Efi fuel pump wont hold pressure

[Just puttering]

When i turn the key on the fuel pressure comes up and when the pump turns off the pressure goes away fast!

I have a fuel pressure regulator on the fire wall with guage for efi and a return to the tank

Why cant i plug the return and see if it holds pressure with key on? This points the the regulator being bad. And if it wont hold pressure then i need to pull the tank to check the fuel pump.

If not how would you rule out the fuel pressure regulator before dropping the tank? I have opened the regulator and do not see anything that looks like it would drop the pressure!

[i.e.427]

What regulator?

[Just puttering]

I missed typing fuel pressure regulator.

https://www.summitracing.com/parts/aei-13130/overview/

It looks like this although probably not that specific part

[michael everson]

I was told by Aeromotive that this was normal.
Mike

[Just puttering]

This is what im trying to find out, do the efi cars have fuel pressure at the guage when the car gets turned off or does it bleed down to zero?

[RickP]

Just puttering,

curious to know what EFI are you running?

[wallace18]

This is what im trying to find out, do the efi cars have fuel pressure at the guage when the car gets turned off or does it bleed down to zero?

It depends on the system. Some bleed down to zero right away, some hold pressure for a period of time. None hold it for hours to my knowledge.

[Itchief]

I have the same aeromotive regulator and it will slowly drop pressure from 50 to 0 over the period of about 2 hours

But there should also be a check valve in the pump

Rick

[karlos]

See item #6 here: https://www.aeromotiveinc.com/tech-help/faqs/faq-efi-regulators/

[Just puttering]

Rickp Efi - direct port injection? 8 injectors with a fuel rail on top of them - brand .... Not a clue!

I turn the key on the pump runs then stops and by the time i look around at the gauge its back to zero.

Some have said this is wrong but karlos pointed to the aeromotive tech sheet that states it may be ok.

I am not sure if i have a non event, or trouble with the fuel system?

[CraigS]

I am not clear as to whether you are driving the car or not. My question would be do you have any starting problems like a long crank before it fires up. One thing I ran into years ago is that, as long as the system is full of fuel, the pump will pressurize it immediately. You may not see pressure on the gauge, but as long as the pump doesn't need to move X number of ounces of fuel first, it will pressurize it just fine.

[Joel Hauser]

I had a similar problem. I installed a fuel pressure regulator on the fuel rail of my 1996 4.6 L EFI engine and was getting very low pressure when the car was running - under 10 psi - and zero when I turned it off. I removed the pump from the tank and found that the short rubber hose between the pump body outlet and the supply tube exiting the tank had become disconnected, and the back flow check valve that sits inside the pump had become dislodged. I replaced the pump and and the problem was fixed. Maybe the check valve in your pump is bad, or maybe there's a piece of crud on it preventing the little valve from closing all the way. These pumps are pretty cheap; I think I paid $65 for the entire assembly, but could have purchase a pump and filter for under $30. Because there is an access panel in the roadster trunk, it was a pretty easy job to replace the pump.
This website has a discussion on the subject, and has a diagram of the valve. https://mustangforums.com/forum/2005-2014-mustangs/581613-oh-no-another-s197-fuel-fill-thread-2.html

good luck
Joel

[Just puttering]

When the pump starts it goes right up into the 40's. Typically it starts quickly!

Maybe its ok just something to monitor if i have issues down the road?

[i.e.427]

I have an Aeromotive rail mounted regulator on my personal F5R and when I called Aeromotive was given the same answer. They directed me to the same web page.

6.) I’ve installed my new Aeromotive bypass regulator. Fuel pressure seems to adjust fine and holds great when the engine is running, but when I shut the engine off, pressure drops quickly to zero. Shouldn’t the pressure hold like it did with a stock regulator?
No, Aeromotive EFI bypass regulators may not seal perfectly when the pump is off. They are engineered for the highest possible performance when the engine is running. OEM regulators must hold pressure for 30-minutes after shut-down to pass EPA emissions standards. At Aeromotive we know our customers priority is to have the best possible flow and pressure control when the engine is running and we don’t compromise this standard to force the regulator to seal when the engine is off. If extended crank or hard-start becomes a concern, first allow the pump to run and prime as long as possible after turning the key to the run position, then start cranking the engine, just before the pump shuts off. If the priming cycle is too short to allow the engine to start easily with this approach, extend the priming cycle in the ECU if programmable, or ad a timer board or momentary button to the fuel pump run circuit.