TBI fuel pump question

[Lewis1129]

I do believe my fuel in my 1991 has gone out. I still have some things to check to make sure, but that is where the facts are pointing. Here is my question. I plan down the road to do a 5.3 swap. With that being said. Could I swap in a vortec pump or a walbro 255 and it run ok with the stock TBI 350? I know it's a bypass style regulator so in theory it should work. But is that too much pressure for the regulator. The truck is my daily driver so right now reliability is more important than preparing for future swaps.

 

[magimerlin]

Yes.... been done a billion times...and asked about just as many times....lol..(I'm messing with you.....but yes it's been done with no complications)... I did it to my 94 k1500... no issues...

sent from what use to be a great country...

 

[tanman_2006]

Running a 97 vortec pump in my 94 C3500.

I have a hard cold start and rough could idle bit the truck has always been cold natured and the old pump was bad when I got the truck so I won't say my idle issue is from the fuel pump.

Otherwise it runs good.

 

[motovate]

I just saw this and it's kind of close to what I am doing. My question - is the intank pump able to flow fuel through the pump with out the pump actually running by hooking up an external pump and sucking through the existing tank connection with the pump still attached???? Wondering also if by doing that would it make the external pump run/pull harder and run hotter or not last? I've never looked at one of the internal pumps so I don't have a clue how restrictive they are if they aren't actually working.

Thanks

LBM

Yes.... been done a billion times...and asked about just as many times....lol..(I'm messing with you.....but yes it's been done with no complications)... I did it to my 94 k1500... no issues...

sent from what use to be a great country...

 

[sntrym]

I'm not sure if it can pull through the existing pump, but an external pump would probably need some sort of cooling device as these pumps are cooled by the fuel surrounding them. You can run a higher volume pump with a TBI without issue. The regulator spring will only allow as much fuel past itself as it's designed for.

 

[motovate]

Thanks. What I'm doing is switching a TBI for a 4 BBL Carb, Kinda going backwards and running a 4-5 PSI electric pump. I was just looking for a way not to drop the tank. I looked up a pump sending unit replacement and was surprised to see 4 hook ups. 1 large one that looks to be the return, one small one that I'm not sure what it does but looks like a vacuum line or maybe a vent ? and 2 medium ones that screw onto what I guess are the fuel lines. In the photo one definitely runs down to and hooks into the pump and one that looks like it runs down the side to the bottom of the fuel pump - can't see where or what it does. I live 35 miles/70 mile round trip from any parts house but I'm thinking it might be worth the trip to figure it out before I decide to drop the tank.

LBM

I'm not sure if it can pull through the existing pump, but an external pump would probably need some sort of cooling device as these pumps are cooled by the fuel surrounding them. You can run a higher volume pump with a TBI without issue. The regulator spring will only allow as much fuel past itself as it's designed for.

 

[sntrym]

The largest one should be the fuel delivery line - 3/8. The second largest one should be a return - 5/16. You won't use the return with a carb. The other 5/16 is probably the vapor recovery line from the canister in the engine compartment, and the smallest one is probably a vent from another part of the tank.

As a side note, you don't need to drop the tank. If you can, remove the bed. It's a hell of a lot easier, especially if you have any rust on the straps or lines. Removing the tank is easy, getting everything back in place is a *****.

 

[motovate]

Thanks. Hopefully I won't need to pull the tank but you are probably right it's easier to pull the water tank & pump off and then pull the bed to get to the top of the tank! I'm getting too old to crawl under and fight the tank and much easier to bed over and fiddle with it!

LBM

The largest one should be the fuel delivery line - 3/8. The second largest one should be a return - 5/16. You won't use the return with a carb. The other 5/16 is probably the vapor recovery line from the canister in the engine compartment, and the smallest one is probably a vent from another part of the tank.

As a side note, you don't need to drop the tank. If you can, remove the bed. It's a hell of a lot easier, especially if you have any rust on the straps or lines. Removing the tank is easy, getting everything back in place is a *****.