My fuel pressure has been acting crazy. Started gradually increasing from 16 lbs to 27 lbs. 

I thought at first that it was due to cold fuel. I live at 9500 ft. 

Had this system for about 35,000 miles or so.

 

2001 2nd generation with DDRP Fass 95 mounted near the fuel tank. 

 It did the same thing a while back and I got the pressure adjusted back to where I wanted it.  Now I have to try it again.

Is it the ball and spring in the Fass pump you think?

Filter?

I am going to change the OEM filter and the in line filter before the pump and see if that helps.

Last time it didn't make any difference.

Thank you!

Where are you reading pressure?  (Between FASS and OEM filter housing, after OEM filter, ...).  It could be a bad pressure sender, possibly affected by the cold or "hammered" by the VP44 (not enough snubber line to protect from pulses).  If the sensor is after the filters, they shouldn't cause a climb in pressure (possibly a drop in pressure due to dirty or restricted filters).  If the sensor is before any of the filters, a rise could indicate a dirty or restricted filter.

You might also want to do the FASS check ball upgrade -- Air Dog 1V-1-00003 17# spring and 3B-10-0.625 Viton ball (better than FASS original ball -- may have a groove in it causing it to stick).  I bought mine from Vulcan Diesel.

 

BTW:  My pump is a FASS TD08095G Titanium  purchased 08/2013 -- only problem was a groove in the OEM check ball after 7 years and I replaced it this past year to correct a fluctuating pressure reading on my gauge.  Now I have 17-18 psi at idle and 15 - 16 psi at WOT.  The Air Dog spring seems to be very accurate.

Edited February 20, 20214 yr by Joe_Pool
To add information

3 hours ago, comanche79p said:

I am going to change the OEM filter and the in line filter before the pump and see if that helps.

Last time it didn't make any difference.

Thank you!

I just now changed these filters and didn't make any difference on the pressure

1 hour ago, Joe_Pool said:

Where are you reading pressure?  (Between FASS and OEM filter housing, after OEM filter, ...).  It could be a bad pressure sender, possibly affected by the cold or "hammered" by the VP44 (not enough snubber line to protect from pulses).  If the sensor is after the filters, they shouldn't cause a climb in pressure (possibly a drop in pressure due to dirty or restricted filters).  If the sensor is before any of the filters, a rise could indicate a dirty or restricted filter.

You might also want to do the FASS check ball upgrade -- Air Dog 1V-1-00003 17# spring and 3B-10-0.625 Viton ball (better than FASS original ball -- may have a groove in it causing it to stick).  I bought mine from Vulcan Diesel.

 

BTW:  My pump is a FASS TD08095G Titanium  purchased 08/2013 -- only problem was a groove in the OEM check ball after 7 years and I replaced it this past year to correct a fluctuating pressure reading on my gauge.  Now I have 17-18 psi at idle and 15 - 16 psi at WOT.  The Air Dog spring seems to be very accurate.

 

Thanks for the reply. My pressure line is at the VP44 and the line goes up to the area by the drivers side battery. The readings are good according to the troubleshooting guide for the pressure sender. 

 

I adjusted the pump pressure again and have it at about 17.5 at idle. Going to leave it there and see what happens again. 

I sent an email to Vulcan asking them about the ball and spring for the Fass and they said they didnt have anything for the Fass pump.

I will call them.

Thanks

To be clear, I have the FASS Signature Series (100) 95 gallon per minute pump that is adjustable.

6 hours ago, Joe_Pool said:

You might also want to do the FASS check ball upgrade -- Air Dog 1V-1-00003 17# spring and 3B-10-0.625 Viton ball

Is this applicable to this style of FASS DDRP?

The numbers I listed are for the style pump below and are installed behind the fitting by the red arrow.  The ball is a 5/8" diameter ball.

 

Loren  --  I believe the DDRP uses a much smaller ball and spring.  You might try calling FASS directly, I believe that they have a stiffer spring to increase the pressure (fewer twists, but heavier gauge).

 

Comanche79p  -- I am not familiar with the pump that you have, I thought you were talking about the type that I have.  Again, you might want to contact FASS as it sounds like your regulator is losing adjustment on its own.  I wonder if the extreme cold could be affecting the regulator components.

 

Sorry for any confusion.

3 hours ago, LorenS said:

Is this applicable to this style of FASS DDRP?

No, mine has a adjustment screw on the end.

I have wondered if the relief valve on the VP is affected by the colder diesel. This week's bout of negative temps is the first I've experienced with this pump on my truck. Also, the first time Ive had pressure over 25 PSI. Then it dropped to ten and waved up and down til settling in at the usual 15-16.

 

Not sure how many miles are on my VP, only had truck for 63k miles or so.

1 minute ago, LorenS said:

I have wondered if the relief valve on the VP is affected by the colder diesel. This week's bout of negative temps is the first I've experienced with this pump on my truck. Also, the first time Ive had pressure over 25 PSI. Then it dropped to ten and waved up and down til settling in at the usual 15-16.

 

Not sure how many miles are on my VP, only had truck for 63k miles or so.

I stuck mine in the 65 degree heated shop overnight and 15 hours later the fuel pressure was the same. I wondered if the relief line was frozen. 

If it's spring and ball issues then you need to modify the spring so the ball doesn't get stuck in it. Weird that this came up, we went skiing today and on the way back I noticed my fuel pressure was barely at 14, came home and took the ball out and it has a nice deep grove all around and one spot had some scuff marks. So I put another ball in (I had a spear) and now back to normal 19psi. These balls do wear out after so long, at least I'm on 3rd one now. 1st one got changed when I got the pump, was bad when pump was new, wouldn't hold pressure, fass send me a  free one. Not sure how long ago 6-7 years now and now another ball went in. Back in business. 

 

20 hours ago, comanche79p said:

To be clear, I have the FASS Signature Series (100) 95 gallon per minute pump that is adjustable.

 

A little trick run the pressure regulator all the way out till it near zero. Then run in back in again. Some time the adjustable regulators stick internally. When you adjust it out you moving the assembly inside and moving the spring nad everything. Now when you reset you might see more stable pressure. I had @JAG1do this trick and it cured his Raptor of this problem. Being that both FASS and AirDog are father and son battle the designs are very similar. Like @Dieselfuture has the style I've got with my AirDog 165 pump. Spring and check ball common store item with Vulcan being he makes most of the parts for AirDog.

 

I just a few washers to adjust my pressure. Tighten the spring and the ball stays closed a bit longer before pushing open on the return line. Stable 15 to 17 PSI for years!

Edited February 21, 20214 yr by Mopar1973Man

25 minutes ago, Mopar1973Man said:

 

 

A little trick run the pressure regulator all the way out till it near zero. Then run in back in again. Some time the adjustable regulators stick internally. When you adjust it out you moving the assembly inside and moving the spring nad everything. Now when you reset you might see more stable pressure. I had @JAG1do this trick and it cured his Raptor of this problem. Being that both FASS and AirDog are father and son battle the designs are very similar. Like @Dieselfuture has the style I've got with my AirDog 165 pump. Spring and check ball common store item with Vulcan being he makes most of the parts for AirDog.

 

I just a few washers to adjust my pressure. Tighten the spring and the ball stays closed a bit longer before pushing open on the return line. Stable 15 to 17 PSI for years!

I sure will give that a try when I get to my place in Kansas later today. I am taking the tools with me in case I have to stop and re-adjust.

I am trying to understand exactly where that ball and spring is located. I went to FASS and tried finding that in their tech manual, but it wasn't helpful or I was looking in the wrong place.

8 hours ago, comanche79p said:

I sure will give that a try when I get to my place in Kansas later today. I am taking the tools with me in case I have to stop and re-adjust.

I am trying to understand exactly where that ball and spring is located. I went to FASS and tried finding that in their tech manual, but it wasn't helpful or I was looking in the wrong place.

In our case it's in the return to tank line fitting screwed into the pump, yours may not have it if you only have 2 lines, on in from tank on out to vp44, we have 3 lines on the pump. That's why on cheaper pump there's a regulator, although I have never held one so I don't know if it has a spring and ball. 

No spring and ball on the 2 line pumps just a spring load check valve. That's why I said to cycle out the regulator so it frees up the regulator valve. Typically returns to the inlet side.

The FASS folks indicates I have a ruptured diaphragm. Sent them my serial number to see if the will warranty it.

I bought it in 2013 from Geno's.

 

Thanks for all the help.