what size is this fuel hose on 87 560SL

[Graham]

Originally Posted by rowdie

This online version of the EPC is not as complete as the subscription version but you will find the fuel system diagrams. https://nemigaparts.com/cat_spares/epc/mercedes/1/107/

That's a useful site Rowdie. Especially seeing I no longer have EPC access!

[funola]

Originally Posted by Graham

That's a vapor line. There are others too and an expansion tank. https://nemigaparts.com/cat_spares/epc/mercedes/1/fg/107048/575/47/015/

My feeling is that it will be easier to clamp the fuel exit hose from tank, disconnect it at bottom then run the fuel into a low level gas tank (I used an outboard motor tank). This after first siphoning most of fuel out of tank. It's not a big deal to do really.

If you do it with vacuum don't apply too much! Don't want to collapse the tanks. Couple of inches Hg at most. Should be enough for a not too full tank. If you plug or clamp one end of your new hose, you may be able to pull old one off and slip new one on without spilling much. Good luck if you try that

Don't know how big the 87 560SL tank is but it is full. Siphoning, draining a full tank is going to take a long time and some fuel will bound to be spilled.

I know how little vacuum it takes to collapse a tank and have a procedure worked out so it will not happen. Like I said, I have done it once before using vacuum with success, i.e. no spilled fuel and no collapsed tank.

[funola]

Originally Posted by Graham

That's a useful site Rowdie. Especially seeing I no longer have EPC access!

Yes, very useful site! https://nemigaparts.com/cat_spares/epc/mercedes/ Covers more than just cars, just about all vehicles Mercedes makes.

Other brands too https://nemigaparts.com/cat_spares/epc/

Rowdie, do they have warehouses in the USA? Are the part prices current?

[rowdie]

I have no experience with them. Someone on BenzWorld posted the link.

[97 SL320]

Originally Posted by funola

Don't know how big the 87 560SL tank is but it is full. Siphoning, draining a full tank is going to take a long time and some fuel will bound to be spilled.

Disconnect a fuel line under the hood and extend it to another car / fuel can. ( Adding a ground strap between the two cars to bleed static is a good idea ) Jumper the fuel pump relay and let it run.

Originally Posted by funola

I know how little vacuum it takes to collapse a tank and have a procedure worked out so it will not happen. Like I said, I have done it once before using vacuum with success, i.e. no spilled fuel and no collapsed tank.

One problem with doing that on gasoline is it's high vapor pressure compared to diesel. Vapor pressure is measured by placing the fluid in a closed container, bringing the contents to a set temperature and reading the pressure.

Gasoline will evaporate more rapidly at reduced atmospheric pressure than diesel so the vac pump will need to outrun the evaporation rate. This will also draw vapors into and through the vac pump creating a hazard.

A quick check shows diesel to have a vapor pressure of 0.10 KPA at 40 * C where gasoline is 54 and 104 KPA .

Gasoline

https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf

Diesel page 7
http://www.cpchem.com/msds/100000100097_SDS_EU_EN.PDF

[ejboyd5]

Most of us who work on cars and boats have made up a transfer pump similar to this:

All parts readily available, oversize terminals make connection to power source easy. Transfer of fuel is rapid.

[Graham]

Originally Posted by ejboyd5

Most of us who work on cars and boats have made up a transfer pump similar to this:

All parts readily available, oversize terminals make connection to power source easy. Transfer of fuel is rapid.

On my boat, I used something like that, but it was for diesel. Actually I used a portable drill pump. But with gasoline, I wouldn't have done that because of sparking from drill.

On car, tank is above ground, so gravity is available. I used a siphon pump to get tank level down as far as possible, then clamped tank outlet, disconnected hose at pump damper suction (you could disconnect where it is now leaking on return line) and let what was left in tank drain by gravity into low level tank.

But we all have our ways. I will be interested to hear how Funola makes out if he uses vacuum.

[funola]

Originally Posted by 97 SL320

Disconnect a fuel line under the hood and extend it to another car / fuel can. ( Adding a ground strap between the two cars to bleed static is a good idea ) Jumper the fuel pump relay and let it run.





One problem with doing that on gasoline is it's high vapor pressure compared to diesel. Vapor pressure is measured by placing the fluid in a closed container, bringing the contents to a set temperature and reading the pressure.

Gasoline will evaporate more rapidly at reduced atmospheric pressure than diesel so the vac pump will need to outrun the evaporation rate. This will also draw vapors into and through the vac pump creating a hazard.

A quick check shows diesel to have a vapor pressure of 0.10 KPA at 40 * C where gasoline is 54 and 104 KPA .

Gasoline

https://www.chevron.com/-/media/chevron/operations/documents/motor-gas-tech-review.pdf

Diesel page 7
http://www.cpchem.com/msds/100000100097_SDS_EU_EN.PDF

1. I do not own any gasser vehicles, and I don't know if my sister's other (gas) vehicle have an empty tank big enough.

2. Are you saying the vacuum pump won't be able to create enough vacuum to prevent fuel from spilling of of an open under the tank fuel return line due to higher vapor pressure of gasoline. I have a feeling the higher vapor pressure will not be an issue.

3. The vacuum pump is a diaphragm pump, there is no spark within the cavity of the diaphragm, exhaust fumes of the pump will be ducted well away from the 12V DC motor that drives it. The vac pump will be powered by a 12 V battery charger with a toggle switch to turn AC power on/ off to the charger to control vacuum levels so as not to collapse the tank. The only spark will be from the toggle switch which will be in an enclosure well away from the vac pump's exhaust hose.

[Graham]

Originally Posted by funola

I have a feeling the higher vapor pressure will not be an issue.

Gasoline doesn't have a single vapor pressure. It is a mixture of hydrocarbons of varying chain lengths. The lighter components vaporize first. What you often see quoted is RVP (Reid Vapor Pressure) which is not the true vapor pressure (TVP) - just a test procedure to classify gasolines by volatility, and it is done at 100F. Summer blend gas with RVP of 7psi would have a TVP at 100F of about 8psi or 4psia at 70F. Winter blend much higher.

Gasoline vaporizes quite easily. If you try your method, don't pull much of a vacuum. You only have to overcome a head of about 1.5ft of gasoline (equivalent to ~1.2ft of water or 1" of mercury vacuum.)

Be careful! Maybe try it on a gas can first.

[97 SL320]

Originally Posted by funola

1. I do not own any gasser vehicles, and I don't know if my sister's other (gas) vehicle have an empty tank big enough.

2. Are you saying the vacuum pump won't be able to create enough vacuum to prevent fuel from spilling of of an open under the tank fuel return line due to higher vapor pressure of gasoline. I have a feeling the higher vapor pressure will not be an issue.

The problem is you might not have a vacuum pump / hose with volume to outrun evaporating gasoline.

Originally Posted by funola

3. The vacuum pump is a diaphragm pump, there is no spark within the cavity of the diaphragm, exhaust fumes of the pump will be ducted well away from the 12V DC motor that drives it.

Be sure to make a vid of this burning down everything in it's path. Most DC motors have brushes and brushes = sparks.


( Not gasoline but still good visuals )
UPDATE: Fifth grader credited with saving man from burning car - Cincinnati News, Weather, Sports from FOX19 NOW-WXIX

https://weldingweb.com/showthread.php?461691-Acetylene-tank-laying-down

[ejboyd5]

The "negative pressure" idea isn't worthy of further comment. Pump out the fuel and be done with it. If you choose another route, please provide a video for our entertainment.