1980 928 5sp no injector pulse ??? Help

[john 928]

Ok guys the car runs like crap with the plug off and I'm getting a ohm reading on pin 27 and 6 but nothing from pin 7 which is airflow sensor output.
Does anyone know what reading I should getting from the plug when it's running.
And nothing from 9 or 8
I checked the ecu for high resistance and I'm getting a high reading from all the injectors
My next step is to cut the plug and splice in another one

[john 928]

Ok from my last attempt I put my noid light while I had the car running and I had a good pulse and when I connected the afm plug the noid light got really dimm and the car stalled so from what I gather I'm losing fuel and that's why its stalling. So I'm either losing 12v or losing ground or I have a short somewhere.
Anyone ever see anything like this.
I took a video I will try to download it

[JK McDonald]

Hey John - Just to back up a bit and verify something once again - Are you saying that you've checked the compatibility of the Computer and the AFM Part Numbers ? Verified that the "Pin Out" connections are correct between the computer and the AFM ? Bench checked the AFM ? Verified that there are no injector wires shorted to ground (computer, AFM, injector plugs disconnected) - Wrung out the wiring harness for good continuity between each wire from the computer connector to the AFM connector (computer and AFM plugs disconnected)- tested for "NO Shorts" between any of the AFM wires - (computer and AFM plugs disconnected) AND there are "NO Shorts" to ground between any of the AFM wires and the vehicle chassis. Verified that only pins 5, 16, 17, 23, 35 of the computer connector are ground (computer and AFM plugs disconnected) ?

One other suggestion to keep from adding any additional problems - You may have noticed the bent or distorted connector plug pins of your AFM. If you stick the round test probes of your multi-meter in between the Bosch style female connector pins they can be distorted and/or severely damaged. This pin damage along with any frayed or brittle wires up in your harness can affect the reliability of the control signals between the computer and all it's needed input sensors. The electrical contact pin tension of the Bosch female connectors are designed to accept "Flat" male pins of a specific thickness.

When checking the reference and control signals at each L-Jet connector it's best to use a piece of safety wire that has been flattened on one end with a hammer. Then attach a short length of generic test lead with a pair of alligator clips to go from the flattened piece of safety wire in the connector plug to the round multi-meter probe. Often a missing input signal makes the older analog L-Jet fuel injection computers go really stupid. The newer Digital computers typically have a "Limp Home Mode" to fall back on if there's a component or signal failure.

Good Luck, Michael

[john 928]

I checked the ecu with the resistance test and had high resistance to all the injectors and a good ground on the ecu. I bench tested the afm and it checked out with good readings to the flap response. All relays have been checLed

[aluminum]

Ok My Guess
Had the same prob with my 80 sat 13 years .
was the fuel Injection relay > Pay special Attention to this relay make sure your looking at the right relay . ( I would put a brand new one in ) now still not working >
Pull the fuse panel down but not off .
*Replace all the Non Copper or Brass Fuses with such Copper or Brass
* Look for green Color Corrosion and remove ( Brass Brush >Cleaning fulid then compressed Air )
* Examine the Back side of the board paying "special Attention " to the Fuel Injection Relay hook up wires . Look at all the wires very close ( down to the hook up point ) Look for Green
Corrosion . they get Corrosion right inside the Hook up point as well .
Check everything that has to do with the Fuel Injection relay .

If the Car starts with gas poured in the Car should run if the relay cuts in when the Key turns back to Run Position .
2
Ignition switch :
if the switch is bad the same thing can happen

get that sorted out and it well start right up

Note unless you make a Puller you well damage / Brake the relays as you try to remove them.
If the Prongs are Green then there is Corrosion inside where they where pulled from .
Blow cleaning fluid in to clean Compressed Aid to blow in and Dry .

Are a huge amount of wires so go Slow > only work on one small area at a time . fix then move on > very easy to get mixed up > reference Photos are a help .

Aluminum Fuse's are no good < Galvanic Corrosion make the Green >

Smoke from the ballast Resistors < that's Normal from a bit of oil that gets on them > you can clean them .

Look for Oil residue on the inner fender panels ( like drivers side )
any on your fingers when you rub ? Pressure wash the whole area and Blow Dry .

you may find something here
remember to go slow with the Panel wires > you can work the relays out with a Bent Pry slipped under > if they brake replace them .

Cleaning fluid : I use Calibrator or throttle body spray fulid

[928gene928]

The last post was very accurate. These are the exact things I did to my 1980 to stop an intermittent starting problem. I believe that the relay was the major problem in my case, however; the ignition switch was also an issue.

[JK McDonald]

Just my opinion but at this point with the provided symptoms and your reported T/S results (?) it doesn't seem very logical that the ignition switch or the ignition or fuel pump control relays would be the issue. Didn't you report that the relays have been electrically bypassed out of the circuitry early on.

Now that you've established that the car only runs (obviously super rich) until the AFM is plugged in - it proves that the injectors can be fired. IF you have gone down through all the previous suggested T/S steps - have you been able to swap out the computer from the local parts car ?

John we are just trying to help - just remember that no matter how complex a problem seems to be - Troubleshooting is simply a process of logical steps to eliminate or verify the correct operation of each component one at a time. In rereading your responding posts throughout the discussion it sometimes seems that you may be skipping over some of the suggested vital test points.

Perhaps Neil can review this posting and add some new informational insight.

Michael

[john 928]

I have t/s almost everything and at this point I'm going to revisit every item. It can't be ign sw if the car runs without afm connected. What I didn't do was replace afm and ecu from the 84 as a set.
I'm going to revisit all the relays and panel for clean connections because from my experience the relays and panel is always bad.
Last night I switched about six relays in the XVI slot and was giving me a intermittent start so I'm going to revisit the panel and keep everyone updated
Just want to say thanks for everyone's help and input .

[aluminum]

Originally Posted by john 928

I have t/s almost everything and at this point I'm going to revisit every item. It can't be ign sw if the car runs without afm connected. What I didn't do was replace afm and ecu from the 84 as a set.
I'm going to revisit all the relays and panel for clean connections because from my experience the relays and panel is always bad.
Last night I switched about six relays in the XVI slot and was giving me a intermittent start so I'm going to revisit the panel and keep everyone updated
Just want to say thanks for everyone's help and input .

Look at the BACK SIDE of the Panel >> the corrosion also gets inside the connections running through the Panel

just pull the wood bar at bottom > remove a very few screws and the Panel pulls away > like I said > only do / Check / Clean > wires in small section at a time >

you well need a good light / A Pick to poke with / A small wire Brush / Compressed Air / Cleaning fluid ( map air cleaner works great .

wiggle each wire and look for Green they get corrosion for the location of the Panel get damp there sometimes . like I said go slow don't pull a bunch of wires at a time > work with 4 to 6 wires at a time . some Tape or ties to bundle wires may help

[neil30076]

DO NOT go pulling the relay panel, in 35 years of owning many 928's and troubleshooting your particular problem, in my opinion its not there!
Your starter circuit is good, could still be a relay, I ASSUME you have the correct/new Fuel Injection relay 928.615.119.01 in XVI, no others will work!
I agree with Michael, so lets try this:
The air flow sensor is a simple piece of hardware, it send the air temp and the flap position to the ecu, thats all. The flap position is pin 7 on the diagram, air flow is pin 27. You will only get valid test readings if both the ecu plug and the afm are plugged in. green/red trace ( 2nd wire from top in your pictures below) to ground with as voltmeter should change as you move the flap, (ign on so the ecu is powered) you will not see any variation on green, blue green, or the other wire.

The following is a comprehensive test of the ecu/afm, with ignition off, disconnect the ecu plug, and check :



This also eliminates the idle shut down and full throttle switches:

1) Accelerator pedal released.
2) Accelerator pedal slightly depressed (throttle linkage play eliminated1
3) Accelerator pedal released.
4) Accelerator pedal depressed (until throttle open more than 300).

[aluminum]

pulling the Panel down to check it out is a diagnostic test , a visual test
is a 10 min job >>a simple test . if the wires look good then then you can call that test results or pick a name . looking at the wiring at the Panel for corrosion is a good thing to do i think .
I have seen many 928 having this problem .
Now what harm can be done to check it ??? 10 min down 10 min back up if it looks fine simple as that
Example you take it down for a look at the back side and it has corrosion / wiring probs would you ignore that ? makes no difference if a relay works if the signal is not going anywhere . Could be a lot of things no doubt however this area is a proven area to look at

That's how you fix car's your diagnose them > not the panel ok move on .

[john 928]

ok guys i was back at it again today and i have forward progress. i recleaned the fuse panel new plugs fully charged battery checked both relays. i got the car to run on its own for 8 to 10 seconds on its own. i noticed that the fuel pump relay clicks constantly while it runs. the car to run on its own for about 8 seconds it idles up and runs smooth then idles down then stalls almost like its running on the cold start injector and when it shuts off it idles down then stalls. before the car would just turn over start and stall. now the car runs with the afm plugged in for about 8 to 10 seconds.
im going to check both temp switches and put my fuel pressure guage back on tomorrow after work to make sure i still have good fuel preesure.

[JK McDonald]

Hey John - I've been out of town for a while - did you come up with a resolution to your missing injector ground pulse ? I know you mentioned trying to sort out this problem after coming in behind the previous owner's troubleshooting attempt to swap some parts around.

In reading through the thread again, if you have completed all the suggested tests and eliminated the remaining external components, did it turn out to be the L-Jet computer itself ?

Michael

[Danglerb]

If anybody is looking for a "new" plug for the MAF, turns out at least as far as I can tell, that the 300zx has the same connector and they sell for $10 to $20 for options from pigtails to ready to crimp with new seals on ebay.

This is one I'm looking at, Fit Nissan 300zx MAF Mass Air Flow Sensor Connector Plug Clips z32 89-97 6 pin