# Fuel pumps **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [September 11, 2008, 6:29pm UTC](https://community.cartalk.com/t/fuel-pumps/19454 "2008-09-11T18:29:57Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![PaulPe](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@PaulPe](https://community.cartalk.com/u/PaulPe)\ **Post date:** [September 11, 2008, 6:29pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/1 "2008-09-11T18:29:57Z")
My fuel pressure guage has read a steady 87# for the 7 years I’ve had my car. Same pressure, regardless of RPM. After my latest oil change I noticed the reading at highway speeds has fallen to 83# and at idle it’ll drop to as low as 40#. My mechanic said it should vary with RPM and must have been stuck before. However, my son’s truck and coworker’s cars with guages all read a steady pressure. Is something wrong with my car now? ---
**Author:** ![SteveF](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/stevef/32/2_2.png) [@SteveF](https://community.cartalk.com/u/SteveF)\ **Post date:** [September 11, 2008, 6:36pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/2 "2008-09-11T18:36:13Z")
Test your battery and charging system. Maybe you are not putting out the normal amount of voltage, especially at idle. ---
**Author:** ![the\_same\_mountainbike](https://avatars.discourse-cdn.com/v4/letter/t/c89c15/32.png) [@the\_same\_mountainbike](https://community.cartalk.com/u/the_same_mountainbike)\ **Post date:** [September 11, 2008, 6:38pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/3 "2008-09-11T18:38:37Z")
Um…it would be really cool to know what you’re driving. And what your son and his coworkers drive. In 40 years I’ve never had a vehicle with a fuel pressure gage. ---
**Author:** ![Joseph\_E\_Meehan](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/joseph_e_meehan/32/21_2.png) [@Joseph\_E\_Meehan](https://community.cartalk.com/u/Joseph_E_Meehan)\ **Post date:** [September 11, 2008, 6:49pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/4 "2008-09-11T18:49:55Z")
In other words, if Steve’s good idea does not fit, then how about some more information. ---
**Author:** ![Docnick](https://avatars.discourse-cdn.com/v4/letter/d/ecae2f/32.png) [@Docnick](https://community.cartalk.com/u/Docnick)\ **Post date:** [September 11, 2008, 7:31pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/5 "2008-09-11T19:31:40Z")
Perhaps we are referring to the oil pressure here. A weakening oil pump would certtainly account for a drop in oil pressure. ---
**Author:** ![MrPhil](https://avatars.discourse-cdn.com/v4/letter/m/ecccb3/32.png) [@MrPhil](https://community.cartalk.com/u/MrPhil)\ **Post date:** [September 11, 2008, 7:34pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/6 "2008-09-11T19:34:02Z")
Fuel pressure or oil pressure gauge? Oil pumps are mechanical and pressure should rise a bit with increasing RPMs. Fuel pumps on recent vintage cars are electric, and should maintain a fairly steady pressure (maybe drop a bit with increased RPMs, as the engine sucks more gas). Old cars had mechanical fuel pumps on the engine and I would expect fuel pressure to vary with RPM. ---
**Author:** ![PaulPe](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@PaulPe](https://community.cartalk.com/u/PaulPe)\ **Post date:** [September 11, 2008, 9:30pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/7 "2008-09-11T21:30:19Z")
Sorry, the subject is oil pressure. My vehicle is a 2000 Isuzu Trooper ---
**Author:** ![tardis](https://avatars.discourse-cdn.com/v4/letter/t/f0a364/32.png) [@tardis](https://community.cartalk.com/u/tardis)\ **Post date:** [September 11, 2008, 9:50pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/8 "2008-09-11T21:50:03Z")
Oil pressure will normally vary with engine speed and oil temperature. Some cars/trucks (Ford is bad about this) that have oil pressure gauges, don’t have real oil pressure gauges. They just have an oil pressure switch such that the gauge reads zero for zero oil pressure and 50% for anything over 10 PSI. I think Ford was tired of dealing with people who didn’t understand why their oil pressure varied. ---
**Author:** ![PaulPe](https://avatars.discourse-cdn.com/v4/letter/p/ec9cab/32.png) [@PaulPe](https://community.cartalk.com/u/PaulPe)\ **Post date:** [September 11, 2008, 11:23pm UTC](https://community.cartalk.com/t/fuel-pumps/19454/9 "2008-09-11T23:23:24Z")
It seems logical that the pressure would vary with RPMs, but why would my guage go from a steady 50% to a varying reading? ---
**Author:** ![BustedKnuckles](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/bustedknuckles/32/25_2.png) [@BustedKnuckles](https://community.cartalk.com/u/BustedKnuckles)\ **Post date:** [September 12, 2008, 12:28am UTC](https://community.cartalk.com/t/fuel-pumps/19454/10 "2008-09-12T00:28:27Z")
Simple, age and wear. The oil pump is driven by the speed of the engine. The faster the engine turns, the faster the pump turns. Pumps have a pressure regulator that will bleed off pressure to keep it from getting too high. However, as the engine ages, wear will increase the bearing clearances, and that will allow the pressure to drop at slower speeds. You did not mention mileage, but 8 years means probably more than 100,000 miles. ---
**Author:** ![shootie](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@shootie](https://community.cartalk.com/u/shootie)\ **Post date:** [September 12, 2008, 2:41am UTC](https://community.cartalk.com/t/fuel-pumps/19454/11 "2008-09-12T02:41:12Z")
If your talking oil pressure.Sounds like a head gasket.Check your oil cap.If the underside is milky looking then its your head gasket .