Fuel pressure idoit

92Rustang · 03-29-2001, 07:10 PM

I have had my FP set to 38 with vacuum line on. After searching this broad I found that I should set it to 38 with vacuum line off? Is this right?And if so will I notice any difference. Next I was talking with a guy at work about were I'm reading my FP. I don't know if it is before or after the regulator? Does this make a difference. I have my gauge in my schrader valve? I'm going to be getting and electric gauge will I us the same spot or will I need to cut into the fuel line. Thanks for answer all of my dumb questions.

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Check my site for mod
www.fordmustanggt.com

jimberg · 03-29-2001, 11:37 PM

You check fuel pressure with the vacuum line off and the engine off. If you left the line on but left the engine off, I don't think it will be a problem.

You read the pressure at the correct location.

There are some FPRs that have a port for the fuel pressure gauge right on it.

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351W 89 Mustang GT Convertible

92Rustang · 03-29-2001, 11:57 PM

I have been adjusting it with the engine running and the line of. I have a holley regulator that does not have a port. Should I pay a new FPR with a port or can I run it of the shrader valve? Thanks again for the help.

------------------
Check my site for mod
www.fordmustanggt.com

jimberg · 03-30-2001, 08:40 AM

Quote:

I have had my FP set to 38 with vacuum line on.

Quote:

I have been adjusting it with the engine running and the line of.

I'm not sure if you meant on or off, but you definitely shouldn't set it with the engine running and the line attached. This will give you a real high setting.

From what I read and hear, the Holley regulator isn't that great. Replacing it isn't necessary, but wouldn't hurt. Hooking the gauge to the Schraeder valve should work and would be preferable to cutting your fuel rails.

When you do fuel line work, trigger the fuel pump cutoff switch in the trunk and crank the engine over a few times to relieve fuel pressure.

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351W 89 Mustang GT Convertible

92Rustang · 03-30-2001, 09:01 PM

Just to get this straight.
Key on, engine not running
Than take vacuum line off
Now adjust pressure to 38
Reconnect vacuum line
Does this sound right what should the pressure be when I start the engine? I think now it is around 20 something?
Thanks again

------------------
Check my site for mod
www.fordmustanggt.com

toms89 · 03-30-2001, 09:41 PM

You need to adjust your fuel pressure with the engine running and the vacuum line disconnected. The motor needs to be running in order for the fuel pump to stay on. You will not get accurate fuel pressure reading with fuel pump off. There is no way to increase fuel pressure then! Only decrease it.
Tom

toms89 · 03-30-2001, 09:45 PM

PS.. When you first turn ignition to on position with out cranking the motor the fuel pump will run but only for a few seconds.

jimberg · 03-31-2001, 06:23 AM

Sorry, yes, the fuel pump must be running. To do this without running the engine, you ground one of the leads in the self-test connector with the key on, engine off. It's also possible to flick the key on, take a reading, adjust, flick the key on, etc., but it's best to just ground the lead.

If you look at the self-test connector there is one flat side and a beveled side. With the beveled side pointing down, the lead you want to ground is on the left side of the connector, or, in other words, it's the one that is closest to the group of four in the middle of the connector.

Fuel pressure with the line connected when the engine is running depends on the engine. It should be set at 38-39 when the engine is off and the vacuum line disconnected.

------------------
351W 89 Mustang GT Convertible

03-29-2001, 07:10 PM	#1
92Rustang Registered Member Join Date: Feb 1999 Location: Smithton, IL, US Posts: 215	Fuel pressure idoit I have had my FP set to 38 with vacuum line on. After searching this broad I found that I should set it to 38 with vacuum line off? Is this right?And if so will I notice any difference. Next I was talking with a guy at work about were I'm reading my FP. I don't know if it is before or after the regulator? Does this make a difference. I have my gauge in my schrader valve? I'm going to be getting and electric gauge will I us the same spot or will I need to cut into the fuel line. Thanks for answer all of my dumb questions. ------------------ Check my site for mod www.fordmustanggt.com

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03-29-2001, 11:37 PM	#2
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	You check fuel pressure with the vacuum line off and the engine off. If you left the line on but left the engine off, I don't think it will be a problem. You read the pressure at the correct location. There are some FPRs that have a port for the fuel pressure gauge right on it. ------------------ 351W 89 Mustang GT Convertible

03-29-2001, 11:57 PM	#3
92Rustang Registered Member Join Date: Feb 1999 Location: Smithton, IL, US Posts: 215	I have been adjusting it with the engine running and the line of. I have a holley regulator that does not have a port. Should I pay a new FPR with a port or can I run it of the shrader valve? Thanks again for the help. ------------------ Check my site for mod www.fordmustanggt.com

03-30-2001, 09:01 PM	#5
92Rustang Registered Member Join Date: Feb 1999 Location: Smithton, IL, US Posts: 215	Just to get this straight. Key on, engine not running Than take vacuum line off Now adjust pressure to 38 Reconnect vacuum line Does this sound right what should the pressure be when I start the engine? I think now it is around 20 something? Thanks again ------------------ Check my site for mod www.fordmustanggt.com

03-30-2001, 09:41 PM	#6
toms89 Registered Member Join Date: Jul 2000 Location: Eldersburg, MD Posts: 182	You need to adjust your fuel pressure with the engine running and the vacuum line disconnected. The motor needs to be running in order for the fuel pump to stay on. You will not get accurate fuel pressure reading with fuel pump off. There is no way to increase fuel pressure then! Only decrease it. Tom

03-30-2001, 09:45 PM	#7
toms89 Registered Member Join Date: Jul 2000 Location: Eldersburg, MD Posts: 182	PS.. When you first turn ignition to on position with out cranking the motor the fuel pump will run but only for a few seconds.

03-31-2001, 06:23 AM	#8
jimberg Registered Member Join Date: Oct 1998 Location: Rogers, MN Posts: 2,089	Sorry, yes, the fuel pump must be running. To do this without running the engine, you ground one of the leads in the self-test connector with the key on, engine off. It's also possible to flick the key on, take a reading, adjust, flick the key on, etc., but it's best to just ground the lead. If you look at the self-test connector there is one flat side and a beveled side. With the beveled side pointing down, the lead you want to ground is on the left side of the connector, or, in other words, it's the one that is closest to the group of four in the middle of the connector. Fuel pressure with the line connected when the engine is running depends on the engine. It should be set at 38-39 when the engine is off and the vacuum line disconnected. ------------------ 351W 89 Mustang GT Convertible