fuel pressure??

[JIMMY76]

I have a 1990 454 ss truck the previous owner swapped the 454 for a 91 vette 350 tpi but he never changed the fuel pump. I think I have a fuel pressure or volume problem does anyone know the the fuel pressure on the tpi should be, and if the tbi 454 pump in the truck can keep up with that motor assuming the tpi is stock thanks for any help.

 

[dyeager535]

Probably nowhere near enough.

TBI is right around 13PSI, TPI pumps will push in excess of 60, but need something like 37PSI.

Did you try any other forums for pump specs? For the SS I would think the pump output would be something folks have investigated.

 

[mrdrinksalil]

I know a 95 vortec 350 needs 60psi for the computer to even open the injectors.

 

[Thunder]

Hook up a fuel pressure guage. Turn the ign on and off a few times to cycle the pump. pressure should hold around 45 lbs. It should hold this pressure for a couple of minutes with only a very slight drop.
Then start your engine. TPI pressure should be 38-47 PSI If pressure is under 38 PSI you probabally need to change the pump.
A TBI pump will only give you 20 PSI max. Usually less than that.
I am not sure if the 454SS used a high pressure pump or not. The only real way to tell if you are getting enough pressure is to hook up a fuel pressure guage.
Most performance high pressure TPI pumps can put out 60 PSI and 255 LPH flow.
Might also want to check the fuel filter it may not have ben changed in a long while.

 

[Jason4x4]

I know that there was a time, I think only 1 year, where gm ran a high pressure tbi on the 454. Don't know exact time frame, but it was only a year or two, so if it is a high pressure tbi, it might be enough.

 

[JIMMY76]

thanks for all the help the real problem I am having with this is when it gets probably below 45ish its very hard to start it and wen it does finally starts it back fire and run like crap I ordered a new coil for it today. the motor is out of a 91 vette and the computer numbers r correct for a 91 so it does not have the 9th injector so I was thinking maybe, long shot but if the current fuel pump cant supply the right pressure or volume when the computer is telling it to give it more gas for a cold start it would do that not too sure I am in guam right now won't be home till mid october so I m trying to find out what the problem is before it get that cold. Thanks again for any help

 

[dyeager535]

Sounds more like the ECM temp sensor isn't working correctly. Make sure the connector is plugged in and the wires are good.

If you've got an autozone that will scan your vehicle for free, drive it over there as cold as possible, and check the ECM engine temp. Once the engine warms up it takes it a LONG time to get back to ambient temp, if the sender is not working correctly only down low, it may only noticeably "act up" when the engine has been sitting overnight. If you don't have a scanner, kind of hard to get a baseline cold engine check.

Or if you can find the resistance values chart that exists for the temp sender, use that to determine if the sender is accurate at lower temps.

Pretty unlikely it would run correctly under WOT with an inadequate pump, if it even put out enough pressure to idle the motor. Which most (if not all) TBI pumps do not.