Hello, I have a 99 blazer and have been having problems with ignition. After a rainy wet day the truck would not start checked fuel pressure which was good and found that I was getting no spark. Replaced the crank sensor and the rotor and cap. Truck wouldn't start.

Reset the distributor which is newer to tdc. Go to start the truck it starts but runs really bad and dies. Realized I didn't plug the cam position sensor back in, which I correct. Try to start the truck no luck. Replace the cam position sensor with a new one, truck won't start. Unplug the sensor the truck starts but runs really rough.

What is the issue? Do I have an issue with the wiring to the sensor? Could it be a faulty new sensor? Should the truck be able to start without the cam position sensor connected?

Any help would be greatly appreciated, thanks!

 

The CMP sensor is only used for misfire detection and will have no impact on engine operation other than setting a code in the PCM if there is a problem.

Follow the steps listed in the EDI Engine Timing thread, checking for proper orientation of the rotor after aligning the two timing marks on the balancer as well as setting CMP Retard to zero (this requires a scan tool capable of displaying CMP Retard).

Have you replaced any of the other ignition components (plugs and/or wires)? A no-start when wet is an indication that there is a problem in the secondary ignition system.

After replacing the CKP (crankshaft position) sensor, a Crankshaft Variation Learn procedure must be done for proper ignition & injection timing. The engine must be running for this procedure to be performed, but not having it done should not prevent the engine from running. It just will not run optimally.

How was it running before you did this work? What prompted you to replace the parts you have already installed?

 

The truck was running good prior to the no start. I did notice hesitation with acceleration the week prior but it only happened once. When looking over the truck I found fuel pressure but no spark. The CKP was looking really bad so I replaced it and still had no spark. Reset to TDC as described and put in a new CMP sensor. New cap and rotor also as the cap had moisture in it, I have not replaced the plugs and wires yet since they are rather new. Though I did pull plug number one and it seemed fine a little bit blackened but it did not seem extreme.

I have been able to get it running with the CMP sensor disconnected, though it runs very rough. Could the TDC distributor install be the issue. I did as explained and looked for air to come out of the cylinder to make sure it was on the compression stroke. What would be the symptoms if I had set the distributor on the exhaust stroke? I'm not sure if I should re do the distributor or if described relearns need to be applied. Though the truck needs to be running for that to happen.

Thanks for the reply.

 

It would not run at all if you had the distributor in 180° out.

On a Vortec V6 you can take the distributor out of the vehicle and crank the engine and still get spark at the coil. In general, if you have spark at the ignition coil, then the crank sensor is working fine. The only thing the distributor does is to send the spark to the correct spark plug when the coil fires. If the rotor is not pointing to the correct terminal on the distributor when the coil fires, the spark will be sent to the wrong spark plug or to ground and the engine will not run right. An engine will run without missing with the camshaft sensor unplugged, so camshaft sensor is not your problem. As I understand it, the camshaft sensor does two things: Tells the computer which cylinder is firing at the moment for the purpose of misfire detection, and also tells if the distributor position is in correct sync with the crankshaft sensor. If the distributor position is not within 27° (if I remember correctly 13 teeth) of expected, then a code is set. Typical reasons for this code and misfires is getting the distributor a tooth or more off.

Conversely, if you don't have spark at the ignition coil, then the problem is not anything with the distributor or camshaft sensor.

I believe the moisture inside the distributor cap was probably your original problem. Spark went in, but went to ground through the moisture. You may have got the distributor out of time by pulling it and putting it back in. There are two marks on the balancer. One goes almost straight down while the other one is lined up with the pointer, right after #1 cylinder has started to see compression. Put your finger in the spark plug hole to tell. At that point the rotor should point pretty close to the #6 stamped inside the distrbutor.

There is a service bulletin to correct moisture in the distributor problem on these engines. Found bulletin applies to 2001-2003 but maybe it is applicable to yours - don't know. I have pasted part of it below. I'm sure you can find the entire thing online.

Because you disturbed the crank sensor (actually replaced it), you will definitley have to do the Crank relearn procedure (or have it done) after you get it running again befoer the misfire detection will work correctly.

Bulletin No.: 03-06-04-041A
Date: January 28, 2005
TECHNICAL
Subject:
Poor Engine Performance - Misfire, Rough Idle, Stalls, Engine Cranks but Does Not Run, Service Engine Soon/Check Engine Light Illuminated, DTC P0300 Set (Inspect Distributor Ignition (DI) System Components and Replace As Necessary)
Models:
2001-2003 Chevrolet Astro, Blazer, Express, S-10
2001-2003 GMC Jimmy, Safari, Savana, Sonoma
2001 Oldsmobile Bravada
with 4.3L, 5.0L or 5.7L Gas Engine (VINs W, X, M, R - RPOs L35, LU3, L30, L31)
Supercede:
This bulletin is being revised to delete a model and add information to subject and inspection of distributor vent screens. Please discard Corporate Bulletin Number 03-06-04-041 (Section 06 - Engine/Propulsion System).
Condition
Some customers may comment on poor engine performance and the Service Engine Soon/Check Engine light being illuminated. Upon investigation, the technician may find DTC P0300 set.
Cause
This condition may be due to high levels of internal corrosion in the distributor, causing misfire, rough idle, stall and Engine Cranks But Does Not Run. This corrosion is attributed to a lack of airflow internal to the cap caused by the vent screens being clogged with debris.
Correction
Remove the vent screens and inspect the internal components of the Distributor Ignition System using the procedure listed below. If the distributor base has to be replaced, the vent screens will also have to be removed on the new distributor. If there is evidence of this internal corrosion, replace the affected component. Refer to the appropriate procedure in the Engine Controls sub-section of the applicable Service Manual.
Important: All of these inspections can be done on-vehicle.
1.Inspect the distributor cap. You may notice a white residue on the cap walls. For higher mileage occurrences, the interior of the cap may have changed to medium brown in color
2.Inspect the distributor rotor. You may notice the presence of black streaks on the plastic surface. More typical evidence would be visible green spots on the copper surface of the rotor segment.
3.Inspect the distributor base. You may notice high levels of surface rust on the distributor shaft or surface contamination on the sensor hold down screws.