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08-21-2017, 03:30 PM
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#1 |
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Registered User
Join Date: Feb 2016
Location: Texas
Posts: 52
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Truck wont start
Recently purchased a 72 truck and cant get it to start. When I bought the truck the PO said it would start but he didn't go through the ignition, I think he just touched some wires together to get it to crank. I never actually heard the truck crank up and run but guy said it would crank up. At the time I really didnt care if it cranked because I was going to replace the engine anyway and didnt plan on messing with it for a while.
I decided to just make it a weekend driver for the time being so I had a buddy come over to look at it and we were able to get it wired back to the ignition but when we go to crank it, the truck engine turns over but never sounds like it wants to start, the engine just keeps turning over. Based on the PO saying the engine cranks, is there anything else im missing that would keep the truck from cranking if all the plugs are good, has gas in it...etc? |
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08-21-2017, 04:30 PM
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#2 |
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Registered User
Join Date: Aug 2017
Location: White Lake, Mi
Posts: 3
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Re: Truck wont start
It needs power to both the starter and the coil. If the wiring was monkeyed with, I would start by checking the + side of the coil to see if it has voltage. If it doesn't, start working down the chain in the wiring to figure out why. It will be important to know not only if it has voltage, but how much. A stock 72 ignition most likely would only have about 9 volts if it had a ballast resistor. A later HEI ignition (coil integrated to distributor) wouldn't need a ballast resistor and should have 12 volts at the positive side.
You can probably find a wiring schematic online. |
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08-21-2017, 04:41 PM
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#3 |
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Registered User
 
Join Date: Dec 2012
Location: North Carolina
Posts: 4,989
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Re: Truck wont start
I'd start with the wiring. Then go through the typical Gas,air and spark
__________________
1971 GMC Sierra 1959 GMC 100 |
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08-21-2017, 05:21 PM
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#4 |
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Who Changed This?
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,081
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Re: Truck wont start
Does it have a wire running from the starter "R" terminal (points ignition) to the coil? It won't start if that wire is disconnected. That is something to check after you check if you are getting power to the coil when the key is just "ON".
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
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08-21-2017, 07:28 PM
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#5 |
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Registered User
Join Date: Jul 2013
Location: LI, NY 11801
Posts: 1,140
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Re: Truck wont start
Cranking is #1
#2 Spark? Y/N #3 Compression? Y/N #3a Is compression roughly equal in all cylinders? #4 Fuel? Y/N
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1970 C10 8' Fleetside, L6 250, 3 on the Tree. The most basic of pickup trucks! |
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08-22-2017, 11:22 AM
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#6 | |
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Registered User
Join Date: Apr 2011
Location: Fairview Park, Ohio
Posts: 1,027
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Quote:
I would first put a timing light on it to check spark. Posted via Mobile Device |
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08-22-2017, 10:15 PM
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#7 |
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Moderator
 
Join Date: Jun 2017
Location: Cherryville, NC
Posts: 2,153
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Re: Truck wont start
Some basic info about the truck will help greatly...
6 cyl or V8 ? Auto trans or manual ? Clean Fuel source? Cylinder compression values? Check oil level in engine and water level in radiator. Dont trust the in place wiring... If this is an auto, make sure it is in Park, handbrake on and if possible, jack the rear wheels off the ground and put stands under the axle to keep tires off the ground. 1/ Fully charged battery. 2/ Find solenoid wire on starter and connect a jumper wire to it long enough to reach battery positive. 3/ Touch jumper lead to battery positive, does motor spin over? Yes or No ? Yes, proceed to 4, No, replace starter or solenoid. 4/ If it spins over, remove spark plug on cylinder #1. 5/ Find coil on engine, there will be two small wires, one goes to distributor, one goes to wire loom...connect second jumper lead to wire that comes from wire loom...to battery positive... 6/ Place spark plug into lead for Cyl #1 and ground the plug to an engine surface. 7/ Crank engine again and check for spark on #1 cyl, Has spark Yes or No? (Remove coil jumper once you have done this test). If all yes proceed to 8/ if No, check distributor for bad points or rotor and cap or broken drive shaft etc. 8/ Bring #1 cylinder to TDC on compression...check distributor is set to point rotor at #1 terminal on cap... 9/ Check firing order 6 cyl...153624 8 cyl 18436572 both rotate clockwise. 10/ Use Timing mark to set Cyl #1 to 7 degrees BTDC static. 11/ Fuel...check carb has fuel, push down on throttle and have someone check gas shoots out of accelerator pump jets. No fuel...better fix that.... 12/ If you have Spark and Compression and Fuel you can put the coil jumper back in place and jump it to start... If all the above is correct, there is no reason why it wont start. Once it does start, to stop it, remove the coil jumper wire. Once you get it running, start working backwards thru the wiring, to get it to crank on the key (usual issue there is bad connector on back of ign switch) to bad coil feed ballast wire lead (usually 9 volts only at coil)... If its an auto trans truck, sometime the neutral start switch acts up or is bad. Above all, have fun and learn as you go...  
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