Firewall fuel return hole

[MARHD]

Hi everyone, 

 

Just a quick question, I couldn't seem to find the answer while searching. 

 

How many holes should there be in the firewall, in the indentation area for the fuel return line. From my searches, I've seen cars with either one or two holes in this location and I'm unsure if this is a year or model difference.

 

Example 1 LHD 71 Carb?: https://www.bmw2002faq.com/forums/topic/242660-re-plastic-fuel-line-routing-71-2002-firewall-area/

 

Example 2 @dlacey RHD 73 Tii: https://www.02forum.co.uk/viewtopic.php?f=11&t=15033

 

This section on my own car is rusted out, so just wondering how many holes I should add when remaking the section. I assume it should be 2 given I have a 71 RHD Tii which is similar to David's car, but in that case I don't know what goes through the second hole. 

 

Any help is appreciated, thanks.

Edited May 19 by MARHD

[bergie33]

US cars have a vapor return line in addition to the fuel return line.  Seeing as yours is a non-US model, your vapors probably vent to the outside via a small hose in the trunk (rather than the vapor recovery tank mounted under the parcel shelf).  So, your firewall would likely have only one hole, only for the fuel return.

[Son of Marty]

Or when the factory updated the fire wall die to allow the 2 holes that the NA cars required did they use that die on all cars and  put a rubber plug in there, I don't know, rhd cars are bit thin on this side of the pond.

Edited May 20 by Son of Marty

[MARHD]

1 hour ago, bergie33 said:

US cars have a vapor return line in addition to the fuel return line.  Seeing as yours is a non-US model, your vapors probably vent to the outside via a small hose in the trunk (rather than the vapor recovery tank mounted under the parcel shelf).  So, your firewall would likely have only one hole, only for the fuel return.

 

Ah ok, so the second hole should be for a vapor return line. 

 

56 minutes ago, Son of Marty said:

Or when the factory updated the fire wall die to allow the 2 holes that the NA cars required did they use that die on all cars and  put a rubber plug in there, I don't know, rhd tii's are bit thin on this side of the pond.

 

That's definitely a possibility. Was there a specific date when the vapor vent system was introduced? It could explain why David's 73 UK delivered car has the 2nd hole.

[John76]

I believe the cars with a vapor tank in the trunk and a charcoal canister in the engine bay all had the two-hole firewall.

The white plastic line is the fuel supply from the tank. The blue plastic line is the vapor line from the vapor tank to the charcoal canister, then to the intake manifold (along with the crankcase vent).

 

 

 

[tech71]

On US spec cars at least that’s the fuel feed  line not return, it goes to the fuel pump. 
The return line installed on later 02s runs under the car along driver side rocker

 

Edited May 20 by tech71

[bergie33]

11 minutes ago, tech71 said:

On US spec cars at least that’s the fuel feed  line not return, it goes to the fuel pump. 
The return line installed on later 02s runs under the car along driver side rocker

 

Except for tii's.  The plastic line is the return line, supply line is steel and runs under the car.

[jimk]

2 hours ago, MARHD said:

Ah ok, so the second hole should be for a vapor return line. 

To be clear it's a vapor vent from the gas tank to the engine.

[MARHD]

12 hours ago, jimk said:

To be clear it's a vapor vent from the gas tank to the engine.

Ah ok, do you know when that was introduced on US cars?

[visionaut]

45 minutes ago, MARHD said:

Ah ok, do you know when that was introduced on US cars?

Realoem shows a  March 1971 start date for the vent pipe ( if you can trust that)

[Mike Self]

If there's a hole (or a plugged one) to the left of the steering column, that's for the manual choke cable.  When US cars were fitted with the auto-choke 2 barrels in late 1972, the hole was plugged with a rubber stopper, as Euro cars were still using manual chokes.  In addition, early US automatics with 1 barrel carbs had auto choke carbs, so that hole was plugged on them also.

 

mike

[Tdh]

My '71 N/A car has two holes....

[MARHD]

1 hour ago, Tdh said:

My '71 N/A car has two holes....

 

From your profile it seems your car was produced just just before the model 71 year changes. Does your car have a vapor tank in the boot?

[Tdh]

6 hours ago, MARHD said:

 

From your profile it seems your car was produced just just before the model 71 year changes. Does your car have a vapor tank in the boot?

It does indeed!

[MARHD]

2 hours ago, Tdh said:

It does indeed!

 

Hmm, then your car pretty much lines up with realoem.

16 hours ago, visionaut said:

Realoem shows a  March 1971 start date for the vent pipe ( if you can trust that)

 

I wonder if anyone has a late 1970 car to confirm