Two fuel pumps? I am a little confused.

[E30SRPower]

Okay. So I was thumbing through some electrical FSM pages for my 87 cabrio... Has a main and auxiliary fuel pump? One in the tank, and one in front of the left rear wheel. This seems kinda strange.

You guys have probably all seem my project post. This thing is gonna need some gas. Right now I have a 255 litre-per-hour walbro outside the tank, in place of the stock one there. I am assuming I still have the stock in tank pump... i never messed with it.

What does everyone else do when they turbo their M20s and put in V8s and stuff? I doubt I have room for a fuel cell in my cabrio.

[nando]

I'm guessing they convert to the later style tank which only has one in-tank pump rather than two.

[E30SRPower]

I'm guessing they convert to the later style tank which only has one in-tank pump rather than two.

Does the converible have a different tank? I would bet it does. It seems like everything behind the front seats is different.

[arsevader]

Re: Two fuel pumps? I am a little confused.

Okay. So I was thumbing through some electrical FSM pages for my 87 cabrio... Has a main and auxiliary fuel pump? One in the tank, and one in front of the left rear wheel. This seems kinda strange.

1987 was the last year for the 2 pump system for the M20.

James

[E30SRPower]

Re: Two fuel pumps? I am a little confused.

1987 was the last year for the 2 pump system for the M20.

James

Thank you James. that is very helpful.

The only refrence manuals i have are the electrical FSM and a chiltons manual (came in the boot of the car). The chiltons manual unly mentions the external pump... And there is a cover under the rear seat which allows access to the fuel level sending unit. I am going to assume the fuel pump is under there too.

I am going to bypass the external pump, and just run an in tank pump. Thanks guys, Problem solved... I believe.

[arsevader]

Re: Two fuel pumps? I am a little confused.

The chiltons manual unly mentions the external pump...

On 2 pump cars, the external pump is the main pump and the in tank pump is the transfer pump which delivers fuel to the main pump. If your in tank pump dies, the car will still run but the main pump will have to work that much harder and will suffer a quicker death.

And there is a cover under the rear seat which allows access to the fuel level sending unit. I am going to assume the fuel pump is under there too.

Yes, the sender is inserted into the centre of the pump.

I am going to bypass the external pump, and just run an in tank pump. Thanks guys, Problem solved... I believe.

Shouldn't be a problem as long as the pump is capable of providing fuel at the the required pressure.

James

[E30SRPower]

Re: Two fuel pumps? I am a little confused.

Shouldn't be a problem as long as the pump is capable of providing fuel at the the required pressure.

James

Yeah it is capable. It will support 400 WHP on the engine I have, by itself. So you say the external pump will draw fuel without the help of the in tank pump eh... I have my pump set up to run in place of the main pump right now... should I even bother putting it in the tank? Or should I just leave the in-tank pump alone?

[arsevader]

Re: Two fuel pumps? I am a little confused.

Yeah it is capable. It will support 400 WHP on the engine I have, by itself. So you say the external pump will draw fuel without the help of the in tank pump eh...

It can but it isn't a good idea. It places extra stress on the pump. One of the leading causes of pump noise/failure on 2 pump cars is failure of the in tank transfer pump.

I have my pump set up to run in place of the main pump right now... should I even bother putting it in the tank? Or should I just leave the in-tank pump alone?

You mean your new pump could be mounted externally or in the tank? If so then sure, keep the in-tank pump and replace the main pump with the new one.

James

[E30SRPower]

Thanks for all the help james.

I am pretty new to BMWs... have some experience in nissans and toyotas though. Some times this german stuff suprises me.

You should have seen the look on my face when I got my rear discs off. I had no idea there was gonna be some shoes under there!

[arsevader]

Thanks for all the help james.

I am pretty new to BMWs... have some experience in nissans and toyotas though. Some times this german stuff suprises me.

You should have seen the look on my face when I got my rear discs off. I had no idea there was gonna be some shoes under there!

Not a problem, glad to be of some help.

BMWs are pretty much all that I have experience in (which isn't all that much but I get by :D ) with a smattering of Volvo and Toyota thrown into the mix.

James