How much vacuum to fuel pump?

Hughboeke

Trying to get this Par Car running for a friend. Not much info. it just stopped running when his girls were riding it. Don't know if it back-fired or not.

What I have found is that compression was very low. Squirted oil in cylinder & it came up to about 85psi. Spark is good. I poured a little gas down spark plug hole & the engine did not start but it made noise like it wanted to.

I rebuilt the fuel pump because it was not pulling gas. Well it still isn't.

Then I checked vacuum to the fuel pump & instead of vacuum it is pulsing pressure. I have read on other threads about blown crankshaft seals. Can anyone tell me if this is what I am likely dealing with?

Thanks to all for any help/advice you can provide.

BGW

__________________
This advertising will not be shown in this way to registered members.
Register your free account today and become a member on Buggies Gone Wild Golf Cart Forum

DOOmsman

The line to the fuel pump is a PULSE line, caused by the piston going up and down.
Worn seals can cause weak compression.

Hughboeke

I understand that the line to the fuel pump pulses, but is it supposed to be a vacuum pulse or a pressure pulse?

This thing is pushing, not sucking!

jeggers

pushing not sucking, is it the right direction?

Check compresion.

Hughboeke

I have the vacuum gauge plugged into the line comming from the crank case to the fuel pump. It is making pressure instead of vacuum.

I am assuming it should be a vacuum reading. Is that correct?

LoudmouthG9

Look at the hoses.

The 2 that have gas in them are easy to see, one from tank, one to carb.

Second hose is the pulse pump to the carb. Pull it off at the carb and put the end into a pop bottle so you can see if you are pumping gas.

Third hose is pulse hose. Take it loose so you can quickly suck and blow back and forth into the hose.

If the pump is good it will squirt a pretty good shot of gas as you blow and suck alternately on the line. If its pumping, its good.

Hughboeke

Thank you to all that have replied with info. to help me.

There is still one bit of info. that I am hoping someone can provide, and that is with a vacuum gauge plugged into the pulse hose from the crankase what kind of reading should I get while cranking the engine?

What I am getting is + pressure instead of vacuum. Can anyone tell me what the reading should be?

Thanks in advance for any help.

jeggers

Both it pumps, there ia a diaphram inside that moves back and froth and check valves that keep it moving in one direction.

DOOmsman

Hugh, you have a interesting question and I believe you are the first
one here to put a vacuum gauge on the pulse line.

Now I will jump in and opine that it will probably show pressure compared
to atmospheric. Blow by will cause a rise in crankcase pressure causing
you to read a base pressure and then the pulsing may be to fast to see on
the gauge.

Anyone else????

jeggers

IMO you will not see much vacuum. In order to have vacuum you need to remove the air in the line completely. In this case the air removed is displaced by the diaphram moving.