1995 3.1 replace crank sensor

rockien · #1 05-27-2010, 05:04 PM

First off I would like to thank everyone on this forum for helping all of us. I have used and refered to this site for several years and there is very good information on here that saves us DIY both time and money.

Problem, 1995 3.1L Grandprix died on my duagter as she was driving it in town. It starts, idles but then sputters & dies in 3 - 20 seconds. As it is 15 years old I figured it was probably the fuel pump/filter. I changed them and they were both original but still has the same problem. Fuel pressure is a solid 40 when idling. After reading some post, it appears there is a bad sensor, so I started poking around. I disconnected the MAP sensor and still same problem. After checking the connector to the crank position sensor, I started the car and it idled ok, then I reached under and moved the connector and wires, then it started stumbling and died. SO I found what appears to be the problem.
I stopped by the auto store and bought a new one at lunch and plan on changing it tonight.
Question now is, what is the procedure for changing this? It looks like it goes behind the pully/balancer. Do I remove the serpintine belt, remove the bolt (might be fun), then pull off the pully to get to it?

tblake · #2 05-27-2010, 10:00 PM

What sensor are you referring to? I did not know you could get to the crank sensor plug behind the balancer without taking the balancer pulley off...

I just hope for your sake its not the crank position sensor behind the block. They are a pain in the ass to get out without leaving chunks in the oil pan.

rockien · #3 05-27-2010, 10:37 PM

It was located behind the crank pully, however I replaced it and then started it up and it ran fine, so I let it run while I was putting away my tools and after about 3-4 minutes it started to sputter and then died. Now it starts up fine and dies within 3-10 seconds. So the crank sensor probably wasn't the problem. Anyone have an idea of what I should try now?

fuel pressure checks the same all of the time when it runs or falters and dies, so I don't think it's a fuel problem unless it's way off. It bounces around some unless I disconnect the vacumm line to the fuel regulator. With it off the fuel is steady at 45 with the motor running and sits steady at 40-42 with just the key on.
I know most people are heading to vacation for the long weekend as I will be also tomorrow, but if anyone has any good ideas for me to try, I'm all ears! Thanks Rockie

rockien · #4 05-27-2010, 10:44 PM

One more thing for details. all of the lights are off when it is running and usually when it starts to sputter and then they come on after it dies. I went to hookup my obdcII scanner to it, but it is a different hookup, so my guess it is the older style obdc. I may need to go see if I can rent one from Autozone

richtazz · #5 05-28-2010, 08:28 AM

I believe the other crank sensor (the nasty one to change in the back of the block) may be your issue.

tblake · #6 05-28-2010, 11:19 AM

Yeah, I was wondering that too Rich.

Just be carefull, take the bolt out, soak it with brake clean, twist back and forth, try to pull out a little, and do this over and over again. If it breaks off, not much you can do other than tap it in and remove it from the oil pan. And you know how easy the oil pan is to remove on these cars.

rockien · #7 05-28-2010, 12:05 PM

Ok, so it has another crank sensor on the back of the block. I did a quick look see this morning and didn't see it, so can you let me know where I should be looking for this. May be the bottom?
tblake, what does the brake clean do to help remove it? I would think something like WD40 would loosen up soemthing tight/corroded. I do have some breake clean around though. I have never had do do much work to these small GM motors other than intake and head gaskets or pulled the pan off of one of these, but it doesn't sound like much fun.
Thanks for the info!

rockien · #8 05-28-2010, 08:11 PM

Ok, I bought one on the way home, and took a closer look. I see it now on the back side. Not much room to play around back there! What is the best way to get to it? By pulling the right side wheel, or underneth the car? I don't think my arm will fit anywhere on the bottom.
Anyways, leaving for the weekend, I will update this when I get it changed out next week.

tblake · #9 05-29-2010, 02:06 AM

If you can get at it by removing the right wheel, then go for it. What have you got to lose, just your time putting the wheel back on?

I think I read a writeup somwhere, I will see if I can find it while you are on vacation.....

richtazz · #10 05-29-2010, 10:10 AM

WD-40 (and other spray lubes) can cause the o-ring to swell, which will make removal harder. Brake clean will help soften the rubber seal, which makes removal easier.

tblake · #11 05-29-2010, 09:54 PM

This is all I could come up with. It doesnt give any tips on how to get it out, but it shows a picture.

http://www.automotiveforums.com/vbul...d.php?t=663352

rockien · #12 06-01-2010, 10:18 PM

Thanks for the help and replies. It was pretty easy to get and change, although you can't see anything. I guess I must do ok in the dark!
It is cooler out tonight and raining, so after changing the crank sensor I started the car and it idled high 2k perfectly for about 2 minutes then started to idle down and spit and sputter. It went up and down from the 2k rpm for a couple of minutes then died. My guess is it is in a cold start cycle when it runs at 2k RPM and once it switches off that mode, is when the problem happens. Now it starts and runs ok for a few seconds then sputters and dieds. Same as it was when I started troubleshooting this.

I read another post that sent me to troublecodes.com to try and get the codes using the jumper and the car doesn't have the B pin to make the connection. That site said if the pin is missing then the only way to read the codes is with a scanner. The SES has never been on, but I know that older OBD is limited.

So anyone know what sensor is not used in the cold start mode, or have any good ideas of what to try now? I would think the IAC is used all the time, but don't really know.

If anyone cares, I had a bad issue with my boat motor this weekend. I either blewn a head gasket or have a hole in the piston. It is a supercharged 502 and blew about 3 quarts of oil out of the dip stick tube. What a mess. Will be pulling that apart this weekend to see the damage.

richtazz · #13 06-02-2010, 09:03 AM

regretfully, your 95 is a hybrid diagnosics system, and the codes cannot be pulled using the old paperclip trick. The only way to pull the codes on your car is with a scan tool with the proper adaptor.

Have you inspected the entire wiring harness from the rear CKPS to the ignition module? You stated earlier in post one that moving that harness caused the car to act up. It is a twisted pair harness that runs very close to moving components (pass side axle shaft, harmonic balancer) and near the exhaust manifolds and may have become chaffed or burned.

rockien · #14 06-02-2010, 09:38 AM

I have inspected the wiring and see nothing wrong. When I was moving the wires, I now think it was just coincidence that I would move them and it would sputter and was never consistant. It was just changing from the cold start mode just like last night. Last night I had it running and I moved the wires and it made no difference at all. I have a friend that may have a scan tool for that, so I will give him a call. I hate to go buy one for this old car, but I will if I need to.

rockien · #15 06-02-2010, 05:41 PM

quick question can this old OBD have codes but not turn on the SES light?
Should I try to disconnect the battery to reset the control module.
Thanks

POST REPLY TO THIS THREAD