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Fuel Pump Relay Fuse Keeps Blowing!!!!

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Old 12-06-2010, 08:38 PM   #1
VistaGT
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Default Fuel Pump Relay Fuse Keeps Blowing!!!!

Hey all,

I need some help. I've installed my blower (Roush M90) and upon trying an initial startup the car cranks but won't start. I checked the fuse and low and behold the fuel pump relay fuse is busted. I put in a new fuse, go to start it, same deal. Obviously the car keeps blowing that fuse

What am I doing wrong here?

Any ideas????

Thanks!
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Old 12-06-2010, 09:42 PM   #2
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Maybe a stupid question but are you sure the right size fuse is going in? Was there any electrical work done to the fuel pump/car at the time of install?
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Old 12-07-2010, 06:29 AM   #3
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yes. 15amp. I did some wiring on the car (I thibk roush piggybacks the IC pump to the fuel pump) maybe I didn't wire it perfectly and there's a short? The IC pump works fine
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Old 12-07-2010, 06:13 PM   #4
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No one has any ideas/input? Rechecked the fuel pressure regulator plug, still blowing the fuse. Could a bad fuel pump blow the fuel pump relay fuse???
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Old 12-07-2010, 06:43 PM   #5
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Did you check your wiring? I find it suspect you did some wiring in regards to the fuel pump and suddenly it's blowing a fuse.
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Old 12-07-2010, 08:17 PM   #6
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did you by chance use the wrong harness plug into the pressure reg? its the same has the one on the Tbody
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Old 12-07-2010, 08:39 PM   #7
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Ditto on the wiring, I'd double check and go through the wiring plugs/harnesses once around again. If you're fuse is blowing up, it could mean a "dead short" in your fuel pump relay wiring somewhere. I doubt that though, unless you really whacked out on your wiring somehow..
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Old 12-08-2010, 08:05 AM   #8
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I don't think I swapped it with the TB wiring. Both the TB wires have the red tabs don't they? If its this fuse consistently blowing I can assume it has to be an issue with a wire from the fuel pressure regulator plug, correct? At this point I guess its a short so tonight ill take apart the entire engine wiring harness and trace those wires to check for cuts in the insulation or bends/pinching. Of this wire did short that section must be replaced right?
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Old 12-08-2010, 09:20 AM   #9
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Quote:
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I don't think I swapped it with the TB wiring. Both the TB wires have the red tabs don't they? If its this fuse consistently blowing I can assume it has to be an issue with a wire from the fuel pressure regulator plug, correct? At this point I guess its a short so tonight ill take apart the entire engine wiring harness and trace those wires to check for cuts in the insulation or bends/pinching. Of this wire did short that section must be replaced right?
If it's actually shorting due to bare wire, yeah. You could just cut it where it's bare (if that is indeed the issue), use heat-shrink tubing to insulate it again, solder back together with a portable soldering iron. Still be a bit thin though, depending on how warm things get where it is and the actual current draw on it.

So long as the fuse is blowing right away there shouldn't be an further Chernobyl action (melted wire)to need to replace the whole line.
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Old 12-08-2010, 09:47 AM   #10
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shouldn't there be a current limiting resistor somewhere in the fuel pump relay circuitry somewhere? if it's blowing fuses, would that mean that the short to ground is after the source of voltage and not before (fuel relay plug), or am I seeing things incorrectly??
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Old 12-08-2010, 10:33 AM   #11
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If all else fails, make sure you didn't accidently strip one of the wires when you were cutting the tape off the factory harness. This is of coars if you used a razor blade to cut the tape. If you stripped the coating off two of the wires the connection could be causing a fuse to blow.
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Old 12-08-2010, 11:28 AM   #12
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I think that would depend on whether or not the relay does have some sort of resistor that limits current. If not, I think the short could be anywhere along the line. Someone correct me if I am wrong. You could start checking the OHMs readings along the power lines to the fuel pump and see where you get some major resistance.
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Old 12-08-2010, 12:08 PM   #13
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If there truly is a short, you should get near 0 ohms as the reading between the hot line and ground, otherwise as stated you could just be looking at something trying to suck too much juice due to either increased resistance or something using that line past it´s rating.
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Old 12-08-2010, 01:08 PM   #14
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I did use a razor blade and perhaps did cut some insulation. This is what I'm going to check for....this and possible pinching. Is a short going to be obvious with dark brown or black on the insulation? At one spot I saw what looked like discoloration but nothing big and I can't be sure. How would I use a volt-meter to check for shorts? Sorry I'm better with the mechanical stuff and not as electric savvy....

Thanks!
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Old 12-08-2010, 01:17 PM   #15
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Yes I'm going to check if I cut a wire BC I did use a razor blade. I'm checking for this and possible crimps. Now would a short be obvious with a brown or black color? I saw some discoloration on one wore but nothing major and idk if its anything.

Also would a volt meter help? How would I use it? Forgive my ignorance but I'm better with mechanical stuff and not as good with electric...

Thanks!

BTW I asked this before: could a bad fuel pump be shorting the fuse? I know that would be highly coincidental but I'm trying to cover the bases here
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Old 12-08-2010, 01:20 PM   #16
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Assuming this is a short to ground, touching the frame or whatever, just set the digital multimeter to resistance measurement. And if it has it, which most newer ones do, put it on audible tone for short. Verify just by touching the 2 multimeter leads together, should hear the beeping, and should show as 0ohms on the meter.

Then just touch somewhere along the line that you believe to be shorted before where it's now lost the circuit in the fuse-box and a good ground point on the frame. It shows near 0, and/or beeps, then that's the prob bob.

Assuming this is the case, you could then just temporarily tape the leads down if you don't have alligator clips handy (or use the gf to hold 'em which they love), while you fiddle around trying to find where it's actually shorted. If the fuel pump itself is the issue, just remove the hot lead to verify.
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Old 12-08-2010, 03:51 PM   #17
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A multimeter can be invaluable in finding electrical problems. You may also notice heat in the wire around the area of the short, but you'd have to be a little lucky to touch the right spot in the area of the short before the lines cool off.
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Old 12-08-2010, 04:12 PM   #18
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A multimeter can be invaluable in finding electrical problems. You may also notice heat in the wire around the area of the short, but you'd have to be a little lucky to touch the right spot in the area of the short before the lines cool off.

I hope to god he can't verify it this way. After knowing you have an issue after blowing more than 1 fuse you should never hook power back up until you can at least try to solve it. Unless your intentionally trying to start a BBQ pit in your car.
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Old 12-13-2010, 08:10 AM   #19
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Okay. So. Lol

I opened the wiring harness, checked the wires - they all looked good nothing obvious. I checked all the plugs and made sure the pins were okay. I used a multimeter AND a test light....NO short????

Turned on the key. BAM fuel pump turns on. Try it a few times and it keeps working and fuse is not blown. Also checked relay it looks ok. So I retaped the whole harness, reassembled the car and it fired up no problem. Ran well and fuse is still good.

So, should I be worried??????
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Old 12-13-2010, 09:15 AM   #20
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So, should I be worried??????
probably not, but just be mentally prepared to call a tow truck sometime
late at night, when you are far from home.
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Old 12-13-2010, 09:15 AM
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01, 2004, blowing, cobra, ford, fuel, fuse, fuses, heat, mach, poping, pump, relay, short, testing

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