TBI Fuel Pump Question

[1-ton]

I have a set of in-tank fuel pumps in my 1991 V3500 Crew Cab pick-up truck that have a maximum 30-PSI pressure rating, and I also have a TBI with an adjustable fuel pressure regulator. My question is...If I have my fuel pressure regulator set at 14-PSI will this mean that the pumps will never go higher than 14-PSI pressure? Or will my pumps spike up to a higher pressure despite what my fuel pressure regulator is set to?

 

[rampage]

I would say that the pressure from the pump to regulator would be somewhere around 30 PSI, while the outlet of the regulator would never get above 14 PSI or what ever you set it to, otherwise it wouldn't be much of a regulator.

 

[Bent77]

/\ this here

 

[AV8TER]

It depends on which type of regulator you have. If you have the 'old school' type with no return line the fuel pump will put out max pressure (unless outlet flow exceeds what it will make max pressure at) to the regulator and the regulator will let just enough flow thru it to control the outlet pressure. This type or regulator isn't the best on rotary pumps as the fuel that sits in the pump waiting to move tends to get hot. This also overheats the pump. The other type of regulator uses a return line. This type is basically a blow off valve. Once the pressure in the line, which is the whole line from the pump to injectors, reaches set pressure the excess fuel blows off and returns thru the return line. This keeps fuel moving thru the pump for cooling and the pump only puts out whatever pressure the regulator is set for reducing the load on the pump. So, if you have a regulator with a return line, the pump pressure will be what the regulator is set for.

 

[1-ton]

My fuel injection system is the stock TBI set up. The adjustable pressure regulator utilizes the stock one integrated into the TBI, thus my TBI system does have the factory fuel return line. My TBI is a bored out unit built by Vic Morse Machine with an adjustable fuel pressure regulator. It also has a set of flow matched Vic Morse fuel injectors Thanks for the replies

 

[1-ton]

Another thing I was worried about is since I am using the stock fuel tank line design and saddle tank selector valve set up, the increased fuel pressure could be too much for it. The TBI fuel lines are originally designed to use only high pressure fuel line with hose clamps (no compression fittings), and the fuel tank selector valve is made of plastic...not the steel of the older carbureted ones.

The stock system came with a fuel pump that only made 13-PSI max (30-PSI max with the new ones), and the fuel pressure regulator set at about 12-PSI. Since my engine is a mild build, I am only going to need to increase the fuel pressure 1 or 2 PSI more over factory, and this should not cause a problem I guess.

 

[mrk5]

Yes, technically the TBI selector valve is not rated high enough. I've done some research on this when I was thinking about FiTech. Somewhere I found the pressure specs.

If you do some searching there's info out there with an appropriate pressure rating. Search for "ls fuel pump with saddle tanks" or something similar.

 

[1-ton]

I found a spec on the selector valve that says those things are supposed to be rated for 65-PSI. That is pretty high.

 

[dyeager535]

I found a spec on the selector valve that says those things are supposed to be rated for 65-PSI. That is pretty high.

If I'm not mistaken, the pressure rating of the pumps is for "dead heading". Unless you exceed the capacity of the return line, you'll never see the pressure the pump is capable of anywhere in the system, as the regulator will just open further to bypass the additional fuel.

 

[mrk5]

I guess it depends on what pump you were planning to use. I was looking at the EP381 which is 80-90psi according to one source I found. I wasn't so much worried that the selector valve would blow up, but more that it wouldn't be able to actuate properly. Based on dyeager's point, it might be fine.

 

[1-ton]

I found another spec on the selector valve as having a 20-PSI max rating. This sounds more logical than the 65-psi rating spec I found on the AutoZone web site.