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Electrical Short Inside Fuel Tank?!?!? eek 

 

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 Post subject: Electrical Short Inside Fuel Tank?!?!? eek
Posted: Fri Apr 29, 2005 12:52 am 
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Ive had thisw problem for a while, and before I go buy a new cradle for the fuel pump, thought Id post it up.
Ive got an EBII wagon, pre smartlock.
Ive gone through(trying) about 5 fuel pumps, all a pain in the a** to replace (and a waste of fuel)... but Im not worried about those, I didn't pay for them.

Now the problem is, my car has a massive flat spot until 2 grand.. and I mean no power what-so-ever, and as soon as 2 grand hits, BANG! whiplash. Ok so after trying alot of fuel pumps, I decided its not the problem, checked the fuel pump relay, um.. holder melted, and relay not working ATM, have to switch it manually.. pain in the a**. :roll:

Here's the big thing, Ive got continuity between the potitive and the ground for the fuel pump power, maybe normaly, doesn't matter fuel pumps aren't great resistance. But the resistance in my other fuel pumps is around the 3-4 ohm mark. The resistance with everything in there on the fuel pump power wires from the boot to the fuel pump measure 1 ohm, just over. Is it really possible to have a short through fuel? I took it out, checked it, no wires touching... its really frustrating... bceause my fuel pump is running at 1.5V!!!!! instead of 12.3V!!!(on idle). the car runs lean as s**t (AFR meter doesn't even show anything until 2 grand).

Sorry for the big post, but its really bugging me.. and so far costing me very bad performance, and lots of time wasteage..


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Posted: Fri Apr 29, 2005 3:46 am 
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When you find melted relays, that can end up being a real big problem.
Sometimes you can also find you have melted wires inside your loom and melted connecters elsewhere.
Also note that when you get melted wires, that's a good indication that the connectors have also overheated and lost their spring tension (making poor contact) which causes lots of intermittant problems.

If you have a wiring diagram for your car, i recommend you study it before checking out your wiring. Even better if your wiring diagram also shows the looms and connectors as some manuals do :)

The way check wiring is to disconnect the battery and check both wires in a circuit for continuity and earth faults. I also check for shorts from the circuit wires to other wires in the loom it passes through.
Pay particular attension to plugs and if they are discolored check the tension of each female connector.

In your case specifically, disconnect the fuel pump connector.
Check for a 12V feed and a good earth.
If you have 1.5V available at the pump, as you have said, i would suggest the problem is in your loom and not the pump itself.
Since the relay is melted, look in the loom from the relay towards the battery for faults.

Whatever you do, never solve fuse blowouts by fitting a bigger fuse, this will just cause bigger problems later.

Failing all that, take the car to an autoelec.

Good luck.
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Posted: Fri Apr 29, 2005 10:05 am 
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the looms have been checked and are ok. I think the relay was melted due to the fuel pump stopping, and drawing obnoxious amounts of power. (no back emf), the looms are fine, and I get a good healthy 12.3 or so volts just before the connector for the pump. The relay issue will be fixed as soon as this one is.

I checked and cleaned the connector for the fuel pump loom, and the wires leading into the fuel tank seem all fine? I guess I'll just buy a new cradle for the fuel pump.

Oh and Ive studied that wiring diagram long and hard. its not the first time Ive had problems with wiring/electronics. I had to check and replace alot of it when I put my battery around the wrong way

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Posted: Fri Apr 29, 2005 11:18 am 
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If you haven't already, you could try your checks with the system running - replace your fuel pump relay so you can check the entire system in std configuration. Earth out the top far right terminal of the diagnosis connector, and turn on the ign - the system will run continously. Then you can test voltages, touch the relay and pump area to see how hot it gets, etc. Good opportunity to also test for correct fuel pressure. You can substitute pumps without removing the original by hooking them up to the output connector - if they need to be immersed in fluid, you could do that too with a separate container - be careful of spillage,etc.

 

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Posted: Fri Apr 29, 2005 5:32 pm 
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yeah, will do.

Cheers for the help! Ill let you know what happened.


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