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carguyjosh
carguyjosh, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2172
Experience:  ASE certified , 16 yrs in field
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97 suburban: tahoe..have swapped the dist., computer, coil..wont start

Customer Question

97 suburban has no spark from coil. we have a 96 tahoe with matching drivetrain and are swapping parts from one to the other to rule things out. have swapped the dist., computer, coil, and the tahoe runs sweet, but the burb wont start at all. please help
Submitted: 5 years ago.
Category: Chevy
Expert:  carguyjosh replied 5 years ago.

The chankshaft sensor has more than likely failed...

Here is a picture for the location....

Thanks Carguyjosh

graphic

Customer: replied 5 years ago.
crank, cam, and knock sensors are all brand new.
Expert:  carguyjosh replied 5 years ago.

Have you checked the power supply to the coil?

Please let me know if you have a multi-meter to perform some more tests...

Thanks Carguyjosh

Customer: replied 5 years ago.
yes i have a multimeter and the coil does appear to be getting a good 12 v feed.
Expert:  carguyjosh replied 5 years ago.

Can you test the pink wire to the crankshaft sensor and also check the pink wire to any fuel injector, we are looking for 12v. with the ignition turned to the run position...

Let me know what you find...

Customer: replied 5 years ago.
i get 12 v to the injector harness(vortec motor, central injector) but the crank sensor reads only 0.01
Expert:  carguyjosh replied 5 years ago.

In the underhood fuse center, I need you to check the 20amp ENG-1 fuse....This is the power supply to the crank sensor....

Let me know what you find...

Customer: replied 5 years ago.
fuse is good......also when i unplug the crank sensor the fuel pump engages. dont know if this is relevant but it may be.
Expert:  carguyjosh replied 5 years ago.

So the voltage is .01 at the pink wire with the crank sensor disconnected?

Can you check the pink wire at the mass air flow sensor, is it also .01volts?

Remember to have the key on......

 

If this is the case, I will give you a list of sensors to disconnect and figure out which one is pulling down the voltage...

Customer: replied 5 years ago.
i have 12 v at the maf
Expert:  carguyjosh replied 5 years ago.
Somewhere in the wiring harness is a break to the crank sensor. what if you jump from the pink wire of the MAF to the pink wire of the CKP(crank sensor) Will it run?
Customer: replied 5 years ago.
negative....still no spark. this truck is really starting to piss me off. the motor ran fine other than a blown head and we replaced it with a reman long block. very distressing. i also am a certified mechanic and this is way beyond me.
Expert:  carguyjosh replied 5 years ago.

Okay, do you have a lab scope?

Let me know and we'll look for some waveforms out of the CKP

Customer: replied 5 years ago.
is there a generic version of the lab scope that a handyman may have??? and somehow we managed to get power to the crank sensor so we are currently checking continuity of all the ignition system wiring. so far we have good wiring between the ecm and the crank sensor, and all but 1 wire we have traced for the coil to the ecm are good too.
Expert:  carguyjosh replied 5 years ago.

There are many different lab scopes out there, You will just need one that is capable of graphing...My thought is, that if the reluctor wheel is missing, the crank sensor has nothing to read and therefore can not generate a signal....

 

We are not checking continuity of the ignition, rather checking the ability to create the signals needed.....

 

If you can get your hands on a scan tool, we can make short work of some of these steps...

Customer: replied 5 years ago.
good call. just pulled the crank sensor and the guy that swapped all the parts faild to swap that. one more question and i will pay you at this point. we no longer have access to the original core. do you know if that part can be swapped from a 454 of the same age range??
Expert:  carguyjosh replied 5 years ago.

I would have my doubts, The physical size would be to large...

I'm so glad you found the missing ring,,,Have a great night...

Carguyjosh

carguyjosh, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2172
Experience: ASE certified , 16 yrs in field
carguyjosh and other Chevy Specialists are ready to help you
Customer: replied 5 years ago.
thank you for your help. i firmly believe that this saved allot of time and headache and should i need assistance in the future i will most definitely use this service. thanks again
Expert:  carguyjosh replied 5 years ago.

Glad to be of service..............Josh

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