Anyone had problems with liquid filled fuel pressure gauges in the heat (ex. Summit) - LS1TECH

Log In 


Fueling & Injection Fuel Pumps | Injectors | Rails | Regulators | Tanks

Anyone had problems with liquid filled fuel pressure gauges in the heat (ex. Summit)

Reply
 
Thread Tools Search this Thread
Old 05-23-2012, 09:01 AM   #1
TECH Resident
Thread Starter
iTrader: (5)
 
Join Date: Aug 2010
Posts: 784
Default Anyone had problems with liquid filled fuel pressure gauges in the heat (ex. Summit)

I have been chasing my tail with this fuel pressure dropping off after the car gets hot (mostly happening when the car gets hot and I park it, then restart it hot). Started wondering if it could be air in the line from the reg to the gauge in the cowl area since my pump has no check valve, but that led to a few post I found about these liquid filled gauges being pieces of **** and reading low (or zero) when they get hot. Something about the gauge compares line pressure to atmospheric and since they are internally sealed as they get hotter the pressure inside the gauge it self increases thus lowering the pressure reading shown on the gauge.

This would seem to make a lot of sense in my application sense the car doesn't seem to run differently when the gauge is reading sometimes as low as 20psi (vs. 43 base), and typically will get better after a few minutes of driving after a hot restart (probably the gauge cooling off a little from the heat soak of sitting in the cowl with no air flow).

Anyone else had a problem with this? I am thinking about just pulling the little plug and letting the liquid bullshit flow out. Upside is this is the cheapest fix I can think of!

Here is a video of a guy putting a heat gun on his gauge (granted it is a carb'd application so the fuel pressure is much lower anyway).

[youtube]ZdkWbRV5JyU[/youtube]

Here is what my car was doing:


Started it up today from dead cold in the garage. Fuel pressure was normal. Drove it up to Firestone (had a weight on one of my front runners come off). Restarted it 10 min later after they finished and the pressure was low (should be ~37psi at idle, was around 30psi per gauge. About 10 minutes into the drive the pressure was back up to ~37psi and stayed there for the rest of the trip (another 20-30 minutes).

Got home. Killed it, waited ~5 min, restarted it and pressure was ~25psi.

Seems like either the gauge is getting heat soaked or the pump doesn't like being restarted hot. Unfortunately I don't have an easy way to use my diagnostic fuel pressure gauge on this car since it hooks to the schrader and all I have on this is the 1/8th NPT on the side of the regulator.
dville_gt is offline   Reply With Quote
Old 05-23-2012, 12:57 PM   #2
11 Second Club
iTrader: (1)
 
Join Date: Apr 2004
Location: F' Reno I live in Sparks
Posts: 590
Default

Quote:
Originally Posted by dville_gt View Post
I have been chasing my tail with this fuel pressure dropping off after the car gets hot (mostly happening when the car gets hot and I park it, then restart it hot). Started wondering if it could be air in the line from the reg to the gauge in the cowl area since my pump has no check valve, but that led to a few post I found about these liquid filled gauges being pieces of **** and reading low (or zero) when they get hot. Something about the gauge compares line pressure to atmospheric and since they are internally sealed as they get hotter the pressure inside the gauge it self increases thus lowering the pressure reading shown on the gauge.

This would seem to make a lot of sense in my application sense the car doesn't seem to run differently when the gauge is reading sometimes as low as 20psi (vs. 43 base), and typically will get better after a few minutes of driving after a hot restart (probably the gauge cooling off a little from the heat soak of sitting in the cowl with no air flow).

Anyone else had a problem with this? I am thinking about just pulling the little plug and letting the liquid bullshit flow out. Upside is this is the cheapest fix I can think of!

Here is a video of a guy putting a heat gun on his gauge (granted it is a carb'd application so the fuel pressure is much lower anyway).

[youtube]ZdkWbRV5JyU[/youtube]

Here is what my car was doing:


Started it up today from dead cold in the garage. Fuel pressure was normal. Drove it up to Firestone (had a weight on one of my front runners come off). Restarted it 10 min later after they finished and the pressure was low (should be ~37psi at idle, was around 30psi per gauge. About 10 minutes into the drive the pressure was back up to ~37psi and stayed there for the rest of the trip (another 20-30 minutes).

Got home. Killed it, waited ~5 min, restarted it and pressure was ~25psi.

Seems like either the gauge is getting heat soaked or the pump doesn't like being restarted hot. Unfortunately I don't have an easy way to use my diagnostic fuel pressure gauge on this car since it hooks to the schrader and all I have on this is the 1/8th NPT on the side of the regulator.
Doesnt matter who makes the gauge, Liquid filled gauges will change pressure based on temp. the fluid expands and causes pressure on the internal membrane thus causing low pressure reading. Change to a non liquid filled gauge or only check fuel pressure after the car has cooled down (not the best for trouble shooting)
cyipher is offline   Reply With Quote
Old 05-23-2012, 08:30 PM   #3
TECH Addict
iTrader: (1)
 
gMAG's Avatar
 
Join Date: Mar 2003
Location: CT
Posts: 2,986
Default

I have this one, and haven't had a irregularities with it.
It's been very steady, although it hasn't had a torch put to it.
http://www.summitracing.com/search/?...d=800199&dds=1
gMAG is offline   Reply With Quote
Old 05-24-2012, 09:15 AM   #4
TECH Resident
Thread Starter
iTrader: (5)
 
Join Date: Aug 2010
Posts: 784
Default

Quote:
Originally Posted by gMAG View Post
I have this one, and haven't had a irregularities with it.
It's been very steady, although it hasn't had a torch put to it.
http://www.summitracing.com/search/?...d=800199&dds=1
that is the one i am running. i don't put a torch to it either, but it is mounted in right in the cowl area under the hood pointing towards the windshield and between my t6 turbo and the air conditioning the heat coming out of that area is pretty crazy.
dville_gt is offline   Reply With Quote
Old 05-24-2012, 11:10 AM   #5
TECH Addict
iTrader: (1)
 
gMAG's Avatar
 
Join Date: Mar 2003
Location: CT
Posts: 2,986
Default

Quote:
Originally Posted by dville_gt View Post
that is the one i am running. i don't put a torch to it either, but it is mounted in right in the cowl area under the hood pointing towards the windshield and between my t6 turbo and the air conditioning the heat coming out of that area is pretty crazy.
Yeah, mine is mounted up front, and the hood leaves alot of room for airflow.
Maybe that's the difference.
gMAG is offline   Reply With Quote
Old 05-25-2012, 12:07 AM   #6
TECH Fanatic
iTrader: (18)
 
Join Date: May 2008
Location: Dallas, Tejas
Posts: 1,617
Default

hi dville, there should be a rubber fitting on the side of the gauge. remove it, dump the liquid, and call it good.
71 chevy is offline   Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
LQ4 pump not priming after heat soak Sam Loffler Fueling & Injection 0 02-18-2016 11:24 AM
Fuel Pressure. rayy Fueling & Injection 0 10-12-2015 07:57 PM
Strange Fueling Issue Plastikk Fueling & Injection 3 06-12-2014 11:09 PM
UPDATE - SPARK PLUGS - High RPM misfires - No MIL or DTCs 1SLwLS1 PCM Diagnostics & Tuning 50 12-13-2011 05:04 PM
Possible Vapor Lock diagnosis help? jdperk-86elco Conversions & Hybrids 22 09-03-2008 11:18 AM


Tags
car, filled, fuel, gauge, gauges, hot, hotter, jegs, liquid, low, ls1tech, pressure, reads, regulator, rises

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are Off



All times are GMT -5. The time now is 01:27 AM.