Mechanical FP gauge

[notlimah]

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? 

[CSM]

20 minutes ago, notlimah said:

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?

Depends on how tight your needle valve is.  I like to see a bump... could be an air or fuel leak if it doesnt build pressure on the initial switch to run.

20 minutes ago, notlimah said:

 

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?

I can hear my pump cycle on and off, i think its normal... but i have never been worried about it.  If it bumps when your pump is steady, id look more at pump cavitation.  

20 minutes ago, notlimah said:

 

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? 

 

I would open it up, but i like seeing more movement.  If it is as tight as you say, the bumps while running are a bit more curious, as they should  be evened out by the valve.  

 

Do you have a stock in tank pickup?

[notlimah]

1 hour ago, CSM said:

Depends on how tight your needle valve is.  I like to see a bump... could be an air or fuel leak if it doesnt build pressure on the initial switch to run.

 

I do have a leak because I'll loose prime when parked uphill overnight. 

 

1 hour ago, CSM said:

I can hear my pump cycle on and off, i think its normal... but i have never been worried about it.  If it bumps when your pump is steady, id look more at pump cavitation.

 

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.

 

1 hour ago, CSM said:

I would open it up, but i like seeing more movement.  If it is as tight as you say, the bumps while running are a bit more curious, as they should  be evened out by the valve.  

 

Do you have a stock in tank pickup?

 

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?

[dripley]

I would open the valve a little more and see if the pressure stabilizes a little. If your draw straw is in the tank and not the basket you might be seeing a little air being sucked in with a low tank due to fuel slosh. I have seen that on a couple of Mike's videos of his truck. Kind of hard to say though. As far as the pump cycling on and off while driving, I would think not. The ECM tells the pump to run until key off or no idle, it should run continuously.

[leathermaneod]

notlimah, I think I may be able to provide an answer to both of your issues as I have experienced both, the first for sure anyway. First, your gauge not registering pressure until after startup is an indication of air in the lines, in my experience. Mine will do that for a few days any time I open the lines to adjust my bypass valve. Once all the are is out, you should see the gauge spike up and fall when the pump primes at key on, and then it should build pressure very quickly when the truck starts. As for the second issue, I had, I believe, the exact same issue back when I had my old FASS lift pump. From what I remember the pressure would just jump around a couple psi in the 15-18 range while driving along with an even throttle. I asked the FASS tech department what would cause it and they were very helpful. They told me it was most likely the overflow valve at the VP44 opening and closing, and that there was no reason to worry about it. I can't absolutely confirm that, but I never found anything to disprove it. You could try replacing the valve or upping your pressure a bit though, and see if either helps. Good luck!

[notlimah]

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.

[Dieselfuture]

My pressure was up and down 3 psi on a brand new fass150, put a new ball and spring on return of fass and pressure been steady, I also modified the spring a bit by curling it a little so the ball doesn't get stuck in it.

[BBHD]

@notlimah I'm running pretty much the same setup as you are. Draw straw V, fass150 and Ev1 mechanical fuel pressure guage. As soon as I cycle the key to run I can hear my pump run for maybe a second or 2 however my guage moves instantly to 7-10 psi with just that short burst and falls slowly until I start it up. I had to fiddle for a bit with my needle valve to find the spot where I could get the guage to react without bouncing(water hammer). Once started it sits steady between 18-19 psi. 

[notlimah]

@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!

[leathermaneod]

As far as the overflow valve opening, I believe you are correct that it should stay open at all times when pressure is above 14 psi. However, I think FASS was saying that it might be hanging up due to age, or that it might be slightly out of spec and so the pressure my pump was putting out was right at the open/close threshold. Honestly though, I think what Dieselfuture is saying makes more sense. I think I've read about guys having similar problems before and fixing it with a new spring. Also the problem of the ball geting pushed into the spring sounds familiar to me. Unfortunately, unless you just bought the system, I don't see them giving you a new spring for free, but I'm pretty sure they are not expensive, as in a few bucks.

Edited May 18, 2016 by leathermaneod

[Dieselfuture]

I told them what I thought was wrong and the guy at fass agreed with me and sent me new spring and ball free of charge, he said it happens sometimes when they sit on shelf too long. My guess is if you don't drive it for a year it may happen also. My truck sits for a month at a time sometimes longer without a problem, so I'm guessing it has to be a longer time period. 

[Dieselfuture]

I told them what I thought was wrong and the guy at fass agreed with me and sent me new spring and ball free of charge, he said it happens sometimes when they sit on shelf too long. My guess is if you don't drive it for a year it may happen also. My truck sits for a month at a time sometimes longer without a problem, so I'm guessing it has to be a longer time period. 

[notlimah]

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.

[leathermaneod]

Oh ok that's good. I would think they will help you out then. They have a very good customer support webpage with emails and phone numbers for their guys. 

[notlimah]

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

[notlimah]

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

[leathermaneod]

I wouldn't totally discount still having air in the lines as a cause for the gauge being slow to build pressure. Wether it was/is caused by an air leak or low fuel issue, you can't rule it out yet. Like with my truck, it takes a few days of driving to purge all that air, for me that's around 200-300 miles. In the future I would say try to avoid going lower than 1/4 tank. It will help reduce the likely hood of dirt getting sucked in as well as prevent possible air issues. The fuel also starts to get pretty warm when you have so little left in the tank and it won't be able to cool the vp44 as effectively. Just my opinions of course.

[notlimah]

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.

[leathermaneod]

Hopefully FASS can hook you up with a quick  and easy and hopefully free solution.

[Dieselfuture]

On fuel temp in vp, my guage says 130ish when driving down hwy. That's coming from my qwadzila. Tank full or empty.