build thread for 2.8 carb to chevy tbi.

[dangerranger83]

Looks like a bad regulator as fast as it dropping, the engine can't be consuming that much fuel. The small fuel pump can support a 300hp engine on its own.

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[Lil-Pony]

Could that be even when i just rebuilt it?


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[cammeddrz]

I still think you need to also rule out fuel delivery. my pressure dropped just like that when my pump was going out.

 

[Lil-Pony]

I plan on doing so...


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[Lil-Pony]

Late night update, ruled the pump out today and redid most of the fuel lines in the engine bay, also found my o2 sensor wire was yanked from the crappy factory crimp, so it was disconnected. Soldered that crap this time. I have noticed an improvement which leads me to believe camm. I can see fuel flow though my fuel filter but i may be getting air in line the some where... Any one know a good method to check this?


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[cammeddrz]

ruled the pump out today

Which method did you use to rule out the pump? which of the 2 pumps is ruled out?

i may be getting air in line the some where... Any one know a good method to check this?

we mechanics have a smoke-machine that can be used to pump smoke into lines to see where they leak/suck air.

but if you are using electric pumps air wouldn't get into the line, fuel would be pushing out of the lines. unless it is sucking air before the first electric pump. then its already low ability to suck fuel out of the tank, would be even lessened by an air leak

even if you were using the OEM mechanical, if air were getting into the line before the diaphragm pump, it could easily cause it to lose suction, and/or vapor lock

 

[Lil-Pony]

I swapped in a supposedly know good fuel pump and the issues still presented them self. Quick q
When the engine is off should the pressure in the fuel line stay at running pressure, cause mine drops to 4-5 psi,

 

[cammeddrz]

I swapped in a supposedly know good fuel pump and the issues still presented them self.

which pump did you do this with? the first? or the second?

the reason I ask, is that rather than swapping parts around/redoing fuel lines etc.

you need to find if there is a fundamental problem. you could re-do the same thing over, and over. if there is a fundamental problem it won't go away, even if you swap in a hundred "good" pumps. if you don't find a way to gravity-feed the high-pressure pump as a means to diagnose/isolate the problem. you won't be able to find a fundamental problem.

When the engine is off should the pressure in the fuel line stay at running pressure, cause mine drops to 4-5 psi,

that depends on the pump more than anything, pumps should have a check valve in them that holds pressure, and it slowly will bleed off. but sometimes that part wears out. but the pump still works fine. if it is holding any pressure at all, i'm sure its ok.

 

[Lil-Pony]

which pump did you do this with? the first? or the second?

the reason I ask, is that rather than swapping parts around/redoing fuel lines etc.

you need to find if there is a fundamental problem. you could re-do the same thing over, and over. if there is a fundamental problem it won't go away, even if you swap in a hundred "good" pumps. if you don't find a way to gravity-feed the high-pressure pump as a means to diagnose/isolate the problem. you won't be able to find a fundamental problem.

I swapped between the two pumps i have, i did notice with the higher pressure ford pump it acted up more, reason i was asking about pressure is i was wondering if the fpr was faulty, ill check that later. As you said i need to go fundamental... Speaking of which where did you place your gravity tank to test the system?

 

[cammeddrz]

where did you place your gravity tank to test the system?

my fuel cell has a fitting in the bottom, and I have a fuel filter, and pump mounted to the bottom of the tank. it always has a gravity feed

I used to have the pump up on the fuel rail, whenever fuel got below 1/4 tank it was above the fuel level. this is what caused me to have all of the issues that I was talking about, with the pump getting hot, failing, acting weird etc. all because it needed to "suck"

once it got moved to 100% below fuel level at all times, I have had years of no problems

I swapped between the two pumps i have, i did notice with the higher pressure ford pump it acted up more,

this tells me that it is most likely an issue of fuel getting to the pump. the higher pressure fuel pump has a higher output (the return style regulator just sends more back to the tank) and therefore needs more supply to it. if the fuel supply to the pressure pump is insufficient, it will do exactly this

 

[RICO9]

I swapped in a supposedly know good fuel pump and the issues still presented them self. Quick q
When the engine is off should the pressure in the fuel line stay at running pressure, cause mine drops to 4-5 psi,

Mine reads 11.5psi even when I haven't driven it in a month.

 

[Lil-Pony]

Im going to see if raising the level of gas in the tank does any thing. I.e. Filler her up
Don't really know to say on the pressure thing my mother decided to take my truck up to mechanic with out me knowing my back and he rebuilt the throttle body so. Ill report back on what im going to do.

 

[dangerranger83]

If you are gravity feeding fuel to something, such as a carb or pump, the lowest of the fuel supply needs to be above the pump. Or like a motorcycle with a carb, it needs to be above the carb.

Remember, shit doesn't run uphill.

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[Lil-Pony]

On paper my gas mileage has increased 3 but due to a gallon losses to me being clumsy and me dogging it around I would guess my mpg is between 14-17 on 33" 3.73


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[Lil-Pony]

Also filling her up helped so I'm going to try and gravity feed her this weekend.


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