2000 Impala 3.8 110k no fuel pressure

kev2

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#31
I was really confused - thought I misread problem -

the fuel PUMP was not being energized -
So I wanted to start at the relay...
- the system will only energize the relay @3seconds then it needs to see a RPM/ CKP signal indicating the engine is running...
> You can jump the relay cavities and get fuel pump running... good circuit there.
>We needed to be sure the wire from cavity to PCM is good - as it WILL start for @2 seconds it seams ok.

I see the problem as -
why the PCM is not energizing the relay after @2seconds.
- am I correct ?

Do you have a tach in dash?
Can you scan for codes- esp the - P1xxx
 

cw41

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#32
Yes i have a tach in the dash which brings me to another thing. When it starts and runs rough, the tach will not register the rpm for a short period. the only way it starts is jumping the relay a3 to b1.

Yes you're correct, the pcm is not being energized to a3 fuel relay pin and I don't know why? I scanned again and get the same p0001 talking about the pressure regulator which is new and no fuel coming from the vacuum port. I have a bad wire somewhere I just need to dig deeper. thanks again
 

The old man

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#34
cw41---just so we are on the same page. If you are checking for power to "a3" from pcm while the engine is cranking, then that is the wrong pin to check. The "a3" is just a wire that goes to the pump motor and is only energized if the pump relay is pulled in and closes from "b1". The pin that you should be checking for voltage when the engine is turning is pin "b3" That is the pin that the signal coming from the pcm (cavity 3 at the pcm) goes to, (not "a3") and will be energized if there is a signal coming from the pcm from cavity 3 of the pcm.
If there is NO voltage there at "b3" when cranking, then go to pcm cavity # "3" and see if there is voltage there when cranking. If voltage is PRESENT at cavity 3 at the pcm when cranking then you have a bad wire or bad connection in the wire going to the relay. If NO voltage at either point, then we will know it is from the pcm back and narrow the search.

I don't think you will have power at these location that I described because if you did the car would be running ok. Why is this? Because when you get it running you can pull that fuel pump relay out of service and the engine will still run because of the backup of the oil pressure switch backup. Why do I know this is because I went to my Buick and pulled it and it run just fine as long as oil pressure is above 4#.

I don't know why you are not getting any codes, but stranger things have happened. Will the icm throw a code or is this relating to pooo1 code since ckp and cam sensor goes through the icm so the icm can send that signal to pcm. Is that what this pooo1 code is all about?

I think we need some actual voltage verifications. If we get this information I think it will help us help you.
 

kev2

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#35
trying to think of a way without a scanner .

the wire colors may change the purpose will not..

let me know if it helps

A- WHITE wire.
ECM control of Ignition Control Module (after the 400 RPMs and above are achieved).
B- TAN with BLACK stripe wire.
5 Volt BYPASS from ECM for Ignition Timing Control.
C- LIGHT BLUE with BLACK stripe wire.
CRANK Position Signal to ECM.
D- PURPLE with WHITE stripe wire.
Fuel Injection Control Signal to ECM.
E- WHITE wire.
Instrument Panel Tachometer Signal.
F- BLACK wire.
CAM Signal from the Camshaft Position (CMP) Sensor.
G- YELLOW wire.
CRANK (18X CKP) Signal from Crankshaft Position Sensor Assembly.
H- LIGHT BLUE with WHITE wire.
SYNC (3X CKP) Signal from Crankshaft Position Sensor Assembly.
J- BROWN with WHITE stripe wire.
CAM Signal from Camshaft Position (CMP) Sensor.
K- BLACK with WHITE stripe wire.
Engine Ground (-).
L- BLACK with RED stripe wire.
Ground that ECM gets thru' the Ignition Control Module.
M- RED with BLACK stripe wire.
CAM and CRANK Position Sensor Ground (-).
N- WHITE with BLACK stripe wire.
12 Volts to CAM and CRANK Position Sensors.
P- PINK wire.
Fused 12 Volts power for Ignition Control Module.
 

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cw41

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#37
The old man said:
cw41---just so we are on the same page. If you are checking for power to "a3" from pcm while the engine is cranking, then that is the wrong pin to check. The "a3" is just a wire that goes to the pump motor and is only energized if the pump relay is pulled in and closes from "b1". The pin that you should be checking for voltage when the engine is turning is pin "b3" That is the pin that the signal coming from the pcm (cavity 3 at the pcm) goes to, (not "a3") and will be energized if there is a signal coming from the pcm from cavity 3 of the pcm.
If there is NO voltage there at "b3" when cranking, then go to pcm cavity # "3" and see if there is voltage there when cranking. If voltage is PRESENT at cavity 3 at the pcm when cranking then you have a bad wire or bad connection in the wire going to the relay. If NO voltage at either point, then we will know it is from the pcm back and narrow the search.

I don't think you will have power at these location that I described because if you did the car would be running ok. Why is this? Because when you get it running you can pull that fuel pump relay out of service and the engine will still run because of the backup of the oil pressure switch backup. Why do I know this is because I went to my Buick and pulled it and it run just fine as long as oil pressure is above 4#.

I don't know why you are not getting any codes, but stranger things have happened. Will the icm throw a code or is this relating to pooo1 code since ckp and cam sensor goes through the icm so the icm can send that signal to pcm. Is that what this pooo1 code is all about?

I think we need some actual voltage verifications. If we get this information I think it will help us help you.
Thanks to the old man. it looks like I'm checking the wrong pin, I'll look again with kev2's info he just sent.
 

cw41

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#38
The old man said:
cw41---just so we are on the same page. If you are checking for power to "a3" from pcm while the engine is cranking, then that is the wrong pin to check. The "a3" is just a wire that goes to the pump motor and is only energized if the pump relay is pulled in and closes from "b1". The pin that you should be checking for voltage when the engine is turning is pin "b3" That is the pin that the signal coming from the pcm (cavity 3 at the pcm) goes to, (not "a3") and will be energized if there is a signal coming from the pcm from cavity 3 of the pcm.
If there is NO voltage there at "b3" when cranking, then go to pcm cavity # "3" and see if there is voltage there when cranking. If voltage is PRESENT at cavity 3 at the pcm when cranking then you have a bad wire or bad connection in the wire going to the relay. If NO voltage at either point, then we will know it is from the pcm back and narrow the search.

I don't think you will have power at these location that I described because if you did the car would be running ok. Why is this? Because when you get it running you can pull that fuel pump relay out of service and the engine will still run because of the backup of the oil pressure switch backup. Why do I know this is because I went to my Buick and pulled it and it run just fine as long as oil pressure is above 4#.

I don't know why you are not getting any codes, but stranger things have happened. Will the icm throw a code or is this relating to pooo1 code since ckp and cam sensor goes through the icm so the icm can send that signal to pcm. Is that what this pooo1 code is all about?

I think we need some actual voltage verifications. If we get this information I think it will help us help you.
I did get the car to run for a few minutes. Fuel pressue was still low at about 40psi and unsteady. After it died, I pulled code P0230 fuel circuit problem. I connected a tsb to it 00-06-04-023. I know the rules of this forum state not to ask for the tsb, it's at your discression. If you have any info on this you can share, It might just lead me to a fix. I've searched all possibilities and cannot find a broken wire, ground or other that is causing this fuel problem. Can a bad crank sensor cause this? I'm thinking this should store a code if it was the problem. Things are leading me to a bad PCM. Thanks for anymore help on this car.
 

cw41

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#40
Thanks kev2!! I looks like a need a two wire harness of some sort going to the PCM that is giving this issue. I'm trying to locate the part number they give to see what it looks like. Thanks again
 
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#41
Looking at the tsb, it looks like the some of the 2000 lesabres and Pontiac had some issue with the ground at cavitiy 16 of the pcm. and ignition to cavity 19.
The 2000 Impala is wired a little different than the 2000 lesabre, so don't know if this concerns the 2000 impala. I guess just check the numbers on you pcm and see if that is the ones the tsb is referring to.

Maybe check your grounds at the pcm connections to see if you have a pcm ground problem with yours. It sure looks like a ground problem on the 2000 lesabre and maybe a ignition power also.

The top is a schematic of your 2000 Impala so you can see a little of what they are talking about.

The bottom is a schematic of a 2000 Lesabre. You will see there is a little different but basically go to the same place in a different way. Had to go over the white wire with a pen. White against white don't show up very good.
 

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cw41

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#43
Yes the check engine light works, the TSB looks like a BOP fix not Impala. I think I do have a ground issue going to the PCM. My next chance I'm going to try to trace the wire from the pcm and see. I did a valve job on it back in may because of an overheating problem which took me to the head gasket being plugged with gunk, so I thought. A second new radiator fixed the problem as the GM shop put a 60.00 cheapie from, well I won't say who, but I put in an ac delco and things are ok. Maybe I broke a wire when I bungee corded the harness out of my way?? Don't know I keep digging. Thanks for the tsb again.