GMC Sierra 2500 Pick-up

2003 GMC Sierra 2500 Pick-up Engine   

Engine shut down and will not restart.Check engine light on at console

The check engine light was on before the engine shut down?

If you have an Autozone store nearby, they will loan you a trouble code reader (for a fully refundable deposit) that you can use to check trouble codes. This is the first thing a garage would do. Let me know which trouble codes you find, via their alphanumeric designation. Examples of these codes are P0300, P0401, etc.

check engine light did not come on until engine shut down.

Okay, were you able to borrow a code reader from Autozone and check the trouble codes?

Yes,I purchansed one for this and future problems. The code read out was PO700 from which I deducted was transmission problems. Where do I proceed?

Well, a problem with the controls for the transmission anyway.

Clear the codes and attempt to start the vehicle. If the vehicle still does not start recheck trouble codes. If no codes appear-

Confirm Key On 'Check Engine' light, indicating the PCM (computer) is powering up.

Check for spark.

Check fuel pressure.

Check for fuel injector pulse.

Which is missing OR what trouble codes are found?

1994 GMC Sierra 2500 Pick-up Ignition System   

HI, I just did a R&R on my 1994 GMC 2500 Pick up. It has a 350. I can't seem to get a spark from the coil while cranking the engine. When i turn the key to run i get spark, then i get another spark when i turn the key back......but no spark when chranking....(NEW CAP AND ROTER) i have never seem this before....any ideas? mhouselander @hotmail.com

you may be getting a spark from the inductance building up in the coil
Can you test the coil to see if it is any good?
What haoppened before this?
Was everything working fine before you changed the cap and rotor?
Give me as many details as you can so I can better access this problem

Hi,

It a coils (Square) located on the engine, i was getting spark from the coil before. The coil has nothing to do with cap and rotor ( i don't think) I conected a spark plug to the coil wire and grounded it. I got a big spark once the key was turned over, but no spark after that and no sparking while turning the engin over. When you turn the key back to teh off position, you get another big spark.

I had ther distributor shaft out (but the coil is not attached to teh shaft) i did have spark going right to the spark plugs before i pulled the engine...i checked by pulling the actuall #1 spark plug out and grounding it out....there was spark.

I have been turing the engine over and over trying to get it to start. I just relized tonight that i wasn't gettting spark while cranking.


Is in normal to get a spark when you turn the key over, and again when you turn it to off position. If so, then sence i am getting a spark when first turning the key over and off again, does that mean the coils is good? this has really got me messed up.

The only other thing i can think of it that the starter, ingaged by itself, not sure why.....i pulled it out anc cleaned the wires.....not sure what that might have to do with the coil and no spark....HELP...

Any Ideas?

This has nothing to do with your starter.
if the electronics are all lined up at TDC there will be a evident spark from turning the key on or off.
You have a spark control module for your truck also an igniter and an ignition control module along with the coil pack.
I am going to look at some tests you can perform to trouble shoot this to componet level.

Was everything working before you put on the new cap and rotor is my major question.

Also do you have 12 volts to the + side of the coil when the truck is in the run position and does it drop out when the key is in the start position.
use a test light and check for a constant 12 volts at the + wire on the coil but it must be while the key is turned and truck engine is cranking.

hi,

I was getting spark prior to replacing the cap and rotor.

I will check for 12volt at teh coil tomorrow and let you know

Thanks

befor you do that If you still have the old cap and rotor ,replace it and see what happens .
The new set that you have is it OEM or after-market?
in a lot of cases it can make the difference,the after-market parts do not fitt exactly right but enough to throw off the ignition system.

I understand what you mean. But i just can't see how it owuld affect the coils spark. I could if the coil was putting out spark, but it wasn't transfering from the coils throught the cap and rotor. then i couls see the problem being cap and rotor.

But if am not getting spark to the cap and rotor......regardles if it old or new...there is something else wrong? I will put the old stuff on anyway, just for the heck of it.

I'll let you know.

I hope I caught you in enough time
If not then we will still be able to do the same test with the old cap and rotor also.
You say there is no spark coming from the coil into the rotor , well I am in agreement with you on that.
We can address that issue now start with a test on the input wires to the coil-pack and check for 12 volts.
I have cut and pasted the earlier thread
when the truck is in the run position and does it drop out when the key is in the start position.
use a test light and check for a constant 12 volts at the + wire on the coil but it must be while the key is turned and truck engine is cranking."
Let me know what your findings are

Hey,

Ok... I tested the input wires going to the coil (from the computer i guess)I used a test light. I have power once the key is turned over, and i still have power when turining over.

I also checked the wires going form the coil to the rotor....they two have constent power when cranking.

Does this mean that the coil is no good?

First thing you need to check next is that the resister is wired in and connected correctly.
Then you need to test the output of the coil
see how much resistance there is from the main coil output lead to the ground or frame of the coil.
Do you have an ohmeter?
get an Ohm meter and
check primary resistance between Pos and Neg terminals on the coil
resistance should be 0.3 - 1.0 ohms

check secondary resistance between Pos term and coil wire terminal
resistance should be 8000 - 11500 ohms

repeat secondary resistance test between Neg terminal and coil wire terminal
resistance should be 8000 - 11500 ohms

check resistance to each terminal and gound(coil case)
resistance should be infinite or unmeasurable.
If this is good then the coil is also goo
Let me know

sorry,

where would i find the resister?

There should be a kittle cylinder or rectangular shaped module also plugged into the coils harness and it should have a end going to ground.
Located within inces of the coil.

the onlt thing i can see is a little black box that is under the rotor. I don't see any wires going straight to ground.

This is the wierdest thing i have ever come across. i do not have a ohm reader. could the coil be bad even thought it gives a spark when you turn the ingnition off and on?

That little box is grounded at the screw and the wire to the coil is the circuit wire.
The coil still can be bad and working periodically, shorted out and repairing itself even can be affected by the temperatures.
If you really want to know if that coil is good then you must use a meter.
You can get a meter for about 9.00 at a autoparts store, this would be a good investment.
You can also rent a scanner and check for stored codes that will pinpoint a malfunctioning part that can usually be found through part replacement only
like the ignition control module the component that breaks up the spark.
So we need to know that the coil is good
The only other way of testing it other than with you grabbing the out-put wire with your hand. {I do not suggest it}

Hi,

OK, i replaced the coil. I still have the same problem. I checked the ground going to the coild and it was weak. (Dull light form my test light) I have a grong wire that was not bolted up, i cleaned the metal on the firewall and attached the ground. I now have a strong ground. But still no spark.

I am so lost right now....this is driving me crazy...
does it matter about the wored to the starter? if they werre hooked up wrong would that metter? PLEASE HELP BEFORE I LOSE ALL MY HAIR...lol

Please Do not lose your hair ,cause you will look like me.
The wire to the starter is another system itself,and it does not matter in this case because it is cranking over.
Now will be a good time to scan the pcm for codes, this can eliminate a lot of trouble and guessing as your car has a an igniter and an ignition control module, that controls and distributes the spark and one could have gone bad.
You can rent a scanner from autozone with just a deposit and get all your money back upon return

IS the contrrol moduale the bloack (flat) box under the cap) the coil wire and another wire harness hook up to it? Do you have an e-mail i could send pictures to?

if the IGNITION MODULE is bad, could that cause this problem?

Yes it most definately could an igniter being bad can cause the same problem and The module is the one under the cap

you can use the same emailI sent the files to you on

My apologies and My email is [redacted]