Fuel pressure

[jeff74]

I thought I had a float height problem, but then was reading about some new pumps putting out too much pressure. I wish I had checked this before I pulled the carb apart

The old Q-jet doesn't like it..

[72SB]

..ah no it would not. Typical mechanical FP would put out around 4-6. What pump do you have?

You could get a FPR but I have never needed one on any SBC with standard FP. I have a Carter.

[jeff74]

I believe it's a delphi mf0001

[jumpsoffrock]

I run a single barrel Holley on an old Ford truck and have had no issues in the last 12 years with flooding as a result of an over filled fuel bowl as a result of excessive fuel pressure.

To make a ridiculously long story short, I started having a problem but it wasn't such a problem that the truck wasn't running, or spilling gas everywhere.

Then the problem got worse. Most people said I needed 1.5-3 pounds pressure. I measured 7 from the mech pump. Set flaot height 10 times. No help
$55 and a trip to Autozone got me a FPR and issue completely gone.

Now I know.

[jeff74]

Yeah, I don't know if I should try another pump, or look into a regulator. I found a spec sheet for the carter pump which says 7.5 - 9 psi, which I don't think will help

[jumpsoffrock]

I don't like telling people how to spend their money, but a regulator makes more sense since it can be used for any pump you apply.

[KQQL IT]

My ac delco nos did 9lbs caused all kinds of grief

[jeff74]

Originally Posted by jumpsoffrock

I don't like telling people how to spend their money, but a regulator makes more sense since it can be used for any pump you apply.

Yeah, I'm picking up what you're laying down..

I messed with it a bit today, I have a return tee just before the carb...I drilled the orifice to 100 thou and that helps. It now reads 5 to 6 psi at the carb with the engine revved up. But I understand that this isn't optimal because there are variables that can change..

It was nice to run it without gas pooling on top of the intake , though

[67 twins]

Originally Posted by jumpsoffrock

I don't like telling people how to spend their money, but a regulator makes more sense since it can be used for any pump you apply.

No. What would make more sense is the manufacturer actually make a pump that meets spec. These trucks didn't need fuel pressure regulators for the first 50 years of life, why the hell would it need one now.
I had this problem with a new pump when I installed a 292 in my truck. Flooded like an SOB found out the new pump was putting out double the pressure of spec. Took it back & put the pump from the 250 on it instead. No problem since.
I personally would try a different pump. Using a pressure regulator to "fix" the problem is like shooting yourself in the foot & then saying everything is alright by putting a band aid on it.

[jumpsoffrock]

Originally Posted by 67 twins

No. What would make more sense is the manufacturer actually make a pump that meets spec. These trucks didn't need fuel pressure regulators for the first 50 years of life, why the hell would it need one now.
I had this problem with a new pump when I installed a 292 in my truck. Flooded like an SOB found out the new pump was putting out double the pressure of spec. Took it back & put the pump from the 250 on it instead. No problem since.
I personally would try a different pump. Using a pressure regulator to "fix" the problem is like shooting yourself in the foot & then saying everything is alright by putting a band aid on it.

.....and my reply is:

Originally Posted by KQQL IT

My ac delco nos did 9lbs caused all kinds of grief

twins, I totally understand that the manufacturers need to get their crap together and make a better product, but I also don't think there is a chance in Heck that that is going to happen.

I don't want to start an argument, but I actually think your logic is backwards: If you keep buying more pumps, there's a chance that they might also be poorly regulated and you'll have spent all that time shooting yourself in the foot and getting nowhere(potentially). If you get a regulator, that's the end of it. Band aid? Regulators don't need to be replaced ever 2-4 days. If I get 5 years out of my $55, I'm, happy. Oil changes--with the stuff I use) cost about that and I do it 3-4 times a year on my daily driver.

Nonetheless a regulator would make any pump work, whether the pump is build to spec or not. I don't consider that a band aid or shooting ones self in the foot. But yes I agree a lot of pumps are way out of spec.

[72SB]

This is the $17 Carter I have. Spec says its 7psi...My edelbrock carb says 6.5psi. Have had zero issues with the Carter FP

https://www.summitracing.com/parts/crt-m4685#overview

If your front block does not have the short 3/8" bolt you remove to then use a longer one to hold up the FP push rod so it does not drop when you pull FP...then use a glob of grease to hold it up to then put FP in. You will need the gasket for the FP mounting plate also as that has to come off to allow you to lift the PR up into the block once it drops when pulling FP. Easier if cam lobe is on base circle to swap a FP so the spring pressure of FP lever is less

[geezer#99]

Here’s what I learned years ago.
Inside diameter of fuel line doesn’t need to be 3/8 inch from the pump to the carb.
Less than 5/16 is adequate.
Pressure is controlled by small inside diameter plus a couple bends in the line.
Check out this cross ram for fuel lines.



https://www.motortrend.com/features/...9-camaro-ever/

[CastIron]

If you're running a stock carb, intake, and fuel pump it should all work together. with no additional parts. Something is giving it too much fuel pressure, which could be the pump or it could be a restriction in the fuel return line.

I run an OEM-replacement Carter fuel pump with an Edelbrock Performer carburetor (got used, rebuilt and switched the jets & needles myself) and mine runs very well. But I also use an Edelbrock heat insulating gasket to prevent hot-soak problems. Without the gasket, it would occasionally crank for a bit before starting hot. And for the record, I use a 5/16" fuel line and it's a basic 350 crate engine.

[LNP]

If you do have a Delphi MF0001 fuel pump its rated at 5psi. You sure your test gauge works good? If it does I would just figure your pump
is defected.

[72SB]

FWIW GM used 2 sizes of fuel lines. 6 cyl and 2 brl v8 used 5/16" and 4 brl V8 used 3/8"

FP are made in both fitting sizes with the 3/8 one providing more GPH than the 5/16" pump

[jeff74]

Thanks for the input guys,

Yeah, I noticed that some pumps have a smaller output fitting.

I'm not sure if that gauge is super accurate, I'll see if I can check it against something else, but with the way it was acting I'd guess it's pretty close. I have a new needle and seat and float.

[KQQL IT]

Originally Posted by jeff74

Thanks for the input guys,

Yeah, I noticed that some pumps have a smaller output fitting.

I'm not sure if that gauge is super accurate, I'll see if I can check it against something else, but with the way it was acting I'd guess it's pretty close. I have a new needle and seat and float.

I used a mr gasket dial a regulator to check if the was in fact the problem.
Then put a holley regulator to get the pressure under the needle and seat.

[1967GMCC20]

Checked mine, 7psi on BBC. Stock AC pump.

[JEM Motorworks]

I just went through the same BS! Got a Napa pump ($38) and it wouldn’t prime or pump, squeezed the rubber line on the pressure side and fuel dripped out the weep hole. Replaced it with another Napa pump and it flooded the Q-jet. Checked the pressure and it bounced between 15-20psi! Ordered a Delphi off Amazon ($17) put the pressure gauge on it, it’s a smooth 7.5 psi. No issues. Unfortunately I’m afraid it’s luck of the draw with parts manufacturers today.

[1967GMCC20]

Originally Posted by JEM Motorworks

I just went through the same BS! Got a Napa pump ($38) and it wouldn’t prime or pump, squeezed the rubber line on the pressure side and fuel dripped out the weep hole. Replaced it with another Napa pump and it flooded the Q-jet. Checked the pressure and it bounced between 15-20psi! Ordered a Delphi off Amazon ($17) put the pressure gauge on it, it’s a smooth 7.5 psi. No issues. Unfortunately I’m afraid it’s luck of the draw with parts manufacturers today.

Thats rough.....