Author Topic: Unusual Fuel Blockage Identified  (Read 3575 times)

Jordan

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Unusual Fuel Blockage Identified
« on: February 21, 2012, 03:22:01 »
Spend the good part of today tracking down a fuel blockage problem that Dan was kind enough to help me out with by telephone.  Thought I would post it here in case anyone else runs into this problem.

I was having problems starting the car lately, having to push the accelerator to the floor to get it started.  Last time it ran for about 30 seconds (engine cold) and then died.  Would not restart.  I should mention I had started to hear a high pitched squeal or whine coming from the engine when I turned on the fuel pump before starting, lasted maybe 2 or 3 seconds before going away.  I suspected I was getting resticted flow somewhere.  Spoke to Dan and we agreed it was probably a blocked fuel line somewhere, or the CSV was plugged.  I started with the fuel line.  I started from the back.

Disconnected return line at fuel tank, turned on pump and no flow.
Disconnected fuel line at dampner (exit point) and blew back to tank (still disconnected).  No blockage, line was clear.
Disconnected at fuel filter just to make sure I had flow from the electric pump, got 1.6 litres in 15 seconds so lots of flow and pressure.
Disconnected on intake side of dampner, no flow.
Disconnected at exit point from FIP, lots of flow out of top of FIP, therefore blockage was between FIP and dampner.
Dan informed me that the banjo bolt on FIP was screwed into a fuel pressure valve (see photograph below, arrow is pointing at pressure valve body).  I turned on the electric pump and no flow through the valve.  I had found my blockage.
Removed the banjo bolt and unscrewed it from the pressure valve and sure enough the pressure valve was not allowing fuel through the opening inside the valve.
If you look inside the valve from the top you will see another screw with a hole through the centre and a flat head slot for a screw driver.  You can remove this screw by unscrewing it out of the body.  Looking from the bottom you will see a small opening into which you can push a thin screw driver or pin and it should show move in and out with a little bit of resistance.  Under the screw from the top is a spring and a plastic plug, which you see when looking through the hole in the bottom.  Fuel coming up and out of the FIP at a certain pressure pushes on this plug and allows for excess fuel to flow back to the dampner and fuel tank.  My screw on the inside had been turned down so much that it did not allow enough travel of the flat plug to allow fuel to push past.  I simply unscrewed the interior screw a few turns, reinstalled in on the FIP and turned on the electric pump.  Fuel came gushing out the valve, as it should.
I put everything back together and I now had fuel flowing out the return line at the fuel tank.  Hooray. ;D ;D
I have not tried starting the car as yet since I am replacing a few sections of fuel line I removed that were hard and brittle.

I should mention that I had replaced a short section of fuel line between the FIP and dampner maybe two weeks ago.  That banjo bolt had come loose in the process and I just retightened it.  I expect when I did that I also put pressure on or turned the screw in the pressure valve enough to have caused this problem.  Dan told me if you run into a problem with something always go back to whatever you fixed or fidled with last and make sure you didn't upset something, which it turns out I did. :-[ >:(


 

« Last Edit: February 21, 2012, 03:27:46 by Jordan »
Marcus
66 230SL  Euro 4 speed

twistedtree

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Re: Unusual Fuel Blockage Identified
« Reply #1 on: February 21, 2012, 04:58:49 »
Is that screw used to set the fuel pressure?  Closed clearly isn't the right setting, but wide open may not be either.  Just wondering.
Peter Hayden
1964 MB 230SL
1970 MB 280SL
2011 BMW 550xi

Jordan

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Re: Unusual Fuel Blockage Identified
« Reply #2 on: February 21, 2012, 13:31:54 »
Peter, I don't know.  My interior screw was screwed all the way in so I unscrewed it 2 turns, making sure there was still enough thread for the banjo bolt to screw in (about 10mm) and tighten.
Marcus
66 230SL  Euro 4 speed