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Old 09-09-2015, 10:19 PM   #1
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Car hard to start when hot

Hey folks,

So I've had the problem with my car being hard to start sometimes when its hot, not everytime but every other day, it's quite embarrassing. In the morning the car starts perfectly, however if i drive it for a while sometimes it cranks for 3-4 seconds and even when it starts it really struggles, meaning that the rpms only go up really slowly and only go up to like 1200. I have replaced the starter 3 months ago when i did my longtube headers and i also got a heat shield for it, so i don't think that it is heat-soaking. Any ideas on what could be causing it? Usually other cars are harder to start when its cold, mine is the opposite lol. So yeah if anyone knows what it could be or what parts to check please let me know, I'd appreciate it.


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Old 09-10-2015, 12:13 AM   #2
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Could it be a loss of compression that goes away with oil pressure?
Try doing a dry compression test with the engine cold. Then add a small amount of oil to each cylinder and do the compression test again. If the pressure readings are not close, the rings are going bad. If both sets of numbers, wet and dry, are low, it is usually the valves.



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Old 09-10-2015, 05:11 AM   #3
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Quote:
Originally Posted by richie895 View Post
Could it be a loss of compression that goes away with oil pressure?
Try doing a dry compression test with the engine cold. Then add a small amount of oil to each cylinder and do the compression test again. If the pressure readings are not close, the rings are going bad. If both sets of numbers, wet and dry, are low, it is usually the valves.



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Will do. What should the reading be and how far off is too much? Thanks.


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Old 09-10-2015, 06:09 AM   #4
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When you say it cranks for 3 to 4 seconds, does it sound like its cranking fast but know ignition? or cranking slowly, like the engine is hard to turn? for example, you in the morning it may be a "RUHRUHvrooooom" and the engine is started. when its hot, would you describe it as "Ruuuhhh....ruuuh....ruuuhruuuhh....RuuuuhVRooooom" or a long "Ruhruhruhruhruhruhruhruhruh" sound?


Does that make any sense?
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Old 09-10-2015, 06:13 AM   #5
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Car hard to start when hot

Quote:
Originally Posted by fenixignition View Post
When you say it cranks for 3 to 4 seconds, does it sound like its cranking fast but know ignition? or cranking slowly, like the engine is hard to turn? for example, you in the morning it may be a "RUHRUHvrooooom" and the engine is started. when its hot, would you describe it as "Ruuuhhh....ruuuh....ruuuhruuuhh....RuuuuhVRooooom" or a long "Ruhruhruhruhruhruhruhruhruh" sound?


Does that make any sense?

---------- Post added at 06:09 AM ---------- Previous post was at 06:09 AM ----------

When you say it cranks for 3 to 4 seconds, does it sound like its cranking fast but know ignition? or cranking slowly, like the engine is hard to turn? for example, you in the morning it may be a "RUHRUHvrooooom" and the engine is started. when its hot, would you describe it as "Ruuuhhh....ruuuh....ruuuhruuuhh....RuuuuhVRooooom" or a long "Ruhruhruhruhruhruhruhruhruh" sound?





Does that make any sense?

In the morning it cranks for maybe a second and it revs up to 1900 and then back down to idle, a perfect start. Now sometimes when the engine is hot it cranks fast(ruhruhruhruhruhruhvroom lol) for like 3 seconds and then it starts really weakly, the rpms seem to struggle to climb to 1100 just a weak start in general. It does not happen everytime when its hot, but here and there it will struggle.


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Old 09-10-2015, 06:27 AM   #6
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Ah ok, i see what your sayin. first thought i would have is fuel issue. whether its a pressure regulator or the pump itself. Im guessing it drives just fine in traffic on a hot day?

The only things the starter would do wrong is not engage properly, if at all, or engage and not let go. Once it spits the gear out and spins the flywheel, the engine does the rest, so a slow start wouldn't be a starter issue. It could be a battery issue involving the heat, but it doesn't sound like a weak start (before ignition).

you may wanna run some tests with starting fluid to try to figure out if its a fuel or spark issue. something is lagging somewhere and doesn't wanna wake up when its hot. it could also be as simple as resistance in the wiring somewhere to the point that 12.5 volts (assuming its a healthy battery) isn't enough to get it going, but once the alternator is spinning, it has the power it needs.
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Old 09-10-2015, 09:19 AM   #7
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Try disconnecting and reconnecting your battery after you warm it up some time.


And try it with starting fluid when it would normally do this.


Im thinking you have fuel system problems (electrical/computer related maybe)


Another possibility is weak coils and/or plugs. Heat shield or not, those heat up when your engine runs, and they get even hotter under the hood after heat soaking does happen.


I'm assuming your crank position sensor is functioning properly at all times-- Im not sure if that's a safe assumption or not
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