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Fuel pressure problem (kinda long) #904245 01/14/11 05:04 AM 01/14/11 05:04 AM
Joined: Jun 2009 Posts: 146 Queensland,Australia T T-bar OP member
T-bar OP member T Joined: Jun 2009 Posts: 146 Queensland,Australia	Hello all, I have problem with the fuel pressure staying consistent in my car. It,s a '70 Cuda 440 it has an electric Aeromotive S series pump from Summit it looks like the one to use up to 750hp. It was in the car when i got it so not sure how old it is either but looks fairly new. I have 1/2" line from the pickup to the regulator also aeromotive. I have also put a aeromotive 100 micron filter between pump and tank. Now the problem is when i start it up it has 8.5 psi at the reg take it for a drive and pull up let it idle and check the it and it drops down to anywhere between 2 and 4 psi (gauge is under the bonnet). The previous owner had a 10 micron filter on and i thought that may have been the culprit while it did help it still isn't right. What should i try next.

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904246 01/14/11 08:08 AM 01/14/11 08:08 AM
Joined: Jan 2003 Posts: 2,521 Richmond Va, KeislerTKO 60... V VanishPt master
VanishPt master V Joined: Jan 2003 Posts: 2,521 Richmond Va, KeislerTKO 60...	liquid filled gauge? Next time you check it , take a rag soaked in ice water and hold it around the gauge for a minute or so. Remove the rag and look at the gauge. does it read higher?

Re: Fuel pressure problem (kinda long) [Re: VanishPt] #904247 01/14/11 09:26 AM 01/14/11 09:26 AM
Joined: Jun 2009 Posts: 146 Queensland,Australia T T-bar OP member
T-bar OP member T Joined: Jun 2009 Posts: 146 Queensland,Australia	Yes VanishPt it is a liquid filled gauge and i will try that. What is the problem? Thanks for the reply.

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904248 01/14/11 09:37 AM 01/14/11 09:37 AM
Joined: Jan 2003 Posts: 2,521 Richmond Va, KeislerTKO 60... V VanishPt master
VanishPt master V Joined: Jan 2003 Posts: 2,521 Richmond Va, KeislerTKO 60...	liquid filled guages are well known for reading low when they get hot. Soak it a few times with ice cold water and see if it starts to go up

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904249 01/14/11 09:38 AM 01/14/11 09:38 AM
Joined: Feb 2003 Posts: 8,677 A Andrewh master
Andrewh master A Joined: Feb 2003 Posts: 8,677	liquid filled gauges cause a problem where it is hot. the liquid inside the gauge generates pressure as it heats up, causing it to read low. that is why I chose a dry gauge for under hood fuel pressure.

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904250 01/14/11 09:39 AM 01/14/11 09:39 AM
Joined: Sep 2006 Posts: 616 TP Exit 7, NJ, USA DANA60 mopar
DANA60 mopar Joined: Sep 2006 Posts: 616 TP Exit 7, NJ, USA	I removed my liquid one because it always would drop as soon as the engine got warmed up. I put a "normal" guage on there and all looked fine since. 6416891-IMG_3311_1_1_1.JPG (62 downloads)

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904251 01/14/11 10:16 AM 01/14/11 10:16 AM
Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska R RapidRobert Circle Track
RapidRobert Circle Track R Joined: Nov 2003 Posts: 36,040 Lincoln Nebraska	Aye mate. You said the 10 micron filter helped. As in it read even lower than 2-4 w the 100 in there? Unless underhood heat as said makes a liquid gauge totally worthless I'd bypass the filter for a 15 minute test (you're not going to pass an exorbitant amt of debris in 15 min) esp since you said going to the 10 micron helped brought the reading up & clean/check the reg and I'm assuming the tank/sock is clean & no pinholes in the hard line/neoprene connector pieces. Holler when you find it live every 24 hour block of time like it's your last day on earth

Re: Fuel pressure problem (kinda long) [Re: RapidRobert] #904252 01/14/11 07:18 PM 01/14/11 07:18 PM
Joined: Jun 2009 Posts: 146 Queensland,Australia T T-bar OP member
T-bar OP member T Joined: Jun 2009 Posts: 146 Queensland,Australia	Thanks for the info on the gauge i will fool around with that. Rapidrobert i went from the 10 to the 100 micron as it was cavitating the pump to much and while that iniatally sent the pressure up from where it was set then i readjusted the pressure all was good until i checked the gauge after driving it.

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904253 01/14/11 10:19 PM 01/14/11 10:19 PM
Joined: Dec 2003 Posts: 2,586 Illinois, Indiana, Louisiana ProStDodge master
ProStDodge master Joined: Dec 2003 Posts: 2,586 Illinois, Indiana, Louisiana	Most liquid gauges have a rubber plug which you can use to fill (or empty) the gauge. If the problem is heating of the liquid, you can use the plug to "burb" the gauge and equalize the internal pressure. Its not the temperature of the liquid creating the false reading, it is the expansion of the liquid due to the heat.

Re: Fuel pressure problem (kinda long) [Re: ProStDodge] #904254 01/14/11 10:34 PM 01/14/11 10:34 PM
Joined: Oct 2003 Posts: 1,371 Costa Mesa, CA C chache876 pro stock
chache876 pro stock C Joined: Oct 2003 Posts: 1,371 Costa Mesa, CA	Quote: Most liquid gauges have a rubber plug which you can use to fill (or empty) the gauge. If the problem is heating of the liquid, you can use the plug to "burb" the gauge and equalize the internal pressure. Its not the temperature of the liquid creating the false reading, it is the expansion of the liquid due to the heat. what if you drained the liquid? would that eliminate the false readings or are they somehow calibrated with the use of the liquid?

Re: Fuel pressure problem (kinda long) [Re: chache876] #904255 01/14/11 10:53 PM 01/14/11 10:53 PM
Joined: Jan 2003 Posts: 163 CT: Corrupticut M Mr71Bee member
Mr71Bee member M Joined: Jan 2003 Posts: 163 CT: Corrupticut	Its the pressure caused by the expanding liquid. Had the same problem. I would say either burp and remove some liquid... or install a non-liquid filled gage or move the gage to outside on the bonnet. Don't bring it into the interior! Mr Bee

Re: Fuel pressure problem (kinda long) [Re: Mr71Bee] #904256 01/14/11 11:58 PM 01/14/11 11:58 PM
Joined: Jun 2009 Posts: 146 Queensland,Australia T T-bar OP member
T-bar OP member T Joined: Jun 2009 Posts: 146 Queensland,Australia	Thanks all, i'll try everything before a new gauge. I did look at an electric pressure gauge for the interior but they are a bit dear (autometer) so i'll stick to the one under the bonnet for now. The non liquid ones are pretty cheap so that might be the go.

Re: Fuel pressure problem (kinda long) [Re: chache876] #904257 01/15/11 06:02 AM 01/15/11 06:02 AM
Joined: Dec 2003 Posts: 2,586 Illinois, Indiana, Louisiana ProStDodge master
ProStDodge master Joined: Dec 2003 Posts: 2,586 Illinois, Indiana, Louisiana	Quote: what if you drained the liquid? would that eliminate the false readings or are they somehow calibrated with the use of the liquid? Yes, you can remove/drain the liquid out and the gauge will work properly.

Re: Fuel pressure problem (kinda long) "Update" [Re: ProStDodge] #904258 01/15/11 09:10 PM 01/15/11 09:10 PM
Joined: Jun 2009 Posts: 146 Queensland,Australia T T-bar OP member
T-bar OP member T Joined: Jun 2009 Posts: 146 Queensland,Australia	Just tried the ice rag on the gauge and pressure reading shot straight up so now i'll remove gauge and drain some liquid. There isn't any rubber plug in the back of it but three screws so i'll take them out split the gauge and see whats there. Thanks again.

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904259 01/15/11 09:33 PM 01/15/11 09:33 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: Hello all, I have problem with the fuel pressure staying consistent in my car. It,s a '70 Cuda 440 it has an electric Aeromotive S series pump from Summit it looks like the one to use up to 750hp. It was in the car when i got it so not sure how old it is either but looks fairly new. I have 1/2" line from the pickup to the regulator also aeromotive. I have also put a aeromotive 100 micron filter between pump and tank. Now the problem is when i start it up it has 8.5 psi at the reg take it for a drive and pull up let it idle and check the it and it drops down to anywhere between 2 and 4 psi (gauge is under the bonnet). The previous owner had a 10 micron filter on and i thought that may have been the culprit while it did help it still isn't right. What should i try next. A return would help alot...You sure you have unostructed flow from the tank? I'd get rid of the 100 micron filter also and try it without for while. I bet that helps alot...

Re: Fuel pressure problem (kinda long) [Re: Challenger 1] #904260 01/15/11 09:41 PM 01/15/11 09:41 PM
Joined: Oct 2003 Posts: 1,371 Costa Mesa, CA C chache876 pro stock
chache876 pro stock C Joined: Oct 2003 Posts: 1,371 Costa Mesa, CA	Quote: A return would help alot...You sure you have unostructed flow from the tank? I'd get rid of the 100 micron filter also and try it without for while. I bet that helps alot... Also, if you already have a sock on the pickup tube, theres no need for a filter between the tank and the pump

Re: Fuel pressure problem (kinda long) [Re: ProStDodge] #904261 01/15/11 09:46 PM 01/15/11 09:46 PM
Joined: Oct 2003 Posts: 1,371 Costa Mesa, CA C chache876 pro stock
chache876 pro stock C Joined: Oct 2003 Posts: 1,371 Costa Mesa, CA	Quote: Yes, you can remove/drain the liquid out and the gauge will work properly. Whats the point of it? Acts as a damper?

Re: Fuel pressure problem (kinda long) [Re: chache876] #904262 01/15/11 09:54 PM 01/15/11 09:54 PM
Joined: Jun 2009 Posts: 146 Queensland,Australia T T-bar OP member
T-bar OP member T Joined: Jun 2009 Posts: 146 Queensland,Australia	I have a return line on it from the reg back to the pickup. The pickup is an aftermarket 1/2"type with about a 3/16" return line in it also. There isn't a sock on the pickup, i would like to put the brass type strainer on but can't seem to source one here that's 1/2".

Re: Fuel pressure problem (kinda long) [Re: T-bar] #904263 01/15/11 10:42 PM 01/15/11 10:42 PM
Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio Challenger 1 Too Many Posts
Challenger 1 Too Many Posts Joined: Feb 2005 Posts: 28,312 Cincinnati, Ohio	Quote: I have a return line on it from the reg back to the pickup. The pickup is an aftermarket 1/2"type with about a 3/16" return line in it also. There isn't a sock on the pickup, i would like to put the brass type strainer on but can't seem to source one here that's 1/2". Then I would say your experiencing cavation, which means not enough free flow into the pump, I'll bet ya. Gasoline is very hard to suck, A hi performance pump needs to be supplied with lot's of gasoline so it don't cavatate.

Re: Fuel pressure problem (kinda long) [Re: chache876] #904264 01/16/11 02:21 AM 01/16/11 02:21 AM
Joined: Dec 2003 Posts: 2,586 Illinois, Indiana, Louisiana ProStDodge master
ProStDodge master Joined: Dec 2003 Posts: 2,586 Illinois, Indiana, Louisiana	Quote: Quote: Yes, you can remove/drain the liquid out and the gauge will work properly. Whats the point of it? Acts as a damper? Yes, the oil is strictly a damper for the needle to reduce vibrations or damper fluctuations to make the gauge easier to read.

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