Anyone know of a vacuum referenced fuel pressure regulator that does not bleed right off when engine turned off? using the aeromotive and have long crank when started after sitting awhile. Told that's normal with aeromotive regs.

 

The TBI system doesn't hold pressure after the pump shuts off.

Does your pump run for two seconds when you turn the key on? That is intended to pressurize the system.

What's the point of vacuum-referencing the TBI pressure regulator? The injectors never fire into a vacuum like port fuel injectors. The only time I hear about vacuum-referencing a TBI injector is when the tune is screwed-up, and they're trying desperately to reduce idle/part-throttle fuel delivery.

 

VRFPR is commonly used with TBI when using big injectors and/or high pressure to reduce fuel at idle/part-throttle. There is no way around it.
The stock ECM cannot be tuned to work with VRFPR, but if upgraded with EBL then yes.

 

Really, how about a large displacement engine with a hot cam, larger injectors and hi cfm Tbody with fuel pressure at 20 psi, how would that idle without dropping the pressure at idle? Do a search on here to see that the VRFPR are being used. And if the regulator doesn't stop drainback and the fuel rail emptys on ANY fuel injection, you will have long crank times or will have to cycle key on and off 3 or more times. That is why the oem regulators prevent complete drain back, not hold pressure. I've replaced many regulators to prevent this at the dealership since efi first started.

 

Drainback on the supply side is handled by the check valve in the pump assembly, not the regulator.

 

I use a "stock" type VRFPR, not sure it is what you'r looking for.







https://www.thirdgen.org/forums/tbi/...rfpr-pics.html

 

Can drain just as easy on the return side, no checkvalve. THATS what I'm talking about. The regulator should be the checkvalve if it seats internally properly, especially with the spring force on it.

 

This sounds correct it is definetely not the FPR.

 

And, it doesn't have to hold PREESURE, just keep all the fuel from emptying. like I said.

 

Of course it drains on the return side. That's what the return side DOES--drains back to the gas tank. There's no pressure in the return side unless the plumbing is restricted.

You have drainback problems on the supply side, you have the fuel pump running a long time to build pressure. You have drainback on the return side...yeah, that's the way it works.

 

If I clamp off the return line, it starts fine, even after hours.

 

And it pulls the fuel thru the external aeromotive regulator and the passages in the TBI and injector wells because of suction and gravity.

 

First Guess: The in-tank check valve has failed. Clamping the return line prevents fuel from siphoning back into the tank past the failed check valve.

Second Guess: Fix the in-tank problem, vehicle starts just fine.

 

Checkvalve is on supply side.






Thanks for replies. No more needed

 

Generally every FPR works the same as the stock one just in different shape and size.

If you clamp the return line, since it is a closed circuit, it will not allow the feed line to drain back, though I do not now how why/how your VRPFR is built to work different than the stock one.

 

Of course the check valve is on the supply side.

 

If using a stock TBI regulator or VRFPR like thomas you can braze up a port in the injector pod that will prevent drainback. This will net in quicker cold engine start times usually (don't have to wait for 2 seconds which sometimes still doesn't get up to desired pressure), but is potentially "harder" on the injector o-rings. I don't see the later being an issue, just be careful when working on the fuel system as it will be pressurized. Fast355 did this on one of his builds... I hate this about the the aeromotive VRFPR I have, wish I would have spent the extra money and bought one like thomas. I was thinking about seeing if I could source a check valve and plumb it in on the return line after the VRFPR but never looked for one.

 

I spoke to Aeromotive and they said their regulators are not built to seal totally when fuel pump is off. So after some thought, I remembered how some diesels have a fuel shutoff solenoid valve. Got one and installed it right after the regulator and wired to ignition power wire, valve is normally closed. That was the solution to my problem. Starts great even after sitting overnite. Yes, the regulator should seal when pressure off. Doesn't have to hold pressure just prevent fuel from draining from the fuel rail, or in this case the injector pod. Could possibly be used on cars with hi pressure, volume pumps without check valves also. May work for you too, morgsie. Amazon has them, search 12 volt fuel shutoff solenoid valve.