Engine/Transmission (1998.5 - 2002) What regulates fuel pressure?

[Sea01Cummer]

Where in the stock system is the regulator located? Is the pressure we see all the lift pump will do? I am trying something new , fuel system wise , i need all the imput i can get.



I am going to attemt to use a Ferd SD pump, they seem to last pretty good but i need to make sure i get the fuel pressure right. I am thinking the regulator needs to be in the return but if there is one hiding somewhere that will cause me some troubles.



Steve

 

[Sea01Cummer]

Anyone?







Steve Oo.

 

[nps]

No regulator that I am aware of. The VP44 has an internal bypass that begins to return fuel to the tank above 14psi. No harm done if the pressure is higher than 14psi.



Some of the earlier 24V trucks reported hard starting when more than 10-12 psi was present during cranking. Once started the truck runs fine. The later 24V trucks don't have this condition.



Some are running FP at 20psi and above. Again - no harm done.



If you want to read more about the fuel system, read the thread titled modifying fuel system so temp input to VP44 ... here on the 24V engine board.

 

[Bob4x4]

The VP-44 has an overflow valve on the return side of the pump. It is nowhere near as criticle as on the p7100. I have never had an issue with one failing .



Bob

 

[Hohn]

The overflow on the VP44 opens at 14psi, yes-- but It cannot bypass much fuel at all, and it's easy to exceed 14psi FP, even with a stock LP. I am.

You can run FP up to 30psi with your VP with no prolems, but you MAY have hard starting issues. The solution is to wire up your big fuel pump off a Hobbs switch rigged to oil pressure (which is easy, since you have a 1/8" NPT oil pressure port near the filter, and Hobbs switches come with 1/8" NPT male inlets).

That way, your fuel pump only comes on after there's oil pressure-- meaning the engine is started. However, this WON'T help you fill the fuel filter canister after a filter change, and it won't cure a dead LP.

So there's no regulator, per se, in the OEM system (but perhaps the restrictive OEM fuel plumbing has that effect). I'd HIGHLY recommend the use of a regulator to keep pressure's down below 25-30psi or so.

There's nothing wrong with the higher fuel pressure by itself, based on reports of some pros (though my gut wonders why Bosch sets the bypass at a low 14psi if higher FP is safe). The problem comes when you start pumping too much fuel and it gets too hot to cool the VP down.

The thread NPS menioned about "modifying fuel system... temp" is a good read, and I recommend it.

Also, see if you can dig up a TDR classic uysing the search feature. "Pumps, lines, and what not" was the thread title-- it's very long.