moore_51

So i'm still working on my 5.3 swap in my 98 c1500. I actually got to drive it the other day. We figured that we were going to need to put a fuel pump in it before we even started the swap, since the vortec 4.3's use less fuel pressure than the 5.3's, which is what was previously in my truck. Well, surprisingly enough, it started and idle's just fine, on 45lbs or fuel pressure. Needless to say we were kind of amazed, considering my dad has trucks coming in with 2lbs under minimum and will not run at all. Well I went and drove it, and it ran fine under normal driving conditions, but when i actually got in the throttle, it fell on its face at about 4500. I assumed that i needed more fuel pressure, considering ALLDATA shows like 62-65 WOT for that motor. I just need to find a pump that will work. If i get just the pump, I can put it on the existing module in the tank. I just havent had any luck finding one yet.

ls1nova71

iTrader: (4)

If you want cheap and your engine is stock and going to stay that way, an AC Delco ep381 should work. If you want something better, you could spend a little more and get a Walbro255, they make them that will fit a factory sender.

moore_51

I don't plan on doing a whole lot with this motor, I'm doing full exhaust and I plan on getting a cam later on. But that's pretty much it. Maybe put an ls6 intake manifold.
So oriellys deals a lot with the shop my dad works at, so I know those guys pretty well, and according to them, the factory 5.3 fuel pump sends the same pressure as the factory '98 4.3 pump, and the 4.3 just has a lower pressure regulator. I had gotten a new sending unit for my truck, since they said it sends the same pressure, but I'm still only getting like 49lbs at idle, when I'm supposed to be getting around 58lbs. I didn't change the filter yet so that might be the cause, a little bit, I've been told. I just wanna get the right pressure that I need.

ls1nova71

iTrader: (4)

What year is the engine? Flex fuel engines run at a lower pressure. If it has a return style fuel rail you can pull the vacuum hose off the regulator and see what you get for pressure. If you dont get above 58 with it unhooked then you need a better pump. Thats if it isnt a flex fuel engine.

moore_51

It's out of an 03 Tahoe. I was never told if it was flex fuel or not and I'm don't know what to look for to determine if it is or not. But I'll give that a try. If I get above 58, do I just need to leave the vacuum hose off the regulator?

moore_51

I have determined that it is a flex fuel engine. I'm gonna get a regulator for the normal gas engine. But is the a difference in the injectors? Would I have to change them out or would it be fine?

ls1nova71

iTrader: (4)

I'm pretty sure the regulators won't interchange, I think the rails are different. And yes, flex fuel injectors are different. If you have a flex fuel engine you should be alright with the lower fuel pressure, just make sure your tune is set up right and you should'nt have any problems.

moore_51

Oh ok. Sweet that sounds good. Is there any other differences in the flex fuel engines vs. regular gas?

Mrpiercings

LS1Nova.... will that AC Delco pump drop right into 1994 Impala/Caprice fuel sending unit? I was going to try and use the caprice gas tank and sending unit for my swap to save money.