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Mark Ogram

Bosch type fuel pump

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Good afternoon,

I am converting my car back to PI, it is a CP UK car, but the previous owner converted it to run on SUs.

I am very nearly there, just need to finish fuel lines / hoses etc.

I have just one question,  initially, I want to connect up the original wiring so I can run up the pump to check for leaks and get air out of the system - am I ok to do this ? I will get the wiring and relay sorted when I can find an auto electrician to come and do it for me.

I have read on several forums that some owners still use the existing wiring for their Bosch pump conversions.

Any advice appreciated.

Thanks.

Mark.

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Hi Mark,

the preference is obviously a fused relay and cut-out switch. It will unload the ignition switch, increase pump voltage and   Improve accident-safety.

But for testing purposes, it should not matter.

One you have the fuel system running, measure the volts at the pump and compare with the volts at the battery  stationary and say 2500 rpm. The smaller the difference between battery and pump voltage, the better.

If you can, it is also good to measure the current draw at both engine speeds.

Waldi

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I would take the power lead off the coil, it will stop it getting hot if you don't start the engine,    But remember to put back on when finished.....

John

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1 hour ago, Mark Ogram said:

Good afternoon,

I am converting my car back to PI, it is a CP UK car, but the previous owner converted it to run on SUs.

I am very nearly there, just need to finish fuel lines / hoses etc.

I have just one question,  initially, I want to connect up the original wiring so I can run up the pump to check for leaks and get air out of the system - am I ok to do this ? I will get the wiring and relay sorted when I can find an auto electrician to come and do it for me.

I have read on several forums that some owners still use the existing wiring for their Bosch pump conversions.

Any advice appreciated.

Thanks.

Mark.

 

Hi Mark !  In the summer of 1972 the wire size from the ignition S/W to pump was increased in size by BL, so when you sort out the pump size wiring go for 3mm sq. because when I tested 2 other sizes this size gave the lowest volt drop during cranking to start the engine. 

Bruce.

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Hi Mark,

if you need a cut-out switch, use Mini/BMW partnumber: 07 13 1 068 856. This switch comes from the first series "new" minis and is more reliable then the original switch.

Peter.

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My Bosch pump ran on the original wiring for years before I replaced it with a heavy  direct feed from the battery to a relay next to it. I wouldn't keep the old system, as from memory, the  feed to the Bosch pump went through the key switch.

When I run the pump without the engine I leave a large battery charger on the battery and pull the LT ignition lead. From previous experience with electric motors  I'm paranoid about low voltage destroying the pump motor due to excessive current  and continuous current destroying the points/electronic ignition.

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