Chevy Corvette - No Start When Hot (The Diagnosis)
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Date: 2020-08-05
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Comments and reviews: 8
tonyfremont
23 seconds in, I'm guessing fuel injectors low resistance (internal coil shorts) causing ECM to shut off the drive to them.
34 minutes in now. You should have given me a call. You're lucky you didn't get the full monty where it just shuts down on the road with no warning. An easy in shop test is to ohm them out cold, then ohm them hot. Any injector experiencing a large drop in resistance is bad.
I wasted my time changing ignition module, then whole distributor before finally figuring it out. Bosch makes some nice yellow ones that fit, the OEM injectors are prone to failure because of fuel additives, and probably ethanol. The factory injectors run the coils in gasoline to cool them, the enamel on the coils dissolves leading to shorted windings as they heat up. Eventually they stop firing, or the output transistors in the ECM go into thermal overload just bringing the engine to a sudden halt, as in my personal case. This symptom was a little different, but probably depends upon how many injectors in each bank are bad, and how bad they are.
When you see this car again, and you will, due to a failed fuel pump, pump relay, pressure regulator, or coolant/IAT sensor. I might be able to splain some strange symptoms that don't set any codes. But your skills are excellent and I expect you'll run down the problem quickly since you have a good collection of special tools. Fuel pump relays like to fail in operation which keeps the engine running, due to a bypass for power to the pump from the oil pressure sending unit, but then won't start, or maybe hard start, since you need oil pressure to keep the pump running on the bypass power. These are fun engines, and easy to fix when you know their common issues. Diagnostic codes will send you down the wrong path pretty much every time, be thankful nine were set to mislead you. ;)
This would be a good time to replace the plugs and wires while you have it apart to change ALL the injectors. A new fuel pressure diaphragm now wouldn't be a bad idea.
Upgrades include 180F thermostat, coolant bypass hose on the intake plenum, the air is hot enough anyway, and icing is pretty unlikely in my stomping grounds, but might be a consideration in New York. Of course the primary cooling fan will still follow 5he e programming for the original thermostat, but there's a fix for that involving changing the coolant temp sensor for the secondary fan.
I have a 1990 IROC with basically the same setup as that C4, but no MAF, it's speed density and also doesn't have the 9th injector for cold starts. These engines are a joke comparing today's horsepower numbers to them, but they still hold their own in terms of torque output. 350ftlb of torque is fun, no matter who you are. TPI induction doesn't breathe well at high rpms, but it's worth the trade-off for the monster torque at low rpms, especially on the street.
Love your videos, you do your customers right, and I know that hurts the bottom line, but it's good to sleep at night knowing you haven't robbed anyone.
reply
23 seconds in, I'm guessing fuel injectors low resistance (internal coil shorts) causing ECM to shut off the drive to them.
34 minutes in now. You should have given me a call. You're lucky you didn't get the full monty where it just shuts down on the road with no warning. An easy in shop test is to ohm them out cold, then ohm them hot. Any injector experiencing a large drop in resistance is bad.
I wasted my time changing ignition module, then whole distributor before finally figuring it out. Bosch makes some nice yellow ones that fit, the OEM injectors are prone to failure because of fuel additives, and probably ethanol. The factory injectors run the coils in gasoline to cool them, the enamel on the coils dissolves leading to shorted windings as they heat up. Eventually they stop firing, or the output transistors in the ECM go into thermal overload just bringing the engine to a sudden halt, as in my personal case. This symptom was a little different, but probably depends upon how many injectors in each bank are bad, and how bad they are.
When you see this car again, and you will, due to a failed fuel pump, pump relay, pressure regulator, or coolant/IAT sensor. I might be able to splain some strange symptoms that don't set any codes. But your skills are excellent and I expect you'll run down the problem quickly since you have a good collection of special tools. Fuel pump relays like to fail in operation which keeps the engine running, due to a bypass for power to the pump from the oil pressure sending unit, but then won't start, or maybe hard start, since you need oil pressure to keep the pump running on the bypass power. These are fun engines, and easy to fix when you know their common issues. Diagnostic codes will send you down the wrong path pretty much every time, be thankful nine were set to mislead you. ;)
This would be a good time to replace the plugs and wires while you have it apart to change ALL the injectors. A new fuel pressure diaphragm now wouldn't be a bad idea.
Upgrades include 180F thermostat, coolant bypass hose on the intake plenum, the air is hot enough anyway, and icing is pretty unlikely in my stomping grounds, but might be a consideration in New York. Of course the primary cooling fan will still follow 5he e programming for the original thermostat, but there's a fix for that involving changing the coolant temp sensor for the secondary fan.
I have a 1990 IROC with basically the same setup as that C4, but no MAF, it's speed density and also doesn't have the 9th injector for cold starts. These engines are a joke comparing today's horsepower numbers to them, but they still hold their own in terms of torque output. 350ftlb of torque is fun, no matter who you are. TPI induction doesn't breathe well at high rpms, but it's worth the trade-off for the monster torque at low rpms, especially on the street.
Love your videos, you do your customers right, and I know that hurts the bottom line, but it's good to sleep at night knowing you haven't robbed anyone.
reply
Desert
I need help! I have a 1954 chevy truck that has a 305 4 bolt main V8 in it. I am putting a car 4 speed in it so I got a flywheel and clutch kit from Rockauto and put it together and the clutch wouldn't disengage, so looking through you tube videos and found one that said their clutch wouldn't disengage because it was to tight, but they never explained what they did to fix the problem. So I am asking for help to fix the problem before I spend more money on another clutch kit, Ken Dodge kdodge3msn. com. Thank you
reply
I need help! I have a 1954 chevy truck that has a 305 4 bolt main V8 in it. I am putting a car 4 speed in it so I got a flywheel and clutch kit from Rockauto and put it together and the clutch wouldn't disengage, so looking through you tube videos and found one that said their clutch wouldn't disengage because it was to tight, but they never explained what they did to fix the problem. So I am asking for help to fix the problem before I spend more money on another clutch kit, Ken Dodge kdodge3msn. com. Thank you
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autos
Eric deserves a beer and a handshake (actually an elbow bump during the corona pandemic) for the time and effort he puts in to his videos. He shows you how to go about things right, armed with knowledge and excellent equipment to logically approach the diagnosis. Fantastic presentation and explanation of how to go about tracing out the problem.
You da man. Hope youre staying safe and healthy in NY state
reply
Eric deserves a beer and a handshake (actually an elbow bump during the corona pandemic) for the time and effort he puts in to his videos. He shows you how to go about things right, armed with knowledge and excellent equipment to logically approach the diagnosis. Fantastic presentation and explanation of how to go about tracing out the problem.
You da man. Hope youre staying safe and healthy in NY state
reply
Edward
I can appreciate professionalism and the way you explain things. Most DYI videos the guys talk down to us as though we don't know a damn thing. But you speak as though we are one of the guys. Because you have to have some knowledge to even be interested enough to even watch videos like this.
Thank you for sharing your experience and knowledge.
reply
I can appreciate professionalism and the way you explain things. Most DYI videos the guys talk down to us as though we don't know a damn thing. But you speak as though we are one of the guys. Because you have to have some knowledge to even be interested enough to even watch videos like this.
Thank you for sharing your experience and knowledge.
reply
Moflydotcom
Love your videos. Have you considered getting a wireless mic with a shirt collar clip? Sometimes you talk softly especially when you are not facing the camera. That's normal for most people. Just a suggestion. I've learned so much from you. Keep up the good work.
reply
Love your videos. Have you considered getting a wireless mic with a shirt collar clip? Sometimes you talk softly especially when you are not facing the camera. That's normal for most people. Just a suggestion. I've learned so much from you. Keep up the good work.
reply
William
Low tech way to find bad injectors if you don't have a scope. Press the tip of a long shank screw driver against the injector, and the end of the handle to your ear. Have someone turn the ignition. You'll hear a click every time the injector opens and closes.
reply
Low tech way to find bad injectors if you don't have a scope. Press the tip of a long shank screw driver against the injector, and the end of the handle to your ear. Have someone turn the ignition. You'll hear a click every time the injector opens and closes.
reply
Marcos
I have a 2006 Ford f-150 xlt 5. 4l and i parked the truck running and 2 months later i tried to start and the truck never start again and know i have the U1900 code please i really need to fix my truck and I don't know what to do
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I have a 2006 Ford f-150 xlt 5. 4l and i parked the truck running and 2 months later i tried to start and the truck never start again and know i have the U1900 code please i really need to fix my truck and I don't know what to do
reply
Gene
This is one of the few I wouldnt be able to figure out. Ive watched a ton of your videos and try to figure out in the beginning. I wouldnt even know where to start. It takes a real expert. You would definitely be my mechanic.
reply
This is one of the few I wouldnt be able to figure out. Ive watched a ton of your videos and try to figure out in the beginning. I wouldnt even know where to start. It takes a real expert. You would definitely be my mechanic.
reply
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