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by Bruce M
Sat Apr 27, 2024 3:40 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

Each injector is typically under 20 ohms which is low enough to get a “beep”, plus 3 in parallel is 1/3 of the resistance of one.
by Bruce M
Sat Apr 27, 2024 12:11 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

Sorry, should have added that’s with the 3 injectors disconnected from their plugs on that bank. Each injector is electrically a simple coil.
by Bruce M
Sat Apr 27, 2024 11:09 am
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

With the ECU plug disconnected, there shouldn’t be continuity between the injector plug pins.

The ECU injector driver probably links the injector signal wire to 12v via a resistor when not firing the injector (a “pull up” resistor) and a semiconductor will sink it to ground when the injector is open.
by Bruce M
Fri Apr 26, 2024 7:46 am
Forum: Pre 1974 - Porsche 911 (longhood)
Topic: Assessing an unknown engine
Replies: 101
Views: 3848

Re: Assessing an unknown engine

Perhaps you’ll need to drill or cut the piston to get access to the rod bolts, ideally without damaging the rod?
by Bruce M
Thu Apr 25, 2024 8:36 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

Pin10 is an input so nothing wrong there, alas.
by Bruce M
Thu Apr 25, 2024 6:03 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

One idea (a stretch). The ecu has a number of earth pins. These may be linked internally within the ECU or may be a “star” earth design where each earth pin has a separate function and they are all linked at one place (as per the wiring diagram, outside the ECU). This prevents earth loops / noise. I...
by Bruce M
Thu Apr 25, 2024 5:34 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

Is Canems a 1-man-band?
Internet suggests he is good & helpful but hard to get hold of. I know I’d have the case open & oscilloscope probes out to trace back the signal, but that’s not for everyone.
by Bruce M
Wed Apr 24, 2024 9:48 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

If you can establish serial comms with the ECU the microcontroller “brain” is not 100% fried. It may have lost the two output channels used for the injection pulses but perhaps just the high current semiconductors that amplify the microcontroller output. It should be repairable, in that situation.
by Bruce M
Mon Apr 22, 2024 11:51 am
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

OK I’ve tried that now I first did the tests on the DME relay and they seem to be working fine - pin 87 is charged up with 12 volts. Then I went to do your test on the injector plug. Tested the first pin and got 12 volts. tested the second pin and got 12 volts again! Not sure what that means. I tri...
by Bruce M
Mon Apr 22, 2024 8:36 am
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

Bit of info on the relay. It has two stages. Stage 1 powers the injectors with 12V plus a couple of other components (idle valve etc). Stage 1 is controlled by a 12v feed from the alarm. Stage 1 output also provides the 12V power to stage 2 solenoid which is activated by an earth side switch by the ...
by Bruce M
Mon Apr 22, 2024 7:41 am
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

Wiring diagram is useful. Injectors work by a continuous 12v feed and a ground side switch by the ECU. The connector you mentioned, is for the injectors. Pins 1 & 2 are the solid 12V feed, via a common point marked [2] on the diagram, being fed from pin 87 on the master relay. Pins 5 & 6 on ...
by Bruce M
Sun Apr 21, 2024 4:56 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

sladey wrote: The gearbox was earthed properly so I would think the starter would have earthed through that
Doh. When you said the earth wasn’t connected I assumed you meant the main earth strap.
Ignore me. [emoji2359]
by Bruce M
Sun Apr 21, 2024 2:27 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

There is a chance you’ve fried a small earth wire (sensor earth or similar) as the starter motor earth would have taken any possible return path. Haltech recommend earthing the ECU & all related components to the engine block for this reason. So there is no alternative path back to the battery,...
by Bruce M
Sun Apr 21, 2024 1:24 pm
Forum: Porsche Restoration Threads
Topic: 1987 3.2 Carrera Backdate project - Sladeys hotrod
Replies: 2448
Views: 257334

Re: 1987 3.2 Carrera Backdate project - Sladeys hotrod

There is a chance you’ve fried a small earth wire (sensor earth or similar) as the starter motor earth would have taken any possible return path. Haltech recommend earthing the ECU & all related components to the engine block for this reason. So there is no alternative path back to the battery, ...
by Bruce M
Fri Apr 19, 2024 9:20 am
Forum: Pre 1974 - Porsche 911 (longhood)
Topic: Assessing an unknown engine
Replies: 101
Views: 3848

Re: Assessing an unknown engine

If there is a chance Loctite has been used, heat up the big nut to release it. I’ve broken big sockets in the past when they should have been okay because loctite red made a big torque into a ridiculous torque, so i play it safe & warm the nut/bolt.