New mechanical fuel pump, faulty?

[Aarons68]

Put new carb on my 383
Attached a fuel pump pressure guage. When I started the car
I noticed there wasn't any fuel pressure maybe 1 psi at best
So I purchased a new pump from napa which was rated for 4-6 Psi.
Installed new pump and noticed right away that the guage was reading at 12 psi.
Does this make sense. I wouldn't think it was normal especially if it's only rated for
4-6 or so that's what the specs were. So becasue I didnt think to much of it I bought
A regulator to regulate it down to 6 psi. All seemed ok until I checked pressure after running the
Car for a bit and I had noticed there was no pressure again but somehow car is still running
I have been trying to figure out whats going on. I have come up with nothing. Just kind of going around in circles

I have a fuel filter before the pump incase anything was getting into the pump, and a filter
Just before the fuel rail. They are new so no clogs there.

And tank vent  tube is not clogged i checked

Tonight I just tried rerouting fuel lines and just to try something different I removed the regulator
And again 12 psi at startup let the car warm up for 5 min then drove 2 min down the road and
Fuel pressure was down to 2-2.5 psi. I'm so lost with this it's driving me nuts and becasue the carb was pushing so much psi
It flooded my bowls and float settings are way off  for me to run this without the regulator


So what do you guys think I should do or any advice would be
Awesome.
- faulty pump from factory
- clog in tank? But that wouldn't explain the pump at 12 psi

[c00nhunterjoe]

Filter should not be on the suction side for one. 12 psi at idle on a mechanical pump sounds like an impossible task. I would use a new gauge. Where are you installing the gauge.  Another thing with a mechanical gauge is that it will flicker the needle at idle, not be a constant.

[Aarons68]

The guage is on the fuel rail and it's a liquid filled guage. I put a filter on the suction side to rule out debris from the tank. Is was put on last night it wasn't there before wasn't  always on there. And yes it pushes 12 psi For a couple min. 

[timmycharger]

12 lbs on a mechanical pump does seem high to me, I would change out the gauge as recommended. I know from first hand experience that the liquid filled gauges are heat sensitive, I had one that would show 6lbs cold then 0 once the engine bay warmed up. I replaced it with a cheapo non liquid filled one for $10 and it has worked fine since.

[Aarons68]

Here is a link to a video I took thismorning
The car was just started and after 2 min of running
It had reached 12 psi
I'm not denying the guage could be faulty but I still think
Dirt or debris stuck in a diaphragm. When I shut the car off
The guage showed no pressure.

https://youtu.be/6jCx27QE56Y

[c00nhunterjoe]

Watched the video. The liquid filled gauge is the problem. Put a regular gauge on it and you will see the difference. It shows it in the video already. The fluctuating needle is normal, as the liquid heats up in the gauge, the pressure differential in the gauge vs atmopshere rises and thus gives a false reading on the gauge. Ditch the liquud gauge.
   

[Aarons68]

Ok I'll try it out. What do you think about the 12 psi
Just guage issue?

[c00nhunterjoe]

Just the gauge. Will probably flutter between 3 and 6 psi with a standard gauge on it at idle.

[Aarons68]

Just as I expected. It was the pump. I picked up a new pump today
And installed it a couple mins ago and it's reading perfectly
I didn't change anything else from the video I took thismorning
Just swapped the pumps and well you can see for yourself. Sometimes new parts are already bad lol. That's why
I was having a hard time blaming the pump.
I appreciate all the advice though. Thanks again

https://youtu.be/1yLDkOcfnSU

[c00nhunterjoe]

Hang on, run this by me again.... you had a regulator in the system, and faulted the pump for too much pressure at the carb? And have a mechanical fuel pump sitting on your work bench that is capable of 12 psi at idle? May i have this pump?

[Aarons68]

12 psi for 5 min then it completely dropped all pressure. Once the pump got warm it wouldn't keep pressure. Pump is no good. That's also why I ran a prefilter just as a precaution  Which there's nothing wrong with for one. Drove the car last night and guage worked fine the whole time Gave me constistant readings throughout. I understand these gauges have been known for some issues but that's not the case in my situation. Thanks again.
If it was pushin 12psi constant I wouldn't have had an issue and we wouldn't be having this conversation lol. I know I thought I was lucky when I saw the readings from this pump

[ACUDANUT]

Hang on, run this by me again.... you had a regulator in the system, and faulted the pump for too much pressure at the carb? And have a mechanical fuel pump sitting on your work bench that is capable of 12 psi at idle? May i have this pump?

It you have 12 PSI from the pump, your carb will fail.

[John_Kunkel]

Years ago I purchased a new Carter M6903 pump that put out 13 psi. I removed the pump and replaced the black spring with a red spring from a stock factory pump and that lowered it to 10 psi. Checked with several gauges.

This was on a Max Wedge clone, the left carb floats held the pressure most of the time but the right carb (rear) didn't...took me forever to find the problem because it's hard to look straight down in the rear carb to see the fuel dripping from the boosters. Rather than risk another pump, I installed a Holley regulator and gauge set to 6 psi....end of problem.

Never heard of anybody having the same problem until now.

[Aarons68]

Years ago I purchased a new Carter M6903 pump that put out 13 psi. I removed the pump and replaced the black spring with a red spring from a stock factory pump and that lowered it to 10 psi. Checked with several gauges.

This was on a Max Wedge clone, the left carb floats held the pressure most of the time but the right carb (rear) didn't...took me forever to find the problem because it's hard to look straight down in the rear carb to see the fuel dripping from the boosters. Rather than risk another pump, I installed a Holley regulator and gauge set to 6 psi....end of problem.

Never heard of anybody having the same problem until now.

That's crazy lol. Yes I tried regulating it. But the problem was after the pump " warmed up" or whatever you want to call it. After a few min the pump would lose pressure and then wouldn't be able to push 6 psi through the regulator and it would go down to 1 psi. I also tried it without a regulator and start at 12 psi then drop to 1 after a bit