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bad fuel pump?

B

bvanetten

New member
Hey, I am pretty new to this site but i was having a problem with my 99 grand prix. I have the 3.8L engine and it is getting fairly high in miles but still a good solid car. I have been having the car die on me occasionally and I thought it was the fuel filter because if you give it a while after it dies it will start again. I changed the fuel filter and yet the same problem... I was going to change the fuel pump but seeing how it is almost 300 dollars I figured i would check and see if anyone had any ideas before I blow that money for nothing if I overlooked something... thanks for any advice.
 


Typically when a fuel pump dies, it goes all at once and won't start back up. When one of mine died, it did give a couple stumbles a few miles before. But they don't usually die and start if the pump is bad.

My first guess would be the CPS. Does the tach ever drop to 0 when driving?
 
Ya, when the fuel pumps go bad they do usually die except i had one on a suburban that would die once it heated up and was under a load... I would wait a little whiole and it would work again. so i wasn't sure if it could be like that... When it dies it usually just dies right away but it is usually when going up a hill or something like that. i didn't notice if the tach went to 0 while driving so I don't think so... What is the CPS? I'm not too sure about wut that is...
 
CPS=Crank position sensor
Fyi my cars been doing the same here and there,ill be driving down the road
and it will completely cut out like it not firing,ive already replaced the fuel pump
and filter also,weird thing is ill get out and move the wire around that connect to my
the bottom of my coil pack and it seems to work o.0,although on diffrent occasions
ive just sat there for a moment and randomly keep trying to turn it over and walla
its starts but with a sh*ty idle then clears out?
also ive noticed that at start up it has a up and down idle like its trying to catch up then it willclear out?
and sometime at stop lights its done it then stalled?

Not sure but it sounds like we may be having the same issues
 


So how hard is it to change teh CPS? I have the 3.8 L in my car and nothing special to it... ya, I had that problem with the fuel pump on my suburban and after it cools off it would work alright again... so that's why I figured it might be the fuel pump... but if anyone had ideas on the CPS and if that would be cheaper to replace first then I might try that...
 
Sl33p3rGt said:
CPS=Crank position sensor
Fyi my cars been doing the same here and there,ill be driving down the road
and it will completely cut out like it not firing,ive already replaced the fuel pump
and filter also,weird thing is ill get out and move the wire around that connect to my
the bottom of my coil pack and it seems to work o.0,although on diffrent occasions
ive just sat there for a moment and randomly keep trying to turn it over and walla
its starts but with a sh*ty idle then clears out?
also ive noticed that at start up it has a up and down idle like its trying to catch up then it willclear out?
and sometime at stop lights its done it then stalled?

Not sure but it sounds like we may be having the same issues
Click to expand...

This sounds more like a bad MAF to me. Try cleaning it or unplugging it next time.

Also, something to watch for with the CPS is when you are trying to start it, does the tach move. If the tach moves, then move onto something else. But if the tach doesn't move while you are starting the car, the CPS is usually the culprit.
 


CPS = Cam Position Sensor (aka ...hardly ever bad in our cars)
CKPS - CranK Position Sensor (aka..frequently bad in our cars)

:th_winking:
 
Lmao me too on the cps
yeah i was wondering about the MAF also,havent really payed attention to
tac i will look at that when i get off work,i did notice when i disconnect the
maf while the car is running there is little to no change in the way the motor runs?
 
well it wasn't the fuel pump... I had a mechanic tell me that's what it sounded like so I changed it and it still has the same problem... I guess I might try the MAF... but if it is the crank position sensor how much do they cost and how hard are they to change? also, the tach does move while starting it so I don't think it is the crank position sensor...
 
Guys.. CPS, CKPS.. it only matters if you say it to a parts guy and he hands you the cam sensor. :D Figured I'd get us up to speed on our abbreviations.

Don't rule out the crank sensor because you have tach at start. It can act up. Part is about $30 and it's easy to install if you have an airgun.
 


So how do u tell if it is the crank sensor then? How do u go about finding that out? Cause I have a diagnostic tool and its not showing any codes and I thought that the crank sensor would most likely throw a code cause I've had similar sensors make the check engine light come on...
 
The crank sensor is a huge PITA to diagnose. They often don't set a check engine light. The car may hiccup, stall etc and it could be a crank sensor.

As a rule of thumb, I shotgun on a crank sensor when it exhibits symptoms. $25-30 for the sensor and 15 minutes.. usually solves the problem.
 
bvanetten said:
So how do u tell if it is the crank sensor then? How do u go about finding that out? Cause I have a diagnostic tool and its not showing any codes and I thought that the crank sensor would most likely throw a code cause I've had similar sensors make the check engine light come on...
Click to expand...

When I said about the tach at startup, I mean does the tach move when you are trying to start it and it isn't starting.
 
Ya, the tach is moving when I am turning it over and it wont run... well maybe I will try the crank sensor then... but does it usually wait for the car to run a while bfore it acts up? Because if I let it sit over night it will start up and run for a little bit... but once it earns up is when it starts acting up...
 
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