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Dan
Dan, Technician
Category: Chevy
Satisfied Customers: 21582
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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Chevrolet Silverado 1500 Classic LS: 99 Chevy Silverado 5.3L

Resolved Question:

99 Chevy Silverado 5.3L died as I stopped at a stop sign after highway driving. No spark
Submitted: 2 years ago.
Category: Chevy
Expert:  Dan replied 2 years ago.
If pink wires at coils have voltage then next thing to do is test crankshaft position sensor which is a common problem. Light green wire at sensor should have voltage, ground on yellow/black and blue/white should go off/on voltage..If all are good other then blue/white replace crankshaft position sensor. Let me know if you have questions, thanks.
Customer: replied 2 years ago.
More information...Bought the Silverado 1 week ago from Used car dealer so we don't know history of truck. Pulled the Crank Position sensor and checked for continuity between pins...checks 30 ohms between one end pin and center pin, 1 ohm between center pin and other end pin. Did not check voltage at the connectors while we had it out. Reinstalled the original sensor. My son (age 23) asked if the security system can cause it to die.
Expert:  Dan replied 2 years ago.
Security system causes no injector pulse...It wouldnt effect spark...Let me know if you run into questions, you can reply at any time even after you accept without any additional fee's. Thanks.
Customer: replied 2 years ago.
Resistance measurements on the Crank Position Sensor...are they normal?
Expert:  Dan replied 2 years ago.
These crank sensors are not able to be tested with resistance tests..You will need to moniter voltage on blue/white wire while cranking.
Dan, Technician
Category: Chevy
Satisfied Customers: 21582
Experience: Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
Dan and 5 other Chevy Specialists are ready to help you
Customer: replied 2 years ago.
well what would be our next step.. better yet what square are we on and where do we need to be and in between..?
Expert:  Dan replied 2 years ago.
Did you check for voltage on wire while cranking? It should vary 0-12v
Customer: replied 2 years ago.
this is damon.. (son) which wire was that? ill go check it as soon as i obtain your reply thanks
Expert:  Dan replied 2 years ago.
It is a blue/white wire should vary 0-12v while cranking...light green wire should have 12v and yellow/black should have ground. Let me know if you have questions, thanks.
Customer: replied 2 years ago.
just to confirm that on the crank sens?
Expert:  Dan replied 2 years ago.
That is correct, its located on rear of engine behind starter.
Customer: replied 2 years ago.
yep .. ok ill go check it now ill be back as soon as possible.. thanks
Customer: replied 2 years ago.
it appears we cant reach the wires while the starter is in place do you have a location we can check them from that can be accessed while the starter is installed?
Expert:  Dan replied 2 years ago.
You can access wires at PCM...yellow/black wire goes to pin 21 of PCM on connector 1..Here is a picture of PCM.

http://db.tt/SGybA3Kl
Customer: replied 2 years ago.
do the blu/wht wire(s) run to pcm as well?... and idk if you're allowed to or not but if you are may we have your # so we can pick your brain while were under the hood if not we'll make do with computer
Expert:  Dan replied 2 years ago.
They do run to computer but testing those wires at computer wont mean much so I'd start with the blue/white wire...light green is at pin 2 and dark blue/white is pin 12...we can only talk over web on this link. Let me know if you run into questions, thanks.
Customer: replied 2 years ago.
to confirm the pcm is in front of the battery driver side next to radiator near main fuse box incased in plastic cover with 2 big plugs?
Expert:  Dan replied 2 years ago.
That is correct, here is a connector diagram and another picture to help locate correct pins/wires.

http://db.tt/NrXq9RXo

http://db.tt/uQib7Ul5
Customer: replied 2 years ago.
ok checking ... will be back
Expert:  Dan replied 2 years ago.
Sounds good, thanks.
Customer: replied 2 years ago.
Two large plugs with 80 pins each on the PCM. I removed one...the one away from the battery, toward the engine, it has blue plastic inside. The other one has red. Which plug is the one that I should be concerned with? The one I took off has no receptical in pin 2, no contact.
Expert:  Dan replied 2 years ago.
You need to backprobe the connector while testing...Connector needs to be plugged in...But check voltage on pin 21 while cranking engine...If should vary voltage.
Customer: replied 2 years ago.
ok will check pin 21 while cranking.. but theres no green wire in pin 2 for some reason well theres no wire in pin 2 at all.. so what do we make of that?
Expert:  Dan replied 2 years ago.
The pin 2 thing is a little odd...Iwouldmakesure all of the other wires are the same so your sure you have the right connector.
Customer: replied 2 years ago.
Which connector is connector 1? The one I was checking out had blue plastic insulation inside the connector, The other one has red.
Expert:  Dan replied 2 years ago.
Yes blue would be correct...Lets just start with checking pin 21 if and voltage doesnt vary you will need to test wiring at crank sensor or just replace sensor depending on what you want to do.
Customer: replied 2 years ago.
ok we found out why we couldnt find a wire in pin 2, the harness and the diagram are backwards of eachother.. were headed out to check the voltage now and well get back to you asap
Expert:  Dan replied 2 years ago.
Sounds good, let me know. Thanks.
Customer: replied 2 years ago.
I need a bit of clarification. Pin 2 is LT GRN (+12 volts), Pin 21 is YEL/BLK (Ground 0 volts), pin 12 is DK BLU/WHT (varies while cranking)? There was a little confusion thru the posts.
Expert:  Dan replied 2 years ago.
That is correct, sounds like I got mixed up on a post or two and said moniter 21 for varying voltage when you need to moniter pin 12 which is dark blue/white..Let me know how it goes or what you find, thanks.
Customer: replied 2 years ago.
We got approx 12 volts steady on pin 2, ground on pin 21, and no fluctuating voltage on pin 12...actually no voltage at all. Does this mean bad sensor, or is something else possible?
Expert:  Dan replied 2 years ago.
Yep, means bad sensor...assuming power/ground between pcm and crank sensor are good...so when you go to replace make sure you have good power/ground at the sensor.
Customer: replied 2 years ago.
OK. Will you be available tomorrow for questions? TNX
Expert:  Dan replied 2 years ago.
Yep, just reply to this link and let me know how it goes. Thanks.
Customer: replied 2 years ago.
thanks
Expert:  Dan replied 2 years ago.
No problem, have a good night.
Customer: replied 2 years ago.
I need more info...is the crank shaft for this engine a forged crank?
Expert:  Dan replied 2 years ago.
Yes I believe so but I havent seen that cause any problems like this.
Customer: replied 2 years ago.
After we bought the truck we found the oil pressure to drop to practically 0. Could hear knocking in the engine. Immediately took it to local repair shop...they flushed engine and put heavier oil in and Lucus oil treatment. Local mechanic told us the knocking was in the lower end...the crank flopping around in the bearings and we might get 10k miles or more yet before it needs junked. We are considering rebuilding it. It seemed to be running fine, oil pressure OK, when it died. Is it possible the crank shifting in the bearings could hit the sensor and take it out...it wasn't broken (visibly) when we removed it?
Expert:  Dan replied 2 years ago.
I doubt it...crank sensors are just common to fail so I think thats most likely the cause...So I would start replace crank sensor before worrying about it being something else. Let me know if you have questions, thanks.
Customer: replied 2 years ago.
Damon wants to know if, after we get the rebuild done, would it be worthwhile to put hydraulic lifters in or does this engine already have hydraulic lifters?
Expert:  Dan replied 2 years ago.
It has hydraulic lifters...I would make sure that you have a good warranty with engine rebuild..I often see places do a poor rebuild job causing problems in near future then try to say its not their fault.
Customer: replied 2 years ago.
Damon has worked in an auto repair shop...not a lot of experience, but has access to tools. Is this something a DIY mechanic with a little experience should tackle? It would be reasonably inexpensive, as he can get parts at cost.
Expert:  Dan replied 2 years ago.
Its not really a DIY job but with a good handbook it would be worth a shot considering it would probably be $400 in parts if he does it himself...At a shop its probably going to be $2500 at least.
Customer: replied 2 years ago.
hello dan i need a bit of help
Expert:  Dan replied 2 years ago.
Whats going on? Thanks.
Customer: replied 2 years ago.
well i got the sens. in and now when i start it it runs like sh*t ive shut it off and restarted it like 20 times but no diff. and thats where im at ... thanks bud
Expert:  Dan replied 2 years ago.
Have you checked oil to see its overfilled with fuel? Also check spark plugs...during the no spark condition you may have flooded oil and plugs which would mean you need to change oil and spark plugs. Let me know, thanks.
Customer: replied 2 years ago.
ok ill check and get back 2 u in about 15-25 min
thanks
Expert:  Dan replied 2 years ago.
Sounds good, thanks.
Customer: replied 2 years ago.
sorry i never came back last night i lost internet for some reason.. anyway i cleand plugs again and again before i found out that my front cats were glowing .. well i took that to be my exhast being clogged idk why it would be but ok.. so i got that out of the way and that what point im at .. at the same time i noticed that the rear 4 cyl are fouling plugs and the front 4 are flooding.. i tend to assume it related but not compleatly sure so i wanted to give you an update and see what you toss back at me here.. seems almost like a rube goldberg truck lol
Customer: replied 2 years ago.
Relist: Answer came too late.
Expert:  Dan replied 2 years ago.
Are any new codes setting?
Customer: replied 2 years ago.
We don't have a code reader available presently...trying to troubleshoot using Old-school. We checked for spark, using an extra spark plug connected between the coil pack and ground. Checked only the front right cylinder. The plug will spark once when it first starts and then no spark on that plug. Apparently, there is spark on the 2 rear cylinders on each side, because it runs for a short time, then dies, and these spark plugs get fouled with carbon.
Expert:  Dan replied 2 years ago.
Replace distributor cap and rotor, let me know if that helps, thanks....Also change oil if you havent.
Customer: replied 2 years ago.
Distributor cap and rotor? Has separate coil pack at each cylinder.
Expert:  Dan replied 2 years ago.
Ok, swap around coils with aother cylinders to see if coil fires when swapping them around...If so coils are bad, then next step is testing wiring to coils. Let me know, thanks.
Customer: replied 2 years ago.
This truck is really getting frustrating. It was running fine down the highway, died when stopping at a stop sign. Crank sensor went bad, replaced it; now it tries to run on 4 cylinders; cat. converters get glowing hot; sparks once on front cylinder then no spark there; fouls the plugs that are fireing. What changed between running fine and now?
Expert:  Dan replied 2 years ago.
I would replace crank sensor again with AC delco part if thats not what you used...
Customer: replied 2 years ago.
We seemed to be getting good information from you and then I got somewhat annoyed with a couple of the last answers you provided...seemed as though you were throwing darts at a target and hit the wrong target, re: dist. cap and rotor and more than one coil pack going bad at once. My son thought the problem may be the computer so we took it to a dealership to have it reflashed...(can the computer throw things so far off it will not run correctly). They did a diagnostic and changed plugs, but did nothing to the computer...they told us the cats were clogged. We cut about 2 inches of exhaust in front of the cats and it is still running bad. We were able to limp home at about 10 mph. We get a spark from all coil packs except one...we replaced it and still no spark from that coil pack. My next theory is timing; is this a realistic diagnosis?
Expert:  Dan replied 2 years ago.
I'm out of suggestions and I did answer your orignal question and got vehicle at least running...You can open a new question at any time without any addiional fee's to see if someone else has some ideas. Thanks.
Customer: replied 2 years ago.
Relist: Other.
The history of our problem is in the previous posts. Is it possible with the symptoms described that the computer can be throwing timing off so far as to not fire on at least one cylinder and fire randomly on others? Or if timing is off, is it feasible the timing chain has jumped far enough that the computer cannot compensate?
Customer: replied 2 years ago.
Is it realistic to think, with the symptoms described, that the computer can be throwing timing off so far as to not fire on at least one cylinder and fire randomly on others? Or if timing is off, is it feasible the timing chain has jumped far enough that the computer cannot compensate?
Expert:  Dan replied 2 years ago.
If it ran good before it stalled orignal time and fact new crank sensor got it running I would replace the crank sensor with a AC Delco part.
Customer: replied 2 years ago.
Well, Dan, you were right re: replacing the crank sensor with an AC Delco Part. We had installed a Borg Warner sensor which got the truck firing, but not running right. The reason I was hesitant to buy the AC Delco was that my son had told me that the AC Delco was about 3 times the price of the Borg Warner. Finally I looked up the price myself and found that it was only about $14 more. Can you give me some clue as to why the AC Delco works and the other one does not? Logically, I conclude that the exciter rings may be defective, covered with sludge or shavings from the bearings and the AC Delco sensor may be more sensitive to pick up the pulses.
Now that we got it running, we get to repair the exhaust where we cut off the cats.
Thanks for your knowledge and the time you spent with us. Also, sorry for the post where I was beginning to doubt your expertise.
Expert:  Dan replied 2 years ago.
I believe the AC delco puts out more voltage which makes the difference...Most sensors I recommend using factory parts such as AC delco. Happy to hear it runs better now. Thanks again and let me know if ou hav questions, thanks.
Customer: replied 2 years ago.
My son pointed out that almost all parts are no longer AC Delco, but are now Delphi on this truck.
Expert:  Dan replied 2 years ago.
Delphi should be fine but i order my parts online to make sure I get AC delco if I cant find them locally.
Customer: replied 2 years ago.
One more question...is this a subscription site that charges my credit card monthly unless I cancel it, or is it a one time payment until I am satisfied my problem is solved successfully?
Expert:  Dan replied 2 years ago.
Monthly unless you cancel. thanks.

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Dan
Dan
Chevy Mechanic
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Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database