Adding an electric fuel pump to a carb'ed T/A
 

I have a 1978 T/A (build thread is on here somewhere...). The engine is a 428 bottom end (69 Grand Prix), top end is all correct 78 T/A parts (6x heads, factory intake, rebuilt original distributor). The carb is the original Quadra-jet that has been rebuilt & tuned as per Cliff Ruggles book. It's a strong street engine but not a race car.

The rest of the car has been ground up rebuilt, including a new fuel tank & reproduction fuel lines (Inline Tube) with a 3/8" supply line.

My issue is fuel starvation. Originally I built the engine with a stock replacement fuel pump (Spectra industries). When I would go to WOT (either from a standstill or from a roll) the car would pull HARD, but only for 2-3 seconds. Then it would stumble & die until I lift off the throttle & give it a couple seconds to "catch up". Last year I tried a second fuel pump (the same kind as before) - no change. This year I switched to a Holley mechanical pump good for 200 GPH or something.... and it got worse, not better.

So at this point I'm not sure what my best option is? I've been kicking around the idea of adding a electric "helper" pump, but I'd prefer not to go solely electric as I don't want to mess up the restored look of the car.

Looking for suggestions...

Nice engine choice. Used to have a 428 with 6x heads. Nice for the street.
Do you have a fuel gage?
I think you should confirm it's fuel starved with a gage.
Your car should be fine with just one mechanical pump.

Does it property venting gas tank? How is it vented?

Sounds like there is more going on than fuel starvation from a weak pump. Even a Q-jet shouldn't run out of gas in 2-3 seconds. You have either a venting problem in your fuel tank or an air leak on the suction side of the fuel line.

I tried removing the gas cap to ensure it was no a venting problem - no change. Still stumbles & dies..

Possible problem with the pickup tube? Maybe I should drop the tank.

FWIW its a stock replacement tank. 3 lines run from the tank forward. Supply/fuel pump return/charcoal canister return. Original (or at least original type ) gas cap.

Depending on the fuel you have been putting thru the tank, the gas out there today may have melted the plastic screen on the inlet of the fuel pick-up. Had that happen with a Mustang tank on a cross-country trip.

Tom V.

Depending on the fuel you have been putting thru the tank, the gas out there today may have melted the plastic screen on the inlet of the fuel pick-up. Had that happen with a Mustang tank on a cross-country trip.

Tom V.

Sorry for the double post, the PY software had a glitch at the time I hit the send key.
Mod please delete on of the posts at your convenience.

Tom V.

What size fuel inlet seat are you using in it?

Let's cover "basics" first before moving to improving delivery to the carb.......Cliff

Taken the situation as a whole, it would seem to be a carb problem. Most likely suspect. Just not enough fuel in the bowl. Float level?
I would switch on my spare carb and try it.
Or switch one from another vehicle.

Float level probably not a player. If it takes off OK then goes bad it's sucking the bowl empty. If fuel delivery was adequate it would continue to run fine.

Fuel inlet seat size is a big player. With a Q-jet you only have one seat to supply the engine, so volume/pressure and size of the seat are big players when you start using one to feed big power levels......Cliff

Yeah. When I was troubleshooting my fuel system I put a gage on a T up by the carb. Duct taped my cell phone to video it and went for a test drive. I don't see any good way around that. Takes a lot of guess work out of the equation.

I've learned a few things over the years about making power and effectively using it.

The size of the fuel bowl is NOT a player here. No matter what carb you are using the fuel has to come out as fast as it goes in, or the fuel level will go low or even empty.

When I first took steps to run really quick with my car around 1999-2000 I IMMEDIATELY ran into fuel delivery issues. I pissed around with several marginal fuel delivery systems and go the car into the 12.40-12.60 range at 109mph. Best ever run was a 12.36 @ just under 110mph. It still felt "flat" above 5000rpm's so I just short shifted and figured it didn't have enough cam in it and the heads needed ported.

I even followed some advice from a few Board members to install a Holley 850 DP carb as it had bigger fuel bowls but the car ran exactly the same. The big Holley worked really good, but I couldn't get much past 160 miles per tank no matter how easy I drove it, the Q-jet would easily go 200-230 miles on the same amount of fuel so I stuck with it.

Over one Winter, must have been around 2002-2003 I sumped the tank, installed a Comp 140gph pump behind the tank, and 8An lines/fittings everywhere.....no other changes.

First runs the next year were 12.0's at 112MPH. I actually over-revved the engine on the first two runs as it revved so quick past 5500 I didn't get the shifter moved quick enough! Just for fun I put the big Holley 850 DP carb back on and it went 12.02-12.05 @ 112mph as well, or pretty much the same as the Q-jet.

So the car picked up equally with BOTH carbs despite the difference in fuel capacity in the bowl(s).

Early lesson learned in pissing around with fuel systems. When you start making your car launch really hard and run quick, ALL the fuel is pinned up against the gas cap on the launch. Sucking it from a tank located front mounted sump nearly 14' thru a bunch of bent fuel lines is likely to give you a nose bleed........when it bounces off the steering wheel when the car noses over at the top of 1st gear!......Cliff

I would start simple first, to see if you're going in the right direction.

* Check all suction lines for adequate tightness, no leaks, no kinks or bends in hoses or lines (fuel pump to carb especially)
* Make sure the fuel filter is clean
* Test fuel flow: Start the car and let it get to op temp, shutdown, at the carb, pull the line, add a piece of fuel line into a can, and idle the car for a few mins watching the stream into a can. Wing the throttle a couple times and make sure it picks up flow
* Drop the tank and check the pickup for obstructions, and if it has a sock, rip that pig off.
* Check depth of pickup, and adjust as needed, It should be close, less than 2" from the bottom of the tank

Once that's all done report back.

When you are experiencing the issues, do you have at least a 1/2 a tank of gas in it?


.

A LOT of TRUTH and HISTORY in the above post.
Are you willing to read and do what has been suggested above.

Years ago, the Boost Guys on some of the websites recommended the McClintoch Fuel bowls that were about 50% larger volume in each bowl.

The Bowl Volume did nothing, the dual needle and seat system in each bowl (with the proper fuel pump system did everything).
Same applies with the spacers that vendors used to sell between the Carb Mainbody and the Fuel Bowl. Did nothing.

Tom V.

Cliff I believe you once said fuel the engine with a garden hose and exhaust the engine with sewer pipes.
I've seen the same issues with my cars over the years. I did start initially with a Holley Blue Pump and stock lines..that worked fine until I started launching harder and increasing the horsepower. Running in the 112/114 range was about the limit..same feeling flat in drive then eventually running out of fuel, Switching to all 8an lines and half inch pickup and a Mallory 140 picked up a few mph at the track and eventually the exact same engine combination went all the way to 123mph. Without adequate fuel supply it would have been stuck at 114mph high 11's.

I agree with the fuel bowl nonsense..without adequate fuel supply it doesn't matter how big the bowl is..one can easily empty both bowls on a Holley, I doubt I would get thru a burnout without emptying them, plus the fuel level should remain at a proper height for proper carb operation.
You will also hear crap like this " my engine made good horsepower on a dyno with a mechanical pump"...sure but on a dyno its not fighting the winding length of fuel line and g forces.
Go to any dragstrip on a testntune day and there are countless cars with poor fuel supplies..its like they hit a wall at the 1/8th mile.

I too suffered through fuel starvation with mine, but only right up toward the end of a 1/4 mile run. At that time I ran a "deep sump" type mechanical fuel pump. It did fine on the street, I don't ever remember issues with fuel in a street situation. I'm sure I could have cured it other ways but I bought a Carter P4070 electric and mounted it to a piece of aluminum angle that I installed between the gas tank strap bolts. If I see that I'm going to hammer on the car, I flip it on. Day to day driving, I keep it off. I also find it useful to prime the system with when the car has sat for a while.

This is also what I did, on all our 455 bracket cars, back in the '70's-'80's. Not high powered. Probably around 400hp/500 torque. Flipped the elec pump on just for the pass. Ran this system down into the low 12's & high 11's. Best ET was 11.82 in the 1/4 mile, 9.85 on a 1000' track. Didn't run any 1/8 mile tracks back then.

Gonna run the same system on my current bracket project. Engine similar but less CR, with 6x-8 heads. Our local tracks are now 1/8 mile. Should provide more than enuff fuel, even with 3/8 line.

Could run 1/2" line. But that would just be overkill, for my power level.

I'm considering doing this at some point. When you're driving normally with the pump off does your mechanical pump just pull fuel through the electric pump or do you have some kind of bypass?