89 1500 tbi to carb swap

[hairisun]

I need advice on fuel system. Cannot get fuel pump to run. How can I test pump with fuel lines disconnected

[bradrhale]

the electric pump for the TBI of mechanical for the carb?? the electric pump is going to need a pressure tester on there as you will have to have 11 to 16psi for the injectors to work. if you are testing a mechanical pump, disconnect a fuel line and run it outside of the truck into a bucket. let the engine turnover with the key to see if it starts shooting fuel out.

[Crmzendrgone]

Are you asking what kind of pump each fuel system has? The mechanincal pump is bolted to the side of the block and runs off of the cam. The electric pump is in the fuel tank itself.

[crabtruck]

Welcome to the forum hairisun.

Which are you doing: 4.8L w/ a Rochester 1MEF 1 bbl;
or the 5.7L or 7.4L w/ the Rochester M4MEF 4 bbl ?

The carbureted engines all use a mechanical fuel pump located on the right side of the engine.
The pump is a diaphragm type pump and is actuated by a rocker arm through a link and pull rod.
Some engines have a special pump with a metering outlet for a vapor return system.
Any vapor that is formed is returned to the fuel tank along with hot fuel.
This reduces the chance of vapor lock because cool fuel from the tank is always circulated through the fuel pump.
The fuel pump rocker arm is moved back and forth by a rod which rides on an eccentric on the engine camshaft
One pint should be pumped in 30 seconds or less.
Idle fuel pressure should be 6-9psi.

Your TBI was using an electric pump with a idle fuel presure of 9-13psi.
That will be too much for carb without modification.

Your question how to test without fuel lines connected:
A) you cannot completely test like that because no pressure or volume.
B) you can test for connection and run.
First check fuses, in particular one for pump. Check @tank pump ground.
Listen for run at key on (10-20secs)
If not, you can supply a fused hot wire to the fuel pump prime wire.
Simply, supply a fused hot to pump from where ever you can get connection.

DON'T MAKE ANY CONNECTIONS THAT MAY SPARK NEAR THE OPEN FUEL LINES.

[hairisun]

Thank you for the info!

I am aware of the pump types and operation. #1. Will fuel pass through the electric pump while not in operation, allowing me to utilize the mechanical pump? #2. Can the "vapor line" be capped? #3 Will an in-line pump work in this application? I have installed a

Holley 600 on the 5.0

I have a wire diagram which shows a "red" wire from the fuel pump relay to the fuel pump prime connector. If I energize the prime should the pump run?

[crabtruck]

Did not mean to imply you had no info, just tend to broaden my answers
for the benefit of future readers. And I have a tendency to keep typing.

#1 - I believe so, but will be a drag on working pump
#2 - I'm clueless but it would seem you have to.
#3 - I do believe there are right presure external electrics for this.

Providing a fused hot to the prime wire should run the pump with the key off.
Turning on key activates relay, moving pump away from that to normal hot.
This remains true until the ECM "times out" at about 20secs,
then ECM releases relay and prime wire can be used again.
However by design, the prime wire should be getting a hot already
from the oil pressure circuit as pressure comes up if engine is running.
Another good reason to always use fused jumpers.

If this is just testing pump, remove relay and jump hot to pump there.

Just for full disclosure: I never met a carb I could kill.

[Crmzendrgone]

Originally Posted by crabtruck

Just for full disclosure: I never met a carb I could kill.

I kill carbs all day long, Jumbo Jack, Bic Mac, Whopper. Oh wait not that kind of carb. ooops

[Crmzendrgone]

Originally Posted by hairisun

Thank you for the info!

I am aware of the pump types and operation. #1. Will fuel pass through the electric pump while not in operation, allowing me to utilize the mechanical pump? #2. Can the "vapor line" be capped? #3 Will an in-line pump work in this application? I have installed a

Holley 600 on the 5.0

I have a wire diagram which shows a "red" wire from the fuel pump relay to the fuel pump prime connector. If I energize the prime should the pump run?

I am ignorant so the way my brain works I can not see how a mechanical pump will pull fuel through a electric pump. Does the electric have to open a valve or plugger to allow flow. I found this online I think it is how any pump works looks to me like there is a plugger that is energized by the coils. I could be way wrong

[crabtruck]

Actually the pump you posted would have less trouble than some others.
It works by siphoning the fuel inside on the retraction stroke
and pushing fuel on the extension stroke.
If you look closely you will see the "flapper" valves are opposing.
Acts much like a pair of Foot-Valves for pipes with long "foot" values.
A second pump pulling from the top or pushing from the bottom
would encounter only the restriction of tight passages.
.

[Crmzendrgone]

Ah. Thanks you for clearing that up for me. Always have to learn something new everyday.