Fuel pressure problems(I guess)

meteg · Post by **meteg** » 05 Jan 2010, 11:06

hello everyone,

I have replaced many components on my 95 850 GLT N/A from long block to fuel injectors from auto tranny to 02 sensors... however one thing remains the jerky throttle response..(this is intermittent) gets worse as the weather cools. (all the stage 0 maintenance is done) Iac valve is cleaned but another interesting thing is the car lets you know about how it will perform when its started.. one day the car starts and sounds strong.. the other day it starts weak and performs weak. I believe my fuel pressure is waving.. which means its sometimes normal and sometimes low.. I have a an non oem pump installed in the fuel tank and I guess it doesnt perform like the old oem one did. tomorrow I will take the car to bosch car service to find out if the pressure is low as I'm guessing.I thinking of buying and oem pump.I also wonder the friends who replaced their fuel pump are you happy with your non-oem fuel pump performance?

Post by **misha** » 05 Jan 2010, 16:41

Tre performance,if i remember well?

I have aftermarket oe Meat & Doria(Pierburg or Hella inside)fuel pump,replaced it last March and im very happy with it.

Post by **confused_al** » 05 Jan 2010, 17:07

How is your fuel pressure regulator? Pull the vacuum line on the bottom of the regulator and check if there is raw fuel there. If indeed there is, your regulator is a goner.

meteg · Post by **meteg** » 06 Jan 2010, 05:47

I have already checked the fuel pressure regulator and it looks ok.my fuel injectors are also brand new I bought them a few weeks ago. my car was a car which my uncle owned before me and the cars maintenance was always lacked.. due to this maintenance lack the long block(engine) was replaced.the auto trans was also damaged so it was replaced. the sensors all the sensors from o2 to maf are also new. the only parts which arent replaced are the fuel pump relay and the pump.so I doubt that the pump is not supplying the fuel with adequate pressure.. but of course to be sure I need to pressure to be tested.the chiltons manual says the pressure should be 43 psi.. is it correct? if so I will take the car to a shop which the fuel pressure can be tested..

FCPEURO · Post by **FCPEURO** » 06 Jan 2010, 07:45

It does sound like it could be the fuel pump. Lets hope when you go to test it that it is having a bad day. Otherwise, it will show up that the fuel pressure is fine. Good luck and let us know how you make out.

Post by **misha** » 06 Jan 2010, 12:32

Fuel pressure should be like this:
-43.5psi after the first prime(without starting the engine)
-about 36psi@ during idle
-around 30-36 psi during normal driving
-43.5psi when driving at full throttle in high rpm's

Also...everything about 35-40psi is acceptable.

meteg · Post by **meteg** » 06 Jan 2010, 12:56

hello again,

since the last time I posted today I started the car on my way back home and the car started and performed strong and the drive was strong.stopped at the supermarket after 20 mins of drive and again the car performed weak. you can feel that the power lacks especially if you apply more throttle.and the throttle response also lacks like the throttle pedal is not pressed.. because its 8pm at the moment I couldnt have the fuel pressure is tested.but tomorrow I will go to a shop before work and have the pressure tested.I believe the pressure is not rising over 30 psi.. but will let everyone know when I have the test done. I have been making many posts here and been taking too much time keeping people busy but I hope that tomorrow this problem I'm having will come to an end.I also took notes of the pressure values on my notebook so I will be able to compare the values..

thanks everyone..

Post by **misha** » 06 Jan 2010, 13:13

No worries,we are here to help each other as much as we can.

Good luck!

meteg · Post by **meteg** » 08 Jan 2010, 12:47

here is the latest development on my 850's fuel problem.. the pressure has been tested. the beginning the pressure is 35 psi.. when the car idles it wonders betwen 25-30 but when you give it full throttle the pressure will not rise over 33 psi. maybe this explains why the car fails to accelerate properly when throttle is more than half applied..

any comments?

Jay Hughart · Post by **Jay Hughart** » 08 Jan 2010, 15:57

I would listen to the pump from inside the trunk with the engine running or have someone cycle the key with the radio off. It should make a high pitch noise if its running right. My pump died while on the road and I beat on the tank, got in running then like a idiot shut it off and had to remove the access cover and beat on the top of it and try to start it like 20 times before it would run. When I bench tested it (after driving 20 miles home and it actually ran ok but I didnt push it hard) the pump made a low growl after tapping on it. So if its the pump it will prob sound like its straining. A plugged fuel filter could cause low readings too. I think my plugged filter caused the pump to go out. Anyhow do you have the TRE-340 performance pump in there? I bought one on Ebay after swapping the pump out of a wrecked car and im trying to decide on whether to put it in my wrecked car or my good one. If your having probs with the same pump I will prob just put it in my junker. But if not my other car is a bit sluggish and the pump came out of a car that would idle at 2500 when started every now and then. Did you ever figure out what was causing yours to do this?, I saw an earlier post on it. Maybe its related to the pump also?