Annoying Fuel Delivery Problem
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From: Virginia
I didn't know if the purge line was large enough to cause a problem with the pressure or not. And then you have the factory air filter system, which can also lower the pressure in that area at high rpms. I figured that along with some air going down the purge line would aggravate the situation and make it worse.
Post Fiend
Joined: Feb 2008
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From: St Albert, Alberta
I didn't know if the purge line was large enough to cause a problem with the pressure or not. And then you have the factory air filter system, which can also lower the pressure in that area at high rpms. I figured that along with some air going down the purge line would aggravate the situation and make it worse.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
I don't have that 3 port purge valve so vacuum is pulled off the other port on the PCV that pulls from the bowl vent & the evap canisters.
I could not get the idle speed down and found I had a vacuum leak. The leak was this vacuum line on the PCV I had to put the smallest Holley jet I had and this helped so I could adjust the idle speed.
I undid this vacuum supply and plugged both the PCV and the evap / bowl vent to see if this would help my poor MPG but I think it is the metering rod that needs looking into.
Dave ----
I could not get the idle speed down and found I had a vacuum leak. The leak was this vacuum line on the PCV I had to put the smallest Holley jet I had and this helped so I could adjust the idle speed.
I undid this vacuum supply and plugged both the PCV and the evap / bowl vent to see if this would help my poor MPG but I think it is the metering rod that needs looking into.
Dave ----
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Joined: Aug 2012
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Hello
I have a 1986 f150 . Had the same issue after sitting I even changed the fuel pump twice. I even stated a chat in the forum here. I live in south florida so gas was evaporating and the crank time was long and sometimes killed my battery. Marvel mystery oil helped sometimes. What I did is install a electric fuel pump inline so I prime the truck. I count to 30 or 40 then it cranks no problem. When hot I don't need to do that only when it has sat for 1 day or more.
I have a 1986 f150 . Had the same issue after sitting I even changed the fuel pump twice. I even stated a chat in the forum here. I live in south florida so gas was evaporating and the crank time was long and sometimes killed my battery. Marvel mystery oil helped sometimes. What I did is install a electric fuel pump inline so I prime the truck. I count to 30 or 40 then it cranks no problem. When hot I don't need to do that only when it has sat for 1 day or more.
FTE Legend
Joined: Nov 2015
Posts: 30,915
Likes: 4,123
From: Angier, NC
Hello
I have a 1986 f150 . Had the same issue after sitting I even changed the fuel pump twice. I even stated a chat in the forum here. I live in south florida so gas was evaporating and the crank time was long and sometimes killed my battery. Marvel mystery oil helped sometimes. What I did is install a electric fuel pump inline so I prime the truck. I count to 30 or 40 then it cranks no problem. When hot I don't need to do that only when it has sat for 1 day or more.
I have a 1986 f150 . Had the same issue after sitting I even changed the fuel pump twice. I even stated a chat in the forum here. I live in south florida so gas was evaporating and the crank time was long and sometimes killed my battery. Marvel mystery oil helped sometimes. What I did is install a electric fuel pump inline so I prime the truck. I count to 30 or 40 then it cranks no problem. When hot I don't need to do that only when it has sat for 1 day or more.
I have heard of adding diesel fuel start off with say half gallon to a tank and work up to 1 gallon.
Dave ----
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Joined: Aug 2012
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Hello
if you look at my post here on the forum people suggested diesel also. But many years ago I filled my 1964 Pontiac 389 with diesel, it was a nightmare I drained the tank at the gas station did not crank yet it was a nightmare. Spark plug kept getting black to the point of miss fire. The oil would get dirty quick and had to adjust carburetor. My 1986 f150 is 16 gallon tank . Marvel is 4 ounces per 10 gallon I put 6 to 8 ounces. I will record a video and put it on YouTube to show my set up on the electric pump, solved my problem. What I like about marvel is that it feels like it boost octane. My truck is stick so if you change the gear to soon you here pinging . With marvel it does not.
if you look at my post here on the forum people suggested diesel also. But many years ago I filled my 1964 Pontiac 389 with diesel, it was a nightmare I drained the tank at the gas station did not crank yet it was a nightmare. Spark plug kept getting black to the point of miss fire. The oil would get dirty quick and had to adjust carburetor. My 1986 f150 is 16 gallon tank . Marvel is 4 ounces per 10 gallon I put 6 to 8 ounces. I will record a video and put it on YouTube to show my set up on the electric pump, solved my problem. What I like about marvel is that it feels like it boost octane. My truck is stick so if you change the gear to soon you here pinging . With marvel it does not.
FTE Legend
Joined: Nov 2015
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From: Angier, NC
Thanks for the reply.
I don't know why the 64 would of had issues if you did not crank and did a complete drain and refill with gas.
It may have run like crap for a tank or 2 but the gas to any left over diesel ratio would have been great I would think.
My motor is some what stock, I am running EFI exh manifolds, stock intake & carb and smog has been removed.
I did have pinging when I first got the truck on the road but don't have a clue where timing is at even now.
I did adjust the vacuum advance with the allen wrench so it was not so bad.
Mid grade gas has taken care of the rest.
Again thanks for the reply
Dave ----
I don't know why the 64 would of had issues if you did not crank and did a complete drain and refill with gas.
It may have run like crap for a tank or 2 but the gas to any left over diesel ratio would have been great I would think.
My motor is some what stock, I am running EFI exh manifolds, stock intake & carb and smog has been removed.
I did have pinging when I first got the truck on the road but don't have a clue where timing is at even now.
I did adjust the vacuum advance with the allen wrench so it was not so bad.
Mid grade gas has taken care of the rest.
Again thanks for the reply
Dave ----
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From: Virginia
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I understand what you say. I thought he same a bandage. But I noticed when i drive the car in south florida and parked it the carb bowl would be dry . Then a couple hours later the fuel filter would start to dry up and by next day it was gone . So when I crank days later it would have to reflow the whole system. Now my 1977 Corvette had 3 lines on fuel pump never had an issue fuel would evaporate from carb and up to filter if days parked. My 1964 Pontiac I pour fuel into carb bowl to start it and fuel would reach filter quick . I could not do that with the truck since I drive it more. Had no issues with vacuum lines or anything else that I could see so the electric prime pump I installed helps me. I could be wrong I'm no expert maybe I have another issue I Don't know about I have my 1964 Pontiac since 1998 and it started to have gas evaporating issue last couple of years. So I feel its the gas
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
I understand what you say. I thought he same a bandage. But I noticed when i drive the car in south florida and parked it the carb bowl would be dry . Then a couple hours later the fuel filter would start to dry up and by next day it was gone . So when I crank days later it would have to reflow the whole system. Now my 1977 Corvette had 3 lines on fuel pump never had an issue fuel would evaporate from carb and up to filter if days parked. My 1964 Pontiac I pour fuel into carb bowl to start it and fuel would reach filter quick . I could not do that with the truck since I drive it more. Had no issues with vacuum lines or anything else that I could see so the electric prime pump I installed helps me. I could be wrong I'm no expert maybe I have another issue I Don't know about I have my 1964 Pontiac since 1998 and it started to have gas evaporating issue last couple of years. So I feel its the gas
It is the gas. Gasoline formulations have changed a lot in the last couple of decades. With Hydrocracking and other advancements in refining heavy hydrocarbon chains have become more valuable and they are not left in modern gasoline thus making them lighter and more easily evaporated throw in the ethanol content and it exasperates the problem further.
Adding diesel into modern gasoline puts the heavy chains back into the gasoline and reduces the evaporation rate considerably. With the advent of ULSD it too is a lighter formulation than it used to be. Back in the day if you mixed diesel with gasoline you would get a mix that would not combust properly due to having too many heavies in the fuel.
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