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Old 01-10-2020, 01:45 AM
randy h randy h is offline
Join Date: Apr 2014
Location: sc
Miles on Grease: 300k
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Posts: 78
Default Have 2 veg tanks, low pressure readings from one.

I have 2 dedicated veg tanks on my 7.3. Each veg tank has it's own racor 2 micron filter. These filters are easy to access and change, vastly extending the life of the screen and Donaldson. Both tanks are "T"d with manual valves to the common wvo fuel line. I switch between tanks as circumstances demand. I've run this setup for tens of thousands of miles.
At the moment, one tank has clean wvo and the other has D2. This is an exception to my normal procedure of running wvo in both of these tanks. As a recent onset problem, I get a low pressure indication when I pull from the tank that currently contains wvo, and a green light when I pull from the tank that currently contains D2.
Attempting to rectify the problem, I changed the racor element on the offending tank (didn't look all that dirty), pulled the pick-up tube and visually examined the opening (nothing noted), back-blew from the Racor with compressed air through the fuel line and pick-up into a bucket (only oil was expelled, no grit or chunks) , replaced the screen at the manifold (it was clean), and replaced the Donaldson at the manifold (for good measure). I also disassembled and cleaned the parts within the Racor canister and the water collection bowl at the bottom of the Racor canister (they weren't very dirty). No joy on test drive.
I even went as far as to switch Racor canisters between tanks, to rule out any problem within the Racor but got the same results on test drive.
Turning my suspicion to the 5 year old fuel pump on the manifold, is it possible that it's getting tired, and now is able to pump diesel but unable to pump thicker wvo (temperatures here have been in the 50s Farenhiet, water temps in coolant system 190F) ? Or do those pumps only fail completely and suddenly?
I'll be grateful for advice as to what could be causing this problem or any other diagnostic maneuvers I should perform.
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Old 01-10-2020, 02:29 AM
greaseguy's Avatar
greaseguy greaseguy is offline
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Join Date: Jan 2014
Location: Gilpin County Colorado
Miles on Grease: 85,000
$ Estimated Saved: almost enough for repairs
MacGyver Rating: 3.8
Posts: 377
Default Sounds like a pump to me

Unless fuel lines are cracked and pulling air or something. Also in my opinion pumps push better than pull. A 2 micro pre filter may help pre screen and filter life but is hard on pump. Again this is opinion. What pump is on your manifold? Maybe time to rebuild pump and replace motor. Pumps can get tired and or die.
1999 early F250 EC, SB, ZF-6 Lariat V3 DFA
425,000 miles and counting
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