1995 Cadillac STS Engine Wont Crank

LANE68

MEMBER
1995 CADILLAC STS
V8
FWD
AUTOMATIC
147,000 MILES

I changed the EGR valve out and afterwards, I cranked the car and it backfired. I have not been able to get it to start now. I put the old EGR back on and it still will not start. The plugs have good spark and plenty of fuel pressure. ANY idea why it will not start now?

Thanks
Lane Eason

3 Replies

OBXAUTOMEDIC

MECHANIC
3,711 POSTS

Hi Lane,

Here is a few thing to check....

Test Electrical System Voltage. The best way to test for electrical system voltage is use a voltage meter. Attach the voltmeter leads to the positive and negative terminals of the battery. To check a battery surface voltage remove the positive terminal protective cover. Connect the +positive side meter lead (red) to the positive side battery terminal. Connect the - negative (black) side meter lead to the negative battery terminal. With the vehicle not running and the car sitting over night the battery voltage should be between 12.4 and 12.6 volts. To test the system without a volt meter activate the headlights, if they illuminate brightly the electrical system probably has sufficient voltage. If the headlights are dim or not working the battery charge is low or the battery has failed and needs replacing.

Check Battery Cable Terminals: The starter circuit of your car is a basic electrical circuit and is subject to corrosion and its effects. The first sign that corrosion is effecting the start is when you activate the ignition key to the start position the whole electrical system of the car shuts down. Once the connection has cooled the circuit will reconnect and car electrical will return. Inspect the battery terminals for corrosion but use caution. These deposits are corrosive, and are by-products of a normal battery charge and discharge function. While wearing protective goggles and clothing, use a garden hose to rinse the battery and surrounding area completely. This will dilute the acid to a non-corrosive state. You can also sprinkle baking soda to help neutralize the battery acid. Use a wire brush on the battery terminals to clean thoroughly and reassemble, recheck charging system as needed. If the corrosion is excessive the battery cables will need to be replaced, battery acid migrates down the cable strands and deteriorates the cable internally.

Starter Voltage/Amperage Draw Test. Turn the headlights on and observe, then activate the ignition key to crank the engine over. If the headlights stay bright the electrical circuit is not connected, therefore no voltage drop. A popular reason for this is the winding inside the starter has shorted or the starter armature brushes have worn out and replacement is recommended. If headlights dim way down it means your battery is weak and needs either replacement or recharge. As a rule of thumb, a typical car battery will last three to four years before replacement is needed.

D. Check Neutral Safety Switch/Clutch Safety Switch. A neutral or clutch safety switch is used to disengage the electrical circuit from the ignition key to the starter motor as a safety device. Automatic transmission vehicle gear selector needs to be either in park or neutral before the engine will crank. If the gear selector is in any other gear sections the engine will not crank over. A standard transmission vehicle clutch peddle needs to be fully depressed before the engine will crank over. To test this circuit a automotive test light is needed. Attach one end of the test light to engine ground and the other end at the starter trigger terminal of the starter solenoid. The test light should illuminate when the ignition switch is activated (crank engine over). If the test light illuminates the starter motor/solenoid has failed and needs to be replaced. If the test light does not illuminate suspect a neutral safety switch or clutch safety switch. A wiring diagram is needed to trace power from the ignition switch through the safety switch and down to the starter solenoid. Replace failed components as needed and recheck system.

For more check out the link below

https://www.2carpros.com/first_things/car_will_not_crank.htm

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Monday, October 20th, 2008 AT 7:45 PM

OBXAUTOMEDIC

MECHANIC
3,711 POSTS

Hi Lane,

First off Please post replies here in forum.

Second I need to apologize - I was working on a couple different thing when I answered your post and I answered it with No Crank meaning the vehicle won't turn over.

So, here is the correct info for your problem of will turn over but not start......

And I know you have done some of these.....

Step 1 - Anytime you have a problem with electronically controlled components such as an engine, transmission, ABS brake, or SRS (supplemental restraint system, Air Bag) inspect all fuses using a test light and check the under hood power distribution center and under dash fuse panels. If all fuses test ok continue to the next step.

Step 2 - To check for problems with electronically controlled components such as an engine, transmission, ABS brake, or SRS (supplemental restraint system, Air Bag) and the fuses test ok a trouble code scan is needed to identify any system trouble. Use a simple scanner tool to retrieve trouble codes and see if they relate to the specific problem, like a crank angle sensor failure code. If the trouble code present does not pertain to the immediate problem like a EVAP code ignore it until a later time, after the car is running. The reason we repair non-related codes after the engine is running is because sometime false codes can be triggered by the engine not running. Once the engine is running again the code present might cycle and turn itself off. You might say "if the engine doesn't run shouldn't it have a trouble code?" Sometimes conditions occur that will not be detected by the computer, example: if the fuel pump fails the computer can not detect the failure, so the engine doesn't start and the computer thinks everything is ok with no codes. If no trouble codes are present proceed to the next step.

Step 3 - Determine if the engine has compression, this can be done a number of ways but the most complete method is to perform a compression check. Remove the spark plugs and perform a compression test on one cylinder. If one cylinder has compression then the remaining cylinders usually will be close to the same. Crank the engine over about 5 seconds, normal compression readings should be between 125 psi and 160 psi on each cylinder. If no or little compression exists additional tests will be needed. The most popular reason for an engine to lose compression is a timing belt or timing chain fails. If low or no compression exists remove the oil fill cap and observe camshaft rotation when the engine is cranked over. If no rotation exists the timing belt or chain has failed. If your engine has a timing belt and you can not see the camshaft easily remove the upper bolts to the timing cover and gain visual access to the belt, recheck cam rotation by cranking the engine over. Sometimes a timing belt or chain can jump causing the camshaft to loose correlation with the crankshaft and therefore causing low compression. The best test for this condition is to remove the timing belt/chain cover and inspect timing marks. If the compression is ok proceed to next step.

Step 4 - Test the ignition system output, ignition systems can vary in configuration but operate on the same principal. Ignition systems can consist of a coil, pick up coil, crank angle sensor, cam angle sensor, spark plugs, spark plug wires, distributor cap, ignition rotor and a distributor and any variations of these components. An ignition coil is a voltage stepper coil that transforms a low voltage (12 volts) signal into tens of thousands of volts needed to jump the gap of the spark plug. This coil is activated by an ignition module triggered by using the camshaft/crankshaft angle sensor, timing is adjusted by the ECM (computer).

Follow the following link for more info, Diagrams and Video.......

https://www.2carpros.com/first_things/car_cranks_but_wont_start.htm

Again Sorry for the Mistake

Mark

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Wednesday, October 22nd, 2008 AT 7:02 PM

LANE68

MEMBER
2 POSTS

Hi Lane,

First off Please post replies here in forum.

Second I need to apologize - I was working on a couple different thing when I answered your post and I answered it with No Crank meaning the vehicle won't turn over.

So, here is the correct info for your problem of will turn over but not start......

And I know you have done some of these.....

Step 1 - Anytime you have a problem with electronically controlled components such as an engine, transmission, ABS brake, or SRS (supplemental restraint system, Air Bag) inspect all fuses using a test light and check the under hood power distribution center and under dash fuse panels. If all fuses test ok continue to the next step.

Step 2 - To check for problems with electronically controlled components such as an engine, transmission, ABS brake, or SRS (supplemental restraint system, Air Bag) and the fuses test ok a trouble code scan is needed to identify any system trouble. Use a simple scanner tool to retrieve trouble codes and see if they relate to the specific problem, like a crank angle sensor failure code. If the trouble code present does not pertain to the immediate problem like a EVAP code ignore it until a later time, after the car is running. The reason we repair non-related codes after the engine is running is because sometime false codes can be triggered by the engine not running. Once the engine is running again the code present might cycle and turn itself off. You might say "if the engine doesn't run shouldn't it have a trouble code?" Sometimes conditions occur that will not be detected by the computer, example: if the fuel pump fails the computer can not detect the failure, so the engine doesn't start and the computer thinks everything is ok with no codes. If no trouble codes are present proceed to the next step.

Step 3 - Determine if the engine has compression, this can be done a number of ways but the most complete method is to perform a compression check. Remove the spark plugs and perform a compression test on one cylinder. If one cylinder has compression then the remaining cylinders usually will be close to the same. Crank the engine over about 5 seconds, normal compression readings should be between 125 psi and 160 psi on each cylinder. If no or little compression exists additional tests will be needed. The most popular reason for an engine to lose compression is a timing belt or timing chain fails. If low or no compression exists remove the oil fill cap and observe camshaft rotation when the engine is cranked over. If no rotation exists the timing belt or chain has failed. If your engine has a timing belt and you can not see the camshaft easily remove the upper bolts to the timing cover and gain visual access to the belt, recheck cam rotation by cranking the engine over. Sometimes a timing belt or chain can jump causing the camshaft to loose correlation with the crankshaft and therefore causing low compression. The best test for this condition is to remove the timing belt/chain cover and inspect timing marks. If the compression is ok proceed to next step.

Step 4 - Test the ignition system output, ignition systems can vary in configuration but operate on the same principal. Ignition systems can consist of a coil, pick up coil, crank angle sensor, cam angle sensor, spark plugs, spark plug wires, distributor cap, ignition rotor and a distributor and any variations of these components. An ignition coil is a voltage stepper coil that transforms a low voltage (12 volts) signal into tens of thousands of volts needed to jump the gap of the spark plug. This coil is activated by an ignition module triggered by using the camshaft/crankshaft angle sensor, timing is adjusted by the ECM (computer).

Follow the following link for more info, Diagrams and Video.......

https://www.2carpros.com/first_things/car_cranks_but_wont_start.htm

Again Sorry for the Mistake

Mark[/quote:7dd5560741]

Thanks Mark.

We have already performed some of the checks you have suggested, however, you did mention some things that we have not checked. We will check those and let you know how it goes.

Thanks again
Lane

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Thursday, October 23rd, 2008 AT 9:57 AM