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BOBBYSS, Master Technician
Category: Chevy
Satisfied Customers: 17466
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Chevrolet: I have a k3500 7.4 silverado dually. Was driving

Customer Question

I have a k3500 7.4 silverado dually. Was driving and truck started chugging missing and stopped. Checked fuel pressure its good. Truck cooled off started back up drove it it died after it got hot again. Could it be the ignition modual?
Submitted: 2 years ago.
Category: Chevy
Expert:  Randall C replied 2 years ago.
Hello, My name is***** will do my best to assist you. Unfortunately, no way to be 100% but by description? knowing underhood heat related, symptoms etc?> yes,, in fact 3 things come to mind,The distributor caps on this engine had many known issues, carbon cracks and can cause this, and,, the ignition module? along side of the coil? yes, 100% can cause this and lastly? the coil wire could be breaking down, Unsure which order to go with but in the shop? we go with cap and wires first especially if aged, problem continues>/ then yes, ignition module. I tend to lean to the module but had to list the other commons for this
Customer: replied 2 years ago.
I have new cap wires. It seems maybe a fuel problem but i have good pressure. What about fuel pressure regulator.
Expert:  Randall C replied 2 years ago.
well, you stated good fuel pressure, what is the reading? does pressure fall off with key off? does engine start with carb cleaner/starting fluid after it stops and will not restart
Customer: replied 2 years ago.
Truck starts but is chugging and when you give it gas it wants to die
Expert:  Randall C replied 2 years ago.
ok, then fuel pressure may still be the problem, I thought it did not run when hot, but fuel pressure needs to be about 52-62 psi, it will not be the regulator unless.. you hook up fuel guage and the pressure drops to zero when you turn key off, if pressur e holds, then reg is not the problem, I was only going by you saying fuel pressure is good and asked for the pressure reading, if you have not checked fuel pressure? then that has to be step one before going to ignition, I was answering based on your initial statement of pressure is/was good, Hope this makes sense
Customer: replied 2 years ago.
If truck sits for 30 min or so cools off it starts up runs fine until it heats back up then starts to make popping noise and wont run when you give it gas. I can hear fuel pump cycling so i figured pump is good.
Expert:  Randall C replied 2 years ago.
ok, that sound does not mean pump is good, One must have fuel pressure guage hooked up, Pumps can go bad and still run. some parts stores will rent the guage or you can buy cheap.I still lean to ignition module as pumps do not usually act up only when warm BUT can, I can only say the pressure readings,, which you have, the possibles, and should it quit running and not start right back up, then spray some carb cleaner in the air intake, if it then starts/stalls? you have fule problem and likely pump is bad, if still not run on crab cleaner? then ignition module
Customer: replied 2 years ago.
Truck starts ok but idle surges up and down and if you give it gas it wants to die
Expert:  Randall C replied 2 years ago.
I understand, I realize you want a 100% answer but I can not give that, I can only tell you how to diagnose and the possibles, You need to read fuel pressure,, I am going to opt out. Open the question up to the other experts. Please.. save the rating for the next expert that can help you. Sorry I could not, I have sent as much information as possible
Expert:  BOBBYSS replied 2 years ago.
Hello, my name is***** am a different expert. Thanks for the question. If I am not online when you return please give me some time to get back to you. Randall is correct that the actual fuel pressure should be tested. If you do not have a fuel pressure gauge most auto parts stores loan them out. The pump may be failing which typically means it either goes completely out or as it starts to fail the pressure drops off as it heats up. I would suspect that it is the ignition module or possibly a failing crank sensor. Both are common heat related failures on this engine. I have also changed a number of failed distributors on this engine also. If you do not have many tools for testing you can remove the ignition module and take it to your local auto parts store and most of them can test it. If it gets hot while they are testing it then it needs to be replaced. I would also make sure that the fuel pressure is above 55 psi. If you have a fuel pressure gauge installed when the problem occurs see if the pressure drops off at that time. If it does then the pump is failing. I hope this helps. Let me know if you would like further help.