Strange Fuel Pump Fuse Problem - Defender Source
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  #1  
Old October 10th, 2004, 08:52 PM
mhill
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Mike Hill
95 D90 ST / 91 RRC Hunter
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Strange Fuel Pump Fuse Problem

I've been having an issue where my fuel pump fuse blows at highway speeds randomly . The pump is less than a year old. I am thinking it may be a tank pressure problem over electrical as the vents at the top of the tank were seaping gas when sloshing around on trails. I dropped the tank and checked for blockage in these lines but to no help. I have noticed that there is no whoosh pressure release sound when opening the gas cap after the fuse blows. Is it possible the pump is over worked if the tank isn't holding pressure??
Any ideas are appreciated.

-Mike Hill

95 D90 ST
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  #2  
Old October 11th, 2004, 12:20 AM
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Robert Dassler
1994 D90
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Mike,
What size fuse is blowing? If I remember correctly, in 1995, some trucks were built with 5 amp fuses instead of the required 7.5 amp fuse and there was an update campaign that included a new fuse and corrective stickers for the fuse box and owners manual. The fuses would blow at random.
Rob
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  #3  
Old October 11th, 2004, 01:08 AM
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jim pendleton
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I saw a similar problem at the National Rally a couple years back. The guy had about a half dozen shops look at the problem before and on the way to the rally. I had to tow him back to the hotel twice. When we had time to look at it that night I pulled his entire injection harness out. My friend Geoff saw the metal fuel injection relay spark against the intake manifold. ding ding ding

Check that the metal fuel injection and system relay have not been crushed and the outer case is shorting to the internal contacts. In the aforementioned case they were shoved tight behind the AC evaporator case.

Also the wiring back to the fuel pump is not the correct gauge in my opinion. You may consider rewiring from the fuel pump up to the fuse box. And check your ground circuit first. Check the voltage back at the pump against battery voltage and look for voltage drop in the circuit.

Good luck
JP
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  #4  
Old October 11th, 2004, 08:02 AM
mhill
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Mike Hill
95 D90 ST / 91 RRC Hunter
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Rob-It's a 7.5 amp fuse that's been blowing.

Pendy- I'll check those specific areas. I figured that this is one of those obscure problems that can be hell to track down the culprit.

Thanks guys for the info - Mike
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  #5  
Old October 11th, 2004, 05:54 PM
BarryO
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Barry O'Mahony
97 D-90 SW LE
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I'm very familar with fuel pump fuse problems. 'took along time to diagnose mine.

Pull the fuse and put an ammeter in its place. Check the current draw when you first turn on the ignition (the fuel pump should turn on for about 20 sec.). I don't remember the current draw, but it's alot less than 7.5 amps.

My problem was that the pump power lead was pinched between the tank and chassis, the insulation had worn through, and every once and a while the lead would short to the chassis. You may want to check the wiring from the engine compartment back to the pump to make sure it's not shorting against anything.
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  #6  
Old July 11th, 2005, 04:08 PM
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Nicholas Orros
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Quote:
Originally Posted by Roadsiderob
Mike,
What size fuse is blowing? If I remember correctly, in 1995, some trucks were built with 5 amp fuses instead of the required 7.5 amp fuse and there was an update campaign that included a new fuse and corrective stickers for the fuse box and owners manual. The fuses would blow at random.
Rob
Fella's...

My D90 has the WRONG sticker on my fusebox inside the cabin.
Does anyone know where to get one of these stickers ?
Or could someone 'scan' your sticker in and send it to me or post online ?
Or even just write down what #'s coincide with what ???

Much appreciated... In a bind here.

Nicholas Orros
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  #7  
Old July 11th, 2005, 04:23 PM
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Mike Hippert
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I'll get you a pic tonight! I'll even take a pic of the 110 one too as it incorperates the rear window stuff too (Defogger and wiper).
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