# 1996 chevy k1500 350 vortec fuel pressure



## allen82o8

What is the GM spec for fuel pressure on the 350 vortec? I have looked and found answers from 50 psi to 70.With the key on mine is 60 psi and running at idle it is 52 psi.


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## mack1

allen82o8 said:


> What is the GM spec for fuel pressure on the 350 vortec? I have looked and found answers from 50 psi to 70.With the key on mine is 60 psi and running at idle it is 52 psi.


Hi allen,

I think you will find that your normal pressure should be 60 PSI. Remember that there is a pressure regulator that is susposed to maintain that pressure. 
The pump's job is to put out enough volume that when you race the engine, the pressure should remain the same. See if you have 52 PSI with the engine reaved up. If not, you probably have a weak pump. 

Hope you are not having problems, just want data.
Very best regards,
Mack1


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## allen82o8

mack1 said:


> Hi allen,
> 
> I think you will find that your normal pressure should be 60 PSI. Remember that there is a pressure regulator that is susposed to maintain that pressure.
> The pump's job is to put out enough volume that when you race the engine, the pressure should remain the same. See if you have 52 PSI with the engine reaved up. If not, you probably have a weak pump.
> 
> Hope you are not having problems, just want data.
> Very best regards,
> Mack1


Unfortunately I am having problems.I bought the truck with a busted block and then bought another motor for it, but had to use my intake from the original motor.Original motor ran great,just poured water out the block.Got the motor set in and it idles and revs up good in the carport (facing slightly uphill),but when I pull it out of the CP (now it is facing slightly downhill) it will idle for a second then start spitting like it is losing fuel and die.I have checked FP and it is 52 idling and goes up to 56 when reving up.Bypassed FPR with it facing slightly downhill and ran the fuel into a jug for about a minute and it ran great,so I tried to run the truck with FPR bypassed but it ran for about 10 seconds and then still dies.I am going to try Fuel Pressure Regulator next. If any of you have any ideas I am open.I have checked all the grounds and plugs on thewiring harness.


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## mack1

Hi allen,
My first thought is the pump isn't picking up the fuel good when vehicle is pointed down hill. Make sure you have enough gas in the tank for the pump to pick it up. 

Can't think of anything else at the moment that would be related to the angle of the truck.

Best regards,
Mack1


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## allen82o8

mack1 said:


> Hi allen,
> My first thought is the pump isn't picking up the fuel good when vehicle is pointed down hill. Make sure you have enough gas in the tank for the pump to pick it up.
> 
> Can't think of anything else at the moment that would be related to the angle of the truck.
> 
> Best regards,
> Mack1


It has about 10 gallons in it.It doesn't make since,with it facing uphill or downhill with the FPR bypassed it pumps fuel.Just when it faces downhill it wont idle.When you dont divert the fuel to the can and let it go the plenum(also with the FPR bypassed) is when it starts spitting and dies.I tried this several times,pumping in the can and then let it flow to the plenum until it dies and checking again to see if it still has flow to the can and it does.Only thing I can think is it has trash in the Fuel pressure regulator.
Thanks
Allen


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## mack1

Hi Allen,
It's not clear to me why you are bypassing the Fuel Pump Regulator. The FPR is used to keep pressure on the feed loop for the injectors (the little popit valves). If you somehow bypass the regulator, isn't the pressure very low? I'm thinking that you need about 60 PSI on the supply rail to get the proper amount of fuel for each cylinder. I know that there is some data out there that tells you how much fuel you should pump in a given time, but I have never used that as a criteria for making the system work. In my view, the pump should put out enough fuel under pressure to keep the engine supplied. A fuel pressure gauge will tell you this. If you speed the engine up and the pressure drops, the pump isn't keeping up. This, of course, isn't your issue. I see no reason that the pressure should be different if the vehicle has an up incline, or a down incline. With constant pressure on the fuel rail, the engine shouldn't care. Aircraft can fly upside down and their system don't care about incline. 

I could only think the the fuel shifted in the tank leaving the pump with insufficient fuel to pump it through the loop to the engine. The regulator is a simple spring and diaphram arrangement that requires a certain pressure to open the return valve. The excess goes back to the tank. The pump is susposed to supply enough fuel for the engine and an excess to return to the tank. 
A few years ago, I invested about $18 in a pressure gauge. It would tell you profoundly if there was a difference in the loop pressure with the truck on two different inclines. 
Wish I could help you further Allen, but I am at a loss. If you find the problem, be sure to let us know. Someone else might have the same problem in the future.

Hoping you luck and wishing you well,
Mack1


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## kjms1

jack the front of the car up so you are always going up hill LOL

10 gal has to be about a half a tank full so i cant see it being a pick up problem ... now that is if your fuel gauge is working right
i have to ask how big is this can and how long does it take to fill 50 psi is going to have a massive volume it might just take it several seconds to fill a gal can ... high PSI with out volume the truck will not run, you need both i have seen good pressure and low volume and it will not run right .... being a 1996 its not a bad idea to change the FBR ... is there good vacuum to the FBR


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## allen82o8

Sorry for the confusion,I am bypassing the fuel pump relay as to make sure that the fuel pump is pumping and not something else causing the fuel pump to shut off. It is a 1 1/2 gallon can. Doesn't fill fast at all I am using the little hose (about 1/8th in diameter) that is attached to the fuel pressure gauge.Fuel pressure is the same uphill or downhill


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## Wrench97

Fuel Pump Relay or Fuel Pressure Regulator?

Does this motor have the spider injector setup?


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## allen82o8

wrench97 said:


> Fuel Pump Relay or Fuel Pressure Regulator?
> 
> Does this motor have the spider injector setup?


 
Fuel Pump Relay and yeah spider injection system.
I put in 2 five gallon cans because I thought there was a problem with the pickup initially.
I am going to hook a 3/8 hose to main line and check volume.
Maybe if there is a blockage in the tank that it is small enough to keep up with the 1/8" hose but not the main line with engine running.


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## Wrench97

Did the motor you installed also have the spider system, I seem to remember a difference in intake gasket shapes(or something causing a vacuum leak) been too long since I've worked on the smaller stuff.


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## allen82o8

wrench97 said:


> Did the motor you installed also have the spider system, I seem to remember a difference in intake gasket shapes(or something causing a vacuum leak) been too long since I've worked on the smaller stuff.


 
Not sure if the motor I bought ran the spider system,it came out of a 2001 van.The mechanic said they were the same.
I used my upper and lower intake off the original motor.


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## Wrench97

The EFI(91 G series) and SFI(96 K series) do use different Cylinder head design and intake manifold gasket, As I remember 1 will work and 1 will not, I think you have to use the 91 gasket and not the 96 gasket.


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## allen82o8

OK I checked volume and with a 3/8" hose hooked straight to the main line it took 2 minutes and 37 seconds to fill a 1 and a 1/2 gallon jug is that good or bad.


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## allen82o8

wrench97 said:


> The EFI(91 G series) and SFI(96 K series) do use different Cylinder head design and intake manifold gasket, As I remember 1 will work and 1 will not, I think you have to use the 91 gasket and not the 96 gasket.


 
I looked up gaskets for the 1996 and 2001 5.7 and they call for both same upper and lower gasket SFI so I believe the 2001 ran the spyder system also

2.37 (give or take a few seconds) minutes facing uphill or downhill on the 3/8" line attached to the main line and ran into a jug


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## Wrench97

Seems like a long time to me for a gal and a half but I've never tested it that way, they do have a sock/screen filter in the tank on the pump that can plug up.


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## allen82o8

I forgot to mention that everyday I have to turn the key on 3 or 4 times before I try to start it or it will not crank.If I try to just crank it,the motor will just spin and not start.Tried it one day for about 10 seconds and it would not start just spin.


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## Wrench97

That sounds like a injector leaking or pressure regulator leaking back.


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