madhat

So...
I had the 392 with the big line kit hooked up in line with the stock LP and was seeing a solid 30 PSI at idle, and 22-23 at WOT. The stock LP dies, and I get the adapter from GDP. Now I have a solid 20, 15 at WOT. All of a sudden, after a hard pull, my pressure is around 5-10, tries to come up to 15 a few times. Get home, shut the truck off, the next day, she reads a shaky 20 PSI, going from 20-18 at idle, and pressure dropps hard(5-7, 0 one time) when I get on it. I changed out the filters, (they were not even a month old), and nothing changes, except the recovery time after WOT, which is good like usual.

??? Time for a new pump, or could it be the check valve? What about the pressure, who else is running the same setup?


TIA!!!

mad

O.T

so you have a walbro pump? does your 392 have its own pick up out of the tank? If you had the 392 in line how was this done. Where are you measuring fuel pressure?

things that can cause low feed pressure.
-cavitation
-bad filters
-plugged by-pass valve
-bad spring in by-pass valve
-pump cannot keep up to injection demand

Rpainter

I would same to change the pre filter the filter between the tank and the pump and the take the bypass apart and clean it with brake cleaner.

skynyrd

sounds to me like the by pass is stuck open for some reason or a weak/broken spring. you sure you don't have any leaks?

Silver 002

i had problem with my filter between the pump and tank. the liitle in line fuel strainer. if not that i would seek out the problem in the bypass as well.

nelrod

I don't know, l would call Richard @GDP

shortbed rv

The bypass on the simflo regulator is preset at 15 to 20 PSI according to Vulcan. I am assuming GDP uses the same regulator. When you were using the Walbro as a pusher pump through the canister pump the canister added pressure. Remember the canister pump is located pass the regulator. When you get 20 PSI at idle with just the Walbro sounds right.

The Walbro is capable of higher pressure but you will need a different regulator.Swagelok has an adjustable regulator from 3psi to 50psi.

http://www.swagelok.com/search/find_...2-3&PG=0&RPR=5

trik396

Madhat, how are you reading fuel pressure??? If you're running an isolator, I'd bet that's the problem.

btw- I made 617hp and my pressure never moved from 20psi. Never moves at all... course I have a different setup but same Walbro 392...

jwb600

im having the same problems madhat. I started a thread the other day on the same thing. same fuel pressure as what you have and everything. mine hasnt got any better either. I dont know if the cold weather is hurting these pumps or what? I had mine put on in the winter im pretty sure and its always done good until now.

trik396

My pump has 30,000 miles on her and a few cold winters without a problem.

Reread my last post.... do you run an isolator???

jwb600

if you were talking to me, I run an isolater with the dipricol fuel pressure gauge I have. the thread I started about mine a guy posted his antifreeze was low in his and he filled it back up. im going to try that also because I did loose some antifreeze not to long ago

Mighty Goat

I run the same setup as Trik396, except i run at 38psi at the injection pump. Even at WOT I can only pull it down to 37psi for a split second. And that's on an inline jegs wet gauge and the Commander. You shold tell us if you have a draw straw.

trik396

Is this the setup I helped you with? Can't remember with all the email/messages I get...

Anyway be careful running over 30psi because some guys reported popping the cap off of the stock fuel filter canister. I've got the same Jegs guage on my bypass regulator...

metal_miner

I had the same pressure fluctuations on my set-up lat year.

Take the regulator apart and look at the plunger. On mine the plunger was machined and had some burrs that folded over. These burrs caused the plunger to "hang up" in the bore. I took the plunger and dressed up the machining with an exacto knife and then cleaned with brake-cleaner. All is well now!

madhat

No Isolator, I get the fp reading off the adapter that replaced the stock LP on the canister, and I changed the filter again last night.
I have the vulcan big line kit in the tank. I have the pump mounted on the frame by the xfer case.
I was looking at the spring kit last night for my pump...

It's just the sudden change that bothers me... I'm thinkin that it's the bypass valve just takin a vacation...