70 psi fuel pressure baffled - ZR-1 Net Registry Forums

Young1 · 07-10-2022

Gentlemen, read my analysis carefully please.

When I got my project running 5 weeks ago the fuel pressure was 50-53 as it should be. Car sat for 5 weeks with fresh fuel and fuel pressures were as following
42 psi one pump
80 psi two pumps. 8.2 amps

I replaced the fuel filter which brought it up to
45 psi one pump
85 psi two pumps
Upon applying vacuum to the OEM Fuel Pressure Regulator there was no change so I purchased a FPR from Jerry. Nice piece BTW.

Pressures are now
51 psi one pump. Perfect.
70 psi two pumps.
80 psi spike for 2 seconds when ignition turned on.

FSM says restriction in fuel return. I disconnect the fuel return line at its union parallel to fuel filter. Slip on a rubber hose into a gas can. Retest
51 psi two pumps. Perfect.
I have a restriction between union and tank.
I carefully inspect the SS fuel line from union to tank looking for damage from a careless jack or rear end collision. All is fine.

I remove rubber fuel line line at tank and blow air from each direction. Seems fine. Reconnect union.
70 psi two pumps.

I splice a piece of rubber fuel line to rubber return line at tank and put it in a gas can.
70 psi two pumps
It flows into the gas can but does not shoot with force as I expected.

So problem is between union and end of rubber fuel line at tank.
Has the 18 inch piece of 32 year old rubber fuel return line internally collapsed from the fresh fuel?
Shall I drop the tank and cut off that hose at its crimp and splice on a new rubber fuel line?
Baffled.

Young1 · 07-15-2022

SOLVED! I found this in the tank return hose. I hack sawed the hard line at the crimp union. This plastic plug was jammed down the hose. Pressure is normal now. Spliced in 11 inches of 3/8 hose.

HAWAIIZR-1 · 07-16-2022

Quote:

Originally Posted by Young1

SOLVED! I found this in the tank return hose. I hack sawed the hard line at the crimp union. This plastic plug was jammed down the hose. Pressure is normal now. Spliced in 11 inches of 3/8 hose.

Wow! Great troubleshooting! Where the hell is that thing from?

Sent from my iPhone using ZR-1 Net Registry

Young1 · 07-15-2022

80881D75-F2B5-46B3-A4ED-34D12480DA0D.jpg

Young1 · 07-16-2022

I have no idea what the cone shaped thing is. I had to push it out with a rod. It did not not fall out. The pressure must have swollen the hose to allow gas to pass by the plug. Crazy huh.

HAWAIIZR-1 · 07-16-2022

Quote:

Originally Posted by Young1

I have no idea what the cone shaped thing is. I had to push it out with a rod. It did not not fall out. The pressure must have swollen the hose to allow gas to pass by the plug. Crazy huh.

Glad you got it resolved and that will remain a mystery. That plug needs a case or frame for your car memorabilia display. That?s a head scratcher for sure!

garyhugo · 07-16-2022

Looks like a tip from a caulk tube. Wonder what the PO thought he was doing by plugging the return line. WOW.

Young1 · 07-16-2022

Maybe PO plugged the line while servicing the pumps. The originals were no longer installed. Forgot to take it out when slipping the hose on the pump assembly.

CamP · 07-16-2022

That's weird! I'm surprised that you discovered it!

Young1 · 07-17-2022

I pushed a wire up the hose and it stopped at the hose crimp. So I cut that sucker off!

07-10-2022	#1
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	70 psi fuel pressure baffled Gentlemen, read my analysis carefully please. When I got my project running 5 weeks ago the fuel pressure was 50-53 as it should be. Car sat for 5 weeks with fresh fuel and fuel pressures were as following 42 psi one pump 80 psi two pumps. 8.2 amps I replaced the fuel filter which brought it up to 45 psi one pump 85 psi two pumps Upon applying vacuum to the OEM Fuel Pressure Regulator there was no change so I purchased a FPR from Jerry. Nice piece BTW. Pressures are now 51 psi one pump. Perfect. 70 psi two pumps. 80 psi spike for 2 seconds when ignition turned on. FSM says restriction in fuel return. I disconnect the fuel return line at its union parallel to fuel filter. Slip on a rubber hose into a gas can. Retest 51 psi two pumps. Perfect. I have a restriction between union and tank. I carefully inspect the SS fuel line from union to tank looking for damage from a careless jack or rear end collision. All is fine. I remove rubber fuel line line at tank and blow air from each direction. Seems fine. Reconnect union. 70 psi two pumps. I splice a piece of rubber fuel line to rubber return line at tank and put it in a gas can. 70 psi two pumps It flows into the gas can but does not shoot with force as I expected. So problem is between union and end of rubber fuel line at tank. Has the 18 inch piece of 32 year old rubber fuel return line internally collapsed from the fresh fuel? Shall I drop the tank and cut off that hose at its crimp and splice on a new rubber fuel line? Baffled. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

07-15-2022	#2
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	Re: 70 psi fuel pressure baffled SOLVED! I found this in the tank return hose. I hack sawed the hard line at the crimp union. This plastic plug was jammed down the hose. Pressure is normal now. Spliced in 11 inches of 3/8 hose. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

07-15-2022	#4
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	Re: 70 psi fuel pressure baffled 80881D75-F2B5-46B3-A4ED-34D12480DA0D.jpg __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

07-16-2022	#5
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	Re: 70 psi fuel pressure baffled I have no idea what the cone shaped thing is. I had to push it out with a rod. It did not not fall out. The pressure must have swollen the hose to allow gas to pass by the plug. Crazy huh. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

07-16-2022	#7
garyhugo Join Date: Feb 2010 Location: Jacksonville,FL Posts: 242	Re: 70 psi fuel pressure baffled Looks like a tip from a caulk tube. Wonder what the PO thought he was doing by plugging the return line. WOW. __________________ Gary 90-1572

07-16-2022	#8
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	Re: 70 psi fuel pressure baffled Maybe PO plugged the line while servicing the pumps. The originals were no longer installed. Forgot to take it out when slipping the hose on the pump assembly. __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

07-16-2022	#9
CamP Join Date: Jun 2012 Location: fort worth Posts: 183	Re: 70 psi fuel pressure baffled That's weird! I'm surprised that you discovered it!

07-17-2022	#10
Young1 Join Date: Sep 2016 Location: Ocala, FL Posts: 899	Re: 70 psi fuel pressure baffled I pushed a wire up the hose and it stopped at the hose crimp. So I cut that sucker off! __________________ Steve Young 1991 ZR-1 Quasar Blue Metallic/Black #729 Second Owner 1991 ZR-1 Dark Red Metallic/Black #2040 SOLD 1990 ZR-1 Dark Red Metallic/Saddle #1670 SOLD Double your happiness.....complain half as much.

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