I can say that it runs and stalls on the cold start but I still have no injector pulse. Your saying if the distributor is off I won't get any injector pulse when everything else tests good. I swaped out the afm with a 84 and no change. I will check the timing but I think I'm chasing a bad ground or bad ecu.
So your saying if my temp 2 is bad I won't get injector pulse?

I just checked the ground resistance on pin 16 to all injector leads and got 0.05 on all 4 injector pins. When I turned the key to the on position I got 12.35 which more than enough volts to operate the system. http://forums.pelicanparts.com/uploa...1472915444.jpg
http://forums.pelicanparts.com/uploa...1472915470.jpg
http://forums.pelicanparts.com/uploa...1472915518.jpg

Computer Output Pins -
 

Hey John - The 4 static resistance tests I'd suggested is an ohm meter reading between the Pin 16 (Grd) and each of the pulsed Ground output Pins (14, 15, 32, 33) "On The Computer Itself" not on the connector cable side.

What you want to see from the circuitry inside the computer is a very high resistance (Meg Ohms ?) for each of these 4 readings. If the output power transistors are shorted internally - each of the 4 resistance readings will indicate a very low resistance value.

Michael

Just a silly question when I disconnected the afs I get injector pulse. When I connect it back I lose injector pulse. Why is that

I did the ohms test and I got a reding of 00.2 on all the 4 injector pins from the computer.

Afm -
 

John - Are you saying that when you disconnect the AFM connector plug that you now have injector pulse grounds being sent out from the computer ? Is this verified using your NOID test light ?

If this is the case it sounds like a wiring issue or component mis-match. Perhaps there is an experienced 928 owner up your way that's close enough to help sort this out.

Michael

I have noid light and when I have it hooked up to a injector and disconnect the afm the car runs and the light flickers but because the afm is disconnected I get black smoke out of the tail pipe I guess it's running rich. When I connect the afm I get no pulse or flickers even when I get the car running on starting fluid thru the afm.
I bench tested the afm and all reading say it's working correctly,should I pin check the harness to the afm I also swapped one out from a 84
I did notice that hole for the afm adj is missing maybe someone was in there and messed with the setting

T/S L-Jet Computer -
 

Hey John - Since you mentioned that you'd bench checked the AFM - were you able to determine if the AFM wiring harness and pin numbers checked out OK back to the computer connector ? It sounds like you may be looking for a pin out error or a short to ground that kills the computer when the AFM is connected.

I was talking about your lack of the injector ground pulses when the AFM was connected with a retired BMW service tech. Even he said this was a strange symptom if the interconnecting wiring harness is good. One of the things he remembered was that the BOSCH L-Jet computer P/N's and the AFM P/N's were normally a matched set. It's not that they couldn't be interchanged between series numbers IF the In/Out pins were verified to be compatible. It was just that the performance of the car may be off a bit. He also said the early L-Jet computers were designed to control either high or low impedance injectors - and the injectors were not interchangeable. The difference is in the match of the output circuitry and the overall shape of the ground pulse to each type (High or Low) impedance injector. There is something different in the leading edge of the start and taper of the holding current sent to the injectors to prevent over heating of the computer driver transistors.

I'm sorry to say that I've not been able to turn up a computer to send you and help in your troubleshooting effort. Perhaps you could ask the previous owner what brought on his original problem and what he did that caused the car to be parked ?

Michael

I can't verify what the previous owner did because he always brought it to a shade tree mechanic and was very cheap from speaking to him so I wouldn't be surprised if this afm is not the one from the car. I have two different style injectors on each side and noticed while cleaning the injectors that the ones that didn't look like they were correct sprayed a bit more fuel. I have a 84 parts car and was wondering if swap over the ecu and the afm from the 84 as a set will it work on my 80.
I was playing with afm adj screw and got the car to run but just idle on its own.
This car is by far the hardest one to get running.
Even my wife is complaining about how much time I'm out there working on the car
Lol

Some Progress -
 

Hey John - The recessed adjustment screw is only for fine tuning the emissions Nox during idle. There is a large flat tip adjustment screw about the size of your thumb nail - down low and just under the front of the intake center plenum that is your primary idle adjustment. If you have your motor at least running a bit - you might try to raise your RPM by turning the main idle screw CCW to see what happens.

What happens if you open the throttle ? If your motor dies as you hit the accelerator - you may be missing the variable resistor (Like the volume control of a radio) signal in the AFM to the computer.

It sounds like you are making some progress -

Michael

When I got the car to idle on its own I tried to adj it from the idle screw and the minute I moved it. It stalled. The fine tune adj screw I don't like messing with because it's set from Bosch. I have the adj tool and marked my tool to top dead center and turned it clockwise till it closed and counted the turns and marked where my tool landed so i know exactly how many turns and where to put it back when I was done playing with it.
I checked the part # for the afm and the ecu and they match so I'm pretty sure I have a matched set for my car. Maybe the different injectors are causing my issue.
These are the 2 injectors

I apologize if I implied that having a mis-positioned distributor might cause the injectors to not fire. What I meant to say is that a mis-positioned distributor would prevent the engine from running because the timing is so far off.

With the AFM disconnected, your injection system will not know how much air is going into it. Look to the WSM for the AFM test resistance measurements that are taken between the various AFM connectors. These measurements are easy to do. Consider performing them with the AFM on the bench, and then perform the same measurements with the AFM in the car by connecting your VOM to the plug to the ECU. The AFM measurements should be the same at both points. If they are not the same, then you have a wiring issue.

According to other references TempII disconnected (or a wire break) will cause the car to run extreme rich. Perhaps(I'm guessing here) what is happening here is that the injectors are fixed full ON? Is your noid light solid lit?

There are test measurements in the WSM for the TempII. Please check this at both the sensor and at the ECU plug.

I understand your frustration here and look forward to hearing what the fix turns out to be.

Hey guys I have a question I just noticed yesterday that the charcoal canister hoses were dry rotted and broken under the rt front wheel. Will that affect the vacuum on the car ?

Missing Injector Grd Pulse -
 

Hey John - So where are you in T/S your missing Injector Grd Pulse ? After going down through the list of steps that normally would have resolved this type of problem - Are you still at the point where you had it running only with the AFM disconnected ? Have you swapped the Computer ?

I'm sure there are lots of us who would are following this post and would like to see how it comes out.......:)

Michael

Injector pulse
 

I was working on the car last night and noticed that the drives side fuel pressure regulator was leaking air but not leaking fuel. I tested the ecu and afm and both show the correct volts on all terminals. I am replacing that regulator today and keep everyone posted.

John, re-check the wiring on the plug going into the afm, I just helped a friend trouble shoot a later 928, the wiring in the harness close to the plug was fused together and causing the car to start then die. With the afm pulled out but plugged in it would run until i twisted the afm around, and then it shorted out and died. I cut the cable end off upstream of the short and it started and ran , albeit badly.

Just a thought....

That was going to be my next move from a 84 parts car that I have.
I double checked the afm just to make sure it wasn't that plus I got the car to run for a bit one day but stopped running after I kept trying to make adjustments. I'm going to replace the fuel regulator tonight and see if that helps. I have the complete harness from the 84 how hard is it to replace the entire harness all the way to the ecu, or am I going overboard

Ok my update so far is that the regulator didn't do much and the car still has the same issue. When I disconnect the afm plug the car runs and I have throttle response but I get small amounts of black sutt out of the Exhuast. When I connect the plug while it's running the cars idle goes up and runs smoother for about 3 to 4 seconds then dies. The wires going into the plug are very hard and not flexible and have cracks on the wires. I think I'm going to cut the harness plug and splice in a new one.
Does anyone have a layout of the plug harness

AFM Harness -
 

Hey John - I think Neil is right on target to suggest that you concentrate on the AFM harness and connector plug area. Why not carefully split the outer hardened plastic sheath covering the AFM harness with an x-acto knife so you can inspect the condition of the individual wires ?

Just gradually work your way back up the harness until you locate the cracked or frayed insulation. It sounds like you are closing in on your problem -

Good Luck, Michael