_Troubleshooting_Manual and look forward to trying everything out myself...sensors,fuel pump, AFM, etc.

The issue where I left off is after all the work done, the bus' gas milage sucked at 12mpg or something (as I remember, have to look back thru the thread) from 19.5 mpg when i got it from California. I thought, well, everything has been replaced and the original shop f****ed with the AFM, soI thought, I might as well get it reconditioned and rebuilt. Upon getting it back (which it looked fabulous), it will start initally, then die after like 2-3 second. It was suggested it controls the fuel pump and since nothing else was changed since this, either a fluke in timing and fuel pump is on it's way out, OR something happened with the rebuild and AFM.

I'll check it out shortly and let you know. Any futher suggestions is appreciated. After I do get it running, it will/may need to be adjusted (thou AFM is supposed to be to factor spec after rebuild).

[equinox]

Ok, well I got the bus into a new VW and Euro mechanic. So far so good. The electric fuel pump, he said was only putting out like 20psi and dropping, so we're gonna replace it. He suggested the temp sensor was not good after an ohm check. It was really hard to find, but Bus Depot had them in, so I ordered the sensor and also the regulator in case that isn't any good while parts are still available and I have NO documentation the sensor, fuel pump, not regulator were ever replaced in all the recipts I have, so I'm good with it. Wish me luck in getting it run, run well, tuned, and FINALLY a full year of use out of it! Good grief!

I have a friend who is a finisher working at the casino, building me a kitchen and kegerator for it! Soo, hopefully in the next week or two, I'll be ready for the season! Again, wish me luck!

[equinox]

GOOD NEWS!

Got the bus back yesterday. The final issue with the engine not starting is indeed the AFM. They must have messed it up on the rebuild, but is under unlimited 1yr or 18 month warranty (had it done last June 2016), so I will be taking it out and sending it back today or tomorrow.

The AFM is not keeping the electric fuel pump going, so it burns up the initial gas, then dies. For now and to get it from the mechanic and settle up, we hooked up a wire from the hot side of the coil to the fuel pump, so when the key is in the on position, the pump runs and when turned off, it kills the coil and the pump.

The work on the bus is excellent. I now have new parts and can put mind at rest. Likewise, the exhaust leak was fixed with new gaskets and it is quieter than it has ever been!

Looking forward to getting the AFM back within the week and getting a full year of fun out of this...finally!

[Randy in Maine]

I assume that your troubleshot the Double Relay already.....

http://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=5459

[KentABQ]

X2.

I had a similar problem, which went away with a new double relay.

You may also find IAC's AFM article interesting...
http://itinerant-air-cooled.com/viewtopic.php?f=50&t=7761
_________________
-Kent-
1976 Riviera, 1.8l FI chrome yellow VAN - "Chloe"

"I must say, how can you be in a bad mood driving this vehicle full of vibrant color.
Cars of today are so bland in comparison. It's like driving a celebration!" ---WildIdea

Bus ownership via emoticons:
---williamM

[equinox]

Yes, I've had 2 different mechanics including the most recent swap out the double relay and said that wasn't the issue!

The engine ran fine (just gas milage sucked) before I did the AFM rebuild by Fuel Injection Corp. Put the rebuilt AFM in and all of sudden starts, runs a couple seconds and dies. It's the AFM.

The new mechanic I took it to and local (Ed from Wurth's Automotive) has like 35 years experience and taught other mechanics for VW. The guys knows his stuff (unlike the hacks at Munks - just putting together laundry lists and stuff you don't even "need). Id checked everything including wire harnesses. He was perplexed at first what was going on, but after eliminating everything logically, he concluded it was the AFM.

We'll see what happens when I get it back by the end of the week (turn around shouldn't be long. Really, really looking forward to a FULL season of use this year and camping. I get this resolved, I think I can have piece of mind as everything has been replaced on this bus and I'm about $20-21k in now!

[rottenkid]

My 78 bus would start and run fine in the cold weather. Now the temperatures are above freezing, the bus starts, but kicks and sputters and backfires.
I disconnected the cold start valve today. The bus started up with a little more cranking, but no more backfiring problems. It runs OK without the cold start valve.

[foxmon]

[Wildthings]

[airschooled]

[KentABQ]

[Amskeptic]

[equinox]

Thanks Colin!

Yes, I know about the AFM tuning document and appreciate the folks that work hard to put stuff like this together (invaluable)!

AFM still in Cali and awaiting feedback on it and pushing to get sent out today so I can have over the weekend and start up Saturday afternoon. Supposed to be in the 70's and Sunny here in Detroit this weekend and perfect days for a ride!

Last year I took it to a muffler shop and had a bung welded into the proper location and installed an O2 sensor. I picked up an LM-2 unit, so I can monitor air/fuel in real time as well as RPM with ignition sender and storage card!

Once I get the AFM back, I will install it. It works, I will install the LM-2 and take it for a ride and also up and down hills and plot the results and see if any adjustments are necessary.

It's unbelievable that I dunno, 5 years ago when I drove it from Cali and parts on their last leg, geometery of pushrods/head, etc all fudged up, etc. I was getting 19.5 MPG @ about 50-55MPH average across country. The previous shop said, I don't think it was that high. I said, listen funkers, I would monitor it on refill and that's what is was and with all of the repairs it has not been at like 11.5-12.5MPG!

Once I get the AFM back and along with the fuel pump, regulator, and temp sensors all new, I'm excite to see what the milage is! lol We'll see. It'll probably be 13 and I'll be like wtf! lol Hope for the best, prepare for the worst, but I'm using this bus all season!

[Hoody]

....

[Hoody]

i would ask them if you pop the top off if that will void the warranty. Hope you get a good one.

[Hoody]

edit

[equinox]

"i would ask them if you pop the top off if that will void the warranty"

No issues. When I spoke with the guy before I sent it back, he actually directed me to pop the top off of the unit and see if I could play with it or by cleaning the contacts with a little sandpaper and if that didn't work, send it in, so with his direction that is was ok, I'd say no. We'll see.

It's been totally cleaned and remanufactured last time and looksed fantastic. The issue is now just in that black connector and assembly portion. Two screws and some connectors to take off and that should slide right out and direct swap. Should take 5 min with a new subassembly,

[equinox]

Spoke with them today. They said it's all set and fixed and shipping today!

They even noted and asked if there was any backfire, and I said yes, as there was when the mechanic was trying to fix it. They said there was a tear in the flap! I asked if they repaired that. They said yes. They did not communicate ANY charges to me, just repaired and shipped!!

[equinox]

Ok, took the bus for a 110 mile round trip yesterday mostly highway.

Something is still wrong. It can die at lights. It appears rich and from the smell. There was one if not two backfires while traveling. I heard what I thought was a backfire, but had the radio up. The second one was clear and like a rifle blast and sharp!

They both appeared to occur under load and while climbing inclines. In fact, I had to keep the throttle at like 10-20%. If I gave it any gas beyond that and on include, it would pulse and want to cut out, I'd remove the footpedal altogether, then do the 10-20% thing. The ride there I was really worried I was not going to make it. On one occasion, I was only a couple miles from my destination and coming to the light. It dies on decelleration and when I tried to start it, it just cranked and when I gave it gas acted like too much, so I would get off the gas and just tap it and luckily I got it to fire, thru it in drive and made it there. I babied it completely on the way back and no issues, but something obviously wrong with air/fuel IMHO.

I don't have time to check it out as heading to Mexico tomorrow, so will have to wait for the weekend and check the air/fuel ratio with the LM-2.

IF it is a rich mixture and beyond AFM, what other causes for this? Timing would not do it, so that's out. What about vacuum leak or any other thing(s)?? Please advise and thanks in advance. I think I am almost there of making it road worthy, but need to solve this problem 100%, but I have my ideas what's wrong and goes make the AFM.