Don Carter

You can "rent" a set of Noid lights at auto parts stores that plug into the FI plugs and light up when they get a signal. If you were closer, I'd offer my set, but probably easier to rent them.

I thought the injectors were wired in sets of 4, so a short only takes out 4 of them and it runs but very poorly, but that may have just been on my 89 with IMS protection.

Houston928

Thanks Don. All the injectors measure almost exactly the same, 3.8v to 4.0v. I checked the voltage at the EZF & LH as per one of the other no-start threads and was 12v.
O Reillys will have a set of 8 noid lights for me tomorrow so will give that a try.

dr bob

Testing for voltage at the injectors is not really beneficial. One side (every injector at the same time as they are wired in parallel) has battery voltage when the LH relay is closed. Without the engine running, the other side of the injectors (again, all wired in parallel) will show a reduced voltage if tested vs. ground, with current flowing through all the injectors in parallel, then through the meter itself. The reading you get is dependent on the impedance of the injectors (known) and the impedance of the meter itself (unknown). So long as it isn't battery voltage, you are assured that the harness is not shorted together.

Since the injectors are wired in parallel, you need just 1 noid light to test with. No need to buy or install 8.

M. Requin

Wouldn't it be resistance, rather than impedance, since you are dealing with DC? And the internal resistance of any decent modern DMM is so high most makers don't even refer to it any more, so I wouldn't worry about factoring that in. Trying to learn, not nit-pick.

All eight might be different, all in my set of 6 are.

dr bob

Since the injectors are wired in parallel, you need just 1 noid light to test with. No need to buy or install 8.
Dealing with a very inductive load, I chose "impedance" out of habit. For a static measurement, "resistance" is probably more appropriate.




My read on his post was that he is waiting for a set of eight noid lights so he could test all eight injectors simultaneously. I bought two individual lights, thinking I might need them to test the left and right injection loops on my '89 with the "ignition protection relay". One is still sealed, the other used on a clinic car; no need so far for even the second one. So far...


The internal resistance of the injectors is amazingly consistent, so it's no trouble with a good DMM to find whether there are shorts or opens in the loop(s) from the LH harness (all at once) or from the protection relay socket (each loop individually). The target values are low enough though that test lead resistance can become a significant component in your measurements, so be sure to measure that (touch two probes together...) and include it in the loop measurements.

For those with a deeper interest, Alan has been working on an electrical guide to the cars as a spare-time project. There was some preliminary stuff available online from his website that may ad some more guidance here.

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I write a lot of technical documentation for the work I do, mostly software process and electrical automation for power plants. The trend seems be that most technical docs are written by folks with a thorough knowledge of the subject, who somehow manage to write to an audience who are already familiar with the subject matter. I try not to fall into that pattern, but sometimes I slip. The challenge is that I don't know how "qualified" the audience is. I might have folks who barely made it through high school, mixed with folks who have extensive technical education, nuke school, etc. I've tried then to write to the "Reader's Digest" level, something that is suitable for everyone. Not over the heads of anyone, while not being boring and dull to an already-informed fraction of that audience. There's sometimes an injection of geek humor that slips in too. Finding the right balance is an art, and sometimes I slip.

M. Requin

Never leave out the geek humor part...

Don Carter

The noid lights are called a "set" because they include different connectors for all the different types of FI sockets out there. There is only one labeled Bosch so you only get one that works with a 928.

dr bob

Got it! I was able to find the Bosch ones individually at the local Advance Auto way back when.

Were I rebuilding the injection harness, I'd be sorely tempted to add a small resistor and LED to each connector, essentially building in the noid light function.

Houston928

Thanks Don & Bob. I had misunderstood a forum write up about checking injectors and thought I needed a noid for each connector. I have ordered a single Bosch noid lamp and will give that a try.

Houston928

Tried the noid light tonight. With all relays in place the noid light does not come on when plugged into any injector connector. If I jump the EZF relay the noid light comes on in every comnector, very brief and quite dim, but comes on.
Was hoping I just had a broken wire somewhere in the injector harness, but it appears not.

Houston928

Got my car started today, thanks for all the help guys. After checking all grounds and as much wiring continuity that I could, I came across a thread about disabling the factory alarm. I did this and the car started on the 2nd turn.

The only other thing I did was replace the kickdown relay ( thanks Roger). When I was pulling and cleaning all relays/fuses I noticed the kickdown relay looked like it had been broken at some point and glued back together.

Tomorrow I will reconnect the alarm, I still have the dash apart, and see if the car starts.

Thanks.

Wisconsin Joe

Try to turn off the alarm.

There is a switch in each lock cylinder (both doors & hatch). Use the long key, and turn to open the hatch or unlock the door.
It's possible that one (or more) of the switches is either disconnected or not working. Worst case, of course is when the switch will arm the alarm, but not disarm it (entirely possible).

Houston928

The reason I disconnected the alarm was I had been changing the drivers side door handle and thought maybe I'd messed something up. Both door locks seem to be working fine.

Wisconsin Joe

You still might have. The alarm switch is a separate 2 tumbler lock at the back of the main lock cylinder. The lock can work perfectly and the switch not (bad contacts, broken wire, not plugged in properly and on and on).

There's a good thread in the "DIY" section that is more focused on the hatch, but it shows the layout of the lock cylinder and alarm switch/lock pretty well:

https://rennlist.com/forums/928/7403...ne-strutt.html