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Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: July 28, 2022 09:46AM

Bought my first fuel pressure tester - an Innova basic fuel and vacuum combo.

The shop manuals describes placing gauge at 1/4" line between carb and pump. I plan to place it at RH secondary.

The Innova has a 1/4" hose and I will take my flare nut to the hardware store to locate a brass male to rubber hose fitting and clamps.

I will disconnect the coil power wire and use a remote crank.

How close does this simulate pressures with engine running?

Northern CA
66 Monza Coupe 4-spd 140

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Re: Methods for testing fuel pump pressure
Posted by: joelsplace ()
Date: July 28, 2022 11:43AM

Buy 2 hose barbs and a T so you can run it. Don't drive it like that of course.

Joel
Northlake, TX
5 Ultravans, 136 Corvairs and counting...

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Re: Methods for testing fuel pump pressure
Posted by: richard1 ()
Date: July 28, 2022 04:30PM


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Re: Methods for testing fuel pump pressure
Posted by: JimBrandberg ()
Date: July 28, 2022 07:42PM

I made a piece that goes from the tee to the right side carburetor on a 2-carb engine. It's just a tee with the 1/8 NPT for the gauge and rubber hoses on the other two. On a 140 I would put that in place and not plumb the Secondary to test.
I suppose pressure is the same in a dead end like the Secondary but I prefer to use the Primary line that has fuel moving through it. Or maybe I just wanted to use the same line for everything except turbos.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: July 28, 2022 10:26PM

I recorded 6 psi when cranking engine over without running.

Same 6 psi when engine was idling 500-1000 rpm.

Shop manual says 4-5 psi is normal. Which means I have 20-50% extra pressure.

Pic below is how I set it up for the RH secondary carb that was dribbling fuel and filling up after shutting engine off.

Questions:

-Shouldn't the ball check fuel inlet handle this pressure?

-How come other 3 carbs are not flooding or dribbling fuel? BTW, I did have trouble sealing all 4 carbs at the inlet nut. Required use of gasoila. But, I attributed that to aged threads.

-If I change the pitch of the float so they are not horizontal.

-How does a mechanical fuel pump increase its pressure with age.

Northern CA
66 Monza Coupe 4-spd 140



Edited 1 time(s). Last edit at 07/28/2022 10:27PM by Saxon.

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Re: Methods for testing fuel pump pressure
Posted by: JimBrandberg ()
Date: July 29, 2022 04:06AM

I've seen aftermarket mechanical fuel pumps as high as 9 PSI.
Different carburetors seem to have different amounts of pressure they will tolerate.
You're right, your ball inlets should be able to handle more pressure.
The threads in the inlet nut should not be what is doing the sealing, the inverted flare is what does it.
I have my own problems with dribbling fuel from the venturi cluster on a regular basis. I can't seem to read enough on that topic. Sometimes I just have to go on to another base without learning anything. Everything seems okay when I remove them 9 times and check the level and everything.
Maybe I should be selling the dribblers to Ted Brown. I've thrown away more than a few. I didn't know that cores were in short supply.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: July 29, 2022 07:05AM

Yes, on the flare inlet nut compression doing the sealing. I should have said Gasoila on the 1" fuel inlet nut.

It's a little comforting to know that dribbling is not an easy nut to resolve.

Some next steps for me to consider:

-Get a new carb as I already tried a used donor and I still had the same flooding.

-Get AZDave's adjustable fuel pump kit

-Go back to a needle and seat, but enlarge the seat hole to see if I can reduce the pressure.

-Increase buoyancy of float by tilting them 20-30 degrees pitched down into the fuel. Just make sure the top is not hitting the upper half of the carb.

-Investigate what may be heating up under that carb to make the fuel expand after shutoff. The spark plug is black, so it's not running lean obviously.

-install a bleed which I have yet to read about

-install a block off plate and start a 3-carb support group

Northern CA
66 Monza Coupe 4-spd 140



Edited 2 time(s). Last edit at 07/29/2022 07:07AM by Saxon.

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Re: Methods for testing fuel pump pressure
Posted by: joelsplace ()
Date: July 29, 2022 10:43PM

-Go back to a needle and seat, but enlarge the seat hole to see if I can reduce the pressure.
A larger hole will make the problem worse. The larger the hole the more pressure the fuel can exert on the needle.

Joel
Northlake, TX
5 Ultravans, 136 Corvairs and counting...

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Re: Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: August 02, 2022 06:37PM

Since the RH secondary carb only dribbled after engine shutdown and it was worse during day than night, I focused on the suggestion about heat expanding the gas in the bowl. So, I addressed with two simple things I could do immediately:

-Lowered gas level in bowl by setting floats to 1.5" They were at 1 3/16" before.

-Cleaned all the gunk in the recesses of the fin and intake manifold on right side.

I tested it in the day and night, the dribbling is gone, but so is my jet squirt, so I will raise the fuel level in 1/16" increments until I get it back.

Afterwards, I also tried the cooling tip about putting in a block off plate on the right hand side top shroud. That resulted in the temp/pressure light coming on after a 20 minute day drive on the side streets. I had to stop under the shade and let the car cool before it came back on again after 10 minutes of street driving. I removed the hose block off plate and the car is running cooler and the light is off.

Northern CA
66 Monza Coupe 4-spd 140

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Re: Methods for testing fuel pump pressure
Posted by: JimBrandberg ()
Date: August 04, 2022 04:57AM

I don't understand what a block off plate on the right hand side top shroud is.

Jim Brandberg
Isanti, MN
CorvairRepair.com



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Re: Methods for testing fuel pump pressure
Posted by: Lane66m ()
Date: August 04, 2022 05:06AM

C9222 plate to block of the fresh air offtake on the fan shroud. Must have had a big hole in a portion of the hose forward of the engine firewall.

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Re: Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: August 04, 2022 07:27AM

It does not look easy to see the flexible hose forward of this firewall

Where is a good inspection point?

Northern CA
66 Monza Coupe 4-spd 140

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Re: Methods for testing fuel pump pressure
Posted by: Lane66m ()
Date: August 04, 2022 08:02AM

None. Jack car up and take off both rear tires/ wheels. Get a bright light and inspect with eyes and fingers the length in front of firewall. Or take it out for inspection. At that point put plate on a round and cap off heater with a clean tunafish can or cat food can.

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Re: Methods for testing fuel pump pressure
Posted by: wittsend ()
Date: August 04, 2022 09:51AM

Saxon wrote: Afterwards, I also tried the cooling tip about putting in a block off plate on the right hand side top shroud. That resulted in the temp/pressure light coming on after a 20 minute day drive on the side streets. I had to stop under the shade and let the car cool before it came back on again after 10 minutes of street driving. I removed the hose block off plate and the car is running cooler and the light is off.

This is a bit confusing. I assume you installed the block off plate because there were suspected leaking hoses further in the system. But the car then ran hotter with the block off plate (odd). Then you say you removed the block off plate (now bleeding significant amounts of air) - or did you reconnect to the suspected leaking hoses - and that made it run cooler again??? This just doesn't make sense. Once a proper block off plate is installed any hoses down the line become irrelevant as a source of leaking air. Pursuing bad hoses on the other side of the firewall is not going to provide anything that the block off plate would have.

I just made a block off plate for the engine I'm in the process of completing. There are only three screw attachment points and those are the clip-on type nuts that elevate anything put on top of them - adding to any distortion from flatness in the shroud. I used silicone to fill in the gap. Did you feel around the block off plate for leaking air?

Just to make sure we are all on the same page here are pictures of the plate I made and the location it was attached. Is this what you did?

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: August 04, 2022 06:27PM

Yes, writing has room for vagueness without pics which I did not take.

I put in a plate exactly where you have yours. I did not check for sealing, but I also installed a circular plate in the short metal duct with blue silicon on both sides for sealing.

I never suspected any tears or leakage in the hosing before or after the modification.

I am curious as well why my temp/press light would go on.

Northern CA
66 Monza Coupe 4-spd 140

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Re: Methods for testing fuel pump pressure
Posted by: wittsend ()
Date: August 04, 2022 08:24PM

Is it possible the wire for the temperature light is grounding on something? I assume it is the same as on my EM where it is just a thermal switch that connects to ground when it gets hot enough.

I was just going through those wires this afternoon on my Lakewood. About a foot of the thermal switch wire was so brittle that attempts to bend it cracked the insulation. And as it crossed the rear of the car it had been broken and the wires simply twisted together and covered with electric tape..., that had unraveled to expose bare wire! Likewise the oil pressure wire was of similar condition but irrelevant because there is a bolt where the pressure switch should be. Anyway, something to check to rule out it being an electrical, not a heat problem.

------------------------------------------------------------------------------

***'61 Lakewood, a "Freebie" in hibernation for 27 years - In the process of applying CPR.***

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Re: Methods for testing fuel pump pressure
Posted by: Saxon ()
Date: August 04, 2022 09:37PM

Yes, possible wires exposed. But, I did inspect them when engine was out.

After the 2nd overheat, I was not able to pull over safely so I turned on heater and blower and temp/press light turned off after a minute.

Northern CA
66 Monza Coupe 4-spd 140

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Re: Methods for testing fuel pump pressure
Posted by: jjohnsonjo ()
Date: August 07, 2022 06:04AM

I'm not saying this is your problem, but I had the thermostat tip brake off. It would then blow the wire around in the air stream and set of the light (and buzzer in my case) when I reached a certain RPM. The fast that you are getting this condition when you have greater air flow makes me think its possible.

J.O.

65 Corsa Turbo Vert
79 Honda XL 500S
69 Honda CL 160 D
2010 BMW F 650 GS
2003 Bounder 36D
2013 KIA Optima SX turbo-AKA ZIPPY (wife,s car)
69 Newport Holiday Sailboat
Baja 150 dune buggy cart
Coleman HS 500 UTV
2016 KIA Sorento SXL Turbo

Bethlehem,Pa


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