Fuel Pump or Carb problem
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Fuel Pump or Carb problem
I have a F350 full ton 1986 351W with a 4bbl Holley carb. I replaced my fuel pump(mechanical) and was told that i can replace my fuel line between the pump and the carb with a rubber hose, i covered the hose in that heat resistant stuff so that the fuel dosnt evaporate before it gets to the carb. Now when i give it gas either with the pedal or directly on the carb it dies, slowly but it dies kinda sounds like a ballon letting out maybe too much air?? I dont know but im gettin a little bothered by it. Is it the rubber hose?? Fuel is getting to the carb thats for sure. Any test i should do. My expertees is not the best si bear with me.
Thanks
Thanks
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From: Niceville, FL.
1. Make sure the remaining fuel lines are good, cracks or loose connections on suction (tank) side let air in. 2. There may be a filter in the tank and/or one between tank and pump that could be stopped up. 3. Bad fuel pump? Fuel pump pressure should be 6 to 8 psi at carb inlet, engine running.
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From: Western Central NV
Originally Posted by Piffery1
1. Make sure the remaining fuel lines are good, cracks or loose connections on suction (tank) side let air in. 2. There may be a filter in the tank and/or one between tank and pump that could be stopped up. 3. Bad fuel pump? Fuel pump pressure should be 6 to 8 psi at carb inlet, engine running.
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not too sure what you mean by inlet of the pump but im sure there is no place for a vaccuum line on my pump theres a in and a out i still think its my fuel line i was told maybe to send some air through the line to see if it gets better. but i think im gonna wait and replace the pump to carb line first
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You gotta use the original metal line for that or go to parts store and make one out of brake line. However bending a new line is a bitch. Believe me I know I have an 1985 F150 with the 351 winsor and the holley carb. I tried to make a new line and I have a lot of experience bending line and it was impossible to copy the original line. I had to run it a different way. So baisically if its all possible use the original line. The problem with using a rubber hose is that you dont get the fuel pressure that you need coming to the carb. It may get the fuel but it doesnt have enough pressure. So good luck and try to use the old metal line.
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Is the fuel level in the carburetor float bowls even with the bottom of the sight plugs? Is the accelerator pump working, i.e. when you move the carburetor throttle shaft does fuel squirt out of the pump nozzles? Is your ignition timing set correctly? Is the carburetor securely fastened to the intake manifold? Is the EGR valve fully closed?
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From: Eureka, KS
I've tried rubber line between the pump and carb before, never works out well at all. There are pre-made ss flex lines and you can make a steel line like said before. I made my own steel line, it is not easy, but it can be done. The more steel line you use the better, if you only had small rubber pieces as couplers for an inline fuel filter that would be great.
I would definately replace that rubber line before considering anything else as the culprit. That ruber line swells up when hot and overpowers the needle/seat in the carb.
By the the time you buy a quality bending tool that won't crimp the line and tubing cutters you'd be better off just buying a pre-made ss flex line. I've been through several junk tubing benders that didn't work good at all. I use to be a plumber, so I already have good tubing cutters and a high dollar flaring tool.
I would definately replace that rubber line before considering anything else as the culprit. That ruber line swells up when hot and overpowers the needle/seat in the carb.
By the the time you buy a quality bending tool that won't crimp the line and tubing cutters you'd be better off just buying a pre-made ss flex line. I've been through several junk tubing benders that didn't work good at all. I use to be a plumber, so I already have good tubing cutters and a high dollar flaring tool.
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BOOYAH, Unless the rubber fuel line has a tight kink in it I can't see how it could cause the symptoms you have described. What was wrong with the original steel line to cause you to change it? Did the problem arise before or after you switched to the rubber line? How did you attach the rubber line to the fuel pump and carburetor inlet? If you used the fittings/ends of the original line then you need to do a double flare on the cut ends of the steel line so that when the rubber hose is clamped, it can't slip off the steel line.
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I had to take the line off because i could not get it off the pump are carb withou twisting the line which in the end broke it, and yes i have the original fitting for the carb end, the pump end is just o clamped on. I have no leaks anywhere. The theory that a rubber hose does not create enough pressure sound about right to me. what else could it be and keep in mind im not fimiliar with how to adjust float levels or adjust mixes.
But if you go slow ill for sure figure it out.
THanks
But if you go slow ill for sure figure it out.
THanks
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From: Eureka, KS
Rubber line doesn't create enough pressure? I don't understand what that means. It won't create nough pressure from vaporized fuel to cause any problems? It very definately will and does.
The problem is gasoline has very low flash point. Rubber line allows the heated gas in the line to expand and vaporize. It creates too much pressure plus it creates vapor in the line, not just liquid gasoline. That high pressure gasoline/vapor mix ends up at the fuel bowl, in particular the needle and seat. You should only have arounf 5-7 psi of fuel pressure and it should be liquid fuel, not vaporized and liquid fuel.
That sound you hear is probably the high pressure vapors blowing open the needle valve.
You shouldn't have to be adjusting your carb if all you did was put a new fuel pump on it.
Wanted to add...gasoline can get very hot in a steel line, but it has no room to vaporize because the steel line doesn't allow expansion.
Always a good idea to replace that little section of rubber line fron the frame to fuel pump when you change out the pump. It will suck air in through a bad connection or cracked hose.
The problem is gasoline has very low flash point. Rubber line allows the heated gas in the line to expand and vaporize. It creates too much pressure plus it creates vapor in the line, not just liquid gasoline. That high pressure gasoline/vapor mix ends up at the fuel bowl, in particular the needle and seat. You should only have arounf 5-7 psi of fuel pressure and it should be liquid fuel, not vaporized and liquid fuel.
That sound you hear is probably the high pressure vapors blowing open the needle valve.
You shouldn't have to be adjusting your carb if all you did was put a new fuel pump on it.
Wanted to add...gasoline can get very hot in a steel line, but it has no room to vaporize because the steel line doesn't allow expansion.
Always a good idea to replace that little section of rubber line fron the frame to fuel pump when you change out the pump. It will suck air in through a bad connection or cracked hose.
Last edited by tgore3; Sep 19, 2006 at 07:24 PM.