BanditDave

iTrader: (11)

Hey guys,

Been doing some trouble shooting on my '78 TA LS1 swap and the one thing that has been a bit weird for me lately is the lowering fuel pressure issue I am having with my '78 TA.

I have been only able to drive it up and down the driveway with some holeshots down the driveway but the latest tests were done in the garage. I purged the system a couple of times then let the car sit and idle for like 15 minutes with occasional throttle blirps and prolonged open throttle shots to watch the fuel pressure gauge at the rail. 58 psi with the corvette regulator and a sumped stock tank with a Bosch 044 pump ran externally. For the majority of the time, I could open up the throttle hold it almost wide open and the fuel pressure woud dip for a second the come right up to 58 again, but every once in a while it would all of a sudden drop down to like 20 psi and the car would cut out. I would turn the pump on without starting the car and burp the rail and it would come back up to 58 and everything would be fine again.

So...I am figuring somehow air is still in the system or it is getting aerating somehow?!?! I am wondering if I need to somehow foam the tank (which seems impossible because of the stocker pick up) or what?

Open to suggestions...thanks!

Dave

BanditDave

iTrader: (11)

Any ideas? Think my baffle holes, though many, are too small.

jetback73nova

I cant see why you would need baffling foam because the car if the car is siting still, all the fuel should be sitting in the sump where you want it. If you look into it baffling foam seems like a bad idea becasue it falls apart with time.

is your pump sitting bellow bottom of the tank?
could one of your fittings befor the pump (low pressure side) be sucking air?

LS1GMCTruck

iTrader: (2)

I had a simular problem while driving along & when I gave it the gas, under acceleration, it would just cut out & stall. My gas gauge always said I had plenty of fuel. Well...I didn't. I was low on gas. My gas gauge was inacurate, AND, at the same time, when I took the pump & module out, that short rubber fuel line on the bottom of the pump, was defective & sucking air. Double wammo. This took me forever to diagnose. Hope it can help you.

BanditDave

iTrader: (11)

I loaded that bitch up with gas today and tried it out and same problem...cut out, stumped, etc... I simply think that puny Jegs sump and the too small of holes I cut in the bottom of the tank before I put the sump on is what is causing the pump to suck air and F me over.

I am going to a Rock Valley tank and never looking back.

Dave

JJFarmer

iTrader: (38)

So, are you going to try the 70-73 efi tank/pump in your car then? Keep us up on this swap. I was just looking at the tanks and wondering if you can do the swap.

Pop N Wood

iTrader: (1)

You can't be having a baffling problem with the car sitting still and the engine not under load. Even at WOT with the car out of gear you are only drawing a fraction of the fuel load you will if say driving up a hill.

You might have dirt in the pump, a loose connection that is sucking in air, a restriction in the line, a bad fuel pressure regulator or some type of vapor lock issue.

One other thing to check is make sure your tank vent is clear and big enough to flow air. Try running with the fuel cap off and see if that makes a difference.

BanditDave

iTrader: (11)

I was originally have the issue while under acceleration only, but the sump is fairly small and with the vette regulator and the Bosch 044 running, a good deal of gas just cycles right back to the tank. I got to thinking about it more last night and realized what it could be.

Like a jackass the pump was telling me what's wrong and I wasn't listening. The pump had gotten a good deal louder over the past few weeks and then it dawned on me....there's got to be something clogging the pre-filter to the pump. So...this morning I ran down to Atco Raceway's speed shop and found a Aeromotive in-liner with removable filter and redid the feed line slightly...

HOUSTON WE HAVE LIFT OFF!!!!!!

Now of course I feel like a douche but sometimes we overlook the simple things. Pump quieted way down and fuel pressure barely waivers.

Now I gotta go drive the damn thing a little!

LS1GMCTruck

iTrader: (2)

Happiness is: "Figuring out a fuel delivery problem." Isn't it? lol

BanditDave

iTrader: (11)

You're damn right it is....my driveway is now proof!!!!