My car keeps popping the green 30a fusible link for the IGNITION SWITCH in the fusebox under the hood. I'd put this in the SR forum but it might not be SR related, I'd put it in tech but it's not really advanced.

This is a long read so I don't expect much help, but it's worth a shot. I’ve really tried helping myself as much I can, but I really need other brains thinking about it, maybe I’m missing something simple. I’m ready to set this thing on fire.

Things I have done:-I have ALL the FSM's. I probably know the wiring diagrams better than most (def. not all).-I've redone all the SR swap connections on the harness.-Traced every inch of the lower engine harness AND all the wires under the fuse box.-Ruled out the ignition switch-Ruled out my alarm system-Went to town for a few days with a DMM-Run a fresh wire straight from the IGN SW to the starter-Every ground I can find is solid-More I can’t think of at the moment

The wires I’ve boxed here:are warm/mildly hot at time of failure. I didn’t discover this until the after it died once I got it back to Gainesville. I’m not sure if the heat is a result of the amount of juice going through these, or if it’s shorting. I need to get a DMM and check it out. Can anyone tell me where these wires go? The FSM’s aren’t very explicit.

I’m thinking about cutting the power wire off the back of the ignition switch and running a new one for it (fused of course)…here’s a diagram I’ve come up with:

People have suggested the alternator is on its way out and causing this. I have a hard time believing that the alt is going bad and blowing only one of the like 20 fuses connected to it. Regardless I plan on pulling it and having it tested, however futile it may be (especially considering my problem seems to be intermittent).

So current theories are the Main Ignition power wires shown in the FRsport wiring tutorial, running a new wire for the IGN power, and the alt.

Short background:

2nd week of March she stalls on me at a light.

Tow her home, find out it's the IGN SW fuse. Put the one from the P/W in and drive it to the autoparts store to buy a new one. Pop it in, drive 5 minutes down the road, pop it again. Put in an extra I bought, drive 20 feet and pop that too.

Tow her home again. Go through the entire lower engine harness, replace the igntion switch with a brand new one which was also alarm free (ruling out both the switch and the alarm). I come to the conclusion that the inhibitor switch line is grounding somewhere so I cut it off the ignition switch and run a brand new wire straight to the starter (bypassing wherever the short is). Works! Drove it all around Clearwater and then back to Gainesville that, drove it around the next day. Third day I get in to go to work, drive 2 buildings down in my apartment complex and blow the fuse.

Now towing this time since it was walking distance from my place I just pushed it into a parking spot. Unloomed the connections in the engine bay for the SR harness and spread them out. Didn't work. Taped them all up. Still didn't work. Loomed them all back up...it worked??? Been fine for the last two is weeks after that magical fixing of itself.

Two nights ago I go for a drive to get a feel for my new clutch. Pops the fuse on me again. I picked up the magical wires just inspecting, put them down and then jumped the fuse. It was working so I put the P/W fuse in and started it up, it was running, so it was time to try to get it home. Pulled a u-turn and it blew the fuse. Played with the wires again, and it was working again, but I had no more fusible links.

Went to Walmart to get a tow strap, had to the idea to get a spade fuse terminal and crimp some disconnects on it. A box of 5 30a spade fuses costs $1.50, 1 fusible link is $3. Do the math! (besides where was I gonna find fusible links at 1am on a Friday night) Got back to the car, put my new fuse setup in and started it up. Drove it almost all the way home, and blew the fuse again. This time no amount of wire wiggling could get it working again so;

I towed it home again.

dumb suggestion since you already said you checked your whole harness, but did you look at the harness running down the drivers side fenderwell? a lot of lowered s13's ive worked on have had damage to that portion of harness. wish i could help more, ill put some thought into it.

Not a dumb suggestion. I already checked to make sure that I didn't rub through, just one of the things I forgot on the list.

you use the same gauge wire? i have this problem also with my fans and a 30amp fuse, it gets really hot and the plastic melts, blowing it. i think it's because i have a 12 gauge going to a 10 gauge, then going back to a 12 gauge. what happens is that the 10 gauge has more power in it but when it goes to a 12 gauge, not all of the power can be put into it so my ten gauge loses it through heat, which makes sense through basic math that i learned in physics and my 12gauge is considerably cooler than my 10

The gauge shouldn't change anywhere. Besides the wiring for the SR swap (which worked fine for 3 weeks) nothing has been changed.

I want to drive my car.

I had a relay go bad on my wifes honda and it blew fuses. Same thing happened on a friends volvo. Never seen it happen on a nissan before...but that is a suggestion.

Let's check the facts, my dear Holmes:

Is affecting only the 30A ignition link.Seems to react to "moving" the harness at some instances.Is intermittent.

I don't think is the Alt., Sounds like a bad connection, proved by moving the harness when the symptoms showed up. The interlock and clutch interlock relays are also part of the portion of the circuit. How were those wired after your swap?? The fusible link is reacting to an overload of high amperage, protecting the portion of the circuit after it. From the ignition switch swich, thru the interlock relays and out to the starter. There is also an important grounding point next to the interlock relays.

Look at the small FSM schematic showing the interlock relays and ignition circuits, trace and check all connections with no power going thru. Just inspect any bare wires, loose grounds,etc. If no faults, then try to recreate the symptoms again. Go for a short ride around the block,etc., When the car stops, feel around the areas already discussed for heat. It should be extremely hot along the white wires from the ign swicht all the way to the guilty party. Did you check the starter, just in case???

Sorry about the long post....

im no technical expert by no means but just going on what I mentioned about the honda and volvo.

in both of those cases we had a fuse that was blowing mulitiple times over. With the Honda, I opened the relay and it was shorting.( burned and blackened throughout with running solder.) I cleaned the relay and resoldered and it fixed the problem. In the volvo the cover of the relay melted and blew fuses. We replace the relay and the fuse and no problems after that, but both cases describe exactly what you are saying.

To smarter members than I: Is there a possibility that he is having a short somewhere in your dash harness that is effecting the flow of current through his ignition system? I have seen mis-wired stereos screw up everything with a fuse or switch in the car before and I wonder if something like that could be effecting him?

also, I have seen alternator failures start with intermittent issues, but I have never seen them spread out over the course of a few weeks without getting significantly worse.

Long post appreciated!

As far as I know those relays were left out at the 5spd swap.

I need to find out where the black and red and blue and red wires on the SR harness go.

The first time this happened, when I jumped the fusible link with a heavy gauge wire and turned the key to on, the ECCS relay buzzed and the wires on the ignition switch got so hot the plastic was melting on the white wire on the IGN SW. (It's been replaced). Also, the wire that goes to the inhibitor switch was getting hot as well, which is why I ran a new wire straight to the starter.

My car was at the tranny shop all last week, and when I got it back, it was the starter pinion gets stuck in the flywheel for a second or two before popping out...and the starter starts very weak...I didn't think it was related though?

When I the car isn't working, it'll blow the fuse as soon as I turn the car to "on". It is not working at the moment. If it's not working and I jump it, the ECU relay buzzes and I assume it'll get so hot wires will start melting again.

Inhibitor switch is used on auto, interlock is for manuals. What do you have??

I would disconnect the starter (all 3 connections) and hook the car to a good battery. Turn ignition switch on and feel for hot temps along the wire harness. Turn everything off, reconnect starter (just the + and -) and try again. Just try to isolate the starter until you feel it gets hot by having the starter in the circuit. Remembe there are 3 connections to the starter, positive, negative, and coil power. Whatever you do, don't let it get hot too long, you might have some hidden wire damage from your earlier overheating episodes....

IIRC, the Blue/Red wire is a supply wire for the coils. The Black/Red is an ignition switched power to the ECU.

The SR and KA use a similar enough wiring harness that you can trace the Black/Red routing through the wiring diagram on page EF/EC 90 in the 91-94 240SX FSM.

EDIT: Looking at the wiring diagrams, the IGN SW fuse gets its power directly from the battery and then routes to the ignition key switch. After that, it pretty much supplies power to anything in the car that requires ignition switched voltage. The ignition system, A/T Control, shift lock, and inhibitor switch are all powered off the Black/Red wire. However, the ATCU, inhibitor and shift lock are all behind a 10amp fuse. That should pop before the 30amp, so I'm thinking there's something with the ignition system. I would double check your EFI harness to make sure there isn't anything exposed and to make sure that where the black/red and blue/red wires were spliced together was done properly and didn't leave anything exposed.

perhaps a one-weekend swap was not such a hot idea? if it were me, id order a new(to you) SR harness and find a junkyard sohc harness and redo your wiring outside of the car, wire by wire, taking your time. also, consider using your single oem ign wire to trip two relays, one for each of the SR ign wires and have the feed come from the battery directly. that way, your factory wire is not strained, and the relays can distribute the brunt of the power needed... two standard bosche style relays can handle 30/40 amp loads... so 60/80 amp loads on the ign shouldnt be a prob. just an idea. also, add grounding points on your car to eliminate high resistance grounds, causing power to backfeed thru the "hot" leads....
Modified by mrgreeneyes at 12:48 AM 4/1/2008

nzmoman: I'll check the relays. I've always figured a relay either works or it doesn't.

amomao: I don't have either! As soon as I turn the switch on it blows the fuse within a second. This is why I have to jump it with a wire, in which case wires start heating up instantly, which is why I'm afraid to leave it on longer than a couple seconds. I will test the starter though!

Hijacker: I tried to trace that black and red wire in person and on paper but I'm confused. I didn't post this up the other night but since you bring it up now...I follow it off the switch, out the door jamb, under the driver's fender, in and across the rad support over to the plug behind the battery. On paper though:http://www.btyproductions.com/...3.jpgThe questionmarks are because the SR doesn't have an IGN coil and I no longer have an inhibitor switch, so I don't know where/ what was done with those wires? I see the IGN relay there, and I'd like to check that like nzmoman said...is that the same relay as the IGN coil? Makes sense since they're on the same line? RE: EFI harness, I unwrapped it all yesterday (again) and fanned it out, nothing was or is currently touching...not the prob.

mrgreeneyes: It is what it is, this thread isn't about my sob story but I'm a full time senior at UF and I work fulltime. I make due with what free time I can get. The harness was wired off the car, and I've since gone over it twice, but that's not to say there isn't something else wrong on it. I will keep your relay idea in mind.

I didn't get much done because it was raining, but once it stopped I took off the coilpack cover and....



Anyone got a coilpack harness?

The car decided to magically not blow the fuse again, so I started it up and while it was running i played with the coilpack and jiggled those wires around thinking the disconnects were arcing against each other because they are so wide they touch each other. However wiggling them did nothing more than cause the motor to stumble. What are the 3 wires...guessing by the symbols on the top...2 power and E for ECU or something?

The 10 minutes I had the car running I felt all the wires and nothing was hot. I violently giggled all the magic wires and nothing. Given the history of this problem, it could run fine for the next 2 weeks or 2 minutes. More research on the morrow!

i dont know if this is a possibility, but could a bad coilpack (one internally shorting) be the prob? does the ecu ground the packs to fire em, or does it fire 12v to them to fire? just throwing ideas out there?

Disregard my last troubleshooting steps, if the rest of your wiring was "modified" that way. You need to check all your connections, splices,etc..This would lead to believe to you have a wiring issue for sure. Make sure you don't have any bare wiring anywhere in the harness.

Oh dude. It's that hackjob crimp fitting. The wiring output on the coil pack is:- ground+ 12v supply (feeds off the 30a Ign Sw fuse)E ECU ground complete

My guess is that the 12v and ground are rubbing against each other, and it's overtaxing the 30a fuse, or backfeeding through it. The 12v supply wire gets its power from the Black/Red wire via the ignition relay. According to EC-120 & EC-121 from the S14 SR manual, the ECU acts as a ground complete (E) for the 12v supply (+), and the ground (-) is for the spark plug. I would fix the wiring ASAP instead of waiting to see if it replicates the issue again. Also, pull that spark plug to make sure it didn't receive any damage from having a constant hooked up to it.

EDIT: Here's a screen cap from the S14 SR manualI list at the bottom of the pic that b/r -> ignition relay -> Blue wire -> coil pack subharness (black/yellow). I think on the S13 SRs, they used a blue/red instead of a blue wire.

On the US side, we don't have that ignition coil relay, although there's a spot in the relay box for it. It's not necessary, but the JDM stuff is set up with it, so just a fair warning if you start referring back to JDM service manuals and are wondering "where the hell is this relay?!"

Claw, West Covina Nissan (thenismoshop.com) sells new SR coilpack harnesses for just over $61+shipping and they are a sponsor.

Coilpack harness ordered from WestCo. Gonna see what else I can find in other parts of the harness.

Thanks guys.

I still don't get why, if this is the problem which it certainly seems to be, I can reproduce it by playing with these hackjob crimps.

It's happening because the #1 power lead is grounding out with the secondary coil. Ignition coils usually work by charging up a primary coil, and then breaking that continuity causes the charge to jump to a secondary coil (the coil that's shown between the spark plug and the shared ground). The charge that jumps spikes in power to somewhere in the neighborhood of 40,000v or more. What's happening is that the power feed is charging both the primary and secondary coil, so when the ECU breaks the primary's ground, the charge jump is backfeeding into the power lead and blowing your fuse.

I'm entering this a bit late, but what year is your 240SX, or whatever it is? I have a 1991 KA24DE model, it using a single coil and a distributor, the weak link in the ignition of my car. My 1992 Ford Explorer uses a 6 coil pack, and it is still strong at 290K miles. So when did Nissan go to the 4 coil pack on the 240SX? I might want to think about a change...

New topic?

He has an SR, hence the coil on plug ignition

Clawhammer wrote:I didn't get much done because it was raining, but once it stopped I took off the coilpack cover and....

Thats not in the fsm.........your speedometer still working at least?

Intermittently. It was intermittent before the SR swap. I put in a new VSS and a new speedo...still intermittent. After the swap it didn't work at all until I plugged it in right, now it's back to intermittent haha.

Sounds like a loose wire somewhere along the way. Check all the plugs that associate with the speedo for corrossion or loose connectors.

Did you do the swap yourself or pay someone to do it?

Hijacker's right, also if you had a broken wire in the lower harness what does that say about the rest of the wireing that came with the swap, where did you get the motorset anyway?

A local schlub, and we did the swap together in his driveway at night. I didn't pay a lot for the swap, but I'm paying for it now, I guess it all evens out.

The speedo has been intermittent for the last 5 years or so (according to the original owner of the car). Apparently this intermittent speedo is a problem with many cars. When I first got the car I searched everywhere for this, I'm come to terms with it lol. It does still bother me though.
Modified by Clawhammer at 1:13 AM 4/2/2008

Clawhammer wrote:A local schlub, and we did the swap together in his driveway at night. I didn't pay a lot for the swap, but I'm paying for it now, I guess it all evens out.

The speedo has been intermittent for the last 5 years or so (according to the original owner of the car). Apparently this intermittent speedo is a problem with many cars. When I first got the car I searched everywhere for this, I'm come to terms with it lol. It does still bother me though.

Modified by Clawhammer at 1:13 AM 4/2/2008

Hmm...never had the speedo problem, hope I never do. It's okay, I paid a lot for my swap, and I still have issues, but I don't want the shop that did it to mess up my car anymore, so I'm dealing with in stages. I'll have to send my harnesses to wiringspecialties to clean up/repair it (I hate auto wiring), or get a new harness and then send that one to them to mod for the swap (did I mention I hate auto wiring?). GL with everything.

Hijacker wrote:It's happening because the #1 power lead is grounding out with the secondary coil. Ignition coils usually work by charging up a primary coil, and then breaking that continuity causes the charge to jump to a secondary coil (the coil that's shown between the spark plug and the shared ground). The charge that jumps spikes in power to somewhere in the neighborhood of 40,000v or more. What's happening is that the power feed is charging both the primary and secondary coil, so when the ECU breaks the primary's ground, the charge jump is backfeeding into the power lead and blowing your fuse.

Exactly...power is been shorted back to ground, kind of reversing leads on a battery and getting sparks...Definetely the culprit here...

homeslicej2 wrote:Hmm...never had the speedo problem, hope I never do. It's okay, I paid a lot for my swap, and I still have issues, but I don't want the shop that did it to mess up my car anymore, so I'm dealing with in stages. I'll have to send my harnesses to wiringspecialties to clean up/repair it (I hate auto wiring), or get a new harness and then send that one to them to mod for the swap (did I mention I hate auto wiring?). GL with everything.

On an S13, auto wiring isn't that bad. It's a totally different story on an S14 though >_<