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1997 3.9L crank no start condition has me stumped

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1997 3.9L crank no start condition has me stumped

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  #1  
Old 12-06-2018, 05:16 PM
mdilly
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Default 1997 3.9L crank no start condition has me stumped

Alright guys, new here but have quite the issue. Ive exhausted myself trying to find this problem so i figured id call on yall to see if you guys might have some answers.

SO my buddy has a 1997 Dalota 3.9L V6. Truck stalled on him in a parking lot and wouldnt start back up, he had it towed to my place to have me try and fix it. SO first checked for fuel, had fuel to the rail, next checked spark, has spark on all 6 cylinders. pulled distrubutor cap to check for issues and found a good amount of corrosion and the rotor contact was bent off to one side so i replaced the cap and rotor. Still no luck. Decided to check fuel pressure, got a reading of about 50PSI so that was fine. Hooked up noid light to an injector to make sure theyre firing, all good there. Went down to the coil and checked for voltage in and also for PCM signal, all good there also. so what in the world could it be?! Its got spark and fuel, the only thing i have left is to do a compression test i and check the timing i suppose but the truck ran fine before and i figured if it was either of those there would be some symptoms beforehand. And since its getting spark the crank sensor has to be good otherwise no spark would be present. Also because there is fuel pressure, spark, and power to injectors the ASD is working. as well.

To sum all that up in bullets:

-New cap and rotor
-Spark to all 6 cylinders
-Fuel pressure at about 50 PSI
-Injectors are getting power (tested with noid light)
-Coil has power in on both wires and power out

Any input is greatly appreciated! Thanks yall!
 
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Old 12-06-2018, 06:41 PM
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Got a scanner? Plug in and see what temp the PCM thinks the engine is. Too much fuel will cause a no start, just like not enough fuel will. If you don't have a scanner, try stomping the pedal to the floor, and holding it there, while you crank.
 
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Old 12-06-2018, 07:53 PM
mdilly
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Will plug in the scanner tomorrow, doesn't have a cel light on so I figured it wouldn't make much difference but I will check in the morning
 
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Old 12-06-2018, 08:43 PM
XSubaruJeepDude
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So you are getting a fuel detonation in the cylinder but it's out of order or not timed correctly in order to sustain a running condition?
Camshaft position sensor maybe?
 

Last edited by XSubaruJeepDude; 12-06-2018 at 08:47 PM.
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Old 12-06-2018, 09:12 PM
mdilly
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It's not getting to the point of firing, there is no fuel igniting in the cylinder. I was thinking it could possibly be timing if the chain jumped a tooth, I'm trying to exhaust all possible issues before having to tear into the engine. I'm gonna test comorrssion tomorrow and double check to make sure firing order is correct. If I'm not mistaken I believe the coil wouldn't get signal from the pcm if the cam sensor isnt functioning.
 
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Old 12-06-2018, 09:14 PM
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With regards to timing, does anyone know if these engines are interference engines?
 
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Old 12-07-2018, 12:19 AM
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Originally Posted by mdilly View Post
With regards to timing, does anyone know if these engines are interference engines?
I believe piston-valve contact is possible, but it would take some doing. I'm not sure how big the quench area is at TDC, but I believe the heads are something like 60cc over the 3.58 stroke (forget the 3.9/5.2 stroke, but it's less with I believe the same rod) and 9.5:1 spec compression would be 60cc+40ci divided 9.5, or 43.5ci/9.5 = 4.21 ci, subtract out the head, leaves 0.7 ci. Divide that by 3.88 bore area equals 0.18 inches between top of piston and bottom of head. Subtract out the 039 head gasket, leaves piston 0.141 in the hole.

Not exact, the actual formula is WAY more involved. But it gives you an idea.
 
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Old 12-07-2018, 11:26 AM
mdilly
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Would I be correct in assuming if there is spark to the plugs that the cam position sensor is working? If there wasn't a signal from that then the coil wouldn't get a signal from the computer to distribute current to the distributor correct?
 
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Old 12-07-2018, 11:36 AM
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Just threw on the scanner and doesn't read any fault codes, the cat, o2 and htc bubbles are red though and system status is yellow.
 
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Old 12-07-2018, 11:52 AM
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Just hooked up the scanner and got no codes from the computer. Got red lights on cat, o2s, and htr for emissions though, don't believe the emissions would cause a no start condition. Could a bad pickup sensor cause a no start? Or would the fact that I have spark conclude that the pickup coil is good?
 
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