[DML] TESTING THE FUEL ACCUMULATOR

[mike clemens <rmclemns@xxxxxxxxx>]

Group (especially Dave S, John H, David T, Martin G, Ken K),

I have been toying with the idea of testing an accumulator off the car, but found no definitive way in any forums, so I devised a test of my own.  Please look at this and see if there are any flaws in my thinking or test.

First, fuel is delivered to the accumulator from the fuel pump via the center connector at the large end.  From there it comes out the right angle connector and goes to the fuel filter.  Any excess fuel comes out the connector on the small end and is routed to the return line.

I was originally going to use a spare fuel pump, some extra hoses, a can of gas, and a lawnmower battery to test this by hooking everything up, just like on the car, but have it on my test bench instead.  Then I realized PSI is PSI, regardless of the source, so here's what I did.

I attached a hose to the right angle side, plugged and clamped off the other end with a pressure gage inserted in the end.  I attached another hose to the input side and left the small end open to the air.  I then took this whole thing out to my wife's Volvo where there I keep an emergency air pump that plugs into the cigar lighter.  The air pump also has a gage on it so I could double check my readings.  I attached the pump to the input hose and fired it off.  According to the manual (Page D:02:01) rest pressure testing starts at 3.3 bar (47.85 psi) and after 10 minutes should be no less than 1.7 bar (24.65 psi).  I ran the pump until I reached exactly 50 psi and the shut it off.  I checked for any air leakage out the small end with soapy water since it should not have opened yet to the bypass point.  I then timed the bleed down and could determine if the accumulator was working as advertised.

I had three spare accumulators plus the one from Josh's car.  One spare was brand new, so I used it as my baseline.  Results:  Josh's was totally shot as was one of the spares.  The new accumulator and one other was good.  One thing I did not test was where the bypass valve opens since I did not know the values for this.  I assume it is somewhere around setting value 5.1 to 5.3 bar (approx. 75 psi), but did not want to risk screwing up one of the good accumulators, if I was wrong.  And when you "assume", all you do is make an 'ass-u-me'.

Does anyone see any flaws with this test?  If not, I'll write it up for the tech section and add pictures.

Mike   TPS   1630

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