Holley HP fuel pump issues

Going out of my mind with my electric fuel pump on my 68 Charger. I am running the HP 125 series pump, mounted on the passenger frame rail just in front of the rear tire. I have the painless relay wiring set up and had it set up with a regulator and no return line initially. I have about 800 miles on it.

About a month ago, not sure if it was a coincidence but during some spirited driving, I hit a pot hole while launching it hard and after the big bang, I lost fuel pressure. The pump still was buzzing like it was pumping but no pressure still.

After disconnecting lines and checking filters which were not clogged, I removed the regulator since this pump is 7PSI and it started working again. I thought that was the issue as it was running fine after that. I then plumbed a return line which I should have done in the beginning due to vapor lock problems last summer and after startup, things looked good, I could hear the fuel going back into the tank from the return line and had a steady 7psi on the gauge.

I was very low on gas so I went to get some and it crapped out on me on the road. Same deal, zero pressure. I could hear the pump buzzing but couldnt hear any fuel flowing back to the tank this time. Literally had my AAA card out and waiting on hold and I checked it again and now I have pressure again.

I quickly did a u turn after starting and about 200 feet from my house it died again, luckily I was going fast and was able to coast into my garage. Same deal, 0 pressure.

I tapped the pump with a small body hammer and it made different sounds and I got pressure again. I thought electric pumps either work or they don't as it is a motor..

Searched the net and found a few guys with the same issues with this pump but no solutions. Thinking of going to a Mallory 110 but I read it is not meant to be used with a return line which doesn't make sense to me.

Avoiding going to a mechanical as I have a modern alternator that is sort of in the way and will need work to make it right. Nevermind all the lines that will have to be re done.

Could I have hurt this pump by not having a return line for a few years? So frustrating!

A lot of pumps have bonded plastic type rotors, wondering if it got damaged. I would disassemble it.

If we look at it as two main parts inside one case, we would have an electric motor and a pump sitting next to each other.

It's possible to have an electric motor that runs okay, and a pump with it's rotor/gerotor star etc either broken or no longer attached to the shaft.

In that kind of scenario the motor shaft spins happily along without any load, and the pump won't operate until physically jarred or bumped a certain
way that allows the pump rotor to grab. When it grabs, it makes fuel pressure.

Not saying that's the issue, I have no idea, but depending how it's built it's a possibility the pothole knocked the rotor loose.

I believe those pumps are designed to run without a return type regulator. I have the HP150 without a return and have never had any issues.

When it stops pumping does the pump sound like it's unloaded? The pump should sound different when it picks up fuel and builds pressure.

Interesting. I may take a stab at taking this pump apart and having a look. Just seems like too much of a coincidence that my issues started after that bang.






The 125 doesn't require a regulator per Holley, but I added a return line because last year I was having horrible vapor lock issues, probably because of the routing of my lines which are now wrapped in heat shield.

The pump sounds were pretty erratic, when pumping, it didn't sound much different than when there was zero pressure.

Does the pump have an internal bypass? My old pump used to have an occasional issue with the pumps bypass valve sticking open and generating no pressure. It can get stuck if you don't have a pre-filter and you get a piece of debris hung up.

Over the weekend I pulled the pump and took it apart. The pics are below along with a short video of the rotor on the shaft. I found some debris on the face of the rotor as you can see in the pics, and looks like some grit got in there. Not sure if the rotor is supposed to be moving around so much on the shaft before engaging, but that is what it was doing.

Wondering if the something internal in this pump caused the zero pressure but the fact that it is intermittent is a mystery to me. I ended up pulling out the sending unit, the sock filter was clean of any debris but I blew it out anyway. I checked the filter before and after the pump, both clean and clear.

I swapped the pump out for a Mallory 110 unit and so far so good.

The big difference between the Mallory and Holley HP is that the Mallory is showing steady 8 PSI on the gauge while the Holley only got to about 7. Both pumps are designed to run w/o a regulator but is 8 PSI too much? My idle is up a few hundred RPM since this pump change, could I be getting gas going past the needle and seat?

https://youtu.be/chvvG6O6UEs

Did you try to run the pump after cleaning it? I had an HP 150 that did the same thing. After cleaning it the pump worked just fine. I think that 8# of pressure is too much.

8# is too much for a carb.. try lesser pressure