Surprise fuel pressure

[wildphil]

After I installed a Walbro fuel pump and a afpr. I bought a cheap pressure gauge at Harber Freight that screwed into the fuel rail and adjusted the fuel pressure to 45 lbs. Today I just finished installing a Stewart Warner fuel pressure gauge in my Typhoons piller pod. I started it up and only had 32 lbs. Then I shut off the engine and turned the key on to see if the pressure changed, Still had 32 lbs. I think that I will go with the Stewart Warner gauge and adjust the pressure up. I was just surprised that there was so much differance between the two gauges.

 

[sy#2921]

Re: Surprise fuel pressure

How are you checking your fuel pressure? Depending on your setup your base pressure should be between 43 and 50 psi. Base pressure is set by either key on engine off or my favorite way is engine running and removing the vacuum line and plugging it. FP doesn't change afr that much but can cause issues.

 

[WyoSyclone]

Re: Surprise fuel pressure

Maybe check the ground for the SW gauge... if you have a bad ground you may read too low of pressure.

 

[wildphil]

Re: Surprise fuel pressure

When I checked my fuel pressure with the gauge screwed into the fuel rail. Initialy I adjusted with the engine running the vacuum line off and plugged. Then I checked the pressure with the vacuum line on but engine not running and key on. Both ways read the same 45 lbs. On my Stewart Warner gauge it is possible that the ground is not adiquit. Since I installed solid motor mounts I thought there may be to much vibration. So I did not mount the sender on the fuel rail. I did use a braided line. Also after the reading was so low I took a piece of jumper wire and touched it to the engine ground and sender still low pressure. So I don't know. I guess that I could temporarily mount the sender on the fuel rail for a good ground and see if the fuel pressure changes.

 

[James Thomas]

Re: Surprise fuel pressure

Ahh Harbor Freight .... made in who the hell knows where? You may have a ground issue but I doubt it. 5 bucks says it's a cheap / bad gauge.

___________
James

 

[wildphil]

Re: Surprise fuel pressure

I just reset my fuel pressure using the sw gauge. I set it with the vacuum line off and plugged with the engine running to 44lbs.fuel pressure. When I hooked the vacuum line back up and let the truck idle the fuel pressure went to 35lbs. Does this sound about right?

 

[sy#2921]

Re: Surprise fuel pressure

Sounds right to me. Tells me at idle you are pulling about 18" of vacuum.

 

[wildphil]

Re: Surprise fuel pressure

Great, I was hoping that was right. Thanks to all who responded to my post.