76 Bus Fuel Injection Troubleshooting- It Runs 8/13/07

[Amskeptic]

With the L Jet manual, the AFC manual, Muir's Guide, advise from everyone at IAC, my $40 Bentley manual, and my useless Haynes manual I'd better be able to get this thing up and running again!

Dang right, but you better listen to us too. Don't try to out-think or out-conceptualize what paths we are taking you on. This can confuse you. . . and it can confuse us. . . and our massive reading audience.

If I say, "ground the alligator clip" of your test lamp, GROUND IT to metal to the car to the negative post of the battery! The #1 coil terminal is not a ground!

Looking at the wiring diagram makes it look like grounding the test light at the body would essentially short the circuit.

You'd be essentially wrong. The test lamp has a natural resistance through its bulb. If the points are closed, the electricity chooses the path through the points, no test lamp. If the points are open, the electricity reluctantly decides to go through the filament to the alligator clip ground of the test lamp. The test lamp does not affect the operation of the points.
To stay ON TRACK with our diagnosis, tell us if the test lamp (tip on #1 coil, clip on ground) pulses when you crank the starter. If you spend the time to check every single other component of the FI instead, well, its good learning in and of itself, but. . . . . . .

Maybe a test light between the positive and negative terminals on the injector harness would serve best- and if it flashes we know the ECU output is good as well?

Errrrrr, uhhhhhhhh, no. IF the #1 coil terminal wire that leads to the FI brain does indeed pulse during cranking, the next step is to check the injectors themselves for proper grounding by seeing if they too pulse during cranking. John, you got our numbered wire list for the injector grounds? NWbuspilot, I cannot continue with my diagnostic track until you answer the question above, cuz now I am confused as to where we actually stand with your specific symptoms.
Colin
(

On a sidenote- the lifters are ticking like crazy due to the gas that washed down the cylinders from all the flooding.

On a sidenote, washed cylinder walls and ticking lifters are not related, the lifters will naturally leak down from cranking without full engine oil pressure, they will pump up once the engine is running properly . . . may take up to 20 minutes of driving)

[soulful66]

John, you got our numbered wire list for the injector grounds?

I just looked thru our notes from your visit, and could not locate them. Perhaps they were accidentally thrown away.

I will try to go through the Bentley and see if I can get it figured out.

Best Regards,
John

[soulful66]

Ok get your your Bentley manual and turn to page 5 Section 10. Do you see the wiring diagram?

1. Power for the injectors comes from terminal 88b of the double relay
2. From the double relay the power goes to the series resistor block (This lowers the power so the injectors do not burn out)
3. From the resistor block power goes to each individual fuel injector

At this point, the injectors have power, but they will not work until the ecu grounds their circuit.

ecu pin 14 is the ground for #1 inj
ecu pin 32 is the ground for #2 inj
ecu pin 33 is the ground for #3 inj
ecu pin 15 is the ground for #4 inj

I do not remember the exact wire numbers for the power or ground side of the injector plugs. All you have to do is unplug each injector plug and put your multimeter on the resistance scale. Now...put a meter lead on the ecu ground pin, and the other on one of the two injector plug wires. The wire on the injector plug that has almost no resistance will be the one that is the ground side of the injector plug.

Did you check to make sure that the ecu pins are ALL sticking out the same height?

It would be very helpful if you would run the tests exactly as they are discribed. Amskeptic is a VW guru, and RandyInMaine is an authority on the F.I. system. The majority of us on here, head to the wisdom of these two when we are in unknown territory.

Best regards,
John

[NWbuspilot]

If I say, "ground the alligator clip" of your test lamp, GROUND IT to metal to the car to the negative post of the battery! The #1 coil terminal is not a ground!


IF the #1 coil terminal wire that leads to the FI brain does indeed pulse during cranking, the next step is to check the injectors themselves for proper grounding by seeing if they too pulse during cranking.
Colin

Ok- with the alligator clip grounded to the metal of the car and the test probe on the #1 coil terminal I get pulsing during cranking.

I'm assuming for the injectors the procedure is to connect the probe end of the test lamp to the positive side of the injector wire, and the alligator clip grounded to the metal of the car. When I do this I do not get pulsing during cranking, I get a solid light, both when the key is turned to the "on" position and also while the starter is cranking.

[soulful66]

[Ok- with the alligator clip grounded to the metal of the car and the test probe on the #1 coil terminal I get pulsing during cranking.

Good. That means that the ecu is getting the signal to operate the injectors.

I'm assuming for the injectors the procedure is to connect the probe end of the test lamp to the positive side of the injector wire, and the alligator clip grounded to the metal of the car. When I do this I do not get pulsing during cranking, I get a solid light, both when the key is turned to the "on" position and also while the starter is cranking.

Ok...this means that the injectors are not being grounded, for what ever reason. Now Let's start looking at why they are not being grounded.

1. have you completed the continunity checks from the ecu connector to the injectors?
2. Have you checked your ecu pin heights?
3. Are you positive that you have good grounding straps on the battery and tranny? If you have any doubts, do a continunity check on them.
4. are the 2 connectors under the left sid intake runners clean and plugged in securely?

viewtopic.php?t=2173&postdays=0&postorder=asc&start=15 Read this topic on my no start/run. The second page has the cure to my problem.

From my AFC manual...Fuel injector circuit test
1. pull off all electrical plugs from injectors
2. connect test light across contacts of one plug
3. operate starter
4. test light must flicker
5. if light stays on, check ecu plug terminal 1. if ok, replace ecu

Now hold on a minute. Let's not jump to a part failure yet. What the manual isn't clear is this> You can have pulse at the coil, but if the wire is bad that connects the coil to ecu terminal 1, you will have the results of a bad ecu, and the ecu is fine. A continuity test of the ecu terminal 1 wire to the neg side of the ign coil should be checked first.

If you want do double check the injectors themselves w/o removing them, pull off the connectors and measure resistance across the injector terminals. You should get 2 - 3 ohms.

Best Regards,
John

[NWbuspilot]

Ok get your your Bentley manual and turn to page 5 Section 10. Do you see the wiring diagram?

1. Power for the injectors comes from terminal 88b of the double relay
2. From the double relay the power goes to the series resistor block (This lowers the power so the injectors do not burn out)
3. From the resistor block power goes to each individual fuel injector

At this point, the injectors have power, but they will not work until the ecu grounds their circuirt.

ecu pin 14 is the ground for #1 inj
ecu pin 32 is the ground for #2 inj
ecu pin 33 is the ground for #3 inj
ecu pin 15 is the ground for #4 inj

I do not remember the exact wire numbers for the power or ground side of the injector plugs. All you have to do is unplug each injector plug and put your multimeter on the resistance scale. Now...put a meter lead on the ecu ground pin, and the other on one of the two injector plug wires. The wire on the injector plug that has almost no resistance will be the one that is the ground side of the injector plug.

Did you check to make sure that the ecu pins are ALL sticking out the same height?

It would be very helpful if you would run the tests exactly as they are discribed. AMSKEPTIC is a Vw guru, and RANDYINMAINE is an authority on the F.I. system. The majority of us on here, head the wisdom of these two when we are in unknown territory.

Best regards,
John

Bentley is showing that terminals 16 and 17 are the grounds. Does it matter which terminal I use to test resistance on the ground wire for the injectors? I'm assuming I'm looking for near zero resistance, and high resistance would mean a poor connection, and infinite resistance a broken wire?

The ECU pins are all sticking out the same height.

[NWbuspilot]

1. have you completed the continunity checks from the ecu connector to the injectors?
2. Have you checked your ecu pin heights?
3. Are you positive that you have good grounding straps on the battery and tranny? If you have any doubts, do a continunity check on them.
4. are the 2 connectors under the left sid intake runners clean and plugged in securely?

1. I ran out of daylight today before I could check for full continuity between the ECU ground terminals and the Injector ground wires.

2. The ECU pin heights are all uniform.

3. I have full continuity from the negative battery terminal to the metal of the car, and the transmission to the metal of the car. I also have continuity between both sides of the transmission ground strap.

4. In the low light I was able to see 1 connector, which went to the Temp Sensor 2. I assured that one was tightly connected. I'll look for/check the other connection in the morning.

viewtopic.php?t=2173&postdays=0&postorder=asc&start=15 Read this topic on my no start/run. The second page has the cure to my problem.

I remember reading that topic a while back. I read back through it before I checked my ECU pins.

From my AFC manual...Fuel injector circuirt test
1. pull off all electrical plugs from injectors
2. connect test light across contacts of one plug
3. operate starter
4. test light must flicker
5. if light stays on, check ecu plug terminal 1. if ok, replace ecu

With all injectors unplugged and the 2 terminals bridged with the test light I did not see any flickering when the starter was engaged, just a solid light. I did this test with the coil-to-distributor cap wire disconnected to prevent starting. Does that affect my results?

Now hold on a minute. Let's not jump to a part failure yet. What the manual isn't clear is this. You can have pulse at the coil, but if the wire is bad that connects the coil to ecu terminal 1, you will have the results of a bad ecu, and the ecu is fine. A continunity test of the ecu terminal 1 wire to the neg side of the ign coil should be checked first.

I have continuity between terminal 1 and the spade connector end of the wire.

If you want do double check the injectors themselves w/o removing them, pull off the connectors and measure resistance across the injector terminals. You should get 2 - 3 ohms.

Best Regards,
John

The resistance between injector terminals is 2.8 - 3.0 ohms.

[soulful66]

1. I ran out of daylight today before I could check for full continuity between the ECU ground terminals and the Injector ground wires

Ok, that is the next step.

2. The ECU pin heights are all uniform

That is good.

3. I have full continuity from the negative battery terminal to the metal of the car, and the transmission to the metal of the car. I also have continuity between both sides of the transmission ground strap

Now we know that the bus has a good ground path. Now we must make sure the F.I. system is connected to it.

4. In the low light I was able to see 1 connector, which went to the Temp Sensor 2. I assured that one was tightly connected. I'll look for/check the other connection in the morning

Ok..Thak was not the connector I was referring to. are the 2 connectors under the left sid intake runners clean and plugged in securely. You really can't see them easily. You can open the eng lid above the eng to get a better view. they are located on the eng case and held by a case bolt. here should be 2 female connectors on a 3 male connector.

5. Does it matter which terminal I use to test resistance on the ground wire for the injectors?

Yes. refer to the terminal list I posted earlier.

6. With all injectors unplugged and the 2 terminals bridged with the test light I did not see any flickering when the starter was engaged, just a solid light.

That means that the injectors are not being grounded

I did this test with the coil-to-distributor cap wire disconnected to prevent
starting. Does that affect my results

No, that will not affect your tests

7. I have continuity between terminal 1 and the spade connector end of the wire

Ok, so we now know that the reference pluse is making to the ecu. So the question is...are we sure the signal is reaching the grounding circuirt for the injectors? Check the ground wires between the injector plugs and their assigned ecu pin.

8. The resistance between injector terminals is 2.8 - 3.0 ohms

Good. We know that the coils inside of the injectors are able to work, proinded they get power on one side and a ground on the other.

Keep plugging away and hang in there!
Best Regards,
John

[Randy in Maine]

I am sure you have this one also...



http://www.notcompensating.com/fimanual ... Manual.pdf

[NWbuspilot]

I am sure you have this one also...



http://www.notcompensating.com/fimanual ... Manual.pdf

That's the one I mentioned in an earlier post! I couldn't for the life of me remember the site it came from. I remembered reading a post on either here or the other site about keeping those manuals in the bus, so I have that one and the L JET manual from type4.org printed out and put into a 3 ring binder.

[NWbuspilot]

I'm heading out to the driveway now to finish up the testing. I was looking back through my notes and discovered something that may have caused the trouble. I originally posted on the "other site." When the trouble first started happening I had my wife crank the starter while I watched the engine compartment. I saw an errant spark jump from the coil tip to the negative terminal side of the coil. The arcing was due to poor insulation boots on the busdepot wires I purchased. I put my old bosch wire back on and didn't have any arcing.

After learning more about the FI system, it seems possible that 20,000 volts jumping to the ECU terminal 1 wire would be ample power to burn out the ecu. Let me know what you all think, no one on the other site thought that the arcing could be the source of the trouble, so I never pursued it.

[NWbuspilot]

Here are the results from my tests:
The connections under the intake runners on the 3/4 side: cant quite see them, but was able to feel them based off of your description. everything there feels nice and snug.

Injector ground test:

Terminal 14 (cyl 1) 15 ohms

Terminal 32 (cyl 2) 15.3 ohms

Terminal 33 (cyl 3) 0.4 ohms

Terminal 15 (cyl 4) 0.4 ohms

On cylinders 1 and 2 they read infinite resistance if the other injector is not plugged in. (1 is infinite if 2 isn't plugged in, 2 is infinite if 1 isn't plugged in) I learned this due to the fact that I still had all of my injectors unplugged from testing last night. By missing the correct terminal I saw that cyl 2 also has about 15 ohms of resistance to cyl 3's terminal (33).

Cylinders 3 and 4 read 0.4 ohms whether or not the other injector is plugged in.

It's looking like cylinders 1 and 2 are the ones having the most trouble? I'm guessing the next step would be to open up the heat tube around the harness and do a continuity/resistance test along the length of the cylinder 1 and 2 injector ground wires after visually checking for breakages and tears in the insulation?

I also performed the tests listed in the AFC manual that RANDYINMAINE posted the link to. I'll put them in a new reply though to keep things organized.

[NWbuspilot]

For the sake of being thorough and not wanting to jump to parts replacement I went through the resistance tests in the AFC manual. I figured testing is free, but parts can be expensive!

Air sensor circuit tests:
in parentheses is the acceptable resistance reading in ohms

6 and 9 (200-400) 313
6 and 8 (130-260) 206
8 and 9 (70-140) 114
6 and 7 (40-300) 53
7 and 8 (100-500) 167
6 and 27 (<2800 @ 68 degrees) 1689 @ 81 degrees

Temp Sensor 2
(2100 - 2900 @ 68 degrees) 1934 @ 81 degrees

Injector wires and resistors ( in order of cylinders) all should be approx 7 ohms
14 and 10 9.2
32 and 10 9.3
33 and 10 9.4
15 and 10 9.4

Ground tests:
16 and ground 0.7 ohms
17 and ground 0.9 ohms

[NWbuspilot]

An Update:

It runs! But roughly. I'm getting ready to put in some fresh oil and run the bus for a while to get the lifters pumped back up. It's clattering like crazy right now.

The guys at the local VW yard just got a running 78 Westy in. They were nice enough to let me test my ECU in it. Before I began I started up the Westy and it purred. I swapped in my ECU and sure enough- crank for quite a while and no starting. Go back to the engine and I can smell flooded gas. I bought the Westy's ECU and put it in the bus. The price was not very pleasant. $120, and sold as-is. I also put a little Marvel Mystery Oil in my cylinders to help the seals out a little bit. Hopefully I'll have the lifters pumped up by the end of the night so I can surprise my wife by picking her up from work in the bus.

Thanks to everyone, especially Soulful66 and AmSkeptic for helping me along!

[soulful66]

=D> You did it! Wow an ecu defect. Great job!!!!!!!!!!

Now, do you understand that you were getting the pulse from the coil into the ecu, but the ecu was not "pulsing"' the injectors on (soild test light) and off (flickering test light).

So..do ya think that the flooding was because the injectors were grounded continulesy (soild test light) and just dumping fuel into the cylinders? Yeah!?

Twas a pleasure to pass on the learning I recieved from my own woes.

Best Regards,
John