Ok, another one of the issues that I have currently is running out of fuel at WOT. With the engine fully warmed up, I have about 5-6 PSI at idle, and while cruising. When I go to give it gas, 3/4 throttle or more, fuel pressure drops to 2 PSI, and the engine stops pulling at about 4500 RPM. Here is my fuel system setup....

-1/2 inch stainless tube bent just like the factory electric fuel pump for the pickup

-That tube goes to a hard tube adapter to connect it to -10 AN stainless steel braided hose

-The -10 line runs all the way up to the passenger side frame rail where I have a large Russel fuel filter. The filter is a large canister type filter that is about 12 inches long and 2 inches in diameter. It has -8 inlet/outlet and flows 140 GPH

-I have the -10 line from the filter to the Edelbrock mechanical fuel pump which is a 110 GPH pump.

-From the pump outlet I am running -6 stainless steel braided hose to an Edelbrock carburetor line kit shown below...


And to top it off I am using an Edelbrock 1407 model 750 CFM mechanical secondaries carb with a mechanical choke. is it possible that the smaller fuel filter that is part of the carb line kit is causing a restriction?? This engine makes 500 HP(or at least it is supposed to) but won't be able to do so until it gets the correct amount of fuel.

 

The fuel tank vent is not big enough, causing a vacuum build up in the tank at high fuel flow. Remove the cap and retest.
The hose on the inlet side of the fuel pump is being sucked closed or collapsing (heat and/or bend in fuel hose).
The pump is bad. Something restricting fuel flow. Junk in the filter or collapsed filter element inside.
Is that the carb fuel inlet pipe with a banjo style fitting?
Definatly restrictive. if you must use a banjo style fitting for air cleaner clearance, use two. One on each side of the carb. Easy modification.
That edelbrock filter looks cute but is pretty dinky. Either eliminate it or run two of them in parallel. One big filter should be more than enough. Move the big Russell filter to the pressure side of the pump.
Edelbrock carbs are very sensitive to hot soak.
install a wooden carb spacer and get a "Seals- It" fuel pump heat shield gasket and bolt set.
www.sealsit.com

Shield the fuel line (especially the feed side from the tank) from heat. the feed side of the pump is under partial vacuum. When a liquid is under a partial vacuum it boils at a lower temp (vapour lock)
On my car I gave up on a mechanical pump. Went to electric pumps and rerouted the lines. At the back to pressureize the fuel lines from back to front. The fuel lines just pick up too much heat. That, combined with the heat picked up at the engine mounted pump and the carbs internal fuel bowl design is just too much. the fuel ends up boiling in the line and fuel bowl. If I draw the fuel from a under hood mounded fuel cell the mechanical pump is fine. but when drawing from the fuel tank at the back, it vapourlocks in high gear on hot days. Third gens have such cramped engine bays and poor airflow around the motor that there is just too much heat buildup. Even stock carbed 305's have heat soak/vapour lock issues. At 360 BHP (350ci motor the mechanical pump was fine. But at about 450bhp (406ci motor) (more fuel flow demand) It hit its limit 'cause of too much heat.

 

F-BiRD'88-Thanks for posting!! About the gas cap. The car was originally equipped with a 2.8L V6 so it had a gas cap that would seal the tank. I took it off yesterday and it seemed better but I was driving it at night so it was cooler. On my way to the parts store today to pick up a vented gas cap, my fuel pressure dropped to 2 PSI at 3/4 throttle and fell on its face.

Out of curiousity, how likely would it be for stainless steel braided hose to get sucked closed? Is that type of hose better suited to positive pressure applications(in tank electric pump) than a sucking one(block mounted mechanical)?

As far as I can tell there are no abnormally sharp bends or kinks in the fuel line anywhere in its length. All of my fuel line, save for the stuff in the tank, is all stainless steel braided hose. Would it be better if it was all steel or aluminum line instead???

Both of the fuel filters that I am using are relatively new so hopefully nothing is wrong with them internally.

Yes the hard line to the carb is a banjo style. I am using it due to hood clearance. I have to use a drop base air cleaner lid so my hood will close. Unfortunately, I cannot use 2 banjo lines. There is only 1 fuel inlet on the Edelbrock carb and it is on the passenger side. The lack of hood clearance also won't allow me to run any type of carb spacer.

I am pretty sure that I can get enough line to reroute the bigger russel filter on the outlet side of the pump. It is a 40 micron unit and probably does prove to be a good restriction. The reason why I put it there was so that if there was any junk in the tank it would have gotten filtered out before it got to the pump.

Honestly, I had suspected the pump of going bad only because of the fact that I had to install the bottom feed kit from Edelbrock so that my fuel lines would fit. In order to install that bottom plate you have to disassemble the pump. I could have messed up when I put it back together for all I know. I was looking at getting a Holley mechanical pump that flows 110 GPH @6.5-8 PSI. Hopefully this will work. I'm not against installing an electric pump. All I'd have to do is tap into my fuel line back by the tank and plumb it in. I'd run an adjustable regulator but the return line is what kills me. Having to drop the exhaust, and then the rear end to get the tank out to hook up the return line is a major pain in the a$$. but if it needs to be down, then so be it.....

I saw that you mentioned that the edelbrock carbs are prone to heak soak. Are they more prone then say a Holley? Due to some major bogging issues that Ihave when the secondaries open up, I have been thinking about changing over to a 750 double pumper. Would you expect that I would still have the same problems with that setup(The Holley fuel pump and carb)??

Anything else that you can think of?? I'd be happy to hear any other ideas or suggestions. Thanks for your time.

 

hmm, are you running an electric low pressure pump AND a mech pump as Damon was mentioning? It sounds like you're only running a mechanical?

I like the return style pump due to the fact that it keeps the fuel cooler. The stock mechanical pump is of that style, but I doubt it'd keep up to 500HP. I'm sure there's a Carter fuel pump that's return style that would hold up to 500HP. It'd be a cheap fix too. I imagine you already (still) have the return fuel line from the V6 days of the car right?

I wouldn't just swap over to a different carb, there's no reason your current carb shouldn't work, if you swap over it's avoiding the problem, and you won't really learn how to fix this type of problem *when* it happens in the future. Don't give up!

You can always bypass the fuel filter temporarily to check it. Same with the air filter (if that means you can temporarily use a different fuel inlet to the carb...)

What's in the way that requires the funky mech fuel pump (bottom feed) ?

 

Sonix- Yes I am running a mechanical only. Unfortunatley I do not have the original fuel return line because all the lines ran on the drivers side of the vehicle. With my carb's fuel inlet being on the passenger side, I removed all of the factory fuel lines and made my own. As far as what was in the way that I had to use the bottom feed it was either the block or the motor mount pad. The inlet/outlet on the Edelbrock pump were 180* apart, and either the inlet would be smack up against the motor mount pad, or the outlet would be against the engine block and there isn't enough room for the ones to go in.

 

Well, I think you've got your tools, now give'r a shot.

Bypass things one at a time, and find out why that fuel pump isn't giving full pressure at WOT. Remove filters, bypass banjo fittings, etc etc.

 

Well I found the major culprit in my starvation issue. The car sat for some time with no gas in the tank, and condensation built up. When the water sat in the tank/lines/filter it ate away at the metal cage that surrounds the paper filter element. As per your guys' advice on bypassing the filter, I pulled it apart and found this....





Once the filter element was removed and the filter was no longer a restriction the engine pulls at WOT all the way up to redline without any problems. Now I can admit that I made a mistake by installing the filter before the mechanincal pump, but by seeing the condition of the filter now, I'm kida glad that I made that mistake. I could not imagin what would have happened if any of this stuff got into the carb. I would have far more issues than I have now.