notlimah

Yea that's basically the only reason I ended up checking it was because the next things to check were either expensive or tougher fixes.

***PROBLEM SOLVED*** So ended up getting this issue fixed!! Turns out the return line JIC fitting on my FASS was just slightly loose. I only turned it maybe an 1/8th of a turn and it has cured my longer cranking issues when parked uphill over night. Subsequently, it seems to have been causing me issues with erratic fuel pressure readings link HERE to that thread. Needless to say, I tightened that fitting up and it took a little bit of driving for the air to work itself out of the lines, so you have to be a bit patient with it. Anyways, just wanted to pass along for future readers what ultimately fixed my issue. I also found a cheaper source for the grommets that go into the TEE from Geno's. Links HERE part number is 3905351 from Cummins.

Issue is fixed! Also ended up fixing my hard start troubles HERE

If there's a leak there's a leak. The FASS won't hold the fuel in the lines. Once all the air is out of the fuel system, it will stay under pressure. If you're loosing prime then there's a leak somewhere. Especially on the return side, you won't see a physical leak, that's why going back through and snugging up any and everything can solve your problem. It fixed mine and I had already done a lot of what you did and turns out it was a simple JIC fitting that was a little loose.

Ok so all seals at the fuel return TEE have been replaced? THIS part from Geno's? Return lines at the FASS are as tight as they can get? FASS filters are tight? Sorry if this seems redundant but your symptoms scream leak on the return side. Only other thing I think it could be would be injector O-rings. Unless you have an original VP44, I don't see anything on the inner 'diaphragm' being the issue as they fixed that.

Alright jigdog, I just got done chasing down every thread possible on this exact issue as I was having the same issues. I'll list out everything I've found that could be the potential, and then what I THINK fixed mine. From my findings, anytime you park uphill and loose prime and park downhill but maintain prime points to a leak in the RETURN side of the fuel system. Possible causes to this could be the following; -Banjo bolt washers at the back of the head -Grommets at the return TEE from the banjo and the VP -Overflow valve at the VP -Crossover tube o-rings -Any return fitting associated with your FASS being loose I started on mine with new washers on the banjo bolt at the back of the head and tightened down the fittings at the TEE directly down from the banjo bolt on the back of the head. No joy Tried tracking down the grommets that fit in the TEE, found some at Geno's but they're back ordered. In the meantime I decided to check my return line fitting for my FASS and I got an extra 1/8th-1/4 turn out of it and it seems to have fixed my issue. With this I was also have erratic fuel pressure gauge readings. I tightened that return line fitting about 100-150 miles ago and TODAY it seems as if all the air that was in my system causing this issue have worked itself out. I no longer have erratic fuel pressures and I'm 1 for 1 on quick start ups after being parked nose up over night. Hope this helps!

Rear diff looks like a 3/4 -14 npt part #03640792 Couldn't find a size associated with the t-case plug

So I was on the phone was FASS and I was sitting in my truck with it idling watching the gauge hop around and all the sudden it just stopped and didn't do it again. Drove all the way home, no issues. Parked for a bit up hill and when I went to start it even bumped the fuel pressure up to like 5psi. Started no problem and no pressure fluctuation. The only thing I can think of that fixed this was tightening the return line on the FASS. That's the only thing I changed. I guess it was leaking a little air in the line and causing some fluctuation in my pressure. We'll see if that fixes my hard start when parked uphill.

I'm in for the sub because I've wanted to do this as well at some point but never tackled something like this! Take lots of pics!!

Gotcha, that makes sense. Now that I think about it, I'm not sure if the gauge did this prior to me replacing the washers on the banjo at the back of the head. Obviously let some air in the lines then, so maybe that just hasn't worked it's way out yet. I'm not too concerned about the gauge being delayed in showing pressure since I'm still above 14psi. What I don't like is the fluctuation is pressure.

@BBHD I meant to ask you, where did you plumb in your fuel pressure gauge?

Alright so just to further experiment with this issue I parked uphill last night and surprisingly, the truck started with little to no delay at all. So my leak on return lines may POSSIBLY be gone?! I did tighten up the return lines on the FASS the other day and got it tiny bit tighter then it was before so maybe that's what fixed/caused it, but who knows. Anyways, I started her up, took about 6-7 seconds for fuel pressure to register and it was bouncing all over the place. Between 16-19psi at idle. While driving it would steady out SOMETIMES but then it'd go back to fluctuating again. So I thought it could just be my low fuel level, since I was at or below an 1/8th of a tank, I figured it could be that. So drove to the gas station and filled up. Started the truck and it took almost 10 seconds for fuel pressure to register on the gauge and it was still fluctuating. So doesn't seem like fuel level was causing these issues. I sent FASS an email so we'll see what they say. Definitely frustrating to be having these nit picky issues with a practically brand new pump, not to mention the on again off again hard starting on an incline

I'll get ahold of FASS and see what they think. I haven't even had it on the truck more then 3k miles so it's still pretty new.

Man this makes me want to get a HAM even more!

@Dieselfuture Did you just call FASS and tell them what was going on and they sent a new one? Or you have to pay out of pocket? @BBHD I backed off the needle valve a bit so I'll see how it reacts in the morning. Although I'm not sure I'll see the bump at key on due to my leak on the return aide somewhere. All awesome points though guys, I appreciate it! I'll see about getting a new spring and ball and I'll adjust the needle valve a bit. Hopefully Geno's gets my new grommets in soon!

Thanks! That does make sense especially since I'm still chasing that leak. Air is never really able to purge itself from the system. Ive never heard about the overflow valve issue. Doesn't it stay open constantly above 14psi? It definitely does make sense as to why the pressure would drop but like you, never heard about that specifically.

That red clay is the worst!

I do have a leak because I'll loose prime when parked uphill overnight. I can't tell if the pump is cycling while driving. I actually don't think I knew it did that. I suppose that would create the rise and fall in pressure. Im running the FASS 150 with drawstraw. I'll open the needle valve a smidge more. I coulda swore I read at one point that needle swing is normal but not sure if that was just minimal water hammer. Im comparing this a bit to my 99's setup but it's not really similar since I ran my tee off the stock fuel filter on the 99 and the 02 is running the tee right off the fuel line coming from FASS. Do you think moving it back to read pressure from the LP itself would help? I'm not sure how accurate that pressure is back there compared to up by the VP?

Ok so since I'm on my second ISSPRO gauge in this truck, I've been paying extra attention to it and the FASS. Well I've noticed a couple things and just wanted to clear the air. I don't think anything a wrong but just wanted to get some extra input before I moved on to worrying about the next thing. Currently have less then 1/4 tank so keep that in mind... If/when I bump the starter, the FASS will run/prime but I don't see any fuel pressure build on my gauge. Once I finally start it takes 5+ seconds before it shows any readings which end up between 16-18 at any given point. - Anything to worry about here? While driving I noticed recently that the needle would bounce around a couple psi with no relation to throttle input. -Could this be because of low fuel? Finally, my gauge is setup with just a tee into the fuel line, to a needle valve, then gauge. The needle valve is cracked literally as little as possible to get a reading on the gauge. The way it's setup now I can't see a cranking pressure (if it takes that long to start) since it takes a bit to build pressure. -Should I open it a little more to get a quicker response from the gauge?

This is amazing! Super easy and puts all tire size and gear ratio questions in one location!

We need pics!! You got me looking into slide in campers now as well.

Nice find!

I have the DOR installed now so I have adjust-ability. I think its fairly centered, I checked it on more level ground and just eye balling it it looks pretty centered.

Yea same here @Dieselfuture she'll drop tp 17 here and there and sometimes be around 16-17 on a colder startup but normal psi is 17-18 @leathermaneod with the FASS 150, this whole issue is happening on my 02

Cool, that's what I thought. I'll have to listen more closely to see if I can hear it all the time, or just at certain times. Either way I'm not too worried about it because the truck starts fine and I have rock solid pressure at 18psi almost all the time, no matter WOT or idle.