Engine/Transmission (1998.5 - 2002) Fass Pressure ???

[MRiley]

Just got done installing my Fass 95 gph with the stock draw straw. I'm getting 16 idle, 14 at 80mph and 10 wot with no load. Is that a normal drop. Maybe I was expecting to much. I keep reading posts of guys who can't pull it below 15. . Is this norm?

 

[MKreiberg]

This is exactly why I haven't done it yet - I want an improvement over what I have now.

Wouldn't the 150 pull down less? / What made you choose the 95?

 

[MRiley]

I thought the 150 might be a little too much for the stock VP. Too much pressure is as bad and too little. I have stock sticks and a Smarty I don't plan on upping the sticks or going to a more aggressive fueling box. The fass is definately an inprovement over what was there. I just did not expect to see it drop to 10 psi.

 

[MKreiberg]

My thinking is that the 150 has more volume capacity, so that under higher demand (wot) the pressure would drop less.

Under normal conditions it would simply be bypassing more fuel.

 

[BLassiter]

My airdog with stock vp and no injectors is 20 idle and wide open throttle with edge 5x5 and smarty on 6 didnt drop below 17

 

[Allnew2Me]

MRiley, your numbers are the same as mine, perfectly normal and acceptable. The shop manual says pressure should never go below 5 so we are fine at 10PSI.

 

[MRiley]

Allnew2me,

Thanks for the feedback. I guess I was expecting more. I've read all these posts like the one from Blassiter and did not expect to see it drop to 10psi. I am happy because the stock pump was falling to 6 and this is a definate improvement. Maybe fuel pressure is like MPG, everyone talks about getting 28 mpg but most people are really getting 20... . I don't know.

 

[Allnew2Me]

I just installed another FASS 95 on a friends truck this week and he gets the same numbers exactly. I wouldn't worry about it, as long as you have at least 10-12 at any time you are well within the requirements of the VP. Drive it and enjoy it. You don't want any more than about 15 or you start to have hard-starting problems. In this case more is not better. What you want is also the flow volume not just pressure. If you have a full 3/8" line all the way to the VP you have plenty of flow and pressure and I don't see needing any more than that. You also have to understand that there are variations in gauges, they all read slightly different so one guy showing 20 and another showing 15 may not be all that much different.

 

[MRiley]

Thanks! I did install the 3/8 line to the Stock filter then it's all stock to the VP. I just checked it with my hand held gauge qand I'm getting 18 at idle on that. Couldn't talk my buddy into going for ride on the hood so I don't know what it looks like WOT. I have had that gauge checked so It should be a good number.

 

[BLassiter]

yup, gauges and it could all be different itself, mine being digital sometimes could tinker with the accuracy

 

[sgoeing]

my autometer fp and my edge attitude both read 19/20 at idle and somewhere around 15/17 at WOT with a decently clean filter. When the filter gets dirty, it's more like 17 idle and 12 WOT (on both gauges).

It sounds like your regulator is set a little lower. Your numbers also sound perfectly within spec for your truck. I'd smile now that the project is done, and drive it with confidence knowing your numbers are really better than most of our's spec wise.

 

[LowFly]

What are you using to monitor fuel pressure?



I get this one a lot with folks with HPFP's and mechanical gauges with isolators. When they open up the system to install the HPFP, the isolator drains back into the fuel line. Then when the system is buttoned up, the isolator has an air pocket in it on the fuel side. This causes a gauge to show drops under WOT.



ALSO restriction before the gauge tap or HPFP can cause WOT pressure drops like you are seeing. Make sure your fuel filter is clean and there is no restriction between the pump and the tank. Did you install the Filter strainer the correct way (Via the Arrow) that came with the kit?



One other thing i have seen on 98. 5-02 trucks is the Edge Juice with monitor. This set up, for some reason, likes to read low fuel pressure under WOT. I dont know why, but i had a guy double check his Juice with a known working mechanical gauge and found it to read 7 PSI low under load.



Remember not to get mixed up by reading pressures on posts as well. HPFP are set to about 16-18 PSI. FASS 95 series unit are about 12-14 PSI at idle. FASS 150 Series unit are about 13-14 PSI at idle. Most drop about 1. 5-2. 5 PSI under full load if everything is correct.

 

[MRiley]

Diesel-Dan,

Thanks for the feedback. I'll try to get to everything. The Gauge on the truck is one of the westach gages. I did bleed the line after the install but I could not get the whip line to seat correctly on the schrader valve (on the inet side of the VP) and it took me forever to get it to read pressure at all... I hooked in my mechanical hand held and got 18 idle but couldn't do a WOT as there is only 6in of hose on it. I put in an new filter at the same time as the pump so it is brand new. I put in the filter that came with the DPP kit. It was a napa filter which makes me wonder how often that should be changed as the main filter needs pretty regular changing. Any ideas on that would be great. I also wondered if that could be causing restriction and if I should swap it out for a strainer? The filter looked like a gasser filter (not saying it is that's just what it reminded me of). But I thought if it is on the suction side any restriction is going to be more pronounced than if it were on the pressure side. I only have a smarty on (level 9) no juice, other than intake and exhaust the truck is pretty stock. I'll have to check the lines in the daylight again but I was pretty careful and feel confident there are no kinks allong the way. The truck seems to run well and no hard start issues, so I'm pretty pleased. I was just surprised that WOT got me to 10, that's a 6psi drop from idle... . With no Load. I haven't hooked up my 5er yet but am wondering what it's going to show under a load?



Thanks again for jumping in

MIKE

 

[LowFly]

Diesel-Dan,

Thanks for the feedback. I'll try to get to everything. The Gauge on the truck is one of the westach gages. I did bleed the line after the install but I could not get the whip line to seat correctly on the schrader valve (on the inet side of the VP) and it took me forever to get it to read pressure at all... I hooked in my mechanical hand held and got 18 idle but couldn't do a WOT as there is only 6in of hose on it. I put in an new filter at the same time as the pump so it is brand new. I put in the filter that came with the DPP kit. It was a napa filter which makes me wonder how often that should be changed as the main filter needs pretty regular changing. Any ideas on that would be great. I also wondered if that could be causing restriction and if I should swap it out for a strainer? The filter looked like a gasser filter (not saying it is that's just what it reminded me of). But I thought if it is on the suction side any restriction is going to be more pronounced than if it were on the pressure side. I only have a smarty on (level 9) no juice, other than intake and exhaust the truck is pretty stock. I'll have to check the lines in the daylight again but I was pretty careful and feel confident there are no kinks allong the way. The truck seems to run well and no hard start issues, so I'm pretty pleased. I was just surprised that WOT got me to 10, that's a 6psi drop from idle... . With no Load. I haven't hooked up my 5er yet but am wondering what it's going to show under a load?



Thanks again for jumping in

MIKE

That 3270 "Napa Filter" we use is actually a strainer. Its 144um and most of the time can just be back flushed with some brake clean. Just shake it up with both ends closed between your fingers, and then release the inlet side of the filter onto a paper towel. Repeat until clean.

 

[MRiley]

Diesel-Dan

Thanks for the information on the Napa filter. I checked all the lines and found no kinks or restrictions. So is a 6psi drop norm???? I know that 10psi is completely within norm bbut I was not expection the FASS to have that big of a drop??

 

[LowFly]

Diesel-Dan

Thanks for the information on the Napa filter. I checked all the lines and found no kinks or restrictions. So is a 6psi drop norm???? I know that 10psi is completely within norm bbut I was not expection the FASS to have that big of a drop??

No, i can't say it is. BUT from working with several folks on issues like this, (AND also for one guy, sending 3 pumps out) we found the majority of the issues to be caused by something outside of the pump. The ONLY time i have seen our pump cause the issue is when debris gets into the check ball seat that regulates the system pressure. This is from initial installs usually. Pieces of cut line cause the problem, and also Thread tape (if too much is used, or applied incorrectly). Chunks will brake off and get jammed in-between the ball and its seat. This will cause our regulator to keep bypassing when fuel demand shifts to the engine and you will note a pressure drop.



I don't have an issue sending a pump out only if I felt that the individual has gone over everything to make sure its not our pump. If you wish to explore this option, have your dealer call me with your serial number and we can go from there.

 

[MRiley]

Diesel - Dan



Thanks for all your help and support. I think I have located the problem. The whip line from the VP to the pressure sending unit was bad. Somthing got in the valve part and plugged it. I replaced the line and now my gauge is maxed out at 16psi and never drops. The pump seems to be working Great. Thanks for all your help and offer to switch out the pump. It looks like you were right it wasn't the pump at all.



MIKE

 

[LowFly]

Glad to see it was an easy fix! Let me know if i can help any further.....

 

[CumminsFarmer]

I have a 95gph FASS, with a Hot Rod VP and Stage 2 injectors. Im 15-16 at idle. 14-13 running the throttle up while shifting, 12 WOT empty, and 12 down to 11 when towing around 10-15,000 lbs. Works pretty good Id say.