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Power to the injectors and fuel pump is the small wires at the battery positive. The pump might run but at reduced capacity. Jumper the relay socket and check voltage at the pump. Should be battery voltage
The injectors get power through the injector relay from a dedicated feeder from the battery. Same poor connect test, this time at the injectors as you did, should be battery voltage and stay close to battery voltage when the lh pulls the other side of the injector towards ground. Note that it doesn't actually ground the low side of the injectors, since there is some resistance in the wiring and connectors, and also in the transistors used as switches. So the high side should be at battery voltage and stay close to that voltage even when the other side drops low. The low side stays at battery voltage until the lh pulls it low. That side should drop to less than one volt, but you probably won't see it with a digital volt meter. You'll want a 'scope to see what's really happening. The DVM averages a number of samples, some at battery voltage and a few pulled low. The noid light switches on and of fast enough to see the pulses, but doesn't ID the resistance in the connections and wiring, including the ground connection on the rear of the intake manifold.
Kevin, so you checked sparks at first and that is ok?
If you can connect a diagnostic tester to the 12p socket near the EZK, and excercise the injector test. You should hear loud clicks at all the injectors. If you do, that is ok for now. You should also hear the clicks while starting (turning over). If all of that seems ok, next stops are timing, fuel pressure and of course good quality fuel.
regards,
Theo Jenniskens, 1992 928GTS
Sounds like the issue I had with my 87 5-speed. It would not cold start but if I could get it to start by tickling the injectors, starting fluid, etc. it'd idle and run. In my case after a lot of screwing around I replaced the LH ECU and it's back to normal.
I could see a little flickering of the noid light and had good spark but it was not fueling enough to start and idle.
Dr Bob - Cleaned the connections at the battery yesterday.
Injection relay testing:
Voltage at 30 of the injector relay is 12.86 today.
12.86 from 30 to 87 key off
.11 from 85 to 86 with key off
12.46 from 85 to 86 with key on
Voltage fluctuates from 9 to 8.6 while cranking the engine
The injector ground is the other ground. The one in your picture isn't in good shape. But, fixing it won't fix the injector problem. You need to check the other one too.
Uhh you need new fuel lines............ sooner rather than later, these appear to be original.
I agree the CPS needs to be replaced not just the connector.
Kevin If this looks like it does ,then its a safe bet you also need both knock sensors and the hall sensor swapped out,
simply putting in a new connector does nothing to return the part to original spec.
there is usually corrosion inside the insulation from 28 years of use.
Those are the injector grounds. They come out of the injection harness. I did do a search and that is why I asked if there was another ground for the injector harness.
Those are the injector grounds. They come out of the injection harness. I did do a search and that is why I asked if there was another ground for the injector harness.
Ok. Your first picture didn't show the driver-side ground. The one that's in really bad shape seems too long for the p-side ground. But, if it was bolted to the pulley console on the p-side then that must be it. Your second picture shows the injector ground disconnected from the d-side of the console.
Originally Posted by Kevin in Atlanta
I am going to join the two ground wires together with a heavier gauge wire with an eyelet and run that to the ground point. Any objections?
Yes. Why wouldn't you fix what's there and return to the stock configuration of two grounds on each side of the block? Anyone that goes in after you is going to see that one of the grounds is missing and go "WTF did the PO do to me" and then have to go in deeper to see that you've combined the two.
Furthermore there may be a very, very good reason that Porsche's electrical engineers didn't want the the injector grounds mixed up with the other grounds. You might be setting yourself up for more electrical woe if you combine them. However, Alan, is the one to opine on that. Not me.
Last edited by worf928; 02-17-2015 at 12:04 AM.
Reason: damn iPad
When you put all of that stuff back together make sure that the throttle cable isn't rubbing on the LH harness or the ground. The ground needs to be bolted under the LH harness clamp or the cable may rub it. I have to wonder if that's what happened to that ground.
Last, replace that CPS now. I wouldn't be surprised if that isn't half of your no start problem. Once they get like that they can cause intermittent fuel cut-off and they can send the wrong 'speed' signal to the EZK which will result in an incorrect fuel pulse width.
When you put all of that stuff back together make sure that the throttle cable isn't rubbing on the LH harness or the ground. The ground needs to be bolted under the LH harness clamp or the cable may rub it. I have to wonder if that's what happened to that ground.
Last, replace that CPS now. I wouldn't be surprised if that isn't half of your no start problem. Once they get like that they can cause intermittent fuel cut-off and they can send the wrong 'speed' signal to the EZK which will result in an incorrect fuel pulse width.
All my previous CPS issues were connector related. I am going to try and resist becoming a parts changer. So, I am going to invest in an
All my previous CPS issues were connector related. I am going to try and resist becoming a parts changer. So, I am going to invest in ... a bunch of connector repair kits from Roger first.
There's nothing wrong with changing a part that's obviously failed. In this case it's a time vs money tradeoff. If your time is less valuable that the cost of the CPS then by all means go for it.
02-14-2015, 11:14 PM
