Honda Prelude Forum banner
1 - 20 of 39 Posts

·
Registered
Honda Prelude BA4 / 1991 / B20A5 / 5-Speed
Joined
·
15 Posts
Discussion Starter · #1 ·
Hi fellow 3rd gen enthusiasts,

after rebuilding the engine and starting the car, I realised that I couldn't turn it off by turning (or removing) the key.
As soon as I connect the battery, the dashboard lights up, main relay clicks and the fuelpump starts humming.

At first I thought it had something to do with the ignition switch, but even when I disassembled it and disconnected the plug from the fuse box, the problem persists.
I tracked down the problem to have something to do with the ACG (S) fuse.
Upon disconnecting the main relay the pump stops but the dashboard is still on.
Radio turns on normally on the ACC position and the starter works fine too.

I hope someone here is able to tell me why this happens and which cable or component is broken.
 

·
Registered
Honda Prelude BA4 / 1991 / B20A5 / 5-Speed
Joined
·
15 Posts
Discussion Starter · #3 ·
Ok so for anyone who's curious I fixed the Problem.
I've been Troubleshooting for 3 days now and after disconnecting most of the connectors and finally figuring out the wiring diagram, I was able to find the broken wires.
Inside the cable sleeve that runs around the back of the intake manifold there were two wires that connect to the alternator:
  • white/green (from battery -> fuse 37 ACG -> to alternator voltage regulator)
  • black/yellow (from IG-1 ignition cable -> fuse 12 alternator/fuel pump -> to voltage regulator.)
    Automotive fuel system Automotive tire Coil Motor vehicle Hood
They were probably damaged by the sharp edge of the cable sleeve and connected the ignition circuit directly to the battery, circumventing the ignition switch.
 

·
Registered
Joined
·
413 Posts
Bloody hell. I have been having charging system hell and recognised those bloody wires in a heartbeat!

Yes, your problem makes sense (literally lol). Sense circuit connects directly to the battery and therefore was energising your ignition circuit which is why your engine continued to run with the key off.

I just pulled apart that same loom a few nights ago and taped it up tonight, but from the alternator socket to just when the wire starts going behind the block. I did see some of the loom had frayed a little, but no puncture marks on the wires.

And thanks for following up on your post to let us know what you found. :)

Motor vehicle Engineering Electrical wiring Automotive design Space
 

·
Registered
Honda Prelude BA4 / 1991 / B20A5 / 5-Speed
Joined
·
15 Posts
Discussion Starter · #7 ·
It's a little hard to see but the loom is cut at the location, where it damaged the wire. Idk If this is normal or If the previous owner did anything to it.
I've already taped the wires inside together but the sharp edge of the loom is still visible.
Hood Motor vehicle Automotive fuel system Gas Electrical wiring

White Light Automotive tire Black Gas
 

·
Registered
Joined
·
413 Posts
Bro, that is exactly where I suspect my problem is- at the intersection of loom! I have a valve cover gasket leak and I suspect oil has got into the wire and causing resistance. This is before and after degreasing the engine wire harness at the location.

Motor vehicle Automotive tire Electrical wiring Automotive fuel system Automotive design


Motor vehicle Automotive fuel system White Light Automotive tire
 

·
Registered
Joined
·
413 Posts
How the hell did you get your engine wire harness out? Did you unbolt it? It looks like such a pain in the ass! I can't bring myself to do it because I will need to jack up the car and I can't do this because my car is parked in the street.

I am planning to take my car to Honda next week and get them to do it. Maybe you can motivate me to remove it. lol
 

·
Registered
Joined
·
413 Posts
Your problem looks like it has been manifesting over time. I noticed there is oil on your wires and it has absorbed into the outter coating. That takes time of heating up and cooling down many times over to absorb like that.
 

·
Registered
Joined
·
413 Posts
Shit man. Your wiring issue is where I had to stop untaping my loom because I cannot re-tape it back up without removing it from the engine bay.

Now am I more motivated in pulling it out myself after seeing yours. My fear is dropping a bolt because then I will need to jack up the car and take the engine splash guard off to find it.
 

·
Registered
Joined
·
413 Posts
Tomorrow I am going to shove my finger into that intersection slut and play around to see if I can feel anything unusual and get a reaction from my alternator.

If you solve my problem IronLeo, I will be sending you a gift from Australia. If you need spare parts, I will send them to you free of charge. Lots of BA4 Prelude's here. :)
 

·
Registered
Joined
·
413 Posts
I know your problem is different than mine but your experience has given me hope. Tomorrow I will pull out my engine wire harness, what ever it takes!

Thanks so much for sharing your problem! If you have any other photos or if you have any advice from your experience then please share them. :)
 

·
Registered
Honda Prelude BA4 / 1991 / B20A5 / 5-Speed
Joined
·
15 Posts
Discussion Starter · #16 ·
Ok many questions haha,
well it's hard to reach without removing alot of things, but what I did is:

- Unplug alternator and move the cable up and back above the valve cover

- Disconnect the fuel return hose above the loom

- There's one bolt kinda hard to reach holding the cables to the intake

- Unplug the cable coming from the loom to the intake

- Remove the 2 bolts at the back of the intake that hold the cables

Now you should be able to lift it up hopefully enough to get your hands in there to work on it.


Posting more photos is a little hard because you can't see very much 😅 but i'll try.

It's from may 91 with 215k km.

I'd be glad to help you if I can no need to worry.

I'll try to send some photos in a bit.

Also I wanna add, that I found the exact location in the loom by unplugging most of the connectors I could find one after one until the went away, which was this one next to the battery:
Automotive tire Motor vehicle Gas Auto part Automotive exterior

Then traced I along and wiggled it until I reached the junction and touched the cable for the oil pressure and the ignition went off again.

Maybe this helps idk.
Also taking a look at the wiring diagram helps alot.

Good luck from germany!
 

·
Registered
Joined
·
413 Posts
- There's one bolt kinda hard to reach holding the cables to the intake
I know exactly which bolt you are referring to. That son of a bitch is the reason I did not remove the engine wire harness the other night. If I drop that bolt........ I don't even want to think about it!

Thanks for ALL of your help! My problem started over 1 year ago. After 2 months I gave up. Now 1 year later I am trying again, and tonight I ran out of ideas. I was going to take my car to Honda next week. But your post has probably saved me at the last minute.

I am going to bed now, no rush on the photos. I will look at them tomorrow before I pull my engine wire harness.

I found resistance on my ignition circuit at the alternator plug last week. 0.400 voltage drop at plug, 0.034 volts at top of engine wire harness. Tonight I chopped off and replaced the alternator plug, still the same resistance at the plug, so the problem can only be in the wiring between the alternator plug and the plug that connects at the top to the side engine wire harness. I bet you I have the same problem as you. It would explain a lot. Now you see why so many questions. :) :)


Motor vehicle Automotive fuel system Electrical wiring Gas Auto part



I will let you know the outcome tomorrow tonight.

Enjoy your Saturday night!
 

·
Registered
Honda Prelude BA4 / 1991 / B20A5 / 5-Speed
Joined
·
15 Posts
Discussion Starter · #18 ·
White Light Black Motor vehicle Automotive tire

So I marked the bolt that holds the bracked, the plug and the intersection in this Image.

Yeah isn't really much more to show tbh and a better view is practically not achievable at least without removing some stuff sorry bout that.
 
1 - 20 of 39 Posts
Top