FredR

The tests suggested earlier were designed to eliminate the ignition switch from the list of possibilities. Unfortunately as I have found out one can test these things many times over and find nothing wrong and yet can still have the ignition switch duffing out somewhat randomly. Another test you can carry out is to make 3 test leads using 4mm2 cable and spade type connectors and jump the three relays over terminals 30 and 87 and then try starting. Do not forget to remove these jumpers after the test.

I always carry one in the car just in case a relay fails and I usually have three of the relays on standby anyway. The ignition switch livens up bus 15 which then directly or indirectly initiates the trigger circuits in the relays. Not sure of your configuration but on mine there is also a connection that passes through the alarm system and if that fails to energise the ignition computer will not power up and everything in the chain remains dead.

Keith Newman

Thanks for the explanation about what ECU should be tested where, that makes a lot of sense. I could not what you suggested but I did makes measurements you suggested, here are the results.

starting conditions: battery disconnected, harness plugged into ECU

injector number. Pin 1 to gnd. Pin 2 to gnd pin 1 to 2
1 10.75kohms 10.74 0.6ohms
2 Same as above for all
3 Same as above for all
4 Same as above for all
5 Same as above for all
6 Same as above for all
7 11.07kohms 0.523Mohms 0.522Mohms
8 11.04kohms 180.4kohms. 3.1Mohms

after I did this I returned to injector 1 just to verify original results and now measure 3.1Mohms pin to pin. So I clearly have disturbed something during all my fiddling.

I then checked all connectors with the noid light and see a faint light from each injector connector. I’m not sure how bright it should be but if I see anything that tells me current is flowing.

I still could not get the car to start, but I am further than I was before. I guess professional injector cleaning should be done to verify those while I track down issues with injector wiring and connectors.

just as FYI I did replace the ignition switch a couple of months ago from a reputable supplier.

Thanks for the leads.

Landseer

Where is this crazy 928?
I hate when they dont start.

Did you jumper the alarm at Z plug?
84 is unique in this jumper connection.

I've got an 84 5 speed panel here, will post a picture of what I jumper to get them going, including the afm relay spot and alarm.

Keep the faith!

Keith Newman

First, I am sorry I did not reply to your comment Fred.

At this point I’m a little muddled in my brain about what you are referring to as regards the jumpering. Do you mean three independent jumpers or one jumper connecting all three together. And I am sorry but I do not know what the third relay refers to. In my mind I was thinking the fuel pump and injector relay, but what is the third one you are referring to? Sorry for my ignorance, have patience with me, I am a willing pupil.

both you and Landseer are talking about the alarm circuit. That’s a new one for me, good, but new.

i will have to read more about that circuit because I am not familiar with it.

thanks a lot for a new avenue to pursue.

Landseer

Forgot to take pics before heading on short trip. Will try to get wife to do it tomorrow morning.

Power distribution plugs across bottom of panel are labeled a, b,c etc, from left to right.

Two are out of place. Y and z are in the middle. They are shorter vertically than the others. The short black plug is Z. That plug is primarily associated with alarm. Alarm disables car. If your car has no alarm, it will have a white jumper plug instead. If it has alarm it will have black z plug with wires. To disable the alarm, you unplug the black z plug and let it lay on floor. Apply a jumper wire on panel from Z4 to Z6. That eliminates alarm as an issue. You can fix it later. Let us know if you find Z plug or white jumper..

Injection relay, aka afm relay, has two 87 terminals. Or one labeled 87a and other 87. Its position xvi on panel. Remove it and check it's part number and report if below. Meanwhile what one does here is make up a three legged wire, each end terminating in a male spade similar in size to electrodes on relays. Assuming you have the correct relay in slot now, use diagram on relay to identify corresponding female terminals on panel. Apply wire into both 87 female slots in panel, and third end into 30. Try to start car.

What city and state are you in? If it says in your avatar I cant see one from this phone.

FredR

Mr Landseer has given you the kind of detailed response I was hoping you would receive and was driving towards. My last post was well past my bedtime over here so I was in somewhat auto mode by then. The principles of what I was alluding to are achieved slightly differently on your model year but in essence you need to ensure that the fuel pump, the L-Jetronic module and the ignition system are energised. The relay functionality on your model year is a bit different in that the switched output has more than one outlet channel as covered in Landseer's post.

If the burglar alarm isolation is not disarmed [for whatever reason] you go nowhere. Just keep plodding away- you will get there.

Landseer

https://rennlist.com/forums/928-foru...ory-alarm.html

There are a couple of documents embedded in this thread above that help describe alarm function for 84 cars despite title. Advice: jumper to disable.


The following link actually shows an 84 fuse panel, I think it is 84 USA like your car. I also owned 84 Euro at that time. Alarm jumper for 84 usa and 84 euro is same, for the record, but underlying wiring is actually different for usa/jap cars. Link isnt embedding right, but if you can access it you will find detailed pics and description of how terminals are numbered within the plugs.

https://rennlist.com/forums/928-forum/646935-alarm-help.html

https://rennlist.com/forums/928-forum/646935-alarm-help.html

Female ended jumper wire is used for this task.

Again, may be a red herring in your case, dont get sidetracked by alarm, just disable and continue trouble shooting

Keith Newman

Ok, before I begin, thanks again for the new ideas and help, it’s very kind of you. So now on to business.

this vehicle does have an alarm system.

it is jumpered between the top and bottom connectors on the passenger size of the Z connector.

the injector relay p/n is 928.615.119.01. Brand new.

fuel pump relay p/n 928.615.113.01. Brand new.

i jumpered injector relay per Fred and Landseer guidance.

i jumpered fuel pump per guidance.

Installed battery connection to post. I hear fuel pump running continuously as expected.

cranks but no start. I tested injector connector 1 and 3 using the noid light but could not see anything. I had all other connectors on their respective injectors when I tested. For my edification, how bright should the noid light be when an injector pulses?

Just as as an FYI my battery is new and has been on a maintainer.

Thanks again for the advice.

Landseer

Two directions come to mind.

Pulling some or all plugs, squirting in a little bit of gas, and seeing if it fires at all.

Running a compression check.

FredR

To get the motor to run you have to have injectors that are opening and closing, fuel pump that is running, viable fuel pressure and plugs firing sparks at the right time and some air.

So what do we currently know?

1. You have new relays- they can be tested independently
2. With jumpers between terminals 30 and 87 in the two relay sockets and still no start you have proven that the relays are not the problem.
3. With the alarm by passed it is reasonable to assume that this is not inhibiting the start.
4. You tried a different known to be working L-jetronic unit in your car and the car still did not start. This tells us that you have a problem independent of the unit but it does not tell us your L-jetronic unit is working- to do that you need to install it in an otherwise working motor.
5. You appear to unsure about the how to read the noid light and it is not clear to me that you are using it correctly- the obvious thing to do is try it in another fuel injected vehicle that is working, I have no idea what noid light you are using but the ones I have seen a re type specific and insert into the connector for a given cylinder- when the engine is cranked or running they emit a bright flashing light as the when the circuit is made- no mistaking such. The primary intent of use is to find a specific cylinder that for whatever reason is not getting the signal. On later S4/GTS models with cats they grouped the firing circuits into two loops- one loop for each group of cylinders fired from a specific distributor and there are sensors that tell the brains whether those 4 cylinders are firing and if not a relay shuts down fuel supply to those cylinders so that unburnt fuel cannot be pushed into the cats and auto ignited. As I a aware this does not apply to your model year but..? Bottom line there should be no mistaking a flashing noid light.
6. The easy way to tell if fuel is getting into the cylinders is to crank the engine, pull the spark plug and smell for unburnt fuel- it should be obvious when looking at the plug electrode- it should be slightly wetted.
7. The fuel pump may be running but that is no guarantee it is pumping enough fuel at the correct pressure- both are essential. There are test techniques for fuel delivery and fuel pressure. Delivery is to disconnect the fuel pump delivery system and measure the flow delivered in a fixed period of time. Fuel pressure is achieved by the FPR [fuel pressure regulator] - this is a self regulating back pressure control valve- to measure this pressure you need a test gauge kit of some kind.
8 . At the moment my perception based on the info presented is that the injection system is still not firing- sound reasonable?
9. The speed sensor signal must be viable on my EZK/LH system to get the LH unit working - presumably a similar principle applies to the L-jetronic system but I do not know that for a fact - Easy to test the CPS signal on a scope- are you sure such is viable at the moment?
10. I assume you have tested for a viable spark?

Trust the above may be helpful in terms of moving forward.

Landseer

Reductor coil within in distributor on Ljet as opposed to CPS in LH car.

Computers and sensors ground thru two previous mentioned pass cam cover grounds. Engine ground strap connects to frame like on S4, near pass motor mount.

Has CE panel been removed, cleaned and inspected for mouse damage behind?

New temp 2?

Keith Newman

Ok Landseer thanks for the ideas.

forgive me but I did not put gasoline in each cylinder, instead I opened the AFM door with a piece of hose and sprayed starter fluid into the opening. The engine started briefly.

pulled all plugs, checked compression, all results in pasig

cyl 1- 180
cyl 2- 180
cyl 3- 185
cyl 4- 175
cyl 5- 200
cyl 6- 195
cyl 7- 205
cyl 8- 205

Landseer

Here's pinout...


From previous posts. Porken and Rich Andrade used to post very helpful stuff for troubleshooting Ljet cars

FredR

I am not familiar with the correct terms for all the components but we are talking about the signal carried in the infamous green wire-

Stan's latest post a few moments ago suggests that the ignition system is working OK if it fired up with starter fuel so the problem is definitely in the fuel management side of things.

I assume the L-jetronic system does not work unless it gets a viable signal from the ignition module.

FredR

Those compression pressures look fine- a bit of scattter on a couple of cylinders but such could easily be explained by a bit of carbon on the valve seats- nothing to worry about or so I would say