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**DaveSmed** · 02-26-2011, 07:51 AM

You no longer need the external pump, but you do need the filter still. The thing on the TRE pump is more of a strainer to prevent pump damage. The filter is finer to prevent damage to the rest of the fuel system.

Also, You will have electrical problems soon with your setup.

Grounding to the fuel sender chassis is inadequate due to the O-ring seal, which will cause issues with the TRE pump trying to find a ground through your instrument cluster. Adding a ground strap from a sender nut to a clean chassis ground will fix that though.

The other part is the connector to the fuel pump. BMW revised that connector on the late model cars with larger terminals and heavier gauge wire to the connector to support a high pressure pump. In your case, to prevent leaks I would use the original connector, but connect both terminals to the power wire of your fuel pump, since you have a separate ground now. Connect a heavier gauge wire between both terminals of the plug and run it down to where the external pump was, and connect to its power lead (which you will see was a heavier gauge). If you do that, you should have a setup as reliable as a late model E30 originally equipped with the single pump.

**jlevie** · 02-26-2011, 07:58 AM

Since you've replaced the low pressure transfer pump with a high pressure pump, you can eliminate the high pressure pump. But you do need to retain the fuel filter.

The cut outs may be from a dying high pressure pump, but they also might be from rust in the tank. Rust in the tank can collect on the in-tank filter screen and starve the pump for fuel. If there is a good bit of rust in the tank you need to replace the tank or acid clean and seal the tank.

**element6** · 02-26-2011, 12:53 PM

Hey guys, thanks for the responses..

Dave, are you sure that the in tank assembly grounds through my gauges? That grounding point that I attached the ring terminal to was the same exact point that the OEM transfer pump was grounded to before I removed it. At the top of the assembly, when you are looking at the fuel line hookups and have the fuel level sender unit removed, there is a connector for the transfer pump plug. If you inspect it closely you can see that the negative terminal on that connector is permanently attached to the complete assembly while the positive terminal goes through the top and is insulated by a piece of plastic until it gets to the point where I soldered the red wire on the inside.

Remember, this is not a late model E30. My in tank assembly looks a lot different than any late model car. It even looks different than an ETA assembly.

The fuel sending unit has it's own positive and negative terminals and I do not see it grounding through in tank assembly.

As for the rust, I know there is some in there.. and honestly I did not like the look of the fuel hose that goes between my high pressure pump and the transfer pump.. nor did I like the look of the return line hose. Until I can drop the tank and replace it, I will have to live with that. It will occur shortly. There honestly isn't that much dirt and rust in there to stop fuel flow though. My engine doesn't begin to cut out until about 30-40 minutes of driving have gone by. It is very consistent with that.. which is why I am going to go with an overworked, dieing high pressure pump.

I found a new Bosch replacement for it for only $45 though, so I think I will keep it in place to retain use of the mounting tabs and all that stuff. I like to keep things fairly original.

**element6** · 02-26-2011, 12:56 PM

PS - the reason I don't believe it is grounding through my gauges is because the in tank pump will cease to work if I pull fuse number 11 (fuel pump). I was sitting there with a voltmeter the other day checking that out before I plugged everything back in.

**jlevie** · 02-26-2011, 01:09 PM

The fuel pump ground and gauge grounds are under the rear seat on the left side of the car.

I hope your problem isn't rust in the tank, but the behavior you describe is consistent with rust being the cause more so than the pump.

**element6** · 02-26-2011, 01:13 PM

I hope not.. regardless, the tank is going to be dropped and replaced in a few weeks. I have to change those hoses. I know for sure that my external fuel pump whining away like crazy all the time is not a good sign of its health though.

**DaveSmed** · 02-26-2011, 04:23 PM

It doesn't normally ground through the gauges, but the connector the power and ground currently go through will heat up and become an issue with time.

I'm suggesting grounding to the chassis and running power through both sides of the connector.

**element6** · 02-26-2011, 05:33 PM

Gotcha. Yeah, guess I will ground it to the chassis back there somewhere with a ring terminal around one of the sender unit screws.

Thanks for the tip.

**jlevie** · 02-26-2011, 05:35 PM

The pump is already grounded to the chassis (see above). You need not do anything with the wiring.

All of the soft hoses can be replaced without dropping the tank.

**Gruelius** · 02-27-2011, 08:52 AM

yeah ive done the same. keeping external because thinking of making a surge tank later on if i can fit it in that area (even a small 200ml one).

also how the eff do you replace those above tank lines without dropping it? the 10mm line wouldnt budge!

**element6** · 02-27-2011, 10:49 AM

You can't replace them without dropping the tank. That's why I am headed over to the junkyard now to pick up another tank so I can have that one cleaned and sealed and ready to go in place of my original tank when I swap those hoses out.

Edit: they may be able to be replaced with the tank in place.. good luck if you try to go this route! I'm not breaking my fingers for that. My tank needs to be cleaned anyways.

**element6** · 03-04-2011, 08:36 AM

Decided to go with a new tank. Wasn't so sure about how much rust was in the tank but judging by what jlevie has said in the past with fuel delivery issues I am pretty sure mine was due for cleaning or replacement. I went with a new tank.

If anybody has any info on retrofitting the 16.6 gallon tank to my early model, please let me know in this thread: http://www.r3vlimited.com/board/showthread.php?t=199834

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Should I remove my external fuel pump?

Should I remove my external fuel pump?

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