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How many PSI should a fuel pump on a 94 bravada with a 4.3 vortec be putting out?


Browning

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Thing doesn't want to start after longer trips(30+ miles) and after trying smaller things like relays, etc I have determined the fuel pump is shot. Sister broke down in Lancaster and usually will have to wait for an hour or so before it will start up.

 

I put a fuel pressure gauge on it today while it wouldn't start and at first got 0psi. Smacked the fuel tank a few times and it jumped to 20psi. Thought maybe I had the gauge on wrong or something so I took it off and retried. Still at 20psi with the key on. Smack the tank a few times harder and it jumped to 60psi but was bouncing back and forth really fast between 55-60psi. Tried to start it and it fired up and died instantly, which brought the pressure down to 45psi. Decided to see how long it would take for it to drop off and within 5 minutes or so it dropped 10psi.

 

First time using a fuel pressure gauge but I am pretty sure this pump is toast, right? I tried playing with the wires also thinking maybe it was a short but it had no affect on it whatsoever. Only thing that does it hitting the tank.

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Sounds like it's clogged to me.

it doesn't cut out or anything like it should if it was clogged. When it runs it runs great down the road. I was expecting relays or something to be the problem but swapped those already. From my understanding you can take as many little 1-2 miles trips in it all day long with no problem at all. Idle always drops just a tad when it starts then picks back up so I assumed IAC, nope. Also, since it seems as if it's something getting too hot and needing time to cool off I had changed the coolant temp sensor. No change. No codes.

 

 

The kicking the tank thing and jumpy fuel pressure just seemed odd to me.

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Just put a pump in it, when you drop the tank make sure everything is clean and looks to be in proper working order, get a new fuel sock if the pump doesn't come with one, and change the fuel filter outside the tank while you're at it. Double check the wiring on top of the tank while its out too. You're working on an older vehicle so make sure you're avoiding issues that could bite you in the future.

 

If you don't get right around 60 psi all the time either your fuel pump is taking a shit (usually the problem) or something is clogged, and since the fuel pressure isn't low all the time its the pump.

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Just put a pump in it, when you drop the tank make sure everything is clean and looks to be in proper working order, get a new fuel sock if the pump doesn't come with one, and change the fuel filter outside the tank while you're at it. Double check the wiring on top of the tank while its out too. You're working on an older vehicle so make sure you're avoiding issues that could bite you in the future.

 

If you don't get right around 60 psi all the time either your fuel pump is taking a shit (usually the problem) or something is clogged, and since the fuel pressure isn't low all the time its the pump.

Thank you.

 

I got a bunch of electrical cleaner I plan to spray on the plug. Going to inspect the tank well for rust, etc. Fuel sock? Is this another name for the strainer?

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Should be a CPI 4.3L - I've owned 2 of them.

 

It's the fuel pump, common problem. DO NOT cheap out on an Autozone unit, as they don't seem to last (not all Autozone fuel pumps are bad, but they are for these motors).

 

If you pull the intake, it is highly likely the plastic fuel lines for the fuel poppets are cracked/leaking (motors are batch fire, and don't use regular fuel injectors but rather an injection unit). Very common issue, and will cause starting problems as fuel leaks into the intake.

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Is it common when a fuel pump starts going that smacking the tank could get a little life out of it?

 

YES!!! Replace it with a quickness. This is the actual recommended way of testing on S10forums lol. srsly.

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If you pull the intake, it is highly likely the plastic fuel lines for the fuel poppets are cracked/leaking (motors are batch fire, and don't use regular fuel injectors but rather an injection unit). Very common issue, and will cause starting problems as fuel leaks into the intake.

 

I'd look into this if the fuel pump ends up not being the culprit. I have fixed several of these. They sell a repair kit at the dealer, and the last time I bought one it was around $100. Fuel pumps are really common though, and as others said, don't cheap out when buying one.

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