Fuel Pressure Issue

[crgjhnsn]

My truck is a 2001.  I have an older AirDog, and an ISSPRO electric fuel gauge.  The issue I'm having is that when I first bump the ignition I get about 15-16psi of fuel pressure.  Then running, or even if you let the pump shut off and then rebump the ignition, the fuel pressure goes up to 26psi.  I really need to get my test gauge on it, but two different sending units and gauges have been put on it, and both read the same.  I was wondering if anyone has any ideas of what I should check?  Is it the AirDog, that's marked as being regulated at 15 psi, did I screw up with how I installed the gauge?  Any input would be greatly appreciated. 

Also, the AirDog was on before I pressure gauge was (I know shame on me....), so I do not know if this is a recent change or has always done it.

[Mopar1973Man]

First off did you directly install the fuel pressure sensor to the VP44 inlet? If so you killing the sensor. You need to remote mount the sensor away from the VP44. 

 

You can check the AirDog regulator it's either adjustable or it's the old school check ball and spring. The check ball and spring is in behind the return fitting of the AirDog.

[crgjhnsn]

Sending unit is installed in the AirDog fuel line probably  1 1/2 to 2 feet from the vp44.  Would I be better off installing it into the AirDog itself?

Edited July 31, 2016 by crgjhnsn

[dripley]

Do you have a snubber or something like it to protect the sender?

[crgjhnsn]

Yes.  Small brass one from Vulcan Performance.

[Mopar1973Man]

Should be a sintered brass snubber not an orifice. Still need to be at least 5 feet away from the tap point to allow the pulses to fade that make it through the snubber.

[crgjhnsn]

I apologize for resurrecting an old post, but need a little input.  I haven't driven my truck very much since I started having these issues.  I am now able to install a mechanical fuel pressure gauge.  I'm looking at the kit from Vulcan Performance http://www.vulcanperformance.com/ProductDetails.asp?ProductCode=EVFP and I was wondering where you all recommend tapping in to the fuel lines, and how (tee, banjo bolt, etc).  Also is there anything that isn't included in that kit that I would need.  Thanks in advance for input on this. 

Edited November 9, 2016 by crgjhnsn
add info

[Royal Squire]

Do you have stock fuel lines?  I think most folks here use a needle valve instead of or in addition to snubber that comes with gage. Someone with more expertise than I will most likely respond also

[crgjhnsn]

27 minutes ago, Royal Squire said:

Do you have stock fuel lines?  I think most folks here use a needle valve instead of or in addition to snubber that comes with gage. Someone with more expertise than I will most likely respond also

No running an AirDog.  Believe they're 1/2 lines.  I do still have the stock fuel filter housing, and a big line kit that goes from the housing to injection pump.  The housing and big line kit just isn't on the truck.

[Royal Squire]

Just have Vulcan send a 1/8" inline tap that you can install in 1/2" hose between factory filter and vp44. Screw your gage fitting into that. There should be an article on this on the site somewhere 

[dripley]

I got the big line kit from Vulcan and ordered a tapped tee along with it. It is installed about half way between the filter canister and the VP. I did not use a snubber, i have the valve barely cracked open. I also used the nylon tubing to go to the gauge. Napa sells some black air line hose that is better but this has held up for 6 years. If it ever fails I would get the air line to replace it. My gauge is in an a pillar pod and I drilled a small hole in the bottom of the pod holding the gauge so I could tell whether it was leaking. some folks do use a snubber also and it cant hurt. Mine still works fine. I got the valve from Vulcan also. A lot parts houses have them also.

Edited November 9, 2016 by dripley

[015point9]

While not totally finished with my install.  I get same psi reading at airdog pump (model df100) of 12 inches away from VP44 and at airdog pump, both using a snubber 

 

I'm not finished installing because other gauge wires in/under dash are fighting with me.  But running wires from each location (just tangling) I get the same psi reading. 

[crgjhnsn]

46 minutes ago, dripley said:

I got the big line kit from Vulcan and ordered a tapped tee along with it. It is installed about half way between the filter canister and the VP. I did not use a snubber, i have the valve barely cracked open. I also used the nylon tubing to go to the gauge. Napa sells some black air line hose that is better but this has held up for 6 years. If it ever fails I would get the air line to replace it. My gauge is in an a pillar pod and I drilled a small hole in the bottom of the pod holding the gauge so I could tell whether it was leaking. some folks do use a snubber also and it cant hurt. Mine still works fine. I got the valve from Vulcan also. A lot parts houses have them also.

 

Thanks!

4 minutes ago, 015point9 said:

While not totally finished with my install.  I get same psi reading at airdog pump (model df100) of 12 inches away from VP44 and at airdog pump, both using a snubber 

 

I'm not finished installing because other gauge wires in/under dash are fighting with me.  But running wires from each location (just tangling) I get the same psi reading. 

 

Sounds like we're both tapped in at about the same place.  It's interesting to me compared to what most other people seem to be seeing.  Thanks for sharing.

[015point9]

Set your air compressor regular for 50 psi, then check it.   Then check the psi at end of a 20 foot air hose. Should be the same psi at compressor and end of hose.  Pressure is pressure.  Matter of fact I made sure my gauge was working before install by using air compressor at 15 pounds.

 

Why wouldn't you see the same pressure that is pumped into a confined space one end or the other?   Maybe the football used in Deflate gate should of been tested at both ends. 

 

Now to see if your pump can keep up with pressure and volume, gauge further away from pump source, better the reading.  But IMO most don't like to install gauge close to VP because of the pressure it generates is not good for gauges.  Matter of fact Geno's Garage wouldn't sell me a gauge without a snubber (elec gauge) when I said VP44...but whatever.

 

 

 

Edited November 10, 2016 by 015point9

[dripley]

The main reason I put mine this forward in the system is that I kept the factory fuel canister with filter in the system. You want to read pressure post filter or filters in my case.

[notlimah]

Another note to consider is if running a needle valve in this setup, I'll just assume it's because you're not using a regulator (because they're terrible! ) and running diesel straight into the cab (like I am). So be mindful of where you tap into your fuel line so you can quickly reach in and shut off the needle valve if need be. 

 

I am not using the stock fuel filter and I tapped in my fuel pressure tee as far away from the VP but still easily hop up on the tire and shut it off if need be.

 

Although I am stealing @dripley's idea of putting a small hole in the bottom of the gauge pod to watch for leaks. Genius I say! 

[015point9]

15 hours ago, crgjhnsn said:

I apologize for resurrecting an old post, but need a little input.  I haven't driven my truck very much since I started having these issues.  I am now able to install a mechanical fuel pressure gauge.  I'm looking at the kit from Vulcan Performance http://www.vulcanperformance.com/ProductDetails.asp?ProductCode=EVFP and I was wondering where you all recommend tapping in to the fuel lines, and how (tee, banjo bolt, etc).  Also is there anything that isn't included in that kit that I would need.  Thanks in advance for input on this. 

 

As far as getting everything you need to install... I questioned that also.  I e-mailed a pic to Vulcan and he sent me everything what I needed. Great service. 

He also told me about (and I bought) a Carter pump that he sells that you can install should the Airdog ever go out on the road.  AN fittings disconnect from airdog and connect to carter pump and change wires and you're back up and running. Think it was $90.00 for everything.  Extra pump worth it to me to not be held hostage at some garage away from home if traveling.

 

[Johnny Chimpo]

I have an 01' with a Raptor pump and an ISSPro mech gauge. Started out with the snubber kit from Geno's connected to the VP44 test port using antifreeze on the gauge side of the snubber. Never could get that side bled well enough to be satisfied with the gauge reading (20-26lb at first then down to 4-10lbs after a week or so) I verified the fuel pressure with another gauge and got 16lbs at idle. I took out the snubber and replaced it with a needle valve (diesel all the way to the gauge). The pressure reading is back at 20-26lbs. I used the entire length of tubing that came with the Geno's kit to soften any pulses from the VPI've just been checking the pressure at the test port periodically rather than rely on the ISSPro readings.

[Mopar1973Man]

Best off going direct plumbed to the gauge. Very few people have gotten an isolator to work right and accurately. 

[KATOOM]

On 11/11/2016 at 6:44 AM, Mopar1973Man said:

Best off going direct plumbed to the gauge. Very few people have gotten an isolator to work right and accurately. 

 

I agree. 

But.....I highly suggest NOT using compression fittings for anyone using this is the plan of action.  Compression fittings are just too easy to leak, and both tightening them too hard or too loose will cause that leak too.  Instead use either JIC or flare fittings.  I use -3 JIC.