I have been fighting a fuel pressure problem for a while, I had a bad by pass valve. I am running a glacier 392 with the 3/8 big line kit and draw straw.

Here's my prob... I am running 30+ psi at idle, and at normal throttle/ 1/2 throttle, but when I mash it, I see my fp drop to ~5psi or so. This kinda makes me mad, cause when I was running the stock LP with the 392, I was only dropping 5-7psi at WOT. (goin from 30 at idle to 22 at WOT)

I am keeping pressure, and it recovers good, but I like having a little more of a buffer. I really don't want to scrap the walbro and get a fass/airdog/ect. Should I get another walbro and run them in series to the fuel filter canister?

Or, should I take the bypass off, and just let the stock fuel return take care of the excess pressure?

I'm about to get tired of having pressure, but not volume...

Any ideas would be great.

TIA-

madhat

 

Check all your filters, mine did that too. I changed all my filters and strainer and that took care of it.

 

Nah, it's not a filter prob... I have went through more filters in the last 3 months than I have since I bought the truck. They are good. No love...

 

Here, how about this...

I know that the pump is putting out a little more than a gallon a minute, unrestricted. Say 70 GPH.

When the truck is idleing, the excess fuel flows through the bypass, going back to the tank. 30 PSI is maintained.

But, at WOT, the fp drops. The fuel will go to the path of least resistance, so this means (to me) that all the fuel is going to the IP, and not through the bypass valve.

So, my truck is demanding more than 70GPH. Somehow, I don't buy this. I could be wrong, tho. This is with the edge on 5 and the MP-8 on 100%. Normal driving, it does ok.

 

I'm tired. what is IP?

Why not shim the spring or put a stiffer spring in the bypass and just increase the idle pressure? Do you have a rail gauge to let you know that the pressure drop is actually a problem? If the rail pressure maintains, who cares if you lose a few psi pre-cp3.

 

Hi Madhat,

I took your advice and pulled the fender liner when I put by pump adapter on. It did make working easier.

What type of bypass regulator do you have? The one at GDP and Vulcan come preset at 20 PSI?

 

Injection pump.

Yeah, here's what I was trying to say with the last post. If my pressure is less than what I have it set for with the spring, and can only maintain ~5 psi, then it is taking everything that my pump can give it. It's more a volume problem than a pressure problem. Fuel is not going to flow through the bypass valve, due to the fact that it has to push against the spring. If the spring is set at 30 psi before it lets fuel flow through, and the IP is drawing 25psi, then all the fuel is going to flow to the IP, and not the bypass.

LMK if I'm confusing anyone...

 

I understand what you are saying but I wonder if when you first get on it WOT if the bypass spring hangs for a minute maybe due to the pressure difference in supply and return. Does the pressure stay down or will the pressure build back up at wot. Just thinking out loud.

 

pick up tube ...strainer problem I assume you have this problems even when tank is full

 

Why not just ditch the bypass from GDP and install a true bypass regulator like I have.
I run the Aeromotive universal bypass. Good for 1 to 60 psi. I have mine set at 20psi and it never moves from idle to insanity...
Costs around a buck twenty...

 

Brand new bypass... but I won't rule it out. It does not build back up at WOT, but it will hold around 5 PSI.

Yeah, just filled it up. The draw straw is inside the stock fuel canister (or what ever the techinical term is,) so the mesh screen is there protecting it. When I put it in there, I made sure that the draw straw would never move from the bottom of the canister.

Yeah, I just dropped a buck into a new bypass from GDP...

Now, don't think that I am knocking Richard Martin at GDP, he has been on time with every problem that I have come to him with, and the pump that I have is not one of his (stupid noobie mistake) so it's not his malfunction.

How about I ditch the Walbro and get one of the mechinical pumps that he's selling? Yeah, just thought of that....