Replacing Fuel Distributor and Pressure Regulator

Ameer Antar antar at
Tue Feb 3 00:00:45 EST 2004

You can test the fuel pump by measuring the output of the fuel return line. The Bentley says you should get about 450mL after 30 sec's when you jumper the fuel pump relay (engine not running). The actual output varies depending on the actual voltage measured across the fuel pump power connector. The 450mL figure is with 10V at the pump. There's a graph on pg 20.21 if you have the Bentley. If you're anywhere near there, you should be OK.

I'd be willing to bet the problem is in the regulator or maybe the dist., but now you can at least rule out ot not. good luck.


---Original Message---
Date: Mon, 2 Feb 2004 16:49:01 -0500
From: "Marc Boucher" <mboucher70 at>
Subject: Replacing Fuel Distributor and Pressure Regulator
To: "Quattro List" <quattro at>
Message-ID: <BAY10-DAV508aZRhQdO000554e3 at>
Content-Type: text/plain;	charset="iso-8859-1"

I am leaning towards accepting the offer of a used CIS III-E repair kit that is known to be working from a member of this newsgroup at a very reasonable price.  However I wanted to review the situation, the investigations, in particular the results of today with those members that have offered assistance.

At this point the problem is narrowed down to either the fuel distributor, the fuel pressure regulator, or the fuel pump.  I will replace the first two, and if that doesn't solve the problem then I'll go at the fuel pump.

Previously I had all but ruled out the fuel pump because there was a healthy flow from the fuel pump and also in the return lines back to the fuel pump, yet no fuel was getting to the top of the fuel distributor when the plate was activated.  Thus the likely diagnosis was a problem with the metering or the pressure regulator.  

I understand that its not possible to fully discount the fuel pump without first measuring the pressure.  But there was a healthy flow on the return side, downstream from the pressure regulator.  To measure the pressure would require towing it to a FI specialist or buying some expensive testing tools right?

Today I attempted to see if it was the pressure regulator.  I pulled the finer gauge line going from the dist. to the regulator near the supply line.  With pump energized it had flow, apparently under high pressure.  I closed this up.  I attempted to check the other line from the pressure regulator (shorter thicker line) that returns to the fuel dist. on the opposite side.  It was simply not possible to remove the bolt (on either the distributor or regulator end) without removing the entire distributor unit.

Then I did something that might not have been too wise.  I wanted to verify if there was fuel getting to the return line that didn't pass through the differential pressure regulator.  So I stopped the fuel flowing to the differential pressure regulator by placing some latex surgical gloves between the diff pressure regulator and fuel distributor and tightening.  The result is that no fuel flowed through the return line when the pump was energized.  However when I removed the latex gloves and reassembled, there was still no fuel flowing to the return line whereas there had been last week.  Thus the possibilities are:

a.) Additional clogging had taken place since last week
b.) A bit of the latex gloves broke off and clogged the entire return flow 
c.) The fuel pump is putting out significantly less pressure since last week.

Anyway this is where I am now...I'd rather have parts to change especially if they can be had at a good price.  Its time consuming to continue pulling parts one at a time and putting them back together and reassembling each time.  That black boot is hard to get off and on.  So I'll try swapping the distributor and pressure regulator parts and if that doesn't work then I'll move on to the fuel pump.  Thoughts?

Thanks all for your time,



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