How much f. pressure is too much?

[Mopar1973Man]

 

Fuel Pressure on my truck is 17.5 at idle and 16 at WOT. So if you losing over 5 PSI I would highly consider looking into your fuel pump and see whats going on. All I got is a AirDog 150.

[Me78569]

I am one of the people who started with the first of the bad runs of airdog pumps.  It is a terrible pump, 10+ psi pressure drops between idle and WOT.

 

4 dead raptor pumps in 2 years.  I now have a spare pump built from old dead pumps.

[Mopar1973Man]

I am one of the people who started with the first of the bad runs of airdog pumps.  It is a terrible pump, 10+ psi pressure drops between idle and WOT.

 

4 dead raptor pumps in 2 years.  I now have a spare pump built from old dead pumps.

 

I'm sorry...

 

I sucks to see people fighting with pumps like this. But hopefully Ed and Charlie (Pureflow) get things back on track.

[joecool911]

I get a 4 psi drop between idle and WOT. Always have. Just now I need to clean the inlet screen cause I'm starting at 17 and going down to 13 when going up a hill with a load. Raptor 100.

[Me78569]

Yea Hopefully, but I am not holding my breath.  Proof is in the pudding.

[KATOOM]

I think the "normal" expectations of pressure drop for the higher pressure / higher volume aftermarket fuel pumps and 1/2 inch fuel lines is in the range of 3-4 psi from idle to WOT.  That said, under normal conditions, additional fueling and/or fuel line size will play a part in that.  What I mean is, running the same size fuel lines, you can’t expect someone running 150's and an Adrenalin to have the same pressure differences from idle to WOT than someone running only an EZ.

[joecool911]

I've got the 1/2" Vulcan big line running from top of tank to the VP. Is there anything else I should do with the tank unit? Draw straw help? I'm looking for an excuse to cut my bed for tank unit access like JAG1 did.

Edited March 26, 2014 by joecool911

[Ilikeoldfords]

If it were me I would either go for a liberty tank module or a tank sump. I am personally going to do the sump so I dont even need to access the top of the tank at all. Check out the Beans Diesel Sump. They had a great install video on their site. Very simple and you never have to touch the top of the tank.

[Ilikeoldfords]

As for pressure drops, I am running 3/8's line from the top of the tank to the VP. All the banjo fittings are gone. The only thing is it is still running through the stock tank module (no in tank pump of course) and I see about a 5 psi drop from idle to WOT. The 3/8's line could have something to do with it but I am also suspecting the tank module is restricting the pressures a bit as well. Thats why I am going to try the sump. I have had that 5 psi drop ever since I installed the raptor brand new. Changed both fuel filters with no improvement.

[mopartechnician]

I see 5psi drop with sump, airdog 2-165, 1/2" lines to stock filter and 1/2" lines with banjo deletes. I dont understand why it would have that much drop but I really dont care as long as its above 14 at wot. Thats also with 100hp stick and adrenaline

[diesel4life]

How far below your tank does your sump hang? I like the idea of a gravity fed line but the vulnerability kinda scares me.

[Ilikeoldfords]

I think they only hang off the tank about 1.5-2 inches. Unless you are offroading a lot I wouldnt worry about it to much.

[mopartechnician]

I have a write-up on here and have a picture of how low it is. Lets just say you are going to tear up more things before you tear up the sump

[Dieselfuture]

As for pressure drops, I am running 3/8's line from the top of the tank to the VP. All the banjo fittings are gone. The only thing is it is still running through the stock tank module (no in tank pump of course) and I see about a 5 psi drop from idle to WOT. The 3/8's line could have something to do with it but I am also suspecting the tank module is restricting the pressures a bit as well. Thats why I am going to try the sump. I have had that 5 psi drop ever since I installed the raptor brand new. Changed both fuel filters with no improvement.

It is because of module, I just went from draw straw out of module and return to filler neck, to ds5 that sucks out of module and returns to module and now my pressure fluctuates about 4psi where before maybe 1. I even drilled out all of the fittings inside of module to 5/16 and it didn't seem to help, I'm now trying to figure out how to suck 1/2" out of module and return from lift pump back module in 1/2" . That way when you step on it pressure wont change that much.

[Me78569]

Increasing line size will not keep your pressures from droping. 

 

From all the work I have done to fix my pressure drop issues, the onyl thing I haven't don't is junk the craptor for a FASS.

[KATOOM]

Increasing line size will not keep your pressures from droping. 

 

From all the work I have done to fix my pressure drop issues, the onyl thing I haven't don't is junk the craptor for a FASS.

 

Increasing the diameter or the fuel line allows a for larger amount of volume (stock) to flow which in turn means that the fuel pump does not need to work as hard to supply the demand required by the engine therefore the pressure drop is less throughout that range of demand.  That said, the smallest diameter in the fuel line is still the most restrictive point in the system so if the fuel module is 5/16” but the fuel line is 1/2” then the true amount of volume is dictated by the 5/16” opening.  But…..thats doesn’t change the fact that there is a long larger diameter 1/2” piece of fuel line after the restriction which is holding excessively more volume to offset the demand loss.  And worth pointing out is that if the engine used more fuel than the 5/16” size fitting could supply at any time then the whole thing would be mute.

[MnTom]

I got into a discussion on another site and here is the gist of it:

 

Quote:

Originally Posted by MnTom

I have always been told 14 psi minimum and a maximum of 20 psi will keep the VP happy.

See and right there is why people burn the pumps up. Anything more than 14.5 knocks the front diaphragm out of the pump.

It made me so mad that I am seriously thinking of walking away from attempting to help anyone wherer this other member is. I asked for clarification (pointed him to the VP teardown thread here) and then got this:

 

I hate snarky comments.........

Figures 8 and 9 cracks those two pieces. People will argue this till the cows come home but these are my findings doing this day in and day out.

See this is sole reason why I don't argue these points anymore. I'll keep to myself and press on building pumps.

[Ilikeoldfords]

Wow. Where has that guy been all this time??? And he rebuilds pumps?? Some people...

[KATOOM]

I saw that MnTom.  Not sure where this guy has been for the past 10 years.....who also claims to build pumps.

Edited March 27, 2014 by KATOOM

[MnTom]

I saw that MnTom.  Not sure where this guy has for the past 10 years.....who also claims to build pumps.

I don't want the name of the person or the forum to be released to the general public. That would be counter productive.