Fuel pressure regulator question

[Chuck]

Fuel pressure regulator

This is an odd situation. The GT has mysteriously just quit running a couple of times, even at highway speed. Today while doing some fine tuning in the shop it did it again. The solution is to remove a fuel line, on either side of the regulator, relieve the pressure, and reconnect the hose. Then it is fine until the next time.

What is odd is that before we shut it down the pressure dropped from just below 3 to 1 pound. After popping off a hose and restarting the engine it stayed at 1 pound of pressure. It took two or three turns of the adjusting nut to get the pressure back up to 2.5 pounds.

My gut tells me that the problem is with the regulator. But not sure why.

When this happens the Holly pumps change sound, telling me they are not pumping. But I believe it is do to the regulator blocking the flow rather than a pump problem.

There is no return line. That would be a challenge with two pumps, two tanks, etc.

Wondering if any one has had a similar experience?

 

[Rich Roy]

I have had a similar dieing issue. I found on warm days after the car sits for a few minutes, 10 to 20 minutes after having driven to full running temp, restart and drive away and in about a block of driving suddenly boggs down and dies out. If I throttle into it and pump the throttle and "catch" it. I can keep it running, but usually dies out. I found that the engine heat is boiling the fuel in the fuel line going over the intake manifold on the way to the carb. Enough bubbling occurs to cause it to cut out. Revving it up and causing the bubbles to pass on through usually helps. Or waiting a few minutes with the boot up to dissipate the heat. On your fuel pressure issue, it seams a bit low. I run a Holley 770 and have the regulator set at 7.5 PSI. Forever Ford!

 

[Jim Cowden]

Chuck

When you say your pumps change note, in what way.
Sucking air type note.

If it is I would be checking if your surge tank is full.
It would make sense,and the pressure dropping off would point in the same direction.
If the tank is full then look somewere else, if its not it maybe a plumbing or lift pump issue.
I have no idea of your set up so I am making assumptions.

Does your return on the reg go back to the surge tank or main tank.
It needs to go back to the surge and a return from top of the surge to the main.??????

 

[Chuck]

Rich and Jim. Thanks for the comments

Yes, the change in note from the fuel pumps is as if they were "sucking air". Vapor lock would seem the obvious explanation.

But it happened yesterday in the garage with an ambient temp of 60 degrees with the clip open while adjusting the engine and it happened to both pumps / tanks.

Fuel tanks are over half full. No surge tank. No return line.

Somehow air may be getting into the system. The regulator is the factor common to both sides. Wondering if somehow it is the culprit.

 

[Ian Anderson]

Hi
I had this on my car a number of years back. I battled each trip as it would sometimes just die. 10 mins later and it would fire up and run faultlessly.

Of all things it ended up being a blocked fuel filter. And was real easy to change / fix.

Ian

 

[Chuck]

Hi
I had this on my car a number of years back. I battled each trip as it would sometimes just die. 10 mins later and it would fire up and run faultlessly.

Of all things it ended up being a blocked fuel filter. And was real easy to change / fix.

Ian

I installed all new filters with our recent rebuild. Indeed the primary filters before the pumps are glass so we can see if any issues develop. The secondary filter is a Cool It water seperator / filter with an extremely fine filter.

 

[Ian Anderson]

I installed all new filters with our recent rebuild. Indeed the primary filters before the pumps are glass so we can see if any issues develop. The secondary filter is a Cool It water seperator / filter with an extremely fine filter.

Hi Chuck

And when did this problem start? After the rebuild?
For a couple of bucks new filters or elements are a quick easy way to rule them out!

Ian

 

[Chuck]

Yes, started after the rebuild. New filters have less than 500 miles and the glass filters are clear of any debris.

 

[Chuck]

It just occurred to me that the new glass filters on the intake side of the pumps may be too restrictive. Will replace with the larger metal filters was using before and see if that solves the problem.

 

[Cliff Beer]

Sounds like vapor lock in the fuel line.... I was having similar problems on my car and installed some heat shielding on the fuel lines in the engine bay...problem solved.

Fire Shield Sleeve for Automotive | Heatshield Products

 

[Jim Cowden]

Is your tank venting Chuck.
When it does it release the fuel caps.

Jim

 

[Chuck]

Good thoughts

It is not the pressure regulator. Swapped out for another one, no difference.

Not a vent problem. Happens with the fuel caps open.

I suspect the new glass filters between the tanks and the pumps are creating resistance to the fuel flow. My understanding is that pumps like to push but not pull. Will swap the filters out time permitting. This is a new problem, these particular filters are new, so seems they could be the culprits.

 

[Jim Cowden]

Chuck
My approch to this issue would be let it happen,
Then work back toward the pumps disconnecting hoses and flow testing into a bucket.
You will soon figure it out.
I would not spend the money on different filters ,just by pass them first then if that fixes it turf them in the bin and fit something else.

If you get all the way to the pumps and you still have poor flow it is pumps or a restriction in the tank like a rag or something from the rebuild, it happens.

Question, do the glass filters still have fuel in them when the pump changes note.

Jim