Pontiac grand am starting issues

cntfgritout

Ok so to start off, my car half cranks, if it sits for 3 hrs or more I can hit the key 3 times and it will start, each crank is only a half crank which is why it takes 3 cranks. Once I drive it any where I can't start it once I shut it off, once again because it only half cranks.I've replaced both crank sensors on the car. I've replaced the battery and the starter. The car does run better after changing those things but still has the same issue. Any help would be appreciated. Thanks 

imidazol97

You're going to have to explain what the car does that you describe as "half cranking." I'd suspect battery cable corrosion at the starter end or where the ground connects to the engine/fender. But I'm only guessing what you are describing.

The car only has one crankshaft position sensor. Are you sure you had it replaced? The usual symptoms on engines with which I was familiar are the the engine would shut off after it got hot and wouldn't get enough of a signal from the sensor that the crankshaft was rotation for the computer to know when to fire the spark. Sometimes cars would die as a symptom usually when the engine speed was very low such as turning a corner. Then the engine had to cool enough for the sensor to make enough voltage for the computer to read it.

cntfgritout

Sorry, the car stops cranking, even when you hold the key in the start position . It will crank for a second or two then stop. It does have two crank sensors, a 7x sensor on the back of the block and a 24x sensor behind the harmonic balancer. I've already checked the ground from the battery. Yes I'm sure it was changed, I'm the one doing the work

thecardoc3

Do you have a voltmeter? If so measure and prove if you losing the power to the starter on the main feed, or the command to the solenoid. If those check OK, see if you are developing a voltage drop on the ground cable between the engine and the negative battery post. If you don't have a ground cable voltage drop and you are not losing the power feeds then you are looking at a starter issue.

Mr_Shiftright

Diagnosing and Understanding Voltage Drop

cntfgritout

Thanks everyone I will try what you have suggested

imidazol97

cntfgritout said:

Sorry, the car stops cranking, even when you hold the key in the start position . It will crank for a second or two then stop.

Thanks for explaining. That sounds just like the short cranks that my cars do when I hold the key over or don't hold the key--just twitch it to crank or hold it and the car cranks over and the starter disengages automatically because the engine speed has reached a running speed and the computer tells the powertrain control module to disengage the starter. It's really obvious on my Cobalt that my key is not controlling the crank.

It does have two crank sensors, a 7x sensor on the back of the block and a 24x sensor behind the harmonic balancer. I've already checked the ground from the battery. Yes I'm sure it was changed, I'm the one doing the work

Two sensors. I'm used to 3800's. Learn something every day. Thanks.

Assuming that's the 3.4L




http://www.revbase.com/BBBMotor/Wd/DownloadPdf?id=80371

thecardoc3

imidazol97 said:

Two sensors. I'm used to 3800's. Learn something every day. Thanks.

There are many variations on this theme. The 7x sensor is the ignition control signal and the 24x was for misfire detection. A lot of the 3.8ls (3800) used a dual crank sensor which created both 3x and 18x signals from one sensor.