bamadzl

I previously relocated my stock lift pump to the frame with the Vulcan kit, but lately my fuel pressure has been getting erratic. It never dropped below 5 psi. At idle it would always jump around between 5 and 13 psi, so I figured the pump was on its way out.

I installed a Holley Blue on the frame last night and my fuel pressure is a little less than I anticipated. I am getting 11 @ idle and around 8 @ WOT. Does this sound right? I was expecting about 14 @ idle. My fuel filter was changed about 2500 miles ago, so it shouldn't be a problem.

I cut the stock electrical connector off the wire and wired it straight to the pump. Am I losing pressure by not using a relay and getting a constant 12 volts from the battery? If I do this will it set off an engine code?

What kind of pressures do you guys get with this set up?

Thanks
Brad

airman

The wire that is feeding the oem pump is already switched through a relay under the hood .The computer just turns it on when the engine starts it does not regulate the pump preasure.You could have a bad relay but I dont think that is the case,They will work or dont waork at all.Those Holley pumps are priety noise,when your truck is running do you here the pump ? is it constant ? if it is running steady you could have a air leak on the line between the pump and the tank.There were also isues with a plastic cap being left on the vent on the tank.I would also check all the wirring connections from the connection you made at the front where the old pump was.Also did you get it wired wright Pos and ground ? they would not work correctly if it were wrong.

bamadzl

I thought I had read where the ecm varies the voltage to the lift pump. I guess that theory doesn't hold.

I can barely hear the pump while the truck is running. This pump is less noisy than the stock pump. The old pump would change pitch with the fluctuations in fuel pressure. The Holley seems to have a constant sound, but not very loud. I will check for air leaks like you mentioned.

My Vulcan kit came with a wire lead that plugged into the stock connector. It also had a connector on the other end that would plug into the pump. I cut off the connector and found a white and black wire. I wired the white wire to the red wire on the Holley. Then the two black wires were connected.

It seems like I have read about a spring replacement that will increse pressure. Maybe I'm thinking of another pump.

Does anyone else have similar pressure as mine, or do I need to send my pump back?

Superduty

https://www.dieseltruckresource.com/...ad.php?t=87890

CTD NUT

One thing most guys don't do when installing the Blue pump on a CTD is to block off the bypass in the pump. Our CTD's use a full flow return style fuel delivery system that does not require an internal bypass in the pump to bleed off pressure. The other thing to check would be the operating voltage at the pump......you will see significant decrease in system pressure if the pump has much less than 14 volts. If the operating voltage of the pump is below 13 volts there will be a noticable loss in performance from the blue pump.

67HotRod

I run the holley blue, have to run the regulator beause the pressure was too high (Was 27psi). Are you running the regulator?

airman

I would be checking my gauge the Blue Holley will not pump that much even with the spring locked down.I drag race for many years using several Blue pumps and the most I ever got out of them was 19 psi.

67HotRod

DOH! Sorry I was getting 19psi just with the Holley. I get 27psi with the factory pump running with the Holley, hence the regulator. I like the two pump setup.

bamadzl

OK. So how do I disable or remove the internal regulator in the pump. I've never broken into a fuel pump before.

Superduty, man that was a lot of reading. I had seen your thread before I posted mine and I believe before I purchased my pump. I was just too lazy to read throught it all. If I had read it I would probably give the Walbro a try. I still might if I can't figure out what's going on with this Holley.

I haven't been able to check the voltage yet, but I'm pretty sure that's not the problem. What kind of pressure should I expect by removing the internal regulator?

Is 8 psi @ WOT bad for my VP44?

airman

Look on the side of the pump there is a big pan head screw just take the screw out there is a spring behind it and then there is a valve becarfull not to loose it just take your spring and give it a good stretch and put it back in it should put you at about 19 psi at idle or close to it.I have done 5 or 6 like that and they worked great.you should be able to get to it with it on the truck.

bamadzl

Thanks airman. I'll give that a try when I get home tonight.

Superduty has me curious about that walbro pump. Does anyone have experience with it on a 2nd gen. with a VP44?

Brad

bamadzl

UPDATE:

I got home tonight and removed and stretched the spring as airman mentioned. I fired her up and the pressure was much higher, but my gauge was jumping all over the place. After a while of idling, the pressure settled at 19 psi @ idle. So I jump in and went for a ride. Everytime I gave it more than maybe 1/3 throttle the fuel pressure gauge would start going crazy again. Jumping from maybe 15 to 25 psi.

On my way back home I decided that maybe I had stretched the spring a little too much. So, I removed the spring again and tried to compress it closer to its original length. This time I fired the truck up and it went straight to 15.5 psi. I went for a ride and could only get it down to about 11.5 psi @ WOT. Pressure stayed around 14 to 15 until I really got on it.

Anyone know why the fuel pressure was so erratic when the spring was stretched more?

Scotty

Just a guess here but perhaps the spring was sticking...stretched too long and binding.

Scotty

newriverSpecon

[QUOTE=bamadzl]I thought I had read where the ecm varies the voltage to the lift pump. I guess that theory doesn't hold.

I can barely hear the pump while the truck is running. This pump is less noisy than the stock pump. The old pump would change pitch with the fluctuations in fuel pressure. The Holley seems to have a constant sound, but not very loud. [QUOTE]

The software of the ECM determines how the LP is controlled. Mine apparently has an old vesion. It causes a pulse sometime. The internal regulator also can cause a pulse under the right conditions. I think a little high regulator pressure like you have done will help that. I'll quote our foreign ECM guru below.

Randy


"OK, I see.
What you're seeing is an OLD software version that runs the LP on PWM ( Pulse with modulation) when you turn the key into the run position. You have two possible ways for a solution.

1)Replace the LP relay you're using with a bigger one ( more amps ). Personally, I run a 50 Amp relay, had no problem with it when I was using the older ECM softwares.

2) Get the ECM software updated by a dealer. Which is in my mind the better solution. With the new software the pump runs only for a split second when the key is turned on."

curtosy of MARCO.

BigBlue

That's the only problem I seem to have with holley's. The pressure spring sticks and it causes low pressure. Take some emery paper or very fine sand paper and LIGHTLY sand the plunger and bore and reinstall everything. Works everytime for me.