Can't figure out fuel problem

[Dave]

Ok, back to the expert panel for help.  Car awakened for summer, started right up, ran ok at first, but then sputtered going up a hill, then kept dying, and acted like it was out of gas.  Barely made it the one mile home. Drained 12 gal. of red rusty gas. 
New tank, fuel pump, and fuel fiter.  Crank and crank.  No start.
Pulled plugs - dry.
Checked outflow after pump - good.
Pump on - no fuel flows back to the tank.
Disconnected return fuel line at the front of the car near the fuel filter at the banjo bolt (is that on the dampner?) turned on pump.  When pump is on fuel dribbles out of hole where the banjo bolt was screwed in to.
Blew from banjo bolt to back near fuel tank  and from the back up to banjo bolth both ways with compressed air - nothing going through.  I put a golf tee into the line and blew from the other end to see if air would go through - nothing.
Now what?  Thanks in advance.

[Cees Klumper]

It sounds like your fuel lines are plugged up. Either figure out a way to clean them out or replace with new (I'd go with the latter ...).

[Dave]

Thanks Cee
What do you think about the gas dribbling out of the banjo bolt?   Should it be a big flow when the pump is on?

[Cees Klumper]

There is a flow rate (# gallons/ liters per minute) posted I'm sure in the technical articles that would likely produce a lot more than a trickle anywwhere along the system. But others should chime in as I am not the expert on fuel delivery (or much else for that matter!).

Good luck and keep us posted please.

[Jordan]

Dave, the banjo bolt screws into a pressure valve on its way out of the FIP.  Maybe you had the same problem I had and the pressure valve was screwed all the way in, not allowing fuel to pass.  Have a read through this thread http://www.sl113.org/forums/index.php?topic=16086.msg111214#msg111214.  Let us know how you are making out.

[Benz Dr.]

Marcus has it right. If you have next to no fuel coming out at the fuel dampner, it could be the pressure relief valve. The 230SL has a small hole in the center of the valve disc while the 280SL doesn't. Regardless of having the hole or not, fuel has to go past the pressure relief valve or the engine won't run for very long due to vapour lock.
 
We had a similar problem on a 280SL earlier this spring. When it was cool outside the car ran great but on the first warm day ( which happened to be the day the owner picked up his car ) the engine wouldn't restart after it was warmed up. We checked the basic fuel pressure at the CSV and found about 8 PSI. This is enough to run the engine but not enough pressure to open the PRV. I think it would take at least 10 PSI to do that so the fuel pump was worn enough to limit the required pressure to open the PRV. We installed a valve plate from a 230SL which allowed some fuel to by pass through the small hole in the  plate. This prevents vapour lock and now the engine runs fine on this car. Not a proper fix but since it works, I suppose it's OK enough.

I would also check your cold start valve. Even if the PRV isn't opening, the engine should still fire on the fuel delivered from the CSV. If you had that much rust in the tank, it may have plugged up the nozzle on the valve. You would need to remove the CSV and then see if any fuel comes out when the solenoid is activated with 12 volts. The pump needs to be running to do this test. I use a wire from the battery running to the solenoid but you should always fix the wire to the solenoid first and to the battery last. Any sparks should be far away from any fuel.

Sounds like you have a plugged line under the car. Remove the hose at the end of this line that goes back into the fuel tank and try blowing into it. If no air comes out the other end, it's the line. I woud also change all rubber fuel hoses.

[Dave]

Thanks Gents for your help.  Take a look at the below picture and if you could let me know if what I'm reporting makes sense.  Still not sure what the dampner is, but I may have it in my picture.

[twistedtree]

Yes, that's the damper.

[ja17]

Make sure that the fuel pump is running, then check to make sure that the inlet screen at the electric fuel pump is not clogged.

[twistedtree]

Since you can't blow air back to the tank through the return fuel line, you have a clear and unmistakable problem right there.  I'd fix that first before worrying too much about other, more subtle problems.

Once you have the return line working properly, then do a fuel pressure and flow test.  If that's in spec then you should be good to go.  If not, you can start narrowing down any remaining problems.

[Dave]

Thanks Peter.  I'm on it. 

[Dave]

Thanks again to all.  It's alive!  Got replacement fuel lines and some hoses from Bud's Benz.  Was pumping from tank, but no return because return line completely plugged.  Now car runs fine and no big "whoosh" from the tank when removing gas cap.