docmirror

Trying to get the S4 (test) started after TBWP and new injectors replaced.

1. Swapped LH/EZK from test car, into running car: Running car runs well with test car LH/EZK
2. Swapped LH/EZK from running car into test car: Test car does not run. Return LH/EZK to running car, still runs fine.
3. Checked continuity LH pin 18 to all 8 Bosch inj connectors in engine bay = ~0.3 or 0.2 ohms(dead short) to right pin. (12V to ground pulse to batch fire inj)
4. Checked continuity from XXV relay(LH) pin 87 to all 8 inj connectors in engine bay = ~0.2 ohms(dead short) to left pin. (12V source to LH and all inj pins)

Car will run when carb cleaner is sprayed in intake. I have good compression, proper timed spark. I have no injector pulse occurring at right pin from LH pin 18 to the injectors. It stays at 12V always, and never pulses down to fire the injectors. The only other thing I can think of is the alarm is locking out the LH from pulsing. I asked before about the alarm, and we have determined that the alarm cuts power to the EZK/LH. Do we KNOW this is how the alarm works? I'm thinking of jumpering it anyway to eliminate the possibility. Did I move the wiring just enough to 'fix' the prev short between pins? Possible. The harness looks to be in good overall cond, and no frayed wires I can see. All inj measure 15.3 - 15.8 ohms. I'm wondering if my LH is just too weak to fire mine, but strong enough to fire the running car? I'm going to test the LH from the 89GT later this week.

The test car is 88 and the donor car was an 89. Doubt that makes a diff. If anyone has a magic bullet, please aim it at me and fire. This is the last thing that is stopping the car from running and driving. Brakes have been refurbed, exhaust repaired, new fuel pump, filter, inj. I'm ready to drive, but need inj pulse. It was running but poorly before I started the work.

Lizard928

worf928

docmirror

I will check those things and get back with results.

I'm beginning to think about the signals from the EZK to the LH via the harness.

Ken P

Some other things to check;
Make sure there is not a relay in the kick down relay spot of a manual transmission car, or an incorrect relay in the kick down relay spot of an automatic car.

Another way to check for proper injector values or a short in the harness - pull one injector and Ohm the harness at the injector plug, it should be about 2.3 Ohms. 16 Ohms / 7 injectors in the circuit. Measure the remaining unplugged injector to be about 16 Ohms.

If you have an O scope, check the speed signal from the EZK to the LH. It can be distorted and loaded down, causing the LH to not trigger the injectors. A relay in the kick down relay spot where one should not be, or the wrong type of relay can load down this signal.
I have also heard the the Tach, which is part of this circuit if I recall correctly, can distort this speed signal.

docmirror

Which pin is the speed signal? I have these pins from EZK to LH, but none of them are labelled as to function:

Pin 3 LH to pin 26 EZK
Pin 2 LH to pin 8 EZK
Pin 25 LH to pin 9 EZK
Pin 1 of LH to pin 13 EZK

I do have an O'scope and have used it before on 928s, familiar with their use. I'll check the relays, but none have moved since it ran before the TB and injector job.

Ken P

The speed signal is the Pin 1 of LH from Pin 13 of the EZK, This also goes directly to pin 31b of the kick down relay and to the tachometer.

In the shop manual this is test point 15 on page D 24-22 in the volume 1 - a.
The manual says to have the EZK connected and the LH connector disconnected. O scope between pins 1 (signal) and 17 (gnd).

worf928

docmirror

Thanks, I'll have a look at that.

Ken P

I just checked my last troubleshooting docs for a little more info and that Speed signal should be a 10 volt, square shaped waveform.

docmirror

Well, more than six months have passed, and I haven't touched the 88 except to sweep around it. John came over and we had at it again. The resolution was in the first post, but I lied a little bit, which turned out to be a big bit.

When I checked the injector pulse with the O-scope, I must have been on the wrong pulse lead at the harness. I never got the pulse. However, this time we used a noid light on the end of the harness where it plugs into the injector. We have a pulse. Likely, we ALWAYS had a pulse, just didn't know it.

My injectors were not new. They were the same injectors that came with the car. They were removed last year, and sent out for cleaning and testing. All of them worked well before sending out. I think you know where I'm going here. Yes, I got them back in a nice clean bag, new pintle caps, O rings and a fancy chart of flow rate showing they were all within a few cc per minute. Being a trusting guy(gullible) natch, I just tossed them in the intake and moved on to the cooling system clean up.

Of course, we know where things went pear-shaped. The injectors were all BAD. We tapped on them while cranking and got one to fire, as the car was cranked, it went calumph,calumph,calumph as one of the injectors cleared up. John brought a set of used injectors with him, so we started swapping. He also had a quick test switch and we double checked all the replacement injectors, getting a nice click on each one.

Then, I picked up a couple of the 'rebuilt' injectors. 3 in a row tested bad, no click at all. I didn't bother with the rest. We put the replacement used injectors in and it fired on the first crank. We then took a break, went for a swim and a beer, chatted about old times, and then got back out and filled the coolant. Found another side-issue. When we put fuses in the two fan slots, the fans come on and stay on with the key. I'll sort that out another time.

The car runs great, good power, solid shifting. The belt tracking looks good, and the only warning light is a brake pad sensor. I know the pads are good, so it's a wire from the sensors, that has been faulted. I'm going to get stainless brake lines, replace the rubber ones, bleed, and fix the pad sensor and I'll have no more warning lights.

The driver and pax seat motors both work, and the pax side window goes up and down. The switch for the driver side is sketchy, and the hatch won't stay latched. A ton of the 'usual suspects' to sort out, but at least it'll move under its own power. I was supposed to have this car on the road back in Feb. I think once I get the mechanicals sorted a bit better, I'll be selling it and moving on.

I've sent three sets of injectors to this company and they have messed up each order. So, never again with InjectorRX in TX.

FredR

Doc,

For what it is worth our injectors can be u/s cleaned, tested and demonstrably working. Leave them without using them a few weeks or so and they can fail to work. Happened to me albeit I only had one fail and that after about 3 weeks of testing that I personally witnessed. This is why I recommend observing the cleaning and testing in person- take them there bring them back and ensure i have the same injectors I started with rather than "refurbished ones" that have been to the moon and back a couple of times and do it just before first use..

Of course if you had to travel a long way to get to such a place I can understand but if sending them to a shop use a highly reputable outfit that one can trust.

Mrmerlin

Doc spray some pb into each injector then tap the inlet a few times on a block of wood then take a 9 volt battery an wire it to test the injectors
this is a common issue with cleaned injectors
once the injector starts clicking add more pb to the inlet and click it some more then you can use them
Glad you got it figured out

Kevin in Atlanta

My local injector refurbisher sells this:



Sold at: Injection Connection

SwayBar

I wonder why those shops don't finish-off the cleaning process with some form of lubricant for the injectors - this can't be isolated occurrences on the 928 forum only.