Fuel Pressure Accumulator FAQ


Created: 9/24/1997 10:10 PM

Last updated: 8/29/99


Author/source: DML


 

To: dmcnews submit, dmcnews(AT)world.std.com

"David" Wrote (somehow anonymously):

>Date: Tue, 23 Sep 97 12:22:12 PDT

>From: dmcnews-approval(AT)world.std.com

>Subject: DML: Fuel Accumulator Inputs/Outputs

>

>I noticed the DMC fuel accumulator has three inputs/outputs.

>Two seem to go towards the back end, and one towards the fuel

>tank front end. Can someone please explain the destination of

>each port and why there are not just two. (My understanding

>was the accumulator kept pressure in the engine side of the

>fuel system while the engine was off, but why then are there

>three lines? does it have any additional functions?). Thanks.

>

>David

 

The accumulator is actually a diaphragm with a spring underneath it. The two large fittings with the Teflon hose on one end are the fuel input (from the pump) and output (to the engine). I don't recall which is which. They are different size and only fit one way, and since there is no check valve in the accumulator itself it doesn't really matter. When you start the car, the pressure is built up and the diaphragm spring is compressed. This, along with a check valve at the fuel pump, is what holds the pressure when you shut the car off. The third hose, the smaller one that is on the end by itself, is to allow the pressure inside the accumulator to equalize as the diaphragm spring is compressed. It is connected in a T arrangement to the fuel return line to the tank. It could, by design, just as easily have been vented to the outside, but then when the accumulator fails (usually a break in the diaphragm) the fuel that leaks through the diaphragm would be dumped on the ground instead of back into the tank. On most of the cars I have looked at, the third hose is much lighter duty than the others since it is under very little pressure.

 

Note that when disconnecting the hose fittings when replacing the hoses, you must hold them from above with a wrench (remove the little package tray at the rear of the console and tear out the access panel) or you'll twist/kink the steel fuel lines. Since the lines are mounted to the top of the frame but beneath the fiberglass body, you can imagine what you'd have to do to replace them.

 

If you are just replacing the accumulator, disconnect the hard line, unmount it and pull it out through the opening in the body. It will then be much easier to disconnect the lines.

 



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