OK, I finally found some time to do a little more diagnosis. And, I received the Elm SCAN 5 OBD-II tool, which I hooked up to the truck.

Upon establishing a connection between the truck and the laptop with Elm SCAN, I tried running the truck, and it ran for almost a minute andthen died. The software on the laptop reported data from the engine, refreshed 2x every second or so. I noticed that the engine rpm was successfully being reported to the computer while the enginewas running.

The tool reported NO DTC (diagnostic trouble codes), even though there are several DTC's related to the crank sensor (see later).

Then, the engine died, and I noticed that the engine rpm while crankingwas 0 rpm.

I put 5 gallons of fuel in the tank, and noticed that the fuel guage increased from 2/3 to 3/4 more or less, so I'mthrowing away the idea that thereis a lack of fuel in the tank.

Then, I performed a spark test. NO SPARK.

And, then, I came to the following hypothesis, that I'm not entirely sure of.If the crankshaft position sensor is not sending a propersignal to thePCM (Powertrain control module, the brain), then evenwhen the engine is crankingthe PCM thinks that the engine is not moving, and will not generate a spark.

Then, I consulted my Haynes manual and found a test procedure with multimeter that Ifollowed. The first step was to determine whether voltage was coming from the PCM, and I got a strong 5.15 volts. The second step was to measure voltage from the sensor. Iused safety pins to pierce the insulationon the two applicable wires and to provide a point to which to attach alligatorclips,confirm 0 ohms between pins and other side of wiringconnector (checkingconnection at pins) [any suggestions on whether there is a tool to do this a little more reliably and with less damage to the wire insulators?] and then measured voltage while slowly rotating the engine with a wrench on the crankshaft pulley bolt.My manual describes that the crankshaft position sensor should generatesabout 0.3 volts when themetal of the flywheel isn't notched, and then spike to 5 volts when there is a notch in the flywheel, which I think happens 8 times perrevolution (from diagram in manual). And while I did measure variation in the voltage, the amount of voltage seemed substantially low, as I measured only about 0.03 and 0.3 volts respectively. So, my test confirmsto me thehypothesis that the crank sensor is not working properly.

The crank sensor will cost me about $110 at Napa. Before buying, I'd be interested tohear from any of you whether you think I should check something else before purchasing it.Also, any thoughts on whethera crank sensor can be repaired?

Thanks for all the suggestions to date - I'll post my results and keep you all, and future readers, informed as to whether I am successful.

 

welcome to DF.. your diagnosis sounds right... 2 things will kill a motor... the IAC valve being dirty or deadwill cause it to die at idle, and the crank sensor... swap it out and let us know how it goes. $110 sounds high though for the sensor, did you shop around?

 

so i'm probably off topic here but i figure its having almost the same type of problem. so the other day i was parking my dad's truck in the garage and for no reason it died out on me while i was in reverse so i popped it in nuetrul and started the truck. which started up ok the truck has about 115,000 miles on it or so. before the warranty expired the fuel pump was replaced and so where the cylinder heads but that was when the truck had about 64,200 something miles. it hasn't had a tune up since then. do you guys think i should do a tune up first before suspecting the fuel pump possibley going bad? and another thing i noticed was whenever i use the turn signal/hazards the light will flash for a few seconds and then freeze and the turn signal/hazard light will stay on until i turn them off. i'm thinking maybe the relay is going bad but i could be wrong. any suggestion on how to fix this? thanks.

 

Thank you Steve for your note of confirmation, which gives me the confidence to purchase the part. I did find the part available online for about $79 shipped from RockAuto, so thanks also for the suggestion to check prices....I'm sort of a backyard mechanic, so sometimes, when I've been able to get to the root of a problem, I "award" myself by not worrying about the prices of the parts I buy. But, with careful shopping, there's no reason not to save even more. Thanks again to you, and to everyone at DF. I'm thrilled to have found you.

 

Based on my diagnosis and confirmations suggested by others, I'd say the best first test you can quickly make to determine whether the problem might be with the crankshaft position sensor is to run a spark test. A tool for such test is available at parts stores for around $10, and is a great tool to have in the toolbox.

If you have a spark, it's NOT the crank position sensor.

If you don't have a spark, it MIGHT be the crank position sensor.

Then, if no spark, you'll have to dig further.

 

ok i'll give that a try first and see what happens.

 

so i bought the tester and tried it out. and yes there was spark. what else do you think it could be?

 

Well, if you have a spark, I'd say it's likely to be a fuel problem....in a fuel injected vehicle, I'm not sure what would be the easiest way to check for fuel....get a manual for your vehicle and follow the procedures....the fuel pump should make a noise when you turn on the ignition....if it doesn't, maybe there's a problem with the pump. If not, it could be a clogged fuel filter? Did you check the vehicle for diagnostic trouble codes? if you have a reader, this might pinpoint the problem. If not, see if you can borrow from friend or shop, or tow vehicle to shop...

cheap code readers are avail. on eBay for about 30-40 bucks.

 

Well, I got the crank sensor from Rockauto. quick ship. And, installed it this morning. Truck runs fine and seems like all is well. However, I had one follow up question about these crank sensors. I noticed that on the one I took out that there was a substantial amount of corrosion on the sensor end of the part (nearest the flywheel), whereas the new part had two clean metal contacts. I am wondering whether I could have fixed the problem simply by sanding off the metal contacts on the sensor. Does anyone know how these things work, and whether this would be a solution with merit? I imagine, but don't know that the sensor involves some sort of magnet on the inside that moves when near the flyweel but then is pushed by spring away from flywheel when notch passes. Not sure, but magnets, as far as I know, don't generally fail....Any thoughts?

 

79 is even high for a crankshaft sensor. autozone has one for my 97 dakota for like 45. nothing near that. i'm having similar problems, but it's not the sensor. i did the exact same testing by rotating the engine manually, and recieved up to 5 volts. i still cant figure out the problem. any other idea's?