Fuel pressure surging

[danc30]

I have -8an feed and return lines, a Holley HP-150 electric pump and a Mallory return style regulator.

When I first turn the pump on, with or without the engine running, I have a steady 6psi of fuel pressure at the carb and the pump and regulator make a steady "sound".

After about 5 or 10 minutes, the fuel pressure surges up to 7 and down to 5 and back again about every 3-4 seconds. The fuel pump sounds like it's surging, (different noise and pitch) and the regulator makes a different sound.

I am guessing that the pump is bad causing it to surge and the regulator is sounding different due to the surges from the pump and making the adjustments to the change in pressure from the pump.

Anyone know what I should try in order to figure out if it is the pump or regulator?

(The fuel filters are clean, the tank is full, and it happens whether the engine is running or not running)

Any help is appreciated.
Dan

[Ron61]

Dan,

Is it possible that you could have some trash inside the tank that is on the pickup? I ran a Holly Blue Pump for years and never had any problem. But from what you describe, it would sound as if it is either losing fuel or getting air into the line some way, which I don't think would be the cause. But if it takes 5 to 10 minutes before it starts, then that would seem to rule out anything in the tank. My pump was mounted where I could change it very easily and quickly and if yours is doing that, maybe if it is easy to change you could try a new pump. I did have a regulator go bad and took it apart after i put a new one on to see what happened, but mine would just drop from 7 pounds to around 3 and stay there within a minute of starting the engine or turning the pump on.

Ron

[Morris]

Try this


Brand: Moroso
Product Line: Moroso Fuel Pump Springs
Part Type: Fuel Pumps, Electric, Pressure Relief Springs
Part Number: MOR-65770
Pressure Range (psi): 18-19
Fuel Pump Spring Material: Stainless steel
Quantity: Sold individually.

Fuel Pump Spring, Stainless Steel, for Holley Electric Fuel Pumps, Each

Check to make sure this part fits your application
Boost the output of your electric fuel pump.
These Moroso fuel pump springs are designed to increase the pressure of your Holley electric fuel pump. They are made of high-strength stainless steel and will increase pressure over stock. The springs will also increase overall fuel volume while maintaining your fuel pump's reliability.

Morris

[undy]

Check your fuel filter..

[danc30]

Thanks for the replies.

Ron- I have another pump on order with Summit. Should be here tomowrrow and I will replace and hopefully it solves the problem.

Morris- That spring won't work with the 12-150 pump. This is the fairly new "gearotor design". HP tech serv. said it sounds like the pump is surging and possibly defective. They suggested bypassing the regulator and feeding the fuel into a gas can and see if the same thing happens. If it does, they will replace/refund the pump.

Undy- The fuel filters, before and after the pump are clean.

I'll update after trying the new pump.

More suggestions of possible causes are welcomed.

Cross your fingers for me.....

[Ron61]

Dan,

Good luck and I hope the new pump solves the problem. Boy, things like that can drive you crazy some times. I have fought a few simple problems for weeks and then when I found the problem I felt really stupid as it was so simple. But when you have several things working together, sometimes it is hard to isolate one of them as the problem.

Ron

[jhv48]

Go simple first before you start replacing things.

Oil filled gauge? If so, they fluctuate when the oil gets hot. Not the best type of gauge.

My bet is trash in the gas tank. Floats away when cold, gets sucked to the pickup after running for a while. Cool and repeat.

That would cause a change in the fuel pump sound as it sucked harder to get some gas.

[danc30]

Thanks jhv48- Had an oil filled gauge and switched it out a month ago after it was giving me a hard time. I'll also check for trash in the tank.

I just talked to Mallory about their bypass regulator and Holley about their pump.

Mallory said that the bypass regulator I have relies on the return line to regulate. If my fuel pump is internally regulating/bypassing fuel, it could create an issue of the regulator trying to bypass the fuel at the same time the pump is. They said to "shim" the bypass spring on the pump and Holley should know what I'm talking about.

Holley said the pump does have an internal bypass and should be used with a dead-head regulator. They also said it can't be shimmed not to self-regulate.

I will try a dead-head regulator first and see what happens. If I don't need the return line at all, I guess I just wasted the time involved in making the return set-up, but as long as it works, I'll be happy.

If it doesn't work, I will replace the pump and use the dead-head. If this doesn't work, I'll drop back 10 yards and punt....

[undy]

Don't go to a dead head single line system. What you have now, as far as good fuel pressure regulating, is far superior to a single line system. Fix what ya got!

I run a Holley black, which is externally regulated, and I have a "Jegs" billet return style regulator. The fuel pressure stays dead on 6 psi all the time. The Holley Black should be good for around 650 to 700 HP too. It feeds my KC 482 quite well.

Just a side note.. I'd hang a volt meter across the electric pump while it's running. A fluctuating voltage source could cause these issues too.

[Jerry Clayton]

And just why aren't you using a mechanical pump on the engine?

Is your pump powered thru a circuit breaker or relay???
Are you using braided stainless fuel lines? With the poor grounds in these cars you might be getting a feed back causinf the surge

[danc30]

I replaced the return regulator with a dead head and it fixed the problem. Now I know what was causing it. It was a bypass regulator trying to work with an internally bypassed pump. These 2 don't work well together. I am still deciding whether to replace the pump with a non-internal-bypass one or stick with the dead head.

The pump I have is run through a relay within 12" of the pump, I have about 4 feet total of braided line between the tank and pump and at the front transitioning from the alum. line to the filter regulator in the engine compartment. I have 1/2" aluminum line from the pump to the front of the car as well as from the regulator to the tank as a return line.

Jerry,
I just want the electric. Also there isn't much room for a mechanical in my engine compartment.

Undy,
You say the black pump is externally regulated. Does this mean I can shim it so it doesn't regulate at all so my regulator in the engine compartment does all the regulating/bypassing?

Thanks for all the help.

[Jerry Clayton]

Do you have a rollover/crash switch wired into your relay?

[danc30]

I have an inertia cut-off wired in and it's working fine.

Why?

[Morris]

Danc

You have the same line as the pressure line and the return line.....that's a no no.....

Unless you are going to run a orfice in the return line...... to make the major adjustment and then use the regulator to fine tune the the pressure adjustment.

Most folks will run a -8 or -10 as a main line and then a -6 as the return line and that seems to work well.......

Also just remove the spring in the fuel pump and replace with a much stronger spring and you'll be fine ..... that's what I meant by the previous post..... that way the fuel pump will pump up the pressure and the regulator will allow you to regulate and maintain consistant fuel pressure.....

Morris

[55312]

danc30

I've been running my system dead headed from day one and other than having a POS Holley blue diaphram pump die a year ago, it's worked fine! I installed a new Holley Gerator pump last spring and it's rock steady and so quiet I can't hear it running. Leave it alone and drive it like you stole it!

Tim

[undy]

Originally Posted by danc30

Undy,
You say the black pump is externally regulated. Does this mean I can shim it so it doesn't regulate at all so my regulator in the engine compartment does all the regulating/bypassing?

Thanks for all the help.

The pump requires no shimming and it'll pump about 14 psi unregulated. Just adjust your return style regulator to 6 psi after you install the pump and that's it.

Dave

[Jerry Clayton]

the reason for a inertia/crash/rollover switch should be self explanatory---I don't like to paint gory pictures, but I have seen several electric fuel pump cars on fire and I can only imagine being upside down in a ditch or against a wall somewhere unconcious with a fuel pump pumping 120 gallons/hour

Its good you got the inertia switch.

Jerry

[danc30]

Originally Posted by 55312

danc30

Leave it alone and drive it like you stole it!

Tim

I think I will Tim. These gerotor pumps are great. Very quite and self bypassing to keep them cool.

Dan

Thanks to all who gave me advice. It's a testimonial to this great site and all of you. My problem has been properly diagnosed and fixed.