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Join Date: Oct 2001
Posts: 497
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Diagnosing a leaking fuel return line
I have chacked and replaced everything from the tank to the injectors and I do not have a pressure drop or leak in that direction. However when the car sits for more than 30 minutes its hard to start and it sounds like air is being sucked into the fuel pump after a few seconds .
I have tracked my pressure drop and suspected leak to the return line. There in no alternative as everything has been replaced and double checked in the other direction. My last two alternatives are these : 1) The fuel lines (main and/or return)in the tunnel are leaking or 2) There is a leak or runback in the return line when the pump stops ! How does the system stop the fuel from flowing back ito the tank in the return line ??? |
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09-11-2003, 04:47 PM
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Join Date: Mar 2001
Location: Marysville Wa.
Posts: 22,558
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there's a check valve. it's in the fuel pump. you can install another one either at the pump, or at the back of the fuel distributor where the return line attaches. two different style valves, depending on where you put it. 75s sometimes have the early style pump, which takes a smaller valve and capnut (1 587 010 001 valve, N0110651 capnut) on the side of the pump instead of the end, like the later pumps,(1 583 386 514 valve, and 1 239 900 053 capnut) or just use the one that fits the fuel distributor. (1 587 010 004)
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09-11-2003, 06:00 PM
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John,
I have replaced the checkvalve on the fuel pump twice and I even got a new fuel pump which has a built in check valve . The problem is not there ! HOWEVER you just said something which took me by surprise ! you said " the back of the fuel distributor where the return line attaches " I have also replaced my fuel distributor BUT there was no and there is no check valve there ???? I think you may have just solved my 2 year long problem ! I have completely replaced my whole CIS system with new and reconditioned parts in an attempt to solve this problem and it still persists. I never knew that there was a check valve at the return line of the fuel distributor ? Does this check valve (1 587 010 004) directly screw into the return line connection of the fuel distributor ? How does this work when the fuel it travelling in the fuel tanks direction anyway ? |
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09-11-2003, 09:27 PM
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Bump
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09-14-2003, 03:56 PM
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Join Date: Mar 2001
Location: Marysville Wa.
Posts: 22,558
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there is no check valve at the rear of the fuel distributor. it's just another place you can put one. it works the same way that the fuel pump one does, keeps pressure in the system. did you replace the accumulator? that item is what pushes fuel against the check valve so it seats well. they go bad too.
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https://www.instagram.com/johnwalker8704 8009 103rd pl ne Marysville Wa 98270 206 637 4071 |
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09-16-2003, 05:10 PM
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Posts: 497
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Thanks john
I will look into that check valve on the fuel distributor. No vapour lock when the car is warm. Within the fist 15- 20 minutes after shutdown it starts perfectly. Its after 30-40 minutes that the hesitation starts. Yes I have put a new accumulator on. Seriously I have replaced everything except the throttle body fuel pressure regulator (its a 1975 with hand throttle). It may be leaking fuel from there ? Q? when a 911 sits for more than 1 hour or so what happens to the fuel in the return line from the fuel disributor to the tank ? does the fuel run back to the tank and let the line fill with air ?? If not what stops the fuel flowing back to the tank and draining the return lines from fuel ?? I think thats my problem ? |
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09-16-2003, 10:46 PM
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