3.9L EFI V8 - Cranking with No Start

[94Disco1]

Ryan McGowan <mcgowanryanj@gmail.com>	Tue, Mar 9, 8:26 PM (18 hours ago)
to me

Hello - some of you may recognize this question from another forum where I've not had any responses. I was recommended by a friend to give this one a try.

I've got a crank but no start situation on my 1994 Discovery 1 V8. The condition first started after a few hours of off-roading. The engine sputtered and died then would not restart.

My initial thought was a bad distributor/amplifier so I replaced both. When I buttoned everything back up and had continued no start I noticed I was not getting +12v to the coil when the ignition was in position 2. The fuel pump is also not getting energized. Neither the fuel pump or main ignition relay are getting power.

I have checked all of my grounds in the footwells and have also replaced both the fuel pump and main ignition relays. I have also bypassed my alarm system in the hopes it was somehow preventing start. Although it is now bypassed I have since learned that a malfunctioning alarm on 1994-1995 D1s will prevent cranking altogether so that wasn't the issue for me. Also replaced the inertia switch but that is only controlling fuel of course.

Upon conducting the RAVE ECU testing procedures I have found that Pin 19 of the ECU is not getting energized. This pin is supposed to be energized directly by the key/ignition switch in position 2. I replaced the key/ignition switch and can confirm I do have +12v coming out of the ignition switch.

According to the simplified diagram in the ECU testing procedures, when Pin 19 is not being energized when ignition is "on", the problem lies in the wiring between the ignition switch and Pin 19. I'm having a hell of a time locating the path wiring takes between those two places...

I can see the wires leaving the ignition. The +12v in position 2 wire connects to a thick green wire that disappears behind the dash. After cutting away plastic insulation in the footwell I cannot find that same green wire. The wire feeding Pin 19 of the ECU looks to disappear with the rest of the ECU wiring into the firewall behind the engine. All look good from the portions I can see. Somewhere that Pin 19 wire should join another wire feeding the positive side of the coil I think.

Has anyone ever chased this particular wire and if so any clue the path it takes?

Of course if you have other ideas those are very much welcome. I read some questionable content that suggested the alternator has something to do with energizing the main relay and pin 19, but that is unconfirmed. I did replace the alternator ~6months ago which is what piqued my interest.

Thanks in advance!

 

[Spark6]

Ah, man... my heart goes out to you on this one. I don't think our experience likely will help you much, as I think the 14CUX is a pretty different beast to the GEMS system we have in ours, but we wrestled a ECM gremlin for what felt like forever. No fun.

That said, do you have continuity between the ignition switch and the connector on the ECU?

 

[FatMcNasty]

Did you by chance check the main fuse box by the battery? Are all the fuses good?

 

[94Disco1]

Hi - posted the resolution to my issue here. Basically water ingress at the relays burned out my F3 fuse in the fascia fusebox. Changed the fuse once and it must have blown again right after preventing ignition. New relays + new fuse = fired right up. Also included a pedestrian diagram for no start conditions in the post. https://landroverforums.com/forum/discovery-i-39/crank-no-start-94-disco-104402/'
Thanks FatMcNasty for your (solo) response to this one!

 

[FatMcNasty]

Its always the fuse!!! LOL

 

[Rocky]

Water is your enemy. Lost an ECU to water....

 

[DiscoClay]

Ryan McGowan <mcgowanryanj@gmail.com>	Tue, Mar 9, 8:26 PM (18 hours ago)
to me

Hello - some of you may recognize this question from another forum where I've not had any responses. I was recommended by a friend to give this one a try.

I've got a crank but no start situation on my 1994 Discovery 1 V8. The condition first started after a few hours of off-roading. The engine sputtered and died then would not restart.

My initial thought was a bad distributor/amplifier so I replaced both. When I buttoned everything back up and had continued no start I noticed I was not getting +12v to the coil when the ignition was in position 2. The fuel pump is also not getting energized. Neither the fuel pump or main ignition relay are getting power.

I have checked all of my grounds in the footwells and have also replaced both the fuel pump and main ignition relays. I have also bypassed my alarm system in the hopes it was somehow preventing start. Although it is now bypassed I have since learned that a malfunctioning alarm on 1994-1995 D1s will prevent cranking altogether so that wasn't the issue for me. Also replaced the inertia switch but that is only controlling fuel of course.

Upon conducting the RAVE ECU testing procedures I have found that Pin 19 of the ECU is not getting energized. This pin is supposed to be energized directly by the key/ignition switch in position 2. I replaced the key/ignition switch and can confirm I do have +12v coming out of the ignition switch.

According to the simplified diagram in the ECU testing procedures, when Pin 19 is not being energized when ignition is "on", the problem lies in the wiring between the ignition switch and Pin 19. I'm having a hell of a time locating the path wiring takes between those two places...

I can see the wires leaving the ignition. The +12v in position 2 wire connects to a thick green wire that disappears behind the dash. After cutting away plastic insulation in the footwell I cannot find that same green wire. The wire feeding Pin 19 of the ECU looks to disappear with the rest of the ECU wiring into the firewall behind the engine. All look good from the portions I can see. Somewhere that Pin 19 wire should join another wire feeding the positive side of the coil I think.

Has anyone ever chased this particular wire and if so any clue the path it takes?

Of course if you have other ideas those are very much welcome. I read some questionable content that suggested the alternator has something to do with energizing the main relay and pin 19, but that is unconfirmed. I did replace the alternator ~6months ago which is what piqued my interest.

Thanks in advance!

I believe [*qualifier necessary because of how long its been since this issue] I had the same problem and it turned out to be a melted **O2 Sensor** wiring harness: the O2 sensor is powered with the same circuit as the fuel [or main] relay... and when the O2 sensor loom/harness came to rest against the exhaust pipe just upstream of the catalytic converter on the port side ("Left hand side" for those who've not "gone nautical" with their Rover).. this shorted out the circuit and killed everything. It took me a while to figure that out.

If you resolved this... let us know what you found the problem to be )

* Note: I am leaving this up.. just in case it is useful for someone else. I finished reading the thread and saw that you'd posted the solution. I actually think that fuse popped in my case as well.. and kept popping.. until I found that short