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I've got a 1993 Mk1 Golf/Rabbit Cabriolet that I picked up as a project car. When I first got it the lifter pump was dead so I replaced it.

About 6 months later, the main pump died and was replaced.

6 months after that, the new lifer pump started overheating and died again and was replaced again.

Now, about a year later, that new, 3rd lifter pump has died and fried the relay.

Would anyone know what could be causing these to die so quickly?

I've got the correct battery installed, but have always had trouble with the terminals. Several times the connections have slipped off the terminals. The terminal connectors also have a few eyelets with additional wiring connected to them (ammeter, radio) that sometimes rattle loose and create heat (on 2 occasions cutting out the engine).

Could this be what's causing them to break?

Fuse to pumps is a 10 amp. No other electrics in the car seem affected.

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One more thing to check is the voltage at the pump. If it is low, then the pump will draw more current, this in turn will cause more heating and heat is the mortal enemy of all things electrical.

That said, I think it is more likely that the problem is due to restricted flow through the pump. Some of the pump's cooling comes from immersion in fuel, but much of it also comes from fuel flow through the pump. If that flow is restricted it is a double whammy – the pump is working harder and there is less fuel flowing to cool it. Since most injection systems return unused fuel to the tank a fuel flow restriction might not be noticed.

Regarding your battery terminals, check to see if they could possibly be installed upside down. The battery posts are tapered and the terminals are tapered to match and thus have a top and bottom. If they are on upside down they will only make contact on a small band at the bottom (which should be the top) and if they loosen and start working up the post they will become progressively looser. But I don't think that is the causing the pump problem, if it was you'd notice too many other problems (like the engine stopping and lights going out).

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There are a few causes for repeated fuel pump failure. A dirty tank with sediment in it will clog the "in tank" filter (also known as the sock). This causes the pump to work harder and hotter resulting in premature failure. Are you changing the in line filter when changing the pump? When the first pump failed it may have deposited debris in the filter clogging it. When I recently replaced my fuel pump the product reviews were full of comments about early failure for certain models and brands. Are you using the exact same unit brand/model each time? Maybe switch brands? I would at the least measure the voltage at the pump connection and check the fuel pressure when the new pump is installed.

  • The sock on the pump is just stuck on with friction. It may have fallen off. Yeah, unfortunately it's hard to get Mk1 parts in Australia so I am limited to Topran parts from ebay or offensively overpriced VDO parts that can run into thousands of dollars. – MeltingDog Dec 20 '16 at 3:01
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Fuel pumps use the fuel they are submerged in for cooling (1/2 tank or more to keep the pump sufficiently cooled). People that keep their fuel tanks at 1/4 or less (I call them the $10 fill crowd) are doing their fuel pump a disservice, as it won't be sufficiently submerged for sufficient cooling. Any chance that's what's going on?

  • Could be. Initially, when I first got the car I kept the fuel low so I could mess around with the fuel lines, pump and tank. Since I got the car registered I only use it once or twice a week so I generally just let the fuel run to about 1/5 then fill it up again. – MeltingDog Dec 20 '16 at 2:53

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