Mechanics

NO SPARK AFTER REPLACING CRANKSHAFT POSITION SENSOR ON A 95 .

1995 Dodge Stratus • 183 miles

It's a 95 stratus, 2.5L V6, 183XXX miles. My bf was leaving work one night when the car stalled. It hasn't started since. The engine light never popped up and it's not throwing any codes. He replaced the crankshaft position sensor and still nothing. It's cranking (turning over) but it won't start. Absolutely no spark. And it's not the fuel pump. Everyone we've talked to (my mechanic family and friends) said it's more than likley one of two things. Either the distributor took a crap or the computer is fried. So I'm coming here for one last suggestion before we junk the car.
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Ktbabyyy
December 28, 2011.



During that time period Chrysler had extremely little trouble with their Engine Computers so that's the last thing to consider.

What led him to the crankshaft position sensor? Is he aware the air gap is critical? New sensors come with a thick paper spacer glued to the end or a thin plastic rib molded onto the end to set that gap. If a used sensor is installed, the remaining part of the rib must be cut off and a new paper spacer must be used.

There are a few different ways to approach this. Most mechanics have a scanner that can display live sensor data. Watch if it shows "no" or "present" for both the camshaft position sensor, (in the distributor), and the crankshaft position sensor, and if it shows they're "in sync". If the signal is missing for either sensor, the computer won't turn on the automatic shutdown relay which powers the coil(s), injectors, oxygen sensor heaters, alternator field, and the fuel pump or pump relay. You can also watch on the scanner to see if the ASD relay is listed as "on" or "high".

If you don't have a scanner, you can also monitor the dark green / orange wire going to the ignition coil, any injector, or either small wire on the back of the alternator. Proper operation is you'll see voltage there for only one second right after the ignition switch is turned on, then that voltage will come back during engine rotation, (cranking or running). You might hear the fuel pump for that first second too. Some digital voltmeters don't respond fast enough to show that one-second blip so a test light might work better. If the voltage doesn't come back during cranking, you have a sensor or timing belt / chain problem. The cam or crank sensor is the problem only about half of the time, so just popping in a new crank sensor without having a legitimate reason to do so is inserting another variable. A shorted sensor can kill the signals from both sensors, and they both have their power and ground wires in common. A corroded splice or a cut wire is as common as a defective sensor. The circuit should be tested before throwing random parts at the problem.

Caradiodoc
Dec 28, 2011.
He explained the issues he had with the car before it died and one of his Dad's "mechanic" friends told him to check into the crankshaft position sensor. Would O'Reilly's have the scanner needed to check it out? If it's something simple we'd rather fix it than junk it. My cousin is a mechanic for Firestone and he said from what he was told he thought it could be the distributor or the computer. But he hasn't been able to look at it and you mechanics know very well that it's very hard to solve such a situation without actually looking at the car in person. Thanks for the advice. I'll pass it on and if I have more questions I'll be back. : ]

Tiny
Ktbabyyy
Dec 29, 2011.
The distributors do cause quite a bit of trouble. GM has had a pile of Engine Computer trouble in the past so a lot of mechanics assume other manufacturers did too. Out of a hundred replaced Engine Computers that legitimately solved a problem, 98 will be on a GM product.

Most auto parts stores will read diagnostic fault codes for free with an inexpensive code reader but those are not full scanners that can display live data. To put it in perspective, a scanner is like your keyboard and mouse. A code reader is like having only the up and down arrow keys and nothing else. What you can do with those two keys is about what you can do with a code reader.

Many mechanics now are buying their own scanners but they're expensive and it's more expensive to update them every few months. That's part of the reason they have to charge so much. Besides reading codes, a scanner will talk with the many computers on the car and it can command them to perform many of their functions so circuits can be tested in the shop. They can be used to change settings and adjustments, as well as display that sensor data.

Most code readers only display Engine Computer codes. Some of the more expensive ones will also access some other computers and display their codes if there are any in memory. They can erase codes too but that's it. Even the best code readers don't do what scanners do, and even the best aftermarket scanners don't do as much as the dealer's equipment, but they do it on more car brands.

It is not practical for someone to buy a scanner for them self if they only have one car. The starting cost of around $3000.00 would pay for a lot of visits to the mechanic.

Caradiodoc
Dec 29, 2011.