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Slantsix83
PostPosted: Mon Mar 03, 2025 5:43 am 
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TBI Slant 6

Joined: Wed Mar 31, 2021 9:40 am
Posts: 196
Car Model: 1983 D150 Slantsix 4 speed
I currently have a 83 d150 slant six. Not really having any issues but every morning it take a good couple of cranks and gas pedal pushing for it to finally start. I want to get it to the point we're with 3 pedal pushes after the next day it starts right up. I heard about the one way check vavle. Anyone have any experience with them. Are they worth it?
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GTS225
PostPosted: Mon Mar 03, 2025 5:51 am 
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Joined: Fri Nov 01, 2002 5:02 pm
Posts: 1830
Location: Waterloo, Iowa
Car Model: '23 T-bucket
Aren't there supposed to be check valves built into the mechanical fuel pump?

Roger
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Slantsix83
PostPosted: Mon Mar 03, 2025 7:24 am 
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TBI Slant 6

Joined: Wed Mar 31, 2021 9:40 am
Posts: 196
Car Model: 1983 D150 Slantsix 4 speed
Quote:
Aren't there supposed to be check valves built into the mechanical fuel pump?

Roger
No clue. If so would an extra one hinder me in anyway?
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MDchanic
PostPosted: Mon Mar 03, 2025 8:04 am 
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TBI Slant 6

Joined: Thu Nov 09, 2023 5:12 am
Posts: 161
Location: Hudson Valley, NY
Car Model: 1964 Dart 270 4-Door
Quote:
Aren't there supposed to be check valves built into the mechanical fuel pump?
The mechanical fuel pump is made out of two check valves.

Check valve on inlet.
Check valve on outlet.
Diaphragm in the middle.
Diaphragm pulls one way, fuel is sucked through inlet check valve, outlet check valve is closed.
Diaphragm pushes the other way, fuel is pumped out through outlet check valve, inlet check valve is closed.

If one valve is leaky, the pump won't work very well (or at all).

I am not the authority, but I see no reason for an extra check valve, and plenty of reasons not to add additional complexity to a system that should work fine without it.

Also, note that the fuel in your float bowl is not being siphoned out and back into the tank.
The fuel inlet and needle valve are at the top, and the fuel drops into the float bowl. There is air between the top of the fuel and the needle valve (or there will be after a tiny amount of fuel evaporates from sitting), so there is no way for the fuel to jump up in the air and sneak back to the tank.

- Eric
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Slantsix83
PostPosted: Mon Mar 03, 2025 10:47 am 
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TBI Slant 6

Joined: Wed Mar 31, 2021 9:40 am
Posts: 196
Car Model: 1983 D150 Slantsix 4 speed
Quote:
Quote:
Aren't there supposed to be check valves built into the mechanical fuel pump?
The mechanical fuel pump is made out of two check valves.

Check valve on inlet.
Check valve on outlet.
Diaphragm in the middle.
Diaphragm pulls one way, fuel is sucked through inlet check valve, outlet check valve is closed.
Diaphragm pushes the other way, fuel is pumped out through outlet check valve, inlet check valve is closed.

If one valve is leaky, the pump won't work very well (or at all).

I am not the authority, but I see no reason for an extra check valve, and plenty of reasons not to add additional complexity to a system that should work fine without it.

Also, note that the fuel in your float bowl is not being siphoned out and back into the tank.
The fuel inlet and needle valve are at the top, and the fuel drops into the float bowl. There is air between the top of the fuel and the needle valve (or there will be after a tiny amount of fuel evaporates from sitting), so there is no way for the fuel to jump up in the air and sneak back to the tank.

- Eric
So for the carb i shoulf open the top an check? On a cold start or after its been driven around. Anyway to check the mecanical fuel pump?
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MDchanic
PostPosted: Mon Mar 03, 2025 7:35 pm 
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TBI Slant 6

Joined: Thu Nov 09, 2023 5:12 am
Posts: 161
Location: Hudson Valley, NY
Car Model: 1964 Dart 270 4-Door
Quote:
So for the carb i shoulf open the top an check? On a cold start or after its been driven around.

I don't think there's any need to open up your carburetor, unless you have never done it before, and have never rebuilt it, in which case, yes, you need to get a rebuild kit and some really nasty carburetor soaking cleaner, or spray cleaner, clean it up, check all settings, and put it back together with fresh gaskets.

I will say that my BBS tends to drain out after about a day or two, and my suspicion is one brass plug directly under the fuel inlet, that is always a tiny bit wet, and that has a suspiciously clean spot just underneath it on the manifold.


Quote:
Anyway to check the mecanical fuel pump?

Testing the mechanical fuel pump is covered in the factory service manual.

You test the pressure at a given engine speed and the volume over a given period (usually 15 seconds is enough).

I won't suggest any particular values for those tests, as your year may be different than mine.

– Eric
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