Fuel pressure with a FASS

[jabird]

I'm having a few issues with fuel pressure readings. As I'm driving, at 65mph. , one day I'll have 15psi. and then the next day I'll have 11psi. What gives??? It's the same 47 mile trip everyday to work, and everyday I'll have a different pressure. I just replace the filter on the FASS unit with no change in readings. Do I have a pump dying on me here, or do I have something wrong with my isolator? I see no air bubbles in the antifreeze in the line from the guage to the isolator, I dont believe thats the issue. Any ideas would be great. Thanks in advance

 

[DLBurns]

If you have this type of isolator then it is probably going south. https://www.turbodieselregister.com/forums/showthread.php?t=119992 My fuel pressure dropped from 16 PSI to 11 then to 7 then to 3.



I just replaced mine last weekend with this one and it is holding steady at 16 PSI

 

[jabird]

I did have that isolator... . it did go south. . I replaced it with the one you have pictured. I purchased it from GENO'S. I'm wondering if it's takeing a nosedive also, or do I have an issue interally with the FASS. I have read in here where people have changed a spring in the FASS unit to increase pressure. Will have to make some calls tommorow and see what Doug has to say. I was hopeing to hear from someone who might have already experienced this

 

[hammersley]

Switch to an electronic gauge.....................

It screws right into the FASS... ...

 

[Big MAK]

Do you have a source or part nbr for that gauge?



I have the isolator pictured (is a diaphragm unit). My opinion on them is they 'bleed' the fluid out slightly over time (I use non toxic antifreeze) and you have to take them apart and top them off every so often. Although I don't see a day-to-day variance; just a gradual decrease over time. Then top them off and back to 15 psi. After 6 months am reading about 13. 5 psi on average now. Doen't "leak" no discernible drops or stains anywhere; just bleeds.

 

[jabird]

Hammersley... . Could one put that "electronic guage" anywhere they wanted in the fuel stream? I want to pull the preasure reading as close to the VP-44 as possible.

 

[Partyat33]

Jeff, the real problem is you need two turbo's.



Dennis

 

[jabird]

You might want to give me a call or talk to Erin about your clutch. I heard he's going to an auto... ... ... dont suppose you know of a set for sale do you Dennis?

 

[Partyat33]

I have two guy interested in my twins already. Hope you get your fuel problem solved. I am getting about 2 psi at medium acceleration on my fuel pump. Wonder why !!!

 

[JCyrbok]

The electric sender can go anywhere in the fuel line. Mine is t'ed off the fuel line about 4 inches before the VP. They are pretty common, I think that you can get them from Geno's. However u would have to have an electric gauge to go along with it. So u may have to weight the cost of a new gauage vs a new isolator.



I just got a digital camera, if u want I can try to take a pic and post it.



As for the pressure.



Mine run's about 12. 8psi all the time, unless I really get into it hard then it drops slightly and rebounds almost immediately. However as my tank gets lower, the pressure will actually drop a bit to 12psi. Maybe thats whats going on with yours. Also depending on how long ago u replaced the fitler, there may still be air in the filter (?) I know mine has weird readings for about 2 days after a filter change.



Hope this helps.



J-

 

[hammersley]

Also - you may need to put the

heavier spring in... ... .

 

[jabird]

What preasure will you see with heavier spring? Are they a pain to put in?

 

[JCyrbok]

I have been toying with the idea of the heavier spring. I think my pressure is lower as I run a NAPA 2 micron filter instead of the stock one that comes with the FASS. Havent run through a Mich winter yet with the FASS, so I am wondering about winter pressures.



Jabird, from what I have read the spring change seems pretty simple. I think u just removed the return fitting pull out the spring and check ball then replace with the stock check ball and heavier spring. Not sure how much it will bump up the pressure.



My take is anything above 10psi is good, too high can cause hard starts. I dont feel that higher pressure equals higher flow, though.



J-

 

[tractorface]

I changed my spring in under three minutes. Not much fuel comes out at all but have a bucket ready anyway. No trouble starting after the change at all. very easy to do. I was running around 20-21 psi and lowered it to 13-14psi.