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

[aerosurfer]

Please print this out and roll around naked in this manual.....

When you feel satiated; organize the pages in sequential numerical order fron lowest to highest and read it....

Fuel injection manual

https://www.thesamba.com/vw/archives/manuals/afc_fi_training_troubleshooting_manual.php[/quote]


All the qurstions you are re-asking, especially about the Fuel injection are answered in that manual. Get to know it and understand it intimately, plus its well written and easy to learn.

I noticed it seems you have been troubleshooting bad gad mileage for 2 years and however much money and mechanics. It seems to the untrained reader you are still on step one in figuring out the problem. Tire pressure, brakes dragging, fuel filter, air filter .... all other sources of causes not (directly) related to FI..
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

[SGKent]

Yes - everyone with a FI bus engine please print, and hopefully read that manual or if you don't work on your own bus, give a copy to your mechanic.

This book, "Bosch Fuel Injection and Engine Management" by Charles O. Probst, SAE. has been mentioned before too. It goes thru the fine points and evolution of Bosch fuel injection systems including L-Jet. It not only covers the theory but the fine points of the systems. It covers how the system gets its signal, how each sender modifies that signal to change the amount of fuel that is delivered to the engine. Between the two books and this forum anyone can get about any L-Jet question they want answered. There are some here too who are good working with D-Jet, which was used on some other air cooled VW engines.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[equinox]

Your help is greatly appreciated as is this manual. Yes, it is amazing and EASY to read and everyone should read it. I "DID" give a copy to my most recent mechanic and he was blown away also and he used to tech and the VW school!

There has been soo much done, that I think I'm not communicating everything either, like for example, most recently new spark plugs, coil, distributor cap, cylinder temp sensor, fuel pump, and regulator all were replaced already!...some DID have issue like the fuel pump was on it's last leg (psi reading). However, none changed the situation of poor idle (dying at times) and poor gas milage (down to whatever I said 12.5-14.5mpg).

I find it funny that I bought it, drove all the way across country from CA to MI and averaged 19.5 MPG, then something happened, old mechanic got their hands in it and it has been the way it is now ever since! Cooinsidence?? Maybe.

I finally got my garage cleared out after 12 years and which it should have been stored INDOORS since I got it, but it is now and I plan on checking things out myself and yes going thru the book. I don't have a lot of time and just wish I/we had a FI bus expert local to me I could take it to and solve the issue and call it a day and I could just pay them, instead of what has been going on.

Looking at the manual, Page 2 suggestions for poor idle and high fuel consumption, what is common between the two? I'll take a look at what has been replaced and what is still outstanding and besides checking for vaccum leaks and such look at these items and may replace them (fuel throttle switch, injectors, cold start valve) and again, maybe, just may I can finally get these thing "RELIABLE" and ENJOY it for the first time and all year long next year?!??

[equinox]

Ok guys. I FINALLY got some time to look at the bus after working on other unfortunately higher priority items...like fixing daily car and water leak in roof of house!!

Ok, I went thru the AFC manual and did as much as I could with one person.

Again, to circle back around, the current issue is that after a lot of work done on the bus, it runs like crap in that the gas milage has gone DOWN from 19.5MPG to like 10.5MPG, so a rich condition dumping fuel and on highway and on incline under load, it was struggling and seemed to be loosing power and even heard backfire out the tail pipe. Also runs rough and will stall say while waiting t a light!

Ok, back to the inital results:

Page 14 EGR - It was noted in all of the mechanic paperwork and I can confirm, the EGR is not hooked up like on page 14 and with the adjustment mechanis, to the throttle. It is held in an OPEN position by spring. Is this ok, or can I get the parts to hook the thing up correctly? Is this going to contribute to the main issue I'm having or only idling and emissions?? what are the parts needed to order to return to stock??

Page 18 - AFM - NO ISSUES - I have the newer 020 in from the originl 018 and no issues. The reading are also more nominal than the 018, so seems to be working perfectly

Page 19 - Head Cylinder Temp Sensor - NO ISSUES - readings good and ws replaced recently as old one was showing like 10-20k and super cold condition.

Page 24 - Fuel Injector Resistors - NO ISSUES - on the high side of nominal, but should be fine. Q: Injectors I belive are original. Could putting a new set in help and also help with a condition of say injector staying open or too long and dumping fuel?? What would be the part number for these? Nice to have on-hand anyway.

Page 40 - Electrical Check and Overall Summary - Potential issue(s)?? The biggest issue in the check is that when the white wire (only one) going to the coil (injector wire) is disconnected, it suggested I should have a 0 ohm reading to ground. That is NOT the case. i checked and rechecked and used a Fluke 123 even and result was that there was no resistence and an open condition! What would cause this and hot to resolve. I took photos of the coil and wires hooked up to it and white wire to ensure I did correctly.

Other things noted:
1. Could not do Pin3 and Pin18 test as there is no Pin3 in the harness. Does this engine even have full-throttle enrichment??
2. Ground to Pin16 is supposed to be 0ohm, but using the Fluke 123 to ensure accuracy, I'm reading 2.3 ohm (so some resistence). For giggles, I checked it from the pin to the battery ground and it reads 0.1ohm! Is this ok or no and should there be a difference?
3. Ground to Pin17 is supposed to be 0ohm, but using the Fluke 123 to ensure accuracy, I'm reading 2.5 ohm (so some resistence). For giggles, I checked it from the pin to the battery ground and it reads 0.2ohm! Is this ok or no and should there be a difference?
4. I could not do Control unit to Double Relay test. I'm pretty sure no issues, but unsure where Double Relay is and where this Pin34 connection is.

Let me know your thoughts based on this feed back and next steps given the current circumstances. i really appreciate all your help. Unfortunately, I'm missing out on summer days...again!

Robb


Page 14 - https://drive.google.com/open?id=1zBbJPeofL79ofK_OLyIz9N_TeQQ0pk3O
Page 18 - https://drive.google.com/open?id=1rsfSsJpJej-waYXnjcYGzr_RrVAl0p6L
Page 19 - https://drive.google.com/open?id=1KhAu24grAkBqaV7GlEpJINBZUHlolX7Z
Page 24 - https://drive.google.com/open?id=1YnXSFlnbXjwnakrNF6roIe7OldJmUbMA
Page 40 - https://drive.google.com/open?id=1Ne2FYQvOJq01sJWjVsYI7xQwHn9AOYpU
EGR - https://drive.google.com/open?id=198QtFfc9B6-Q9ye5wJ-XFwhbpOSrZmuq
Coil 01 - https://drive.google.com/open?id=1Fs4xVpH4Wk_9vrGrE7ha7DXjzubCtBSd
Coil 02 - https://drive.google.com/open?id=1eUkmeevsDuB3CttKTTHY1u8AwF0lveWQ
ECU Connector - https://drive.google.com/open?id=1QquTdkBqAZPJcTxmVW35GILdcZl0Kd0I
Head Temp Sensor - https://drive.google.com/open?id=1eGIBHCsYi3EQK2llRJD4rROW4UBdhXcA

[furgo]

[Tcash]

[SGKent]

put a block off plate on the EGR for now. Make one from a pepsi can and slip it under the gasket where the EGR bolts to the plenum. Do all your initial tuning with it blocked off. Restoring the EGR is a project in itself. If you have already done this ignore me.

The EGR inserts inert already burned no oxygen left air into the plenum. This will alter the mixture ratio. The EGR is supposed to turn off at idle and at wide open throttle (WOT). If it is on during idle the engine will run like crap. There is also a 45 year old diaphragm in it. If it perforates or cracks then it creates a vacuum leak. Also there is a tube in the plenum that disburses the inert gasses equally to all cylinders. It cokes up. Once it does only one or two cylinders get the inert gas so they really go wacko on you.
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[furgo]

[equinox]

"Did you clean up harness terminals 5, 16 and 17 to remove oxidation? That can certainly add some Ohms to your measurement."

No. I didn't spray anything to remove oxidtion, just tested per manual.
--------
"The double relay is just below the series resistor pack."

Ok, but I'm not certain where the series resistor pack is either! A pic will help.
--------
"You did not do the test correctly."

ok, i just tested it s outlined. It shows a little resistance <1.0 (e.g. - 0.x ohm). I don't know why a few of these tests should be 0 and show some resistence?!? Myabe oxidation. maybe something else??
---------
"put a block off plate on the EGR for now. Make one from a pepsi can and slip it under the gasket where the EGR bolts to the plenum. Do all your initial tuning with it blocked off. Restoring the EGR is a project in itself. If you have already done this ignore me. "

ok, but got to run out of town in the morn and gone all week, then busy Fri and Sat, so soonest I could do this is Sunday or thereafter.
---------
"The EGR inserts inert already burned no oxygen left air into the plenum. This will alter the mixture ratio. The EGR is supposed to turn off at idle and at wide open throttle (WOT). If it is on during idle the engine will run like crap. There is also a 45 year old diaphragm in it. If it perforates or cracks then it creates a vacuum leak. Also there is a tube in the plenum that disburses the inert gasses equally to all cylinders. It cokes up. Once it does only one or two cylinders get the inert gas so they really go wacko on you."

Well, that sucks and could be an issue and at both points I'm having issues with...idle running like crap and stalling and WOT and issues I'm having with hesitation, loss of power and exhaust back fire?!?
---------

[Tcash]

1977 FI Fuel Injection ID Pics

[equinox]

Oh man, THANKS for the marked=up photos. Hugely awesome.

I just flew in yesterday and tied up all day yesterday and today with an event. Hopefully I can get back on this Sunday. Stay tuned!

[aerosurfer]

This thread is becoming someone trolling the rest of us.....

In 3 years you are still working on the same troubleshooting over and over...

Post some damn pictures of what you are dealing with already...

You said is one post recently your fuel injector series resistor is fine,yet later down the same page you ask where the series resistor is located....

The manual states full throttle switches were deleted after chassis number xxxxx, which was sometime mid 76. There is even a picture of it on page 25. Look at your TB, is there a switch and wires? No, then ignore other text about a full throttle switch.

Again post some fricken pictures of your motor.... for all your headaches, you may have a simple vacuum leak or misplaced hose
_________________
Rebuild your own FI Harness..My Harness

77 Westy 2.0L Rockin and Rolling Resto!

72 Sportsmobile (sold)
79 Tran$porter... Parts car money machine (gone)

[SGKent]

[skills@eurocarsplus]

[raygreenwood]

[skills@eurocarsplus]

well, you can lead a horse to water but you can't force it to drink....
_________________

[SGKent]

I think an alternative is they wake up from a drug induced stupor, notice a dead bus in their side yard and recall there was something wrong with the FI when their uncle parked it two decades ago - not to mention that the mice living in it have been hand fed because someone thought it was a cute thing to do...
_________________
“Most people don’t know what they’re doing, and a lot of them are really good at it.” - George Carlin

[raygreenwood]

[furgo]

@equinox:

I jumped into the thread recently, so I've only had a glance at the discussion on the previous pages.

I concur with aerosurfer that posting some pictures would be extremely helpful for those who are trying to give you a hand. I think you can see how frustrating it can be for folks trying to remotely help you to do it blindly. Some small things which may give you a lot of grief (e.g. misconnected hose) could be pointed on the spot, which in turn would save a lot of back and forth.

As per the "injector resistors", you initially confused me too. What you measured when you connected your multimeter in parallel with each injector's terminals was the resistance of their internal solenoid. It's not a resistor per se. It's a coil, essentially a piece of wire, which to put it simply, behaves like a resistor when measured with a multimeter in resistance mode. The measurement is an indirect way of determining whether it is still in one piece (i.e. resistance within spec) and thus can still open the injector valves. Typical failure modes would be a short (0 Ω) or open circuit (infinite Ω).

Instead, when someone mentions "injector resistors", "series resistors" or "resistor pack", it's usually to refer to the four big-ass external ceramic resistors sandwiched within an aluminum cover as a single unit. The AFC manual does not show what they look like unfortunately. But you can spot them above the double relay on the driver's side, screwed onto the firewall panel in the engine compartment. I'm sure you saw them already on the pictures TCash posted. They are 6.5 Ω each, plus/minus tolerance.

Note: page 24 on the AFC manual tells you that the injector resistance plus a series resistor is 7 Ω, which will most likely not agree with your measurements. In fact, it's more like 9 Ω (ca. 3 Ω/injector coil + 6.5 Ω/series resistor). Page 40 is more correct regarding that measurement.

In any case, I think that you started doing the right thing the moment you picked up the manual and started following the diagnostics there. So I'd humbly suggest to post those pictures of your engine compartment and continue with the tests on the manual. If you post the results, then we can take it from there with less back and forth and less guesses.

Good luck!
_________________
'79 Westy, P22 interior, FI 2.0 l Federal, GE engine (hydraulic lifters)

Decode your M-Plate

[Randy in Maine]

The second post in this series from May 26, 2015 was right on the money...