Good afternoon,

 

I have a quick fuel pressure question.  I recently noticed that my FP gauge reads between 14-14.5 psi while driving, it was reading 17psi-18psi a few weeks go.  I assumed that the filters may need replacing, although they only have 2500 miles on them if that.  I have not swapped filters out as of yet, but noticed something odd today.  I bumped the engine over and FP gauge showed 16psi, but when I fired truck up the gauge would fall to 14ish psi.  Would the VP44 drawing fuel cause the gauge to drop.  I have adjusted the Airdog 4G in the past to show the 17-18spi while running.  the gauge "T" with sensor is approx 20 inches away from VP44.   

 

I just think it is odd that a few weeks ago fuel pressure was good and the past few days it has dropped and that there is a drop when engine is running compared to when Airdog is solely running.

 

Any help is appreciated.  

 

I have not checked voltage at the pump yet, plan to hopefully this weekend.

 

Tim

Should help.

Good evening everyone,

 

Small update - I let the truck warm up in high idle before work and when I got in the truck to leave for work after about 10 mins the FP Gauge read 21 psi. Tomorrow I will let the truck warm up and reset the FP to 17-18psi.

 

Thanks,

 

Tim 

30 minutes ago, Collinst15 said:

Good evening everyone,

 

Small update - I let the truck warm up in high idle before work and when I got in the truck to leave for work after about 10 mins the FP Gauge read 21 psi. Tomorrow I will let the truck warm up and reset the FP to 17-18psi.

 

Thanks,

 

Tim 

I would advise to let it be for now and settle in. Mine seemed to move around a little on the first pump. 21 psi is not going to hurt anything at all. I dicked around with first one several times until it settled in. As I stated 21 psi hurts nothing. The most important pressure in the 14 psi you want to equal or surpass at WOT. That will keep the VP happy, along with some 2 stroke oil.

 Mine sits at 20.5 psi and all is good.

Edited January 18, 20196 yr by dripley

10 minutes ago, dripley said:

I would advise to let it be for now and settle in. Mine seemed to move around a little on the first pump. 21 psi is not going to hurt anything at all. I dicked around with first one several times until it settled in. As I stated 21 psi hurts nothing. The most important pressure in the 14 psi you want to equal or surpass at WOT. That will keep the VP happy, along with some 2 stroke oil.

  Mine sits at 20.5 psi and all is good.

I did a small test pull from WOT 30mph to 60mph and psi went from 21psi to 17psi.  Ill give it a few days and see if it settles in.   I will be driving the truck for the next week as a daily.  

 

Tim

If that stays pretty constant for the week back it off some and see how that settles in. Mine has always been a bit wonky till you let settle in. Dont know why, but a weekly or even bi weekly will find the pressure you are looking for. Just be sure to keep the low side at 14 to 15 and you will be good.

I'll throw in my two cents here since your in NY. Your pressure will drop if your running tight filters.  Anything over 15psi is good, but keep it under 20. My fass 95 would routinely see a drop in pressure when its cold out and your into the 20's.

I learned this, and since the weather dropped ion the last week I think it's well worth mentioning this. better have to have a larger micro filter for winter use, and a tighter filter up in the engine room.


As for me I have my T fitting with a shut off valve, followed my grease gun hose to protect the line, up into the cab followed by 1/4' air line hose with compression fittings armed with the brass sleeves. i haven't had any issues with this set up since I've done this. I highly recommend the grease gun hose for the road debris!

Edited January 18, 20196 yr by pepsi71ocean

I wont disagree 20 or below is good for a high pressure but you still have to have it high enough to see 14 or more for a low pressure. Mine sits at 20.5 at idle and about 16 as a low pressure. One day I will turn it down a bit, but for now I am not worried. Several folks here run above 20 regularly. so 20.5 or 21 seems to me not to be an issue.

1 hour ago, dripley said:

I wont disagree 20 or below is good for a high pressure but you still have to have it high enough to see 14 or more for a low pressure. Mine sits at 20.5 at idle and about 16 as a low pressure. One day I will turn it down a bit, but for now I am not worried. Several folks here run above 20 regularly. so 20.5 or 21 seems to me not to be an issue.

 

Why do you have a 4 psi drop? I don't even see that with my fass 95 100hp injectors and my smarty turned up.

I figure it is the 3/8 pick up in the fuel basket. Thats what my AD came with for the in tank pump replacement kit that came with the AD 165II I bought 8 years ago.. The 4 psi drop has never bothered me as long it stayed at 14 or more. I would turn it down some but I just dont see any need to. 

So I drove it home tonight in 22°F weather with a real feel of 12°F.  I let truck warm up 5 minutes in high idle mode and fuel pressure was a steady 18psi.  While cruising at 55mph FP was 16psi.  I did a 40mph-70mph run and FP held at 15psi WOT.

 

Not sure why it would change other than it was 30°F when I went to work today.

 

Tim

51 minutes ago, dripley said:

I figure it is the 3/8 pick up in the fuel basket. Thats what my AD came with for the in tank pump replacement kit that came with the AD 165II I bought 8 years ago.. The 4 psi drop has never bothered me as long it stayed at 14 or more. I would turn it down some but I just dont see any need to. 

 

I have a 1/2 draw straw, and 3/8's from draw straw to fass, but I'm using marine grade fuel line for now. After i pull the bed this coming week I'll be converting it to 1/2 to fass and leave the rest at 3/8's.

 

1 minute ago, Collinst15 said:

So I drove it home tonight in 22°F weather with a real feel of 12°F.  I let truck warm up 5 minutes in high idle mode and fuel pressure was a steady 18psi.  While cruising at 55mph FP was 16psi.  I did a 40mph-70mph run and FP held at 15psi WOT.

 

Not sure why it would change other than it was 30°F when I went to work today.

 

Tim

 

I see 18 at idle and 16 under load. as long as your above 15psi 80% of the time your fine. IMO people get freaked out about fuel pressure more then the temperature of the fuel.

 

Abnormal or erratic fuel pressure swings happen more with the newer Raptor 150's. I recently installed a new one to both my trucks and both had the same strange acting pressure swings. Mopar Mike said to run them up and down, high and low on the adjustment screw. This helped a lot, but need to do it seven times instead of one time for better results.

Edited January 20, 20196 yr by JAG1

Like I'm an old school check ball and spring and just bending the spring wrong will create some wild up and down pressure swings when the check ball can't center properly. Yeah I've got to replace the spring again.

7 minutes ago, Mopar1973Man said:

Like I'm an old school check ball and spring and just bending the spring wrong will create some wild up and down pressure swings when the check ball can't center properly. Yeah I've got to replace the spring again.

 

Call and ask for a bigger spring. I'm running a FASS 150 spring in my fass 95. It took some cutting but I to my spring down to 18psi at idle, and even under the heaviest acceleration I don't see much of a drop, and that was 35,000 or so miles ago.