Malpassi Regulator failure?

[djorevich]

I have a 76 with a weber 38 downdraft.  I'm using a Carter P4070 electric fuel pump and a Malpassi filter King regulator.  I have a fuel pressure gauge between the regulator and carb.  on startup, I have 2 psi.  After it runs a bit, the pressure will drop to zero, then vary between zero and two.  I will run the bowl dry running the car hard, but after a while it will build pressure.  Do you think it's a bad regulator?  Anybody else using this combo?

[halboyles]

You could have a supply line leak so that you are drawing in air or the pump has a bad connection or is going bad.  Check/replace all soft lines/clamps from the tank forward.  Make sure the fuel sender sleeve is in place and not cracked.  If you need a new sleeve, let me know and I'll send you one gratis.

[esty]

why do you need a regulator?

 

[djorevich]

The pump pushes about 5.5 psi.  Weber's like 2-3.  I did check the pickup for leaks previously and replaced that sleeve.

 

Edited August 3, 2021 by djorevich

[Mike Self]

Presume you have the pump back near the tank, and not up in the engine compartment.  While mechanical pumps like to suck; electric pumps work better when they're pushing--why EFI cars have the pump either in the tank itself or very close by.  So if your pump isn't back near the tank, moving it will probably help.  Unless there's a leak somewhere.

 

mike

[djorevich]

Yep, it's in the back.  Maybe i need to pull the pickup?  I've never had debris in my fuel filter though.

[m42002]

My malpassi failed, but in the other direction. Just quit regulating. Only a couple years old. A quick test with a gauge before and after it should remove any guesswork. Don’t even need a tee, just straight into the line. 

[djorevich]

Was your pressure constant, or would it go down and up?

[djorevich]

I think I'm going to pull the pickup assy from the tank to see if it's somehow restricted. 

[m42002]

Mine was as consistent as the pump

[djorevich]

Well, I pulled the pickup and the screen was in the bottom of the gas tank.  Also, I replaced the sleeve with a piece of tubing that actually pushed back into the hose when I connected it.  I may have been sucking air.  I actually think the regulator was good.  We'll see.............