turns over but won't crank - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Montagne · 11-12-2016, 03:59 PM

Ok, Ill start with a little back ground. When I got the truck it would crank but when i gave it gas it would bog down and die. I have drained the tank, replaced the fuel pump, and replaced the fuel filter. Now she turns over but will not fire. I have checked to make sure the pump is receiving and sending gas and it appears to be working just fine. What am I missing?

Willie 66 · 11-12-2016, 04:54 PM

I think most of the time, starting problems deal with timing. My problem was a lot like yours - it would fire a few times but never actually start. Turned out to be way retarded timing. Also check spark and compression. Harbor Freight has some cheap tools for garage hobbyists like me that do this stuff once every 26 years.

leonphelps · 11-12-2016, 07:10 PM

buy a spark tester at harbor freight. $7. Remove a plug wire, install tester, crank and look for it to glow. It will tell you if there is spark. You need spark, compression and fuel.

Also, did you smell the fuel? Stale gas will not fire.

Brad54 · 11-12-2016, 07:27 PM

Actually, you don't need to buy a tool to check for spark: Just pull a plug, and with the plug wire still on it, hold the threaded part of the plug to the exhaust manifold and crank the engine--if you see a spark, you've got spark. If not, you know where your problem probably is.

I always put an inline glass fuel filter between the fuel pump and the carb, as a diagnostic tool for the inevitable "damn, why won't it run now?!" It immediately eliminates (or confirms!) one problem.

This sounds like an over-simplification of things, but it's not:
An engine needs fuel, compression, spark and timing. If it has those four things, it can't help but run... it has no choice. So if it isn't running, you only have to check four things.
An old man told me that.
He also told me "90-percent of all fuel problems are electrical." And I have yet to prove him wrong, on either.

-Brad

Slow Build · 11-12-2016, 11:44 PM

Have you tried starter fluid? That will give you an idea if it's a fuel problem.

urmyboyblue · 11-13-2016, 10:11 PM

Check for spark- it it hasn't been tuned up recently, replace the cap and rotor (and points if it has them. Also new plugs and wires won't hurt.

Turn the engine over and see where the timing is at. Static- set it for around 4 degrees to get it to crank.

Check for fuel at the carb (loosen the line and crank the engine over to see if fuel comes out)- some carbs have a fuel filter built into them where the fuel line connects, clean it if there is one and you haven't.

If fuel is getting to the carb, look down the throat of the carb without the engine running and pump the throttle with your hand. You should see gas entering the carb. If not, either the carb is not getting gas or the accelerator pump is bad. It is also possible that the carb needs rebuilding- some gaskets may have shrunk and allows gas to run into the intake- emptying the fuel bowl and depriving the accelerator pump of having fuel to spray into the engine.

Check the choke- see if it is working.

The problem is probably ignition or fuel. However, check to see if the distributor is turning as well. If you broke a cam or timing chain, it won't turn and nothing will crank.

11-12-2016, 03:59 PM	#1
Montagne Registered User Join Date: Jul 2016 Location: Birmingham,Al Posts: 10	turns over but won't crank Ok, Ill start with a little back ground. When I got the truck it would crank but when i gave it gas it would bog down and die. I have drained the tank, replaced the fuel pump, and replaced the fuel filter. Now she turns over but will not fire. I have checked to make sure the pump is receiving and sending gas and it appears to be working just fine. What am I missing?

11-12-2016, 04:54 PM	#2
Willie 66 Registered User Join Date: Mar 2014 Location: Houston, TX Posts: 44	Re: turns over but won't crank I think most of the time, starting problems deal with timing. My problem was a lot like yours - it would fire a few times but never actually start. Turned out to be way retarded timing. Also check spark and compression. Harbor Freight has some cheap tools for garage hobbyists like me that do this stuff once every 26 years.

11-12-2016, 07:10 PM	#3
leonphelps Registered User Join Date: Oct 2016 Location: Pa Posts: 69	Re: turns over but won't crank buy a spark tester at harbor freight. $7. Remove a plug wire, install tester, crank and look for it to glow. It will tell you if there is spark. You need spark, compression and fuel. Also, did you smell the fuel? Stale gas will not fire.

11-12-2016, 07:27 PM	#4
Brad54 Registered User Join Date: Aug 2006 Location: Athens, Georgia Posts: 1,456	Re: turns over but won't crank Actually, you don't need to buy a tool to check for spark: Just pull a plug, and with the plug wire still on it, hold the threaded part of the plug to the exhaust manifold and crank the engine--if you see a spark, you've got spark. If not, you know where your problem probably is. I always put an inline glass fuel filter between the fuel pump and the carb, as a diagnostic tool for the inevitable "damn, why won't it run now?!" It immediately eliminates (or confirms!) one problem. This sounds like an over-simplification of things, but it's not: An engine needs fuel, compression, spark and timing. If it has those four things, it can't help but run... it has no choice. So if it isn't running, you only have to check four things. An old man told me that. He also told me "90-percent of all fuel problems are electrical." And I have yet to prove him wrong, on either. -Brad __________________ '61 Suburban daily driver: off the road due to 180-pound 8-pt buck! '62 K-10 long-step project '61 C30 Camper, aka "Valdez" There's no cool like Old School

11-12-2016, 11:44 PM	#5
Slow Build Registered User Join Date: Sep 2009 Location: California Delta Posts: 2,163	Re: turns over but won't crank Have you tried starter fluid? That will give you an idea if it's a fuel problem. __________________ Name: Rich Current Ride: 1964 C-10 Short Fleetside Daily Driver: 2005 GMC crew cab short fleetside /2001 Chevy Tahoe Past GM Trucks: 1959 GMC short stepside 1968 GMC short stepside-4x4 1973 Chevy short stepside 1989 Chevy short fleetside-reg cab 1993 Chevy short fleetside-Xcab 2002 Chevy short fleetside-Xcab Save the dinosaurs, use synthetic oil.

11-13-2016, 10:11 PM	#6
urmyboyblue Registered User Join Date: Feb 2015 Location: Montevallo, AL Posts: 272	Re: turns over but won't crank Check for spark- it it hasn't been tuned up recently, replace the cap and rotor (and points if it has them. Also new plugs and wires won't hurt. Turn the engine over and see where the timing is at. Static- set it for around 4 degrees to get it to crank. Check for fuel at the carb (loosen the line and crank the engine over to see if fuel comes out)- some carbs have a fuel filter built into them where the fuel line connects, clean it if there is one and you haven't. If fuel is getting to the carb, look down the throat of the carb without the engine running and pump the throttle with your hand. You should see gas entering the carb. If not, either the carb is not getting gas or the accelerator pump is bad. It is also possible that the carb needs rebuilding- some gaskets may have shrunk and allows gas to run into the intake- emptying the fuel bowl and depriving the accelerator pump of having fuel to spray into the engine. Check the choke- see if it is working. The problem is probably ignition or fuel. However, check to see if the distributor is turning as well. If you broke a cam or timing chain, it won't turn and nothing will crank.



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