Danlerb

86porsche · 04-14-2008, 02:44 PM

Im back to you with this problem again. just wanted ask you a few more questions on my dash lights and no start.

First can you tell me if you know what the (F) connection on the fuse board energizes. iv found it supplies the mirrors but what else does it control if you know as i might be able help me track my issue. specifically im wanting to know what the yellow wire on this connection does?

secondly, I have found that when I disconnected my LH brain (with the ignition on) and plugged it back in again, it started to run my fuel pump for a few seconds. I could here the LH relay click when i just twiddled around with the connection of the brain.( I know i shouldn't have probably done this but hope i didnt damage the ecu) anyway i went to start the car and it ran for a few seconds. seemed to just use up the gas i gave it but then died. I can jump the fuel pump relay and hear the pump run but she will not start this way. could it be i have a bad earth that i have not found that could link these two problems? or do you think my ecu is toast?

Danglerb · 04-14-2008, 11:18 PM

I'm nothing like an expert, I just try to fill in while some of the guys that really know this stuff are having their cape dry cleaned.

Looking in the workshop manual diagram 97-251 that shows connections to the central electric panel I see 8 fused circuits (6 to 13) on what appears to be a buss 15. Starting at fuse 6;

Lamps keyboard light switches time delayed relay interior lights.
Seat Heater
AC system
empty
Instrument lights
rear wiper
backup lamp, mirror adjustment.
Aux AC system.

F14 goes to about a 20 pin connector with all the stuff in the door going through it. The only yellow wire I notice goes to the central locking (motor).

***********

Messing with the LH without unplugging the battery is risky, and I don't think what happens for a few seconds afterward tells us much. The sequence of power being removed, and reapplied vs signals, power down modes, and power up modes, too many variables.

I'll try and look over the early threads and see if I think of anything.

Alan in AZ · 04-15-2008, 08:22 AM

Your ECU will be toast if you keep doing that... stop!

If you can't figure out good diagnostic methods - take it to a shop - if you blow up your ECU its going to get really expensive really fast.

If the ECU is operational and it sounds like it still is then it isn't keeping the fuel pump running for a good reason. It either thinks the engine isn't running or that the EZK isn't generating spark.

On initial cranking you get fuel - but you don't get more if the engine doesn't start...

If the ECU's dont detect the engine rotating the fuel pump won't continute to run. If for any reason the EZK isn't generating spark the LH will not activate the injectors and will stop the pump - this is so you don't pump raw fuel into the exhaust.

The first places to look are the inductive rpm sensor (crank sensor) - without an rpm signal from this the car will not run...

Alan

86porsche · 04-15-2008, 02:44 PM

Thanks for the reply guys.

if it is my crank sensor then how do i check this? can i remove it from the bell-housing? is there any other checks i can do to determine what the problem might be? I'm not able to swap the ecu`s with anyone here as these cars are very rare in Ireland and i don't think many auto-electricians would have worked on one, but someone has been round the electrics of this car before as many wires are spliced and it had an I'mmobilizer which is now disconnected! so I'm abit on my own and still only learning about the car and its a real pain not to have it going as i would get over everything else.

I just want to let ye know that i do have spark when i crank her, iv tried today to jump the ezk and LH between 30-87 but no start! should i also jump the fuel pump when doing this or could i flood her? what can cause the ecu to fail? i have never jump-started the car. how much would it be to replace and where they used on any other car so i could try and find a used one? thanks again for yer patience.

Alan in AZ · 04-15-2008, 03:03 PM

Do you have access to an oscilloscope? I'm guessing its a long shot... this is the best way to test the crank sensor.

Since it seems you have spark - verify you have spark on both banks - they have seperate drivers.

if you are generating spark on both banks - the crank sensor should be OK - validate you are getting injector pulses - do you have a noid light? or can you get access to a listening device for the fuel injectors (to verify if they click).

Alan

86porsche · 04-16-2008, 02:13 PM

No i dont have a oscilloscope unfortunately. I could get a device to listen to the injectors alright. i got a feeling they are not been activated as well as my pump but i do have spark at both distributers. shouldnt my plugs be wet if the injectors are running? could anything else cause the no start?MAF?

I heard you where the one to ask about electrics! so could these be linked in anyway to the ecu? relay EZF continues to get power at pin 86 even when i switch off at the ignition, so my dash lights and and everything else remains ON!e.g everything on the C.E to windows ect. except the radio, until i either pull the relay or pull connector W,F, or the the second connector on the fuse board which has everything from the switch going to it. both these problems accured around the same time which leads me to think they are linked.what you think?

Danglerb · 04-16-2008, 07:42 PM

Rubber hose works for listening to the injectors, they click loudly when working.

Noid light you might actually be able to see from inside the car with the hood up.

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=310041713669

Alan in AZ · 09:20 AM

Do you have an alarm - did you bypass it recently - how?

When this happens try jiggling the ignition key (switch between ignition - off a few times...?)

The EZF relay getting power on pin 86 alone will not cause your light to stay on - there is more...

Test CE plug pin B23 when the key is out what voltage do you see?

Alan

86porsche · 04-17-2008, 12:34 PM

OK thanks for that link Danglerb, I will see if i can buy one of them here locally.

Just on the ignition switch Alan, I have bought a new switch. I can actually pull the switch of the electrics at the back and dash lights stay on. its not just my lights either but iv power to everything on the C.E board. relay xvi is keeping everything on when it switches over to pin 87 and wont switch off unless I pull it or disconnect the negative of the battery or the other connectors as iv explained.

This might be a stupid question, but where is connection B23? I have connectors on the bottom of the fuse board from A-W. On connector B I have ten wires. one side is blue the other side black with five wires on each side labeled 1-5. this connector controls my starter motor and two black wires from the ignition out, the others I don't know. I get 12v at these black wires when I switch on the ignition and continue to get 12v when I switch it off both at connector B and at the back of the switch. I have tried everything to fix this problem but don't understand whats causing it. any other ideas would be greatly appreciated as I don't want to loose faith!

Danglerb · 04-17-2008, 01:03 PM

B23 means B connector, second column, third wire, should be small diameter Black with Red stripe and goes to the Alarm system separating plug pin 4.

You just need one Noid light, any that work with Bosch or Ford etc should be fine.

Alan in AZ · 04-17-2008, 01:26 PM

Try pulling the rear defroster relay (double) and see if it makes any difference.

Alan

86porsche · 04-17-2008, 01:45 PM

Ok il have a look for that wire tomorrow. I have pulled the rear defroster relay and everyother relay and problem is still there. I forgot to mention that the cars alarm/immobilizer has been cut out of it. i found it with all four black wires cut which had been done before I got the car and when she was running. this would explain why i have spliced wires on the back of the C.E that were i presume were connected to this at one point. Im not sure if this was the original alarm. Im at a loss as to what has caused this as there is nothing obvious that I can find. I know its hard for ye to diagnose with little info but il do my best to to check anything ye suggest.cheers

Normy · 04-19-2008, 03:26 PM

Quote:

Originally Posted by 86porsche

secondly, I have found that when I disconnected my LH brain (with the ignition on) and plugged it back in again, it started to run my fuel pump for a few seconds.

Uhmm...wait a second. Let me get this straight: Did you really disconnect your LH box while the battery was connected and all the busses were powered?

I've always heard that that was a VERY bad idea-

N?