302 engine issues.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
The fuel pump output is a critical because everything else depends on it being correct, in particular the specific fuel height in the carburetor bowl must be maintained at all times under all conditions. The float and bowl sort of looks like a toilet tank but unlike a toilet the fuel level doesn't rise and fall.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Tedster9, when I get my vacuum/fuel hose leak free what should I do to have a accurate fuel pressure reading? keep it hooked up until fast idle goes off? rev the truck to 3000 rpms? Will or should revving the truck change fuel pressure?
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Ideally you probably want to check it with a T fitting right near the carb at idle, but a "deadhead" connection will work too. 9 psi is too high though. This is a big problem with modern manufacture pumps.
The fuel pump output is a critical because everything else depends on it being correct, in particular the specific fuel height in the carburetor bowl must be maintained at all times under all conditions. The float and bowl sort of looks like a toilet tank but unlike a toilet the fuel level doesn't rise and fall.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
The fuel pump output is a critical because everything else depends on it being correct, in particular the specific fuel height in the carburetor bowl must be maintained at all times under all conditions. The float and bowl sort of looks like a toilet tank but unlike a toilet the fuel level doesn't rise and fall.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Okay so I got a new fuel hose to hook up my vacuum/fuel gauge today. I hooked it up and turned on my truck, at high idle the fuel pressure maxed out at 10psi, at normal operating temperature and idle my fuel pressure was still a high 9.5 psi. So now I know I need to get a fuel regulator to bring my fuel pressure to some where around 6 psi to make my Holley 600 cfm model 4160 carburetor happy. Does anybody have any good recommendations on what kind of fuel regulator I should purchase?
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
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Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
If you have a mech fuel pump, then the driver's side inner fender will do. Or if you want it on the firewall and have a dual feed line on that Holley, you could reverse the fuel line and shorten the distance from the line to the firewall. This is what I did on an 89 V8 Ranger
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
"Similar to the float in the tank of a toilet, there's a float attached to the needle valve in a carburetor. The float rides up and down with the level of fuel in the bowl and acts on the needle valve. Unlike the tank in the bathroom fixture, however, the goal of the carburetor float, needle and seat is keeping the fuel level constant in the bowl, regardless of the demands of the engine. The carburetor float bowl does not empty and fill as the tank of the bathroom fixture does."
https://www.hemmings.com/magazine/hcc/2015/02/Bowl-and-Float-Assembly/3746461.html
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
I think the fuel pump is actually defective from the numbers you describe. The shop manual for your truck lists the fuel pump pressure spec. Find out what it is. I bet it's 4.5 to 5.5, something like that. All things being equal, I'd rather have a mechanical fuel pump that is within the factory spec, vs. trying to tamp it back down by half with a dial regulator. Have you checked the pump for volume?
It's possible, even though the unit has nearly twice the fuel pressure output spec, it is unable to supply sufficient fuel volume under high demand. A pressure regulator won't remedy that.
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Elder User
Joined: Jun 2015
Posts: 664
Likes: 2
From: York Pa.
Don't even have to start the engine. Just crank it over with the ignition disabled for 5 or 10 seconds will tell the tale.
I think the fuel pump is actually defective from the numbers you describe. The shop manual for your truck lists the fuel pump pressure spec. Find out what it is. I bet it's 4.5 to 5.5, something like that. All things being equal, I'd rather have a mechanical fuel pump that is within the factory spec, vs. trying to tamp it back down by half with a dial regulator. Have you checked the pump for volume?
It's possible, even though the unit has nearly twice the fuel pressure output spec, it is unable to supply sufficient fuel under high demand. A pressure regulator won't remedy that.