1989 porsche 928 no start
02-14-2010, 09:44 PM
#107
Team Owner
the lettered connections indicate the connectors along the bottom of the CE panel.
Once you pull off the connector look at its face and you will also the numbers of the wires.
Pull out and Slide the locking tab to the left to unlock the connectors
Once you pull off the connector look at its face and you will also the numbers of the wires.
Pull out and Slide the locking tab to the left to unlock the connectors
02-15-2010, 12:16 AM
#108
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Just to be 100% sure I will be doing Dr. Bob's steps correctly please verify this.I will plug W connector back in, both lh ecu and ignition ecu, and connect battery.I will unplug the U connector and stick the red wire from the multimeter into #12 hole (assuming this whole exists) and the black to the ground. Now if the results are says it reaches battery terminal voltage I then plug back in the U connector, unplug the W connector and start testing the W connector?
02-15-2010, 12:28 AM
#109
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Mr. merlin after reading your post a couple more times I am asumming you just look at the numbers and plug the u & w connectors back in, then from the back of the connectors I will inset the multi meter pin to get voltage.
02-15-2010, 08:31 AM
#110
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If you have the Morehouse CD compilation set we all keep talking about, there is a section of supplemental documents about the electrical system that takes the mystery out. Roger has them I think.
You are probably beyond this point, but just to keep the plug naming conventions straight:
You are probably beyond this point, but just to keep the plug naming conventions straight:
02-15-2010, 10:10 AM
#111
Team Owner
thanks for posting this connector picture
02-15-2010, 10:47 AM
#112
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The plugs start at the left end with "A" and go up - there is no "I" plug. They are identified.
The connections on the plug are:
15 25
14 24
13 23
12 22
11 21
You can connect to the circuit from the outside of the plug if you have a thin probe.
Always check the wire colors to ensure that you are on the correct plug and circuit.
The connections on the plug are:
15 25
14 24
13 23
12 22
11 21
You can connect to the circuit from the outside of the plug if you have a thin probe.
Always check the wire colors to ensure that you are on the correct plug and circuit.
02-15-2010, 01:12 PM
#114
Chronic Tool Dropper
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Just to be 100% sure I will be doing Dr. Bob's steps correctly please verify this.I will plug W connector back in, both lh ecu and ignition ecu, and connect battery.I will unplug the U connector and stick the red wire from the multimeter into #12 hole (assuming this whole exists) and the black to the ground. Now if the results are says it reaches battery terminal voltage I then plug back in the U connector, unplug the W connector and start testing the W connector?
02-15-2010, 10:14 PM
#116
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02-15-2010, 10:36 PM
#117
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You will be reading DC volts, so the switch should be in exactly the position shown in the Amazon illustration. The display in the picture is showing mV (millivolts). Since this meter autoranges, you'll be looking for a V or the word 'Volts' on the display when you are testing a circuit. Battery voltage will be in the 12.3 to 12.7 range so look for that reading as you test.
03-01-2010, 08:23 PM
#118
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https://rennlist.com/forums/928-foru...o-start-3.html
I'm having the same no start problem that you went through with 88porsche 928 and am looking at this diagnostic procedure that you identified for him. in post 43.
I have 2 ohms from LH 18 to ground, so I assume there is a short. I'm trying to track that down now. In step 2 you indicate LH connector 18 to relay socket 1A, which relay are you talking about?
Later you refer to "protection relay", which relay are you refering to?
By the way, this is on an 87 if that makes a difference.
Thanks
Rod
I'm having the same no start problem that you went through with 88porsche 928 and am looking at this diagnostic procedure that you identified for him. in post 43.
I have 2 ohms from LH 18 to ground, so I assume there is a short. I'm trying to track that down now. In step 2 you indicate LH connector 18 to relay socket 1A, which relay are you talking about?
Later you refer to "protection relay", which relay are you refering to?
By the way, this is on an 87 if that makes a difference.
Thanks
Rod
The meter tests I shared are extremely definitive when diagnosing harness problems on '89+ cars. Did you find a short in the harness, an open circuit, or a short to ground? If not, it's possible to create new problems while 'fixing' the old harness, where no problems existed before.
Test procedure simplified:
-- With the ignition protection relay out:
A1) Ohms between LH connector 18 and relay socket terminal 1A should be about 4 ohms. Much more means an open in a connector, injector coil, or a broken conductor in the harness.
A2) Ohms between LH connector 18 and relay socket terminal 1A (same test...) should be about 4 ohms. Less than 2 ohm means you have an internal short between conductors in the harness. This is the damage you reported when cutting open that first connector boot.
B1) Ohms between LH connector 18 and relay socket terminal 1B should be about 4 ohms. Much more means an open in a connector, injector coil, or a broken conductor in the harness.
B2) Ohms between LH connector 18 and relay socket terminal 1B (same test...) should be about 4 ohms. Less than 2 ohm means you have an internal short between conductors in the harness. This is the damage you reported when cutting open that first connector boot.
C) Ohms between LH connector 18 and ground should be infinite. If they are less than 1 ohm, you have a short to ground on the LH side of the harness, and it could be at any injector.
D) Ohms between LH connector 18 and ground should be infinite. If they are around 4 ohms, you have a short to ground on the power side of the harness, and it could be at any injector. Proceed to E1 and E2 to narrow down where it might be.
-- E1) Ohms between protection relay socket at 1A and ground should be infinite. If they are less than 1 ohm, you have a short to ground on the power side of the harness, and it could be at injector 2, 3, 5, or 8.
-- E2) Ohms between protection relay socket at 1B and ground should be infinite. If they are less than 1 ohm, you have a short to ground on the power side of the harness, and it could be at injector 1, 4, 6, or 7.
*** Do these tests BEFORE you remove any of the injector connectors. The resistance values presume that you still have all the injectors plugged in. Each injector coil is real close to 16 ohms. Two coils connected is about 8 ohms, 3 connected is a little over 5 ohms, four connected is 4 ohms. On the '89, the harness is separated on the power side and is fed through those two contacts on the protection relay; with the relay removed they are connected only on the ground (LH brain) side, and to the brain through LH terminal 18. With that protection relay installed, the power sides are connected to each other through the relay contacts, and also to the heating coil on the oxygen sensor, even when the LH power relay is not energized.
PLEASE POST WHAT YOU FIND WITH YOUR METER.
--
Test procedure simplified:
-- With the ignition protection relay out:
A1) Ohms between LH connector 18 and relay socket terminal 1A should be about 4 ohms. Much more means an open in a connector, injector coil, or a broken conductor in the harness.
A2) Ohms between LH connector 18 and relay socket terminal 1A (same test...) should be about 4 ohms. Less than 2 ohm means you have an internal short between conductors in the harness. This is the damage you reported when cutting open that first connector boot.
B1) Ohms between LH connector 18 and relay socket terminal 1B should be about 4 ohms. Much more means an open in a connector, injector coil, or a broken conductor in the harness.
B2) Ohms between LH connector 18 and relay socket terminal 1B (same test...) should be about 4 ohms. Less than 2 ohm means you have an internal short between conductors in the harness. This is the damage you reported when cutting open that first connector boot.
C) Ohms between LH connector 18 and ground should be infinite. If they are less than 1 ohm, you have a short to ground on the LH side of the harness, and it could be at any injector.
D) Ohms between LH connector 18 and ground should be infinite. If they are around 4 ohms, you have a short to ground on the power side of the harness, and it could be at any injector. Proceed to E1 and E2 to narrow down where it might be.
-- E1) Ohms between protection relay socket at 1A and ground should be infinite. If they are less than 1 ohm, you have a short to ground on the power side of the harness, and it could be at injector 2, 3, 5, or 8.
-- E2) Ohms between protection relay socket at 1B and ground should be infinite. If they are less than 1 ohm, you have a short to ground on the power side of the harness, and it could be at injector 1, 4, 6, or 7.
*** Do these tests BEFORE you remove any of the injector connectors. The resistance values presume that you still have all the injectors plugged in. Each injector coil is real close to 16 ohms. Two coils connected is about 8 ohms, 3 connected is a little over 5 ohms, four connected is 4 ohms. On the '89, the harness is separated on the power side and is fed through those two contacts on the protection relay; with the relay removed they are connected only on the ground (LH brain) side, and to the brain through LH terminal 18. With that protection relay installed, the power sides are connected to each other through the relay contacts, and also to the heating coil on the oxygen sensor, even when the LH power relay is not energized.
PLEASE POST WHAT YOU FIND WITH YOUR METER.
--
03-02-2010, 12:18 AM
#119
Chronic Tool Dropper
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Rod--
This is a parallel response to ypur PM'd questions:
Rod--
The protection relay is in cars '89 and newer, reads a couple thermocouples in the exhaust and disable one bank of injectors when there's a temp difference big enough to indicate ignition failure on one distributor/coil of the other. Your signtuare dosn't have any '89+ cars in it, so I'll ASSume that you are working on an earlier car. If that's a valid assumption, continue with me a bit.
The impedance (same as resistance for the static testing) of each injector is about 16 ohms. In your car, you have eight in parallel. ASSuming that they are all the same impedance, we can use a simple 16/8formula to determine the parallel resistance as 2 ohms. If you are reading 2 ohms between LH connector pin 18 to ground, you have something carrying current to ground on the power side.of the circuit. To isolate the power side from all possible loads, remove the EZK connector to eliminate the EZK brain as a possible load, and next connectors U and W from the bottom of the CE panel.CE if there's still a path to ground.
For the '89+ cars, removing the ignition monitoring/protection relay does the first-level isolation. The goal is to see no continuity between the harness and ground where you are now seeing that 2 ohms.
It's probably easiert to understand what you are looking at if you have page 10 of the wiring diagrams for your year, opened in front of you as you troubleshoot.
This is a parallel response to ypur PM'd questions:
Rod--
The protection relay is in cars '89 and newer, reads a couple thermocouples in the exhaust and disable one bank of injectors when there's a temp difference big enough to indicate ignition failure on one distributor/coil of the other. Your signtuare dosn't have any '89+ cars in it, so I'll ASSume that you are working on an earlier car. If that's a valid assumption, continue with me a bit.
The impedance (same as resistance for the static testing) of each injector is about 16 ohms. In your car, you have eight in parallel. ASSuming that they are all the same impedance, we can use a simple 16/8formula to determine the parallel resistance as 2 ohms. If you are reading 2 ohms between LH connector pin 18 to ground, you have something carrying current to ground on the power side.of the circuit. To isolate the power side from all possible loads, remove the EZK connector to eliminate the EZK brain as a possible load, and next connectors U and W from the bottom of the CE panel.CE if there's still a path to ground.
For the '89+ cars, removing the ignition monitoring/protection relay does the first-level isolation. The goal is to see no continuity between the harness and ground where you are now seeing that 2 ohms.
It's probably easiert to understand what you are looking at if you have page 10 of the wiring diagrams for your year, opened in front of you as you troubleshoot.
03-02-2010, 08:37 PM
#120
Rennlist Member
Unplugged U and W on the CE and pin 18 still showed ground with the EZK and LH unplugged.
Tested injector wiring:
Cylinder No.1,2,3,4,5 all indicated 5 ohms of resistance - continuity between pins, 6 indicated 7.5 ohms resistance - continuity between pins, 7 indicated 15 ohms of resistance - continuity between pins and no. 8 showed no resistance and no continuity between pins.
We took the insulation off No. 8 and the wires on the other side showed no continuity.
Doc., Does this help?
Any narrowing it down or is it just stripping off the outer cover until we find the point. It looks like a failure and two partial failures likely at the same point?
Rod
Tested injector wiring:
Cylinder No.1,2,3,4,5 all indicated 5 ohms of resistance - continuity between pins, 6 indicated 7.5 ohms resistance - continuity between pins, 7 indicated 15 ohms of resistance - continuity between pins and no. 8 showed no resistance and no continuity between pins.
We took the insulation off No. 8 and the wires on the other side showed no continuity.
Doc., Does this help?
Any narrowing it down or is it just stripping off the outer cover until we find the point. It looks like a failure and two partial failures likely at the same point?
Rod
Last edited by Rod Underwood; 03-02-2010 at 10:42 PM.