Tpi to carb - Fuel pump elimination?
 

The 84z I recently bought with a built 350 SBC stalled today at an intersection. I checked the fuel filter and the back line had a bunch of pressure from the tank when I removed the filter. The filter was nasty so I cleaned the carb and replaced the filter. On the way home the car stalled again. This time there was even more pressure on the line and it kept spraying gas. I had previously capped any unused lines and wondered if any of those lines might be leading to the tank. I uncapped a line on the passenger side of the motor and the pressure released, venting the tank. After releasing the pressure, the car ran fine. I assume the previous owner left the fuel pump from the original tpi system in the car and then just vented the tank. When I capped the line, pressure was building way to high and flooding the carb. My question is....do I need to figure out how to disconnect the fuel pump or is the vent deal ok to leave as is? Anyone ever run across this?

Re: Tpi to carb - Fuel pump elimination?
 

So the car ran fine, you plugged a line then it ran poorly, now you unplugged same line and car runs fine....id leave it alone, or plug line and put vented fuel cap on. Just what i would do.

Re: Tpi to carb - Fuel pump elimination?
 

Well thought the problem was fixed, but died on the way to work today. When I pulled the fuel line at the inline filter, huge pressure build up all the way to the carb. I'm thinking it may be a fuel pressure problem? Where should I put a regulator, on the intake line or return line? I have a Edelbrock 1406 Carb. Should there ever be that much pressure going into the carb or am I misjudging it. When turn the engine, I can shoot a huge stream of gas a few feet.

Re: Tpi to carb - Fuel pump elimination?
 

there should be no pressure build-up on a low pressure carb system if the tank is vented. however if you are running an electric fuel pump you need to regulate the pressure before the fuel enters the carb.

IF you are using the stock TBI fuel pump, it has too much pressure.

5-7 psi max for a carb. The regulator should be plumbed on the supply side before the fuel line connects the fuel bowl(s) also make sure the excessive fuel pressure has not altered the float setting.


A regulator with a return feed is better than a "dead head" regulator, it will eliminate vapor lock issues on a street car. So if the return line is still in the car take advantage of it.

Make sure you are venting the gas tank, if you removed charcoal canister and plugged the line you are sealing the fuel tank, so you will need a vented gas cap.

good luck

Re: Tpi to carb - Fuel pump elimination?
 

Edelbrocks hate anything over 6psi, if you get an adjustable regulator do 5.5psi at idle.

Re: Tpi to carb - Fuel pump elimination?
 

What did the PO do with the factory return line ?
Originally went tank - reg- return to tank.
The in-tank factory pump relies on fuel passing through it all the time to keep it cool ; is not designed to dead head like a external Holley blue or similar.

Get a 3 port carb regulator
http://www.summitracing.com/parts/maa-4309/overview/

install it on the fuel supply line in the engine bay , connect the bypass port at the bottom to the factory return line and connect another port to the carb supply.

Plenty of pump info in the 3rd Gen Carb section

https://www.thirdgen.org/carbswap

Re: Tpi to carb - Fuel pump elimination?
 

There is a mechanical external pump that dead heads to the carb, I assume the internal pump was eliminated.....there is a return line not being used, which I capped, but due to pressure build up in the tank, I uncapped....it was previously uncapped, not sure if it should be capped or not, but its just serving as a vent at this point.

I put a regulator on it and dialed the pressure down to 5.5PSI at idle, but the car still stalled about a mile down the road.

I pulled the top of the carb, floats were set to 7/16 down, but when inverted the factory says they should hang to about 15/16 and one was about 1 3/8" , so I set to factory recommendation. Also pulled the jets and soaked them overnight, will put it all back together when the gasket comes in today. Not sure if this will solve the problem or not, but stalling out and working on the side of the road is getting old quick.

Re: Tpi to carb - Fuel pump elimination?
 

It sounds like floats were set wrong and starved the engine of fuel.

Always best to set carb to factory specs and fine tune from there.

Re: Tpi to carb - Fuel pump elimination?
 

Actually think it was flooding, everytime I drained the bowl, the car would start back up and run for a short while before dieing.....assume it was too rich? Just don't know how it became a problem all of a sudden :confused:

Re: Tpi to carb - Fuel pump elimination?
 

Reset float, cleaned everything, put back together, cranked right up, ran for 3mins, stalled and will not start back. Assume I can drain the carb and restart it, that is usually the case......What do I try next? Could it be a problem somewhere else that I have looked at?

Re: Tpi to carb - Fuel pump elimination?
 

Ok......retarded the timing about 7 degrees, car is no longer flooding or stalling....is now skipping on initial take off which may be a vacuum leak? as I only replaced the air horn gasket, may need to do a complete rebuild kit with all seals, etc..