Vacuum repair- No engine start now
10-19-2013, 03:09 PM
#46
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Hey Tom -
It sounds like you've narrowed it to an electrical failure that's keeping the injector signal from reaching the injector.
If you look at John's drawings on the first page of this (post #15) the LH pinout shows the injector signal coming off pin 13. I don't know for *certain* this is the signal that ends up on the two injector harnesses? If so I'd check to see if you're getting signal here first? If so you may have nailed it to the harnesses themselves vs. the LH.
Good sleuthing so far! Whatever the problem is, you're very close.
Good luck,
It sounds like you've narrowed it to an electrical failure that's keeping the injector signal from reaching the injector.
If you look at John's drawings on the first page of this (post #15) the LH pinout shows the injector signal coming off pin 13. I don't know for *certain* this is the signal that ends up on the two injector harnesses? If so I'd check to see if you're getting signal here first? If so you may have nailed it to the harnesses themselves vs. the LH.
Good sleuthing so far! Whatever the problem is, you're very close.
Good luck,
10-19-2013, 03:50 PM
#47
Rennlist Member
The injectors at 16 ohms each are all wired in parallel so with 7 of them plugged in to the harness, and measuring between the terminals of the missing one, you would expect about 2 ohms.
You must have the 25way connector unplugged from the LH ECU to make any meaningful measurements between the injector harness pins and ground. Red/white wire should be open circuit to ground and zero ohms to pin 13 LH 25way.
Brown wire should be open circuit to ground and zero ohms to the output of the fuel pump relay.
Did you measure a.c volts at the pin 1 of the LH ECU plug ? You should get 3-4v when cranking.
You must have the 25way connector unplugged from the LH ECU to make any meaningful measurements between the injector harness pins and ground. Red/white wire should be open circuit to ground and zero ohms to pin 13 LH 25way.
Brown wire should be open circuit to ground and zero ohms to the output of the fuel pump relay.
Did you measure a.c volts at the pin 1 of the LH ECU plug ? You should get 3-4v when cranking.
10-19-2013, 04:38 PM
#48
Burning Brakes
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Tom, you said you had 2.8 ohms terminal to terminal on the harness? This matches John's "about 2" and my calcs of 2.2. Can we infer then that the harness itself is good? Maybe John would clarify?
10-19-2013, 05:14 PM
#49
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Yes, that is correct..... harness is OK if if passes the other tests I suggested.
10-19-2013, 06:21 PM
#50
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10-20-2013, 02:26 AM
#51
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Sorry for the belated input. Glad to hear that due to the ohms measured, the harness appears intact.
I did the jumpering to ground from the LH and had continuity.
This would lead to two things I believe of I have understood everything:
Either the LH has failed as the fuel pump does not run and there is no ignition pulse to injectors
Or, the low A/C voltage on crank from the CPS is affecting the LH which in turn, cascades to ignition.
But why do I have a spark? Isn't that tied in to the CPS as well?
Could I test the CPS at the local connection to see if there is A/C there on crank?
Thanks for the concern and help!
I did the jumpering to ground from the LH and had continuity.
This would lead to two things I believe of I have understood everything:
Either the LH has failed as the fuel pump does not run and there is no ignition pulse to injectors
Or, the low A/C voltage on crank from the CPS is affecting the LH which in turn, cascades to ignition.
But why do I have a spark? Isn't that tied in to the CPS as well?
Could I test the CPS at the local connection to see if there is A/C there on crank?
Thanks for the concern and help!
10-20-2013, 06:13 AM
#52
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Yes, thinking about it again, the fuel pump and aux air valve are still connected to the red/white side and those represents a low resistance to ground. If you remove the FP fuse the low resistance to ground should vanish...
It is possible the EZ-F isn't working properly, they can often fail to synchronise to the gap in the timing ring teeth. THis gives an erratic improperly timed spark...
You checked there wasn't a relay in the kickdown relay slot, didn't you ?
It is possible the EZ-F isn't working properly, they can often fail to synchronise to the gap in the timing ring teeth. THis gives an erratic improperly timed spark...
You checked there wasn't a relay in the kickdown relay slot, didn't you ?
10-20-2013, 12:05 PM
#53
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No kickdown relay installed in XV.
I do not like throwing parts on the car hoping that it "might" fix it. But I am going to get a new CPS and see if that changes anything. The back of its harness is cracked, but I have good contact and ac volts measured impulses on the 25 pin connector...
I wonder, how would the Porsche Dealer fix this? What is their trouble shooting fault tree look like?
I do not like throwing parts on the car hoping that it "might" fix it. But I am going to get a new CPS and see if that changes anything. The back of its harness is cracked, but I have good contact and ac volts measured impulses on the 25 pin connector...
I wonder, how would the Porsche Dealer fix this? What is their trouble shooting fault tree look like?
10-20-2013, 01:11 PM
#54
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Thanks for that - I was pretty sure you said you had checked.
It seems rather unlikely the CPS is faulty. If anything my money would be on EZ-F failure.
Is there anyone who can loan you one, or supply on a sale or return basis - 928Intl ?
It seems rather unlikely the CPS is faulty. If anything my money would be on EZ-F failure.
Is there anyone who can loan you one, or supply on a sale or return basis - 928Intl ?
10-20-2013, 01:37 PM
#55
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I'm out of town at the moment and won't be back till late tomorrow, but I have an Innovate LM2 and a bridge and the analog in/out cable to connect it between the 25 pin harness and the EZF or LH. I don't know that it will give you any answers but may give you opportunity to gather a little data which may be useful. I can lend it to you for a bit if you like. I wouldn't be able to ship it out till Tuesday at the earliest though. If interested just let me know.
10-20-2013, 03:43 PM
#56
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Hey Tom -
I may have compatible electronics on my 85 parts car that I know are good, at least they when I last started the car about a month ago. If someone can give me an overview of how to remove them I can loan them to you for a few weeks, I have the intake manifold and injectors out of it now and it will be down while the manifold gets re-powdercoated. Let me know if you're interested (and can tell me how to get it out
I may have compatible electronics on my 85 parts car that I know are good, at least they when I last started the car about a month ago. If someone can give me an overview of how to remove them I can loan them to you for a few weeks, I have the intake manifold and injectors out of it now and it will be down while the manifold gets re-powdercoated. Let me know if you're interested (and can tell me how to get it out
10-21-2013, 02:38 PM
#57
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Simon, Pm and Email sent...
Scott, thanks for the offer, hopefully the Innovate can crack this issue open and pinpoint the deficiency. If not, i most certainly would appreciate all the help
V/R
TMcD
Scott, thanks for the offer, hopefully the Innovate can crack this issue open and pinpoint the deficiency. If not, i most certainly would appreciate all the help
V/R
TMcD
10-30-2013, 08:47 AM
#58
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Car engine repairs
As far as your listed problems you need to go on to get professional help. Hopefully there is no engine repair required as the no start up condition refers to some kind of other problem. With periodic maintenance of vehicles checking their oil and fluid level we can avoid whole lot of car engine repairs. Timely maintenance is the key to a trouble free driving.
link deleted, G
link deleted, G
