Long Crank or Extended crank, Hard start, and how to diagnose properly
In this video, I will show you how to quickly diagnose a long crank, extended crank, or a hard start on a Chevy pickup truck. 5.7l or 6.0l engines
This is just a recap of what you should do first to determine if your long crank is fuel-related.
First, before you try cranking the engine over, turn the ignition key to the run position, then back off without cranking the starter. This will run the fuel pump, and in most cases, you will be able to hear the pump running. Do this 3 to 4 times before you try starting it.
If, after you have circled the key a few times, the engine starts normally, then you now know for sure you have a fuel pressure leak-down problem causing your hard start.
How to Check Fuel Pressure
Once you have determined that your hard start is due to fuel pressure, you are going to need a fuel pressure gauge. You can get them relatively cheaply on Amazon if you don’t all ready have one. Here’s the link: Fuel Pressure Tester
Hook your fuel pressure gauge up to the fuel pressure test port. ” I’ll show you where that is in the video below. Once the fuel pressure gauge is hooked up, cycle the ignition key on and off a few times to build fuel pressure in the system.
Once the fuel system is pressurized, “it should be about 55 to 60psi” check to see if the fuel pressure starts to drop off. If the fuel pressure drops more than 10psi in ten minutes, then we definitely have a problem. Most fuel systems should maintain pressure for several hours, if not days, and when this fuel pressure bleeds off, you will experience a hard start or extended crank.
How to Isolate a fuel leak down the problem.
OK, so where could this fuel pressure be going? Well, there are several different places. He is a list then after I will show you how to check each one.
I will start from the most likely problem, so start from the top when checking.
- Fuel Pump
- Fuel pressure regulator
- Injector
- Line or fittings
OK, so there are four potential problems. Not too bad “right”? So now let’s go into how to check all the components so we can determine what is causing the extended crank or hard starting problem. Also, these diagnostic checks will work on almost all vehicle makes and models, not just chevy trucks.
How does the fuel system work?
Before we can check these fuel system components, we need to know how an automotive fuel pressure system works. Well, the one we will be testing today is a return-type fuel system. This means the fuel that is not used is returned to the fuel tank, and pressure is held in the system by a check valve on the return side. The check valve on this Chevy truck is part of the fuel pump.
Here is an example of the return-type fuel pump system.
How to check leaking fuel injectors for extended crank
OK, here we go. So first, we’ll need to block off or crimp the return fuel line to isolate the fuel injectors. You can use something like this to get the job done “Hose Pinch Pliers Set
Once we have the fuel injectors isolated, we want to check our fuel pressure gauge again to see if the fuel pressure is still dropping after blocking off the return line. If it is not, then the fuel injector is not our problem, and we know the return line is where it is going. So if that were the case, the fuel pump would be the culprit.
Now, if after blocking off the return line, we are still losing fuel pressure, it could still be one of our four possible causes. We will start by checking the fuel injectors. To do this correctly we will need to activate each injector individually. The easiest way to do this is with a scan tool capable of activating the fuel injectors. Most people do not have access to a scan tool with this capability. If this is the case, there is an alternative. It is possible to pulse the injectors with a unique hand-held tool.
You can find the cheapest on Amazon: OTC 3398 Fuel Injection Pulse Tester
How to Pulse Fuel Injectors for long crank
Then will need to pulse each fuel injector while checking the fuel pressure gauge. After activating each injector, you will need to reenergize the fuel system by cycling the key on and off a few times. Record the pressure drop of each injector. If one drops more fuel pressure than the others, suspect a bad fuel injector.
If all the injectors check out well and dropped the same fuel pressure, then we will move on to checking the fuel pressure regulator.
How to check for a bad fuel pressure regulator?
This is probably the most straightforward check of all. First, remove the vacuum hose from the fuel pressure regulator and check for fuel. I will show you how to do this in the video below. If you have fuel coming out, then you know for sure the fuel pressure regulator is bad and will need to be replaced if the fuel injectors test well, along with the fuel injectors. The only thing left is the fuel pump or a leaking fuel line.
How to check your fuel lines for leaks
Checking for leaking fuel lines is self-explanatory; in most cases, a fuel smell will be very apparent. But you will still want to do a quick visual inspection of the fuel system for leaks and repair it as needed.
Last but not least, let’s check the fuel pump.
How to check the fuel pump for a pressure leak?
Now that we know all of our other components are good. Now we can easily isolate the fuel system.
Once the fuel system is energized, block off or crimp off the feed and return lines using a tool like this “Hose Pinch Pliers Set”
Check out the video below for a few quick, easy checks you can make. Help support my blog by liking or sharing this content if it is helpful to you in any way. Thanks
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More about me:
I’m Reggie Curtis, AKA “The Flat Rate Mechanic” I am a 25yr master certified automotive mechanic. My goal here is to help people repair their cars. Automotive repairs are costly and time-consuming, and over the years, I have learned mean tips and tricks that can save people time and money on their automotive repairs I would like to share with the world. Find out more about me on social sites: Flat Rate Mechanic.