problem with blown fuse 24 civic 93

[gummer]

Hi everybody, it has been a long time since I used to be active on the forum but today I have some problem with the fuse #24.

Last night I passed over a little bump and the car shut down, so I towed the car to my house, today in the morning I checked the fuses and only fuse 24 was blown, I raplaced it and it blows when I turn on the ignition switch, so I checked the under dash wires, I simply moved them, replaced the fuse and the car starts again.

Two hours ago I used the car and again on a bump it turned off, I have checked continuity between the two fuse terminals, it has continuity only on the bottom terminal even when the ignition is off, also I removed the main relay and the fuse doesn't blow, but as I connect the relay the fuse blows, I think there's some short circuit between the main relay and the fuel pump, but I don't know how to diagnose it, or where to start looking.

Could you guide me on the right way?? am I right with the short circuit??

 

[AlaskaB16]

Certainly sounds like you have a short to ground some place. Have you done any recent mods, installed anything new, moved anything?? Been in a hard rain storm perhaps or spilled anything?

 

[gummer]

Certainly sounds like you have a short to ground some place. Have you done any recent mods, installed anything new, moved anything?? Been in a hard rain storm perhaps or spilled anything?

No, that's the most strange

 

[gummer]

Update

I disconnected the main relay and checked continuity on each pin against body ground, there was continuity on pin 2 and pin 7, pin 2 is the main relay ground, but pin 7 goes to the fuel pump, I disconnected directly from the fuel pump, and now there's no short even on the fuel pump connector nor on the main relay connector.

What could it be??? Should I change the entire wire from main relay to pump???

 

[AlaskaB16]

If you have both ends disconnected and it doesn't show ground, you're good. When you have the fuel pump connected, you're reading to ground at the pump. Verify that your pump itself isn't bad and that it's installed correctly. Remember, when looking for wire continuity, you will get false readings if you don't have both ends disconnected (Or every end that's associated with that wire). Often times when you think you've found a short by shooting one end of the wire, you're actually seeing case ground and running a wild goose chase.

I'm an electrical engineer so this is what I do for a living. Fix wiring problems. If you are dead set on a wire being bad and you want an easy way to verify, rather than replace everything and go through all that hassle, just connect a jumper wire and string it along the ground or through your car some place. Make it easy on yourself. Don't change anything until you are 100% sure that's the problem. Too many times I see mechanics that aren't strong electricians just change parts willy nilly because they don't know how to verify the problem.

 

[gummer]

Another update

I have disconnected both ends as you said and there's no short, so the problem is with the pump, it never been replaced since I bought the car 5years ago, the curious thing is that it failed with the jump of the bumps then worked again and then failed again with a bump, is there some way to check the pump? Does it have some internal circuit to check?

 

[AlaskaB16]

Yes, you can check the pump. Apply 12 v direct power and ground. Most people will bring the battery to it, or take it out and hook it to their battery... Or what ever 12v source you have. It's a pretty easy test. I'm not convinced your problem is your pump but it's hard to troubleshoot online (though I do it weekly with my mechanics out in the field trying to fix our helo's before I have to fly their myself to fix it). If you're blowing fuses when you hit the ignition, that means something is grounding out (as you know). It's unlikely (but not impossible) that your fuel pump magically broke a wire loose internally and is now touching case ground. You said you moved the wires around under the dash and fuse stayed correct? Try putting in another fuse, shake those wires by hand and see if the fuse blows again. If so, your short is likely under the dash some place.

Let me check my diagram (I have a 94 coupe). Fuse #24? That under the dash? I'll note some things for you to try if you haven't already found it by then.

 

[AlaskaB16]

As I see it, 24 sends power directly to the fuel pump after the relay contact is closed by way of fuse 18 and 31. My diagram isn't detailed enough to tell me what pins to check, but I see the wire colors. Pin 7 as you said, must be yel/grn correct? With the fuel pump disconnected, you should have NO continuity on that yell/green wire. Look inside the connector at the pump. Does it look like it's shorting in any way? Any loose wires or something stuck inside? Do the fuel pump test as mentioned above.

If that doesn't work. Your relay may be bad which is harder (but not impossible) to test as well. Let me know if you need my help. I'm more than happy to. Good luck!

 

[gummer]

I have checked the fuel pump directly on the connector and there is continuity from both pins to chassis ground, one is supposed to be ground and the other is the signal from the main relay, so I suppose the power wire inside the pump is short circuited.

Is there a way to open the pump?
Do I have to get the pump out of the gas tank?

 

[AlaskaB16]

You will need to remove the pump most likely. check it for bad wiring. Not sure if you can internaly repair it though. Give it a shot. Maybe you'll see the short when you get it out.

 

[Just a honda!!]

My budies fuel pump was going out and it was blowing fuses we replaced the pump and it works fine now just sayin


Sent from tapataalllkk

 

[gummer]

Sorry for long time with out news, but I have had a lot of work, but finally last weekend was able to continue diagnosing the problem.

I didn't find anything, the short seemed to be on the fuel pump, but I connected 12 volts directly and it worked alright, I was irked so I put everything back together, insulated all the lines and harnesses with electric tape, cranked the engine and it started like nothing had happened, no more blown fuse!!!

I don't know what was the problem but it seems to be fixed, I think it has a short on some wire and was fixed with the tape.

Anyway thank you for your help "AlaskaB16" and "Just a honda!!"