1980 928 5sp no injector pulse ??? Help
 

Ok guys I got this 1980 that I've been working on and I thought I would of never got to where I am with the car. So far I have the car running on fuel down the throttle body.
I have checked fuel relay and the XV1 relay,I have 30 psi fuel pressure all the regulators are good. The aux air and cold start inj work with pulse.i checked the ecu and have power to all injector terminals 32,33,14.15 and power to afc terminals 10,29.
I have good ground to the ecu and all ground terminals 5,16,17,36 but no ground to the 02 sensor shield ground 23.
I have good ground to the 2 rt side valve cover grounds at this point I'm leaning towards a bad ecu.
Did I miss anything silly any help would great thanks guys
John
516-322-3422

Fuse/Relay Panel Grounds -
 

Hey John - Have you seen the car run previously or is this a new project to you ? Although the computer can fail - they are pretty tough. Make sure to check and clean all the critical fuel computer ground terminals just above your fuse/relay panel, inspect the computer connector plug and the injector harness for damage.

Since it sounds like you have a reasonable spark and the signal from the distributor (green wire) to the ignition unit is good - If you have the cold start injector wired and plumbed correctly - as the starter turns the motor over it should try to run for a short period on the cold start injector.

Next - make sure the distributor (green wire) or "Engine Speed Pulse Signal" is also reaching the computer connector - Pin #1. This signal is used to tell the computer to alternately apply the fuel injector grounds in pairs. If the computer is correctly receiving the "Engine Speed Signal" a NOID LIGHT can be used to see a flash at each fuel injector connector.

One other point - make sure you have a good hot battery. If there is any question as to your battery status - add a second battery at the jumper post up front. There have been several instances where an owner has been chasing a "No Start" condition only to find out that it was a questionable battery or it's ground straps. If there isn't enough of the +12 volts remaining while the battery is being loaded by the starter - the fuel computer will not wake up.

Keep us posted - Michael

I have not seen the car run before I got it. It was sitting under a tree for about 4 years. I replaced the green wire with a new one and put a new battery new fuel pump& filter drained and cleaned the tank and removed all injectors,rails and regulators and cleaned entire lines.i also replaced all the fuses,relays and cleaned the fuse panel. I also put a battery charger on it to start it while I'm working on it . The car does start for about 2 seconds then stalls. I have a niod light and get no pulse from any of the injectors

When you say pin #1 you are referring to the 35 pin connector
Ljet right that says engine speed from TZS 16

Injector Pulse -
 

Hey John - Yes - Pin #1 is the pulse that tells the computer that the engine is turning over. It sounds like you've gone through all the basic T/S steps.... Perhaps someone has a spare computer that they will loan you to verify whether this is the problem. I think I have one for a 1982 for an automatic transmission car - I'll see if I can find it. Not sure if the In/Out pins are correct but will do some research.

Michael

I have a 84 Atm parts car not too far from me. Does a 84s auto work on my 1980.
This is the part number on minehttp://forums.pelicanparts.com/uploa...1472607694.jpg

Spare Computer -
 

Hey John - I've dug through my spare parts storage container and have yet to find a working computer for an early 80's 928. I did find one marked dead - but I will check with a couple of friends who may have something. I'm not sure about the interchangeability of the computer from the 84 you mentioned.

I realize a missing injector ground signal is probably your major issue but just for some peace of mind have you pulsed your injectors using one of the little testers to make sure they are not stuck closed with old fuel ? Also check to make sure the AFC "door" is not frozen closed and moves smoothly.

There are many owners on this site with lots of 928 experience - I'm sure they will think of something you may have missed.

Michael

Thanks for looking. I ohm out the afc to make sure it was good and also swaped it with one I have in stock. When I pulled the injector rails off I took each injector and bench tested each one running carb cleaner thur them to rule out bad injectors. I went last night and checked pin #1 and had a good light pulse from my test light when I cranked the motor. I'm going to try a few things and see if the 84 ecu is the same
I appreciate the input and help
Thank you

I have a known working L-Jet computer I could loan you if you can't find one closer. You're only gonna need to borrow one for about 30 minutes, for gosh sakes. PM me your address if you can't find one closer.

Thanks guys
I have some local sources hopefully I can find one .
I'm starting to realize it's good to have lots of test equipment
Lol

ECU - In Put Power Check Under Load
 

Hey John - I was going over some notes that I'd taken while helping to sort out another "No Injector Pulse" problem on a 1982 928 a while back. There is supposed to be a voltage stabilization circuit inside the ECU that can temporarily keep it's internal operating voltages boosted up (I assume some large capacitors) if the external battery drops below 9 or 10 volts during start. We'd determined that this circuit had failed and was dragging down the internal operating voltage in the old 82 computer I still have - marked bad.

Just a suggestion but you might test your ECU supply voltage during start just to make sure your external power source is over the 10 volt mark.

Good Luck, Michael

Thanks I will try that when I get home .
There are 2 12volt power pins #10 & #29
Both say afc relay xv1 87 should I check both
Pins?
Thanks

Pin layout
 

Here's a pic of the pin layouthttp://forums.pelicanparts.com/uploa...1472744337.jpg

Relay XVI -
 

Hey John - You had stated early on that you had CHECKED the L-Jet Computer Power Relay XVI ? I thought we were well past this component but - for T/S purposes and to eliminate a potential relay problem make up a THREE WAY SPADE JUMPER WIRE. Remove Relay XVI from it's base and jumper socket pins 30 - 87 and 87 together (There is one (1) pin 30 and two (2) 87 pins in the internal relay circuitry). ..... This will provide a good solid +12 volts to the computer and tell you definitely if Relay XVI is or is not the issue.......

Also after rereading the rundown on some of your original problems - you mentioned that the two large resistors near the P/S pump reservoir were smoking. Just to eliminate a potential trouble spot, disconnect and clean the resistor terminals. Then verify that one reads (aprox) 0.4 Ohms and the other reads 0.6 Ohms. These are your voltage dropping resistors used to protect your coil during start and run. Don't mix their electrical wiring positions up.

Keep us posted - Michael

I made a jumper to 30 and the 2 87 spots already
And the same issue I also checked voltage at the 35 pin connecter
And with a fully charged battery I got 12.4 volts at both 12 volt terminals.
I will check those resistors but they cause a no voltage reading on the injectors?.
I was looking for a ecu and the part # ecu that I have they are saying it's hard to find

Progress -
 

Great - John you are definitely making good progress. It is often just a matter of completing a series of logical steps to check off what is working correctly before you will get down to the source of a problem. We have all had one issue or another chase us around a few laps as an unfamiliar car is brought back to life. There is a reason why such a limited number of these outstanding cars are in the hands of such a select few. The slack jawed 928 Porsche filling station gawkers are often still talking to themselves as we pull out and head back toward the on-ramp.

Continue On - Michael

This is so true, I always look for a good car with good history that someone gave up on and can't fix it and don't want to spend any more money because they can't fix it themself. This one by far has been a pain in the ass chasing all the electrical issues. But that's how you learn and the next one is easier to get running.
I love these cars and will always have one.
This one I think needs a ecu

Some of what I am going to say here is a GUESS. However, I have spent a LOT of time poking at and analyzing the L-Jet system on my 1981. I even bought and read the book!

The public opinion is that the controllers on the L-Jet rarely go bad.

My understanding is that the L-Jet ECU boxes versions .02, .03, & .04 are interchangeable. The .01 version (what you have) is SPECIAL, probably (GUESSING here) because the AFM was changed and presents different test resistance values between early models and the later models. If you change to a newer ECU, then you should consider also changing to a newer AFM. I can point you to the magic date stamp on the AFM if you need to see it to verify the model - it is HARD to find.

I don't know if the Temp II sensor differs between the L-Jet years. Please look it up. These three (ECU, AFM, and Temp II) should probably all be for the same year. VERIFY THE WIRING. It might have changed along with the ECU/AFM change between the .01 and .02 versions.

I found a spare .03 ECU on e-bay cheap and I have swapped between the .02 and .03 versions on my 1981 (with the newer style AFM) without any apparent change in behavior. My AFM is definitely the newer version.

I don't see many .01 or .04 ECUs on e-bay. Maybe those cars don't get parted out as much. You may have problems finding a .01 ECU if yours is bad - but this is unlikely.

I feel it is more likely that your AFM is having troubles. There is a 944 web site that discusses testing and tweaking these items. Google it.

My understanding is that if your Temp II is bad or disconnected, your engine will run so rich that it will not fire. Verify this.

Check spark timing - I had to remove my distributor for other work and I re-installed it one tooth off. It didn't start.

A lot of people on these boards claim that their engine fires for a second and then dies. My GUESS is that they are running off the cold start injector and that their ECU isn't doing its job. Are you seeing this behavior or are you not seeing any fire at all?

Good luck with this - I had the advantage of starting with a running system and so it was easy for me to make a change, look at the effect, and then make a decision on what to do next.

I can say that it runs and stalls on the cold start but I still have no injector pulse. Your saying of 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 by I think I'm chasing a bad ground or bad ecu.
So your suing if my temp 2 is bad I won't get injector pulse?

L-Jet Computer
 

Hey John - How is your search going in locating a L-Jet 928-618-106-01 computer ?

From one of my Bosch Fuel Injection Control books it looks like the slight difference between the 1980 - 1984 computer P/N includes some of the external inputs and/or sensors. There are naturally some electronic tweeks internally as well - but the last two series digits (01, 02, 03 and 04) primarily designate variances between the early vs later performance, emission spec's, AFC calibration, timing, acceleration curves, etc..... Your computer 928-618-106-01 provides for the earliest set up. Although there is no indication mentioned in the results of updating your car to a later series I'd assume that you need to at least stick to the correct auto/std transmission.

As a last resort there are Bosch Service Centers on the internet that can repair your computer. They would also be able to provide a definitive answer as to cross reference part/series information.

One other static test that you might try (if you haven't already) is to use an ohm meter to check the resistance BETWEEN one of the computer ground pins (pin 16) and each of the output injector ground signal pins (14, 15, 32, 33). If there is a very low resistance reading between each pair of pins (16 - 14, etc...) it's output amp is damaged or shorted.

I don't think qdac is saying the distributor being off a tooth or the Temp II sensor would prevent the injectors from getting the ground pulse. Qdac was faster than I was in providing some good information... :)

Good Luck, Michael

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