Fuel pressure only one psi

Reply Subscribe

Thread Tools

Search this Thread

Jul 1, 2015 | 01:46 PM

jrockdiddy

Thread Starter

Fleet Mechanic

Joined: Dec 2012

Posts: 1,257

Likes: 1

From: Scottsdale, AZ

Fuel pressure only one psi

Last week it was six at Idle, now is only one at Idle. Any ideas?

Brand New holly mechanical fuel pump

Jul 1, 2015 | 02:01 PM

ALBUQ F-1

Fleet Owner

Joined: Jul 2004

Posts: 27,283

Likes: 1,046

From: NM

If your pressure gauge is liquid-filled, and in the engine compartment, it is likely damaged.

Jul 1, 2015 | 02:17 PM

jrockdiddy

Thread Starter

Fleet Mechanic

Joined: Dec 2012

Posts: 1,257

Likes: 1

From: Scottsdale, AZ

Quote:

Originally Posted by ALBUQ F-1

If your pressure gauge is liquid-filled, and in the engine compartment, it is likely damaged.

You are correct sir. How come?

Jul 1, 2015 | 02:36 PM

emay

Senior User

Joined: Aug 2012

Posts: 211

Likes: 0

From: Hampshire, IL

Liquid filled gauge under hood is a no no. They don't play well in the environment. We always ran a dry under hood or brought the gauge to the interior. A liquid filled gage - especially a low pressure gage, will change readings as temp and barometric pressure change. When a liquid filled gauge warms up the liquid expands and pressurizes the case internally. This creates the illusion of falling fuel pressure, i.e. the gauge reads lower and lower pressure as it gets hotter and hotter. Over time they end up reading all wrong.

Jul 1, 2015 | 02:39 PM

Smitty49

Senior User

Joined: Feb 2011

Posts: 298

Likes: 1

From: Huntsville, Al

Liquid filled gauges are normally filled with Glycerin to reduce fluctuation in the needle. The heat from the engine will cause it to build pressure within the gauge and effect the readings. Most liquid filled gauges have a relief in the body that you can relieve that pressure which it should be mounted in a way the relief is in the up position so as not to loose any fluid if that should need to be done.

Jul 1, 2015 | 05:04 PM

jrockdiddy

Thread Starter

Fleet Mechanic

Joined: Dec 2012

Posts: 1,257

Likes: 1

From: Scottsdale, AZ

Wow... I didn't know that. Thanks guys. I'll switch that out immediately before I start inspecting my fuel lines and connections.

Jul 2, 2015 | 09:43 AM

bjmayberry2

Lead Driver

Joined: Dec 2012

Posts: 9,688

Likes: 814

From: Wentzville, MO

jrockdiddy, Thanks for the post. Learned something I didn't know. I've always seen fuel pressure gauges under the hood but never knew they weren't or shouldn't be liquid filled.