Post Reply 
Thread Rating:
  • 0 Votes - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
1999 Elantra blowing ECU fusible link...
11-02-2013, 09:26 AM
Post: #1
1999 Elantra blowing ECU fusible link...
I have a 99 Elantra sedan with about 120,000 miles on it. 2.0 liter engine and automatic transmission. I live in central Maine, USA.

Here's what happened - the car started to overheat and my Daughter thought she could get back to the house before 'anything bad happened'... She was 10 miles away.

Needless to say, she didn't make it. When I went and looked at the car, the first obvious issue was the upper radiator hose, well what was left of it, and the ECU fuse (the fusible link under the hood) was blown. Towed the car to the house, replaced the hose and fuse. Tried to start it and got a 'whirring' sound from the starter and the ECU fuse blew.
I replaced the starter and the fuse and when trying to start, get the 'click' from the starter and the fuse blows. After some advice from a friend, I checked all of the wires under the hood and didn't find any bad or improperly grounded wires and the black ground wire from the battery was screwed on to the frame. When I got to the alternator, the connection wires were bare (someone had obviously tried to rig it). I taped the bare ends of the wires that lead to the alternator (it's disconnected that way, right?), turn the key, click, blown fuse.
Pulled the ECU from under the dash and it looked like new. Left the ECU disconnected, turn the key, click, blown fuse.
Someone told me to check the blower motor, so I pulled that and wired it directly to the battery and it worked fine. I replaced the blower motor resistor while I was under there, reconnected the blower motor, turn the key, blown fuse.
I pulled the spark plugs. They were rusted on the business end and it took quite an effort to get them out. Tried to start and... you know.
So, as of now, the alternator and computer are disconnected and the spark plugs are out.
The radio, dash lights, dome light, head lights, tail lights, cigarette lighter, and power windows and locks work fine.
I'm at my wits end. I can't afford another car (disabled veteran pension amount prevents that from happening) and at 3 bucks a pop, the fuse bill may bankrupt me Sad

I'm putting new plugs in later today and I got a new connector to fix the alternator problem.

While typing this, I realized that I never tried to start without the blower motor disconnected, so I'll try that today too.

If anyone has any suggestions, I'd be very appreciative Smile

Find all posts by this user
Quote this message in a reply
11-02-2013, 11:13 AM
Post: #2
RE: 1999 Elantra blowing ECU fusible link...
I think that I would physically follow the the wire from the blown fuse to each end. Look at the color of the wire and the tracer on it to ensure that you are following the correct wire. If it is blowing the fuse instantly it has to be going to a dead short. Somewhere along the line you will likely find that it has rubbed through or got up against the exhaust and burnt through and is touching a ground. If the wire isn’t touching ground the component that is at the end of the wire is likely shorted out.

If you need to keep testing, temporarily wire a Circuit Breaker in where the fuse that keeps blowing is now located. You can pick one up for a couple of dollars at any parts store. Once you find and repair the problem you can put the proper fuse back in its place.

Please let us know what you find &/or stop back for more advice.

Thanks for using the forum,

Interested in Mining? Look here: Coal Mining, PA
Visit this user's website Find all posts by this user
Quote this message in a reply
11-02-2013, 11:33 AM (This post was last modified: 11-02-2013 11:35 AM by Rupe.)
Post: #3
RE: 1999 Elantra blowing ECU fusible link...
You say the ECU fuse blows when you try to crank the engine so presuming this is one of those small plastic fuses that's about 15 or 20 amps that's probably the circuit you need to look at.

Now, I am not an expert on Hyundai but knowing a bit about fuel injection systems there's lots of things they all have in common: When you crank the engine the fuel pump is triggered to run at the same time as the starter so the system is primed with gas. That puts us at the idea where you can disconnect the fuel pump relay and the small wire at the starter to see if the fuse stays intact. If so then reconnect the fuel pump and see what happens. Turn the key to crank and you should hear the pump run with the starter disconnected. If the fuse is still ok then you need to follow up on the starter circuit. My hunch is that if you don't find a burned up wire going to one of these then the fuel pump itself is due for replacement, especially if it's on the same fuse and it takes several seconds for that fuse to blow. IOW, a direct short will blow the fuse right away but a high draw (read: tired) pump will take a bit longer.

Try doing the diagnosis with all of the accessories turned off. It will help to lower the confusion level.

The other thing to consider here is a series of issues. IOW, the over heating may have lead to her pulling off the road, in which case she drove over something and damaged wiring or the fuel tank in the process. Obviously you need to get it started to make sure you have the coolant issue resolved but what I am getting at is to not let one problem cloud your thoughts on fixing the other even if they are related in the long run.

Oh, also make sure the battery is fully charged. A weak battery can have the best of us pulling our hair when trying to sort out electrical situations.

Let us know if this helps.

(edited to say: I got up for another cup of coffee and Garner beat me to the punch line)
Find all posts by this user
Quote this message in a reply
11-08-2013, 10:25 AM
Post: #4
RE: 1999 Elantra blowing ECU fusible link...
Thanks for the info everyone Smile I've been down with the flu so I haven't looked at this for a while. Weather permitting, I'll get out there today. (You know what they say about the weather in New England).

The ECU fuse that's blowing is the fusible link in the relay box under the hood.

The wiring for the fuel pump is inside the car, the pump is actually in the fuel tank, which is under the back seat.

I checked all of the wiring to the fuel pump and it all looked ok. I was wondering - IF it IS the fuel pump that is causing the short, would pulling the fuel pump relay from under the dash effectively remove that system and the potential problem. (If I pull the relay and the problem stops, can I assume that the relay and/or fuel pump IS the problem?) I want to not mess with the fuel tank unless it's absolutely necessary.
Find all posts by this user
Quote this message in a reply
11-08-2013, 11:03 AM
Post: #5
RE: 1999 Elantra blowing ECU fusible link...
Now you are thinking logically! (and we have a better picture)

Yes by all means, pull that relay and any related fuses. The engine will not start but you need to go through the motions with the key to verify the fuse is not blowing. If you can remove the back seat and find the plug leading to the fuel pump at the tank you can disconnect that too. It's going to be a process of elimination as you either pull things out of the circuit or add them back in to see where the problem is. I have seen interior wiring damaged (pinched, burned) under the carpet from seat bolts, seatbelt bolts, and overheated exhaust, or chaffed due to major rust. If you can follow that harness route to the rear and inspect it the full length that's another path to consider.

I like Graner's suggestion of using a temporary circuit breaker. For a few bucks you can have a 25 amp breaker and use some clip leads to tie it in. It's one of those tools I keep in my box that I don't use often but when you need it you need it.

Hint: The old timers taught me a trick where you can use an inductive amp meter or even a toy compass to follow the wire to the short. Just put it near the wire in question then activate the circuit. The needle will swing each time the breaker makes / breaks. Move slowly along the harness and when you pass the short the needle will swing in the other direction so you back up. This is the cat's ass for locating a short in a big bundle of wires or under a carpet. Once you narrow it down within a few inches you know where to inspect closer and solve the mystery.
Find all posts by this user
Quote this message in a reply
12-20-2013, 11:18 AM
Post: #6
RE: 1999 Elantra blowing ECU fusible link...
OK, I'm back ;/ It's been like 4 degrees here, and snowing, so I put this to bed for a while.

Thank you all for the great info Smile

I disconnected the fuel pump and pulled the fuel pump relay and had no luck. (I tried with just the pump dc'd, both dc'd, and just the relay dc'd).

Last night, it was pitch black outside so I had my son go out with me in hopes of maybe seeing a spark or hearing something when the key is turned. We tried a few times but (still) all I get is a click (starter) and the link blows. (haven't gotten to the store for a circuit breaker yet). On the last attempt, I told my son to try another link. Turned the key and got the click. (btw - my neighbor loaned me his battery boost machine during all this). So, we're looking in the engine compartment and about 2 minutes later, smoke. There's a wire harness running along the fuel injector rail and off of that is a connection to a sensor that goes into the top of the engine. That burned. I disconnected the battery and went to change the link again. My son had put a 50amp in instead of 20amp (couldn't see because of the dark).

I'll get a breaker today.

Anyway, is there any chance this might be caused by the fuel filter clogged or broken, etc...?
Find all posts by this user
Quote this message in a reply
12-20-2013, 12:01 PM
Post: #7
RE: 1999 Elantra blowing ECU fusible link...
A clogged fuel filter will not blow a fuse but a bound up fuel pump might, which is why we covered disconnecting it at the tank. That would give you a clue as to a pump issue or a harness problem.

Now, just so we don't change the focus let's jump back to basics for a moment. What's blowing out is a fuse link and not a fuse, correct? A fuse link will be feeding either several smaller circuits (and going through smaller fuses) or feeding a heavy draw circuit like the alternator "big" wire (for battery charging) or similar. ABS controllers also fall into this category. It would be nice if we had a wiring diagram or at least a list of what was connected to this fuse link. OTOH, because of the overheating problem I am still leaning toward a chaffed harness or maybe something that's too close to the exhaust manifold and heat damaged. This is just a gut feeling based on years of experience.

Now, since you have "smoked" a wire I would focus on that first. I would open up that harness to do repairs and leave it open as a temporary measure while you see if it helps the problem at hand. You just never know if the smoke was a sign of your original problem.
Find all posts by this user
Quote this message in a reply
12-20-2013, 12:28 PM
Post: #8
RE: 1999 Elantra blowing ECU fusible link...
This is what's blowing - it's in the relay box near the battery. The diagram on the box top says 'ECU' for that spot:

[Image: th?id=H.4745231414920616&w=144&;pid=1.7]

OK, I'll fix the smoked wiring. Then I'll get back to the basics and go over the entire harness again, focusing on the areas near the exhaust manifold.

Thanks Smile
Find all posts by this user
Quote this message in a reply
01-21-2014, 12:22 PM
Post: #9
RE: 1999 Elantra blowing ECU fusible link...
OK, the temp outside got up to -zero- so I looked at the wire harness that is near the exhaust manifold.

I can't find any wires that look bare, broken, melted or anything like that. I found a rubber hood/boot and risked removing it and looking at what is under it. It's an upstream O2 sensor. The sensor looks to be in great shape, but the connector is a different story. I'm adding a picture of the connector. Would this type of thing cause the symptoms that I have? If we don't get Polar Vortex'd today, I'll go out and look around some more Smile

[Image: car11.jpg]

The picture isn't very clear, but the connector is pretty much all white, inside and out. The hood/boot thing is coated on the inside with white stuff.

Also, when I went to replace the wire that smoked (turned out to be the camshaft position sensor wire), the sensor broke. Half is still in the engine block. I was told to drill a hole, insert a screw, and pull it out. Will that work?

Thanks Smile
Find all posts by this user
Quote this message in a reply
01-21-2014, 12:37 PM
Post: #10
RE: 1999 Elantra blowing ECU fusible link...
Yeah, the crank sensor is usually held in place with a single screw / bolt so the only other thing holding it will be an o-ring. Guessing a small hole with a well placed sheet metal screw might give you enough to grab on so it can be yanked out. Don't drill too deep. Would guess a half inch or so should be enough to stay out of trouble.

On the O2 sensor the white stuff is a special grease to ward off rotten connections. (dried out with heat) The heater circuit in that sensor is only a few amps tops normally so a rather small wire. (#14 - #16?) If it smoked then the sensor or the wire has a direct (to ground) short. The heater circuit also feeds the other O2 sensors, so look around at those too. That short could have fried the ECM with the big fuse. Time will tell.
Find all posts by this user
Quote this message in a reply
Post Reply 

Forum Jump:

User(s) browsing this thread: 1 Guest(s)