Fuel Pump Fuse Blows intermittently - Chevy Impala SS Forum
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Old 05-25-2012, 12:04 PM
TimG TimG is offline
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Default Fuel Pump Fuse Blows intermittently

Hi all,

I am having a weird problem with my car and it has me and the people at the Auto Electric Shop stumped, I could really use some ideas.
My car seems to blow the fuel pump fuse intermittently. When it does blow, I am pretty sure it does it when I shut the car off. This is after I have driven it several miles so it is warmed up. After it blows, usually I would just put a new fuse in it and it would start right back up.

The other day it blew 4 in a row after i stopped for gas, so I had it towed to the shop. They did not get to it right away and the next day when they put a new fuse in it and it was running fine again. They cannot seem to get the fuse to blow for them. They say they have checked all the wiring and it looks fine. WE have replaced the pump and filter, and it has a new gm sending unit in it that is less than a year old. I have also replaced the Fuel pump relay, and it made no difference.

I initially suspected a few pump or filter because when driving up to Oregon on the freeway, it would kind of stutter when i was doing 65-70 like it was losing fuel for a second. Though for most of the trip it was fine. I believe now it was just a precursor to the fuse blowing.

Anyone have any ideas on what else it could possibly be? Could the PCM cause this problem? I notice in my Factory service manual, that its on the same fuse.

I have been without my car for mostly 2 weeks now, and I just want to get the problem solved and on the road again.

Thanks for your help,

Tim
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Old 05-25-2012, 05:07 PM
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4DoorSS 4DoorSS is offline
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Intermitent problems can be difficult to troubleshoot. If I had to guess, I would lean toward the Fuel Pump and/or the Sending unit wiring. Both of which are in the tank and you will need to drop the tank to get to them.

There is a thread here for "refubishing your sending unit. It will walk you thru the process and would be the first place I would be trying to fix.
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Old 05-25-2012, 05:29 PM
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anytime a fuse blows, you usually have a short(unwanted path) to ground meaning that more current than that circuit is designed for is coming across that fuse. A mechanical resistance on the load(pump) part of the circuit can do the same thing. The ecu cant do it because its on the ground side.All it does is provide a path to ground I would check wiring form the realy back to the pump and sending unit and check voltage at the realy first . You should have 12 volts at pin 30. Look at wire size,corrosion, loose contacts. Too big of a gauge of wire will draw more amps. Make sure the wires arent contacting metal some how. (A screw through the ground wire, a pinch in the wire to the frame.If you have an ohm meter take a resistance measurement at the fuse while its cold and then when it blows another fuse take another one while its hot. The reading shouldnt change. If it goes up when its hot, I would start with all connections from there back. You may just have a loose connection at the pump or sending unit. If you drop the tank, take an ohms reading across the pump. I dont remember what the spec is but im sure you can find it here. If its above that spec then your pumps going bad.
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Old 05-25-2012, 05:34 PM
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As stated above, suspect the in-tank harness. Did they replace that when the pump and sender was done?
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Old 05-25-2012, 05:56 PM
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Here is the thread to refurbish the sending unit and wires.
http://www.impalassforum.com/vBullet...h+sending+unit

I know from experience what it's like to have to drop the tank twice in 1 week due to faulty wiring . We thought it was the pump and later discovered a bad ground wire on the bulkhead harness in the tank.

Of course all of your basic Ohm's Law stuff applies to current, voltage and resistance with the wiring/circuit. So use a DVM to check all the wiring from the Fuse panel back. Another thing to try and maybe narrow this down....hopefully you can get it to continually blow fuses and try this... Back behind the Rear bumper is the 3 wire plug that goes into the tank. This is the connection for the in tank harness. If the fuse keeps blowing, unplug that connection and then see if the fuse blows, if not, then I would bet that the problem is either FP and/or the sending unit. Hope you figure this out. You don't want to get stranded like I did 500 miles from home.
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'95 Caprice SS conversion - Bonny Buckets - 96 Column, Shifter and Console - 3.73 Gear and Herter tune - Z/28 Cluster - Blazer OH Console - Green/Pink bushings - Chromed Impala Wheels - Eibach Springs and Bilstein Shocks - Corvette Engine Dress - the list goes on and still more to do...it never ends.
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