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| Lost fuel line pressure after warm-up https://www.slantsix.org/forum/viewtopic.php?t=22877 |
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| Author: | Flyntgr [ Tue Apr 24, 2007 7:57 pm ] |
| Post subject: | Lost fuel line pressure after warm-up |
After running the hyperpak Eddie carbed 500 CFM and hopped up engine a few minutes, the line pressure drops from the 6 to 8 lb range, down to about 3lbs. The gas cap is drilled larger to vent, and we've even removed the cap entirely, with no effect. After sitting an hour or so, it's back up to 6 ot 8 lbs pressure on this hyperpak. We've tried the Holley Blue (no better, and much too loud), and the quieter Edlebrock, but no better. Is the filter sock in the gas tank clogged? If so, why 6 to 8 lbs when cold and running strong (till engine heats up)? Is fuel line of 3/8" too small; factory was only 1/4" I believe. The pump is good, and lower than the tank. We can't figure what's going wrong with the loss of fuel pressure. The quarter mile e.t.'s and mph's vary greatly due to this problem. This is a hooped up 15 second quarter mile STREET car. Does Anyone here have any ideas as to cause and cure? Thanks! |
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| Author: | Flyntgr [ Tue Apr 24, 2007 8:02 pm ] |
| Post subject: | Lost fuel line pressure |
P.S. I can remove the gascap, cup my hands and blow as hard as I can into the gas filler tube and ADD 3/4 lb. of fuel pressure (indicated by the pressure regulator) while the car is idling. Once I quit blowing into the gas filler the pressure immediately drops to about 3lbs of pressure. |
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| Author: | slantvaliant [ Tue Apr 24, 2007 8:20 pm ] |
| Post subject: | Re: Lost fuel line pressure |
Quote: I can remove the gascap, cup my hands and blow as hard as I can into the gas filler tube ...
 Quote: Is the filter sock in the gas tank clogged? It could be. Fine particles can build up and clog the sock and/or filter while the engine is running, then fall off after the engine is shut down for a while. Soft fuel hose on the suction side can also give this symptom. I think the stock lines and hoses are 5/16". |
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| Author: | Flyntgr [ Tue Apr 24, 2007 8:45 pm ] |
| Post subject: | fuel starvation, loss of pressure |
The fuel lines are metal. I'm not sure of the exact size, but they are about the same size as my mechanic's 500 c.i. bigblock fullrace bracket car, so they should be big enough. The particles could be the problem, but I'll have to take off the gas tank to check that out. |
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| Author: | Dart270 [ Tue Apr 24, 2007 8:59 pm ] |
| Post subject: | |
It's not the line diameter for sure. Sounds like clogs are most likely... Lou |
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| Author: | 1969ronnie [ Wed Apr 25, 2007 5:22 am ] |
| Post subject: | |
hi,also check all your rubber fuel lines carefully for cracks or splits. i have seen rubber fuel lines suck air, which is not a solid, liquid form but an aerated fuel/air mess that can cause your problem. a few years back, crew chief tim richards was having a fuel delivery problem on the bud top fuel car. on one of the test runs he took a espn camera and pointed it down, at the main ,clear fuel line. during the run , the fuel went from a solid to a aerated mess , then back to a solid. he found the problem and fixed it. nhra has frowned on any more "camera" runs . ron |
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| Author: | 1969ronnie [ Wed Apr 25, 2007 5:34 am ] |
| Post subject: | |
i also agree with slantvaliant about the soft or mushy fuel line. we use ethanol fuel here which turns the rubber hose to mush. you can't use the regular 30r7 fuel line{# that is ink stamped on side of hose} you have to use 30r9 which is fuel injection hose. it won't collapse or fall apart internally like the 30r7 will ,especially on ethanol or race fuel. ron |
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| Author: | Rug_Trucker [ Wed Apr 25, 2007 6:07 am ] |
| Post subject: | |
I changed my filter before I went racing last weekend. No trash! I had a fuel problem. I changed pumps. Still had a problem! A pin hole on the rubber line back at the tank where it hooks to the metal could be a problem. (my lines are original from 72) I need to pull my sender and pickup to check for a tank clog. I put on a plastic Purolater filter it is really clean! So it is back towards the tank! |
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| Author: | Flyntgr [ Thu Apr 26, 2007 6:21 pm ] |
| Post subject: | problem solved |
The cheapo fuel pressure regulator was apparently bad. The first we had was a liquid filled unit: don't ever get one of those. The second was an el cheapo std type, but tomorrow we go out of town to a REAL auto parts store to get a good one. Thanks for all your comments and suggestions. I do appreciate your help in running down the alternatives. |
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| Author: | Sam Powell [ Thu Apr 26, 2007 7:59 pm ] |
| Post subject: | |
Keep us in the loop, and let us know how it goes. I am very interested in your outcome here, as I suspect fuel pressure problems also in my set up.. Sam |
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| Author: | Flyntgr [ Fri Apr 27, 2007 6:50 pm ] |
| Post subject: | Fuel issue |
I change out the ourtageously loud Holly blue for a quieter electric pump and it lost about 4/10 seconds, and 5 or6 mph, but it's possible to drive without listening to a chain saw in the back of the car. Mid 15's at 90 or so is good enough for me. My other cars are a '61 Chrysler 300G and a 2005 Viper SRT, so the slant six is fast ENOUGH for street use. I think it'll take any new Chrysler 300 or Charger V6. |
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| Author: | Flyntgr [ Fri Apr 27, 2007 6:53 pm ] |
| Post subject: | P.s. |
The diagnosis finally was the fuel pressure gauge mounte to the regulator. The pressure was good all along, but the guage was faulty. It was a Marshall liquid filled unit, and the vendor says nix them. Go for the dry units. I have a better one, $30 instead of $15, so it should work as intended. |
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| Author: | Sam Powell [ Fri Apr 27, 2007 7:28 pm ] |
| Post subject: | |
Again, keep us posted. Let us know if the new regulator was OK, and also what brand you used. Thanks. Sam |
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| Author: | Flyntgr [ Fri Apr 27, 2007 8:50 pm ] |
| Post subject: | New Regulator |
It's a Marshall, too, but twice as expensive and not liquid filled. It seems to working perfectly. |
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| Author: | slantzilla [ Sat Apr 28, 2007 5:33 am ] |
| Post subject: | |
Liquid filled fuel pressure gauges are junk, especially those little chrome ones everyone sells that just screw in. Liquid filled gauges will not react properly without being vented. When they get hot, they show low pressure. I have a good Autometer liquid filled gauge that I have had for years. It would show less pressure when the sun shined on it until I removed the factory fill plug and left it out. It still reads 2 psi high against my good nitrous flow gauge.
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