Fuel Pump

D

DARROW 74

Well-known member
Joined
Mar 24, 2008
Messages
406
Location
SAN CLEMENTE CALIF
Should a fuel pump put out a steady pressure. mine is jumping from 0 to around 7 pounds is this right?

Reason for question. Trying to clean up a couple of bugs from last week end, I noticed the carb bowls were very low on gas
And I have been having to turn it over a bit more then I think it should to start it. I was at 1 or 2 turns to start now a lot more.
Do I have a problem with the fuel pump?
 
IF i'ts a Qjet, open up the chokes and throttle bladed, shine a light down there, and see if the floor of the manifold/plenum is wet before you go try to start it.....

leaking fuel bowel....

:crap:
 
The stock pump has a check valve in it to prevent drain back. Will cause long cranking with a Quadrajet, but probably not with a Holley.
We has this issue with Scott's Holley. Had to install a higher volume pump, then adjust the float levels.
 
I just cranked it over to fill the bowls about an hour ago and it is starting to drain down, it looks like it going back to the tank. is there a check valve in the fuel pump? With a new carb I don't want to think its leaking into the motor....
 
Yes. The pump has a check valve built in. Even the ones with a return line.
 
In your climate Darrow with that Pro Form carb and no choke one pump of the throttle and hit the key it should fire right up. In the summer here i only have to pump mine once as it gets colder sometimes it takes 2 pumps and it always fires right up :thumbs:
 
Best way to check for flow is to disconnect at the carb, put a temp long fuel rubber hose on into a bucket and crank. Should get enough to fill bowls on any carb within 10 seconds.

If my carbs are dry after a couple weeks, I crank for 5 seconds, then pump twice and release, crank again and they will start.

As Gene said, check the plenum anyway.
 
Pinch off or clamp the large rubber hose at the fuel pump that is going to the tank-if this stops your flow then the check valve in the pump is leaking(its probably not actually the check valve in the pump its the rubber doghnut around the check valve that is usually whats bad-still needs a pump)When you buy your new pump put a vacuum on the inlet and see that it holds.
 
Great Info

Well it has been 24 hours and the primary bowl level is still in the glass. It did not take long for the secondary to drain out it is leaking through the carb the butterfly s are wet.
Also when I undo the fuel line I can watch the fuel drain back down the line (check valve not working) But the fuel leaking from the secondaries well thats another thing. Any suggestions ( remenber this is a new 750 pro form carb, vacuum secondaries.)
 
A quick search found three causes:
1)Fuel level too high
2)Perculation from latent heating after shutdown
3)Defective rear block casting

I have also asked Lars for his advice.
 
big2bird said:
A quick search found three causes:
1)Fuel level too high
2)Perculation from latent heating after shutdown
3)Defective rear block casting

I have also asked Lars for his advice.
Click to expand...


Thanks bird I need all the help I can get:sos:
The level is 1/2 site glass
I don't see it being a heat problem It was cold when I brought the level up,
Defective Thats a good thought....
What do you mean by rear block casting ?
Where are you getting your info?
 
18436572 said:
Pinch off or clamp the large rubber hose at the fuel pump that is going to the tank-if this stops your flow then the check valve in the pump is leaking(its probably not actually the check valve in the pump its the rubber doghnut around the check valve that is usually whats bad-still needs a pump)When you buy your new pump put a vacuum on the inlet and see that it holds.
Click to expand...

I will try this over the week end sounds like a good test.
 
DARROW 74 said:
big2bird said:
A quick search found three causes:
1)Fuel level too high
2)Perculation from latent heating after shutdown
3)Defective rear block casting

I have also asked Lars for his advice.
Click to expand...


Thanks bird I need all the help I can get:sos:
The level is 1/2 site glass
I don't see it being a heat problem It was cold when I brought the level up,
Defective Thats a good thought....
What do you mean by rear block casting ?
Where are you getting your info?
Click to expand...

Just an internet search.
Set the fuel level to the bottom of the sight glass.
 
DARROW 74 said:
18436572 said:
Pinch off or clamp the large rubber hose at the fuel pump that is going to the tank-if this stops your flow then the check valve in the pump is leaking(its probably not actually the check valve in the pump its the rubber doghnut around the check valve that is usually whats bad-still needs a pump)When you buy your new pump put a vacuum on the inlet and see that it holds.
Click to expand...

I will try this over the week end sounds like a good test.
Click to expand...

If your Quad required more than two cranks to start after sitting, it's the check valve.
 
I seem to recall some quality control issues with Proform when they started.
 
DARROW 74 said:
Well it has been 24 hours and the primary bowl level is still in the glass. It did not take long for the secondary to drain out it is leaking through the carb the butterfly s are wet.
Also when I undo the fuel line I can watch the fuel drain back down the line (check valve not working) But the fuel leaking from the secondaries well thats another thing. Any suggestions ( remenber this is a new 750 pro form carb, vacuum secondaries.)
Click to expand...

Hey, I'm all over this. Will be calling you.:tomato:
 
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