Fuel pressure problems

I drive a factory stock and our rules are basically 4412, unaltered heads, intake and exhaust manifolds. At idle my car will hold 7-8 psi of fuel pressure but when I get out on the track, after 2-3 laps on the 3/8 mile track it falls to 0. After that it will go for about half the straight then coast around corner and come back to life when I hit the straight for about 1/2 the straight again and continue on like that. Heres a GoPro of what I'm talking about, problems start at about 3:18. We have brand new fuel filter, pump and no foam in the fuel cell. Any help would be greatly appreciated

http://www.youtube.com/watch?v=4cETu...ature=g-user-u

Either sucking a fuel line shut or pickup in the cell is sucking on the side of the cell.. I have also seen the element style fuel filter have the element installed backwards...

Have also seen the exhaust blowing on the fuel line causing vapor lock too...

What size is your fuel line? Also, how old is your fuel pump? Are you using a stock pump? Also, have you checked your float level in your carb? If could be set too low.

Is the vent line to the tank plugged? As fuel is removed from the tank air needs to replace the volume of fuel removed. If the volume is not replaced with air the fuel pump cannot over come the vacuum formed in the tank. Just something else to check.

Mike 26B owner driver

There was a marginal section of fuel line that was cut out and spliced, fuel cell filter was taken out, the line is 3/8th braided steel, the pickup line in cell was shortened massively to alleviate any chance of getting sucked to side or bottom, I had 2 element style fuel filters and replaced with canister style in which I blew thru to see which way was highest flow, fuel pump is brand new 100 gph, also running 82 jets, and we run stock iron exhaust manifolds and I have no exhaust leaks.

Has anyone tried with any luck tried insulatating the fuel line to keep cool? This problem only came after this crash http://www.youtube.com/watch?v=7qbHjVZrgG4&feature=plcp in which I replaced the front clip and everything else on the engine was fine.

Thanks for all your help everyone, we've had 3 straight races of this and its the most frustrating thing ever

[QUOTE=26-62 racing;1547263]Is the vent line to the tank plugged? As fuel is removed from the tank air needs to replace the volume of fuel removed. If the volume is not replaced with air the fuel pump cannot over come the vacuum formed in the tank. Just something else to check.

Mike 26B owner driver[/QUOTE
Agreed , it takes a few laps to start a suction on the tank, dropping the fuel flow from the tank. Roll over valve could be stuck.

How do I check the valve or should I just buy a new one?

How hard did you hit the wall? When everything has a sudden stop from race speed weird thing happen. Depending on the type of rollover valve in your fuel tank it could be stuck in the closed position. Check it out, if it is the ball and seat style it may just need to be released. Do you have a filter on the vent line, could it be plugged? Do not get discouraged, keep looking. Have you checked the fuel pump? Fuel pumps should be checked two ways pressure and volume. Gauge checks will show ok pressure, but with out checking volume, their may not be enough fuel flow to keep up with engine demands. Did the motor move on the mounts when you hit the wall, could fuel lines have had internal damage from motor movement. Is the return spring on the fuel pump damaged? Is it keeping the arm against the fuel push rod? Just some thoughts Hope this helps.

Mike 26B

Quote:

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Originally Posted by Redalert144

How do I check the valve or should I just buy a new one?

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Blow on the vent line into the tank. There should be no restriction. If there is, take the outside line loose and push on the ball. Happened to a racer I knew, took a few races to figure out.

Thanks will check it out tonight, That does seem like something that might mess up in that big wreck I had

Ball valve in the fuel cell seems to work fine, any other ideas?

Quote:

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Originally Posted by 26-62 racing

How hard did you hit the wall? When everything has a sudden stop from race speed weird thing happen. Depending on the type of rollover valve in your fuel tank it could be stuck in the closed position. Check it out, if it is the ball and seat style it may just need to be released. Do you have a filter on the vent line, could it be plugged? Do not get discouraged, keep looking. Have you checked the fuel pump? Fuel pumps should be checked two ways pressure and volume. Gauge checks will show ok pressure, but with out checking volume, their may not be enough fuel flow to keep up with engine demands. Did the motor move on the mounts when you hit the wall, could fuel lines have had internal damage from motor movement. Is the return spring on the fuel pump damaged? Is it keeping the arm against the fuel push rod? Just some thoughts Hope this helps.

Mike 26B

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Brand new filter, 100gh fuel pump and ARP push rod. the engine didnt seem to move or the fuel lines being damaged

Ya Jeff we are in the mist of one of those situations. No foam in the cell and have a JAZ vent but there is a rubber pick up hose which seems to be in good condition. Sucks but the only thing thats really left is replacing the whole fuel line front to back and getting a metal pick up tube in the cell.

One last thing, is it possible that I'm boiling the fuel before it gets to the carb? If so, any thoughts on ways to insulate the fuel line. It was in the mid to high 90s this last race and my engine compartment is basically stock, meaning its virtually sealed off besides the wheel wells

3/8" steel braided line throughout, def look into the line wrap Thanks

Installed a hose end on a braided years ago, some how the rubber line inside the braided steel balled up inside the fitting, not completely closing off the fitting but severely restricting flow. Talk about something hard to find. This is very rare, probably not it, just some of the goofy stuff that happens.

Mike 26B

imo you are sucking a line together or have a hole in your pick up line in cell as long as it is placed correctly I agree I highly doubt you're vapor locking and it really doesn't sound like a carb prob imo

We decided to replace the fuel line from front to back with 1/2". Our racing schedule here is off for the summer, so we won't find out if there's a pin hole somewhere till September. Thanks for everybody's help, time to start working on next years IMCA stock car