Hope everyone is well, it's been awhile since I've had time to jump on the forums.

So I just installed a fuel pressure gauge finally and have some disturbing results. I swapped out my FRX spring to the black one because with the gold I was only seeing around 55psi at idle. Pressure went up after the swap, but it falls off A LOT!!! Here is a video I just took today.

I focused more on the fuel pressure gauge, so sorry you can't see boost or mph.
Video starts rollin at around 45mph, boost is normal around 4psi cruising and peaks around 32... First acceleration is about 2/3 throttle maybe to around 60mph and then let off... Then hit a stop light and the fuel pressure tanks momentarily. Roll into it from stop and then stabbed it over 3/4 throttle, but not pinned to the floor. The pressure tanks big time to 10psi!!!!


Any thoughts? In tank problems? Worn out pump? Something else? Hope I can figure this out with some input and help from the brotherhood.

Thanks in advance for all the help!!!

271,000 on the clock now, original pump!

 

Is the pressure transducer mounted before or after your fuel filter? If it's after your filter, it could be a plugged up filter. If it's before your filter, you could have clogged tank screens. Have you ever dropped your tank? I think if your pump was weak, you'd see low pressure all the time. When my pump failed, it just died without warning.

 

The boost sensor should be the same as the fuel sensor so swap them over and make sure that the sensor is reading correctly and then switch them back. Next thing to look at would be the spring. There is a small plastic lip inside the cap of the FRx that likes to hang up the spring so open it up and reposition the spring to make sure it is centered in the cap. The gold spring should give you 60-65 psi but you said you only had 55 so did you have the same drop off issue with the gold spring or did you switch out the spring before you had a chance to use the gauge? If these two things check out, move onto the fuel filter and make sure that is clean, make sure the bowl does not have any nasty's floating around in it and if that is all good, it could be a pump issue.

 

Sensor is after the filter on passenger side of fuel bowl... Filter is only a few months old. Can't hurt to check anyway.

Boost gauge is mechanical so no go on switching them. I got the same drop off with the gold spring in as well, just pressures where lower at idle.

Never dropped the tank, original pump. Guess it's finally time to do the "Hutch mod"!

 

Not sure if a hutch mod is going to fix that amount of pressure drop. I have not done one either but I would be more inclined to put in a new fuel pump before I dropped the tank but that's me. I would imagine that if you did drop the tank and do all of that you would most likely put in a new pump anyway.

 

Hey Chris!

It builds nice high pressure, but the volume of flow can't keep up with the fat squirts from your ACs. I read that as a good pump, but clogged screens starving it.

A temp fix would be some low pressure air blown back thru the line to the tank to clear the screens. Remove fuel cap, disconnect the line behind the pump at the clip pictured, and enjoy the mess. I guess a hose pincher to stop the fuel during the setup and duct tape holding the two lines together would be neater. If that's the issue you should see improvement on the gauge.

Get all the bits and pieces and I'd be glad to help with the Hutch mod next time Andy hosts a GTG.

 

Correct... I would be replacing the pump and well.

That kind of pressure drop seems unreal almost... Not good on injectors, that's for sure!

 

Hey David!

That was my thought, it's building pressure fine until the truck gets thirsty... I think I'll probably go ahead with both, with 271k on the original pump, wouldn't hurt to drop in a new Bosch. Hope there is another gtg soon in "man town"! Thanks for the offer!! Good thing my truck is lifted, because with the spray on bedliner, pulling the bed is out. Gonna have to perform surgery from the bottom...

 

271k on the pump is suspect. You don't ever want to see it below 41 psig. at the fuel bowl test ports. Stock is between 55 - 65 psig and is more than adequate for non modified injector systems.

Firmer / Heavier springs without the necessity shortens the pump life. The pump is electromagnetic and is cooled by the fuel moving through it. Larger springs prevent some flow at idle.

There are two ways to determine if the pump is doing it's job. One is to perform an AMP draw test and the other is to test the pressure at the pump. HOWEVER, you should check the mixing chamber screens before diagnosing the pump as "bad". The pump life of both the present and new will be shortened if the screens are dirty.

Another important area to ensure is the Fuel Bowl and Flow Stop Riser are functioning properly. Always use an OEM or quality OE Cap and filter to ensure the standpipe is fully opened.

I personally have not seen improvements from the "Hutch Mod". Others state they have seen minimal to drastic differences. The "Harpoon Mod" on the other hand allows for easier filling of the tank AND extends mileage before fill ups, Mine for instance went from about 225 miles to 360 miles.

If you decide to pull the sending unit replace the gasket as they are prone to leak after removal/installation. And, DEFINATELY replace it if doing the Harpoon Mod as the fuel exceeds the height of the seal.

It should only take 4 - 8 hours to pull and install tank and change the pump. The only special tools required are a 5/16" and 3/8" Quick Disconnect Tools for the lines and a PVC Cutter for the Harpoon Mod. Guzzles has a nice write up for the Hutch Mod.

 

You and I had the same "Oh Gawd" moment on the first footfall after installing a fuel pressure gauge.

The stock fuel pump can handle Stage 1s just fine, Stinky's Stage IIs get all they need from a stock pump (FRx gold spring 60-65 PSI)... but I installed a new OEM pump as a preventative measure at about 265K miles.

I have the Hutch/harpoon mod and it made a huge difference on Stinky (before the FP gauge) - I was sucking in as much air as I was fuel. Once I installed the FP gauge, I learned my mistake was the choice of prefilter:




Don't do that. This is the one that works:



The in-tank mods helped, but replacing the fuel lines and getting rid of the quick-disconnects was the biggest issue.


Fuel pressure gauge - top-middle:

 

Thank you all for the replies, kinda confirmed my suspicions. Hopefully I can get these things done soon and reap the rewards.

You guys are great!

Rich, truck sounds nice! Glad you've gotten all the kinks worked out.

 

I would do as suggested above before you do anything.... Blow air backward through the fuel line into the tank. Don't forget to take the fuel cap off so the air has a place to escape from. That could answer your questions of curiosity and possibly save you a few dollars.

 

I'm not disagreeing with anyone's advice- it's all pointing you in the right direction. From blowing out the lines to doing the hutch & harpoon mods - it's all good.

I have a similar dancing fuel pressure gauge on my F-250. Luckily I left the fuel pressure gauge from the ITP (now Strictly Diesel) regulated return on under the hood. My darn fuel pressure gauge in the cab starts dancing around like yours making me thing I'm either gelling or have a restriction. When I pull over and check the "under the hood gauge" she's still sitting on 65 psi. I have someone press the the throttle and the in cab gauge starts to dance (stage I's, regulated return , stock pump, Hutch & Harpoo mods) again. So I'm waiting to install a new sending unit - but in the mean time - when I unplug the wire harness at the sending unit attached to the fuel bowl - wait a few secs and plug it back in - well it all goes back to reading normal for a while. Just figured I would bring this up for you to try - that way your not chasing a ghost around if your in a similar situation.

Mine's either a bad gauge, sending unit or ground......

 

ya buffalo, i'm in/was in the same boat. For some reason, my (GS) gauge would do the same thing. Once it read high enough for my disliking, i'd smack the wires for the trailer connection, and bam..all gauges..(oil pressure and fuel pressure) would settle back down/back up..haha

ot...with this thread and one from Tug..its almost 100% safe to say that, its a mandatory 5 gauge setup for a cozy comfy feeling for our trucks....L/R pyros, fuel, trans, boost