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'98 1500 5.2L no start, no spark, plugs dry

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'98 1500 5.2L no start, no spark, plugs dry

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  #1  
Old 03-06-2018, 08:52 PM
5mall5nail5
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Default '98 1500 5.2L no start, no spark, plugs dry

Hey all - have my ol' reliable '98 1500 4x4 5.2L I barely drive. Just use for Home Depot runs and construction errands around the house. Used it just a few weeks ago to put basement demo/debris in the bed to run to the dump but never got over there so I just parked it in the street with the bed full. Now we're expecting snow so I want to move it off the street and no start.

She cranks strong - good charge on the battery, etc. I put a timing light on the drivers side front plug wire - no flash while cranking. Tried another timing light. Same deal. Went to Autozone and grabbed a Duralast coil in a hail mary and replaced it - nada. Pulled passenger front spark plug - bone dry. It's low on fuel but ran fine last I shut it off and like I said I've got no spark. I do hear the fuel pump hum/buzz when I turn the key. Plug wires aren't in very bad shape.

So considering I am not seeing spark based on timing light (two of them - doubt that the connection would be bad on both) and the #2 plug is bone dry, what could the culprit be? I had some cracked wiring at the PCM but I manage to tape it up and salvage it - it drove a few weeks ago but now won't start and hasn't moved since. I am not super familiar with these trucks - mine has been pretty damned reliable overall. Any thoughts are appreciated - going to have to try and push it into the driveway for now

Oh one last thing - I put a cheap code reader I have on it - turned key to the run position and hit "READ" - no codes.

Thanks all!
 
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Old 03-06-2018, 09:45 PM
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I would suspect a bad crank sensor...... That would account for no spark/no fuel...... Does the fuel pump run while you are cranking the engine?
 
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Old 03-06-2018, 10:04 PM
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Originally Posted by HeyYou View Post
I would suspect a bad crank sensor...... That would account for no spark/no fuel...... Does the fuel pump run while you are cranking the engine?
It's hard to tell - I am by myself and cranking the truck is pretty loud. I read that a bad crank sensor would be an injection issue but the truck would spark?
 
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Old 03-07-2018, 07:16 AM
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Nope. Crank sensor tells the pcm the crank is turning. That information is used for ignition timing. Cam sensor (pick-up coil in distributor) is used for injector timing. But, if the PCM doesn't see the engine turning (via crank sensor), it won't fire the injectors either.
 
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Old 03-07-2018, 09:23 AM
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Originally Posted by HeyYou View Post
Nope. Crank sensor tells the pcm the crank is turning. That information is used for ignition timing. Cam sensor (pick-up coil in distributor) is used for injector timing. But, if the PCM doesn't see the engine turning (via crank sensor), it won't fire the injectors either.
Ok cool thanks. Do you know if the crank sensor is a hall effect type or VR? Another question is - in the wiring diagram in the service manual, how do I locate each of the three connectors at the PCM? I just want to make sure all of the wiring is in tact but to be honest it was hard to sort out the diagram. I have a yellow wire with a black stripe with a crack in the insulation on the connector to the right of the middle/white one (when looking at the PCM from the passenger wheel). On other cars I've worked on yellow has been +5vdc supply for sensors. Thinking if the crank is a hall sensor and this wire is cracked/split... maybe the vref is not getting to it and other sensors.
 

Last edited by 5mall5nail5; 03-07-2018 at 09:26 AM.
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Old 03-07-2018, 04:41 PM
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Yep, Hall affect switch. It generates a square wave, I do believe...... at least, it is supposed to.

I am showing a violet/white wire as vref..... connector 1, pin 17. C1 is closest to the engine.
 
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Old 03-11-2018, 02:09 PM
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And... a few more...



They got me for 4 spark plug wires, the crank sensor... and something else - it's a grey connector near the drives side valve cover with 3 wires in a flat cable:



Any help ID'ing that connector above? I was able to pull/cut the loom around the small chewed off section coming off the engine harness and I believe it's where the crank sensor pigtail should connect:



Now I have to figure out how to lengthen that and repair it. Sigh.
 
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Old 03-11-2018, 03:44 PM
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Have you checked your relay fuse? I had the similar thing happen to me and after replacing the plugs,plug wires and tps I found out it was a relay fuse and my truck fired right up after I changed it
 
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Old 03-11-2018, 04:49 PM
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Check the images above lol - no reason to check anything, I got rodent chew damage.

Anyone able to help with the purpose of that grey 3-wire flat cable connector in the third image?
 
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Old 03-11-2018, 04:58 PM
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How about a shot a bit further away. I don't recognize that one at all....
 
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