12V fuel pump installation placement - Defender Source
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  #1  
Old January 18th, 2018, 02:03 PM
daniel_FL
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12V fuel pump installation placement

Hi folks,

I've got a 1986 Land Rover Tithonus Defender 110. The mechanical lift pump seems to be going out, and won't keep it's prime. I have a new lift pump to replace it, but I'm looking to install a 12V electric fuel pump as well, per Robert Davis's suggestion often mentioned on these forums. The mechanic I'm working with has agreed that it'd be a good idea to install the electric pump in addition to the new replacement lift pump, but he disagrees with the placement of the electric pump recommended here.

He wants to install the electric pump *after* the lift pump, and before the fuel filter, to "assist" in pulling the fuel forward, rather than "pushing" fuel toward the lift pump, as he thinks that could cause issues with the mechnical pump. Additionally, it makes the electrical wire setup a bit simpler, I think.

Is there any reason that setting it up after the lift pump would not be ok, or should I stick with Robert Davis's recommendation of installing it at the rear of the vehicle, after the sedimenter, so that it is between the sedimenter and lift pump?

Would appreciate any advice on either implementation.

Thanks,

Daniel
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  #2  
Old January 18th, 2018, 02:56 PM
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If placing the 12V pump after the lift pump were the preferred location, then that would be the location I recommended, but it is not.
The scenario being recommended by your mechanic adds no value and is a very very very bad idea.
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Old January 18th, 2018, 03:38 PM
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Double check the recommended fuel pressure for your engine. It’s pretty low pressure for a 200tdi like 4 psi or so.
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Old January 18th, 2018, 03:44 PM
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The mechanical pumps last for years and are easy to replace, why add the electric?
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Old January 18th, 2018, 03:50 PM
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Quote:
Originally Posted by headdamage View Post
The mechanical pumps last for years and are easy to replace, why add the electric?
Remove your fuel filter and replace it or develop an air leak and you'll know why.
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  #6  
Old January 18th, 2018, 03:56 PM
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Quote:
Originally Posted by BlackField View Post
Double check the recommended fuel pressure for your engine. It’s pretty low pressure for a 200tdi like 4 psi or so.
The electric pump, and lift pump for that matter, only feed the FIP. It ensures there is always fuel in the line when the FIP calls for fuel. The FIP boosts pressure to the thousands of PSI.

Make sure your mechanic installs a low pressure pump, I personally have had good luck with THIS one. Do not install something like a Walbro 255lph.

If it was my truck I would install it before the lift pump. I can imagine some weirdness with the electric pump trying to pull through the lift pump and its cam driven pulses. If you do it the other way, please report back how it works out.

I've considered removing my lift pump altogether.
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Old January 18th, 2018, 04:09 PM
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Electric pumps are far better at pushing than pulling. Robert’s advice is spot on as priming these beasts is a PITA. The lift pump is a diaphram pump and will actually benefit from the low pressure provided by a low pressure pump and you won’t lose a finger frantically pumping the lift pump manual actuator 10 million times trying to get it primed or an eye to spraying diesel when you crack open a filter fitting trying to let the air out.
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Old January 18th, 2018, 04:52 PM
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Quote:
Originally Posted by AdamSanta85 View Post
Do not install something like a Walbro 255lph.
This made me laugh (coming from the Honda / DSM tuning world)
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Old January 18th, 2018, 05:05 PM
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Originally Posted by sonoronos View Post
This made me laugh (coming from the Honda / DSM tuning world)
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  #10  
Old January 18th, 2018, 08:00 PM
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I've owned rover diesels since 1999 and not had this problem. However I will admit to resorting to a low pressure electric pump in one of my old series trucks when it was having vapor lock problems in hot weather. In that case I installed the electric pump under the seat base by the tank so that it pushed fuel to the mechanical pump.

The manual prime can be a pita when the cam lobe gets in the wrong spot for priming.
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Old January 18th, 2018, 08:37 PM
daniel_FL
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Thanks Robert. It ultimately didn't make sense to me either, having the 12V on the other side of the lift pump, but just wanted to make sure. I'll instruct him to place it as you recommend.

Quote:
Originally Posted by rdavisinva View Post
If placing the 12V pump after the lift pump were the preferred location, then that would be the location I recommended, but it is not.
The scenario being recommended by your mechanic adds no value and is a very very very bad idea.
Quote:
Originally Posted by daniel_FL View Post
Hi folks,

I've got a 1986 Land Rover Tithonus Defender 110. The mechanical lift pump seems to be going out, and won't keep it's prime. I have a new lift pump to replace it, but I'm looking to install a 12V electric fuel pump as well, per Robert Davis's suggestion often mentioned on these forums. The mechanic I'm working with has agreed that it'd be a good idea to install the electric pump in addition to the new replacement lift pump, but he disagrees with the placement of the electric pump recommended here.

He wants to install the electric pump *after* the lift pump, and before the fuel filter, to "assist" in pulling the fuel forward, rather than "pushing" fuel toward the lift pump, as he thinks that could cause issues with the mechnical pump. Additionally, it makes the electrical wire setup a bit simpler, I think.

Is there any reason that setting it up after the lift pump would not be ok, or should I stick with Robert Davis's recommendation of installing it at the rear of the vehicle, after the sedimenter, so that it is between the sedimenter and lift pump?

Would appreciate any advice on either implementation.

Thanks,

Daniel
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