Is my fuel pump man enough???

[eightbanger]

Today from a rolling start of about 20mph I floored the go pedal, the kick down came in, the 454 sprang to life and away we went. I could only have reached about 60? hell the trans had only started climbing through the gears when the engine ran out of steam and started spluttering and the power dropped off sharply. I pumped the gas pedal and it would pick up and die off again the whole thing felt exactly like I had ran out of Gas, as the revs dropped and the truck slowed down she picked up again and I drove home. This has happened a couple of times before but I've been lazy about posting the question, is it possible that my mechanical fuel pump is unable to supply enough gas in these circumstances...ie heavy righ foot

Thanks.

[cdowns]

ever thought of clean out the gas tank?

[eightbanger]

A logical thought but I have a glass filter and it is showing clean, no signs of anything being sucked up from the tank.

[Southcity]

What is the condition of the rubber hose(s) from between gas tank & Carb? (assuming of course that your rig has any rubber gas line) If it does and they are in poor condition, it may have collapsed somewhere and is choking fuel delivery.

[FRENCHBLUE72]

How full was the gas tank??

[eightbanger]

Originally Posted by Southcity

What is the condition of the rubber hose(s) from between gas tank & Carb? (assuming of course that your rig has any rubber gas line) If it does and they are in poor condition, it may have collapsed somewhere and is choking fuel delivery.

Yeah I could check the ones under the truck Southcity, the lines to the carb are all new. I may even have to go with what cdowns suggested and check the tank out.

Originally Posted by FRENCHBLUE72

How full was the gas tank??

Plenty of fuel in there Frenchblue.

Thing is when I give it some from standing starts and smoke the tires it all goes good, the occasions when this has happened have all been when I was already rollin, I put the pedal to the floor the trany kicks down and it builds up speed and the revs climb, then all of a sudden it dies it feels like it runs the carb dry.

[Southcity]

looks like it will be troubleshooting through "process of elimination" time. Inspect all your rubber fuel line and replace if necessary. You mentioned the glass fuel filter looks clean but then again, they are relatively inexpensive (well at least they are here in the states) so I suppose it would not hurt to replace it anyways for peace of mind and go from there. Good luck and give a shout out on your progress.

[eightbanger]

Will do...

[gonzo6869]

I don't know if this will work, but try that again and once it starts to happen, shut her done and check your float level. If it’s empty or near empty then you'll at least know it’s a fuel delivery problem. You might also want to check to see if you have two fuel filters. The previous owner of mine put an additional filter that I did not know about and it caused problems like your describing. Last, is the fuel pump new? A good fuel pump should be able to keep up with a thirsty carb and heavy right foot.

[Blazer1970]

What was the original engine in the truck? If it was a 6 cyl. the truck was plumbed with 5/16" fuel line. V8s were plumbed with 3/8" line. The sending unit is also different (5/16" vs. 3/8"). The 5/16" line has been known to choke a healthy big block. The sock in the tank could also be coated with varnish.

[eightbanger]

Originally Posted by gonzo6869

I don't know if this will work, but try that again and once it starts to happen, shut her done and check your float level. If it’s empty or near empty then you'll at least know it’s a fuel delivery problem. You might also want to check to see if you have two fuel filters. The previous owner of mine put an additional filter that I did not know about and it caused problems like your describing. Last, is the fuel pump? A good fuel pump should be able to keep up with a thirsty carb and heavy right foot.

Thanks Gonzo, im not sure how to go about checking the float, do you mean in the carb? Definately sure on the extra filter though i've only got the glass inline one.

Originally Posted by Blazer1970

What was the original engine in the truck? If it was a 6 cyl. the truck was plumbed with 5/16" fuel line. V8s were plumbed with 3/8" line. The sending unit is also different (5/16" vs. 3/8"). The 5/16" line has been known to choke a healthy big block. The sock in the tank could also be coated with varnish.

Thanks Blazer, there's no spid so how could I tell the original engine size? when I bought the truck one of the first things I replaced was the sending unit and found out quickly that I needed different unit as I had a BB.

All good suggestions to consider and go through one by one...Thanks

[cdowns]

do you have the gastank vented properly?? could be a vaccume lock if improperly vented// easy to check by removing gascap when this happens and if theres a whoosing sound you have a problem

your tank should vent by a rubber hose at the top that runs up th passenger door pillar and is hooked up to a fixed high loop ,from there a hose went to the charcoal cannister under the battery// i'd always just cut the hose eliminate the canister and run the vent line back past the end of the cab in the frame channel

[mclairmo]

What kind of fuel pump? I run a Holley High Volume on my 396 with 750 CFM 3310 Holley with a Summit hard line/gauge combo with a Summit steel braided line from the pump to the carb with no issues. You may want to run fuel pressure guage to the fuel line and tape the gauge to the windshield and see what the fuel pressure is at speed. Should be 5-7 psi. Also, make sure there are no restrictions in the fuel lines like a sharp 90 degree bend or elbow. You can find hi flow fittings that are made with mandrel bends to plumb the pump to the carb to avoid a restriction. Also, make sure you have full throttle operation when you floor it. Sometimes, the throttle cable/rod is not adjusted properly. Also, those little glass fuel filters are dangerous and restrictive. I would run a hi flow steel/aluminim unit instead. Also, check the distributor out very carefully, it could be that at hi rpm the coil is crapping out or that the advance mechanism is screwed up somehow. Many supposed carb problems are actually caused by ignition issues. The ignition system has to work much harder at higher rpms and against more extreme combustion pressures. Make sure the plugs, wires and all ignition components are 100%.

[gonzo6869]

Originally Posted by eightbanger

Thanks Gonzo, im not sure how to go about checking the float, do you mean in the carb? Definately sure on the extra filter though i've only got the glass inline one.

Yes the Float level of the Carb. If you have a Holley, I believe I read your Sig. correctly, then it should have a little glass window on the side of the carb, you should see fuel.

[chevytruckluver]

Agree>>>You may want to run fuel pressure gauge to the fuel line and tape the gauge to the windshield and see what the fuel pressure is at speed. Should be 5-7 psi.
Another problem I have seen before is the sock on the sending unit, it can suck itself closed, that was a bi%#$ to figure out because it was on a replacement sending unit! It will show up with a fuel pressure gauge though. good luck

[hayhauler71]

Originally Posted by chevytruckluver

Agree>>>You may want to run fuel pressure gauge to the fuel line and tape the gauge to the windshield and see what the fuel pressure is at speed. Should be 5-7 psi.
Another problem I have seen before is the sock on the sending unit, it can suck itself closed, that was a bi%#$ to figure out because it was on a replacement sending unit! It will show up with a fuel pressure gauge though. good luck

X2 on pressure but also you would like to see about 1/2 gallon per minute of fuel volume. Disconnect fuel line from carb, disable the ignition so you have no spark and crank the engine for 15 seconds with the hose dispensing into a container to get your volume of fuel.