So my 2004 blazer 4.3 had died on me while driving home from work one morning. I got about maybe 1km before the engine stopped, and wouldn’t start again. Pulled over, cranks good, no start. I’ve had a check engine light for a while for crankshaft position sensor and a camshaft position sensor. I have replaced those now. No go. I hear my fuel pump priming. I did a fuel pressure leak down test and it held pressure while the key was off, held at 55psi. When I go to start it it cranks and kinda puffs out the intake and a couple puffs out the exhaust. But it doesn’t sound like it’s about to start. It has ran perfect for the few years I’ve had it. Not sure what it could be.



Update. Distributor gear was chewed up. Replacing it. What would cause it to be worn so bad?

 

Might just be an old distributor, alternatively if its a rebuilt motor it may have a high vol oil pump as les had tossed at me when i mentioned wanting to use one in an OE Performance build. those can wear the gear down quicker.

 

So quick update, I replaced the distributor for a stock one but I swapped the new camshaft position sensor and old cap and rotor. In the process of getting engine to TDC I broke 2 plug wires so I replaced them. Got it all running and oil flushed and changed to get rid of metal filings. Now driving to work my check engine light started to flash at me, then solid, then flash, then solid. I know it’s a bad thing. Not sure if I did something wrong here

 

check for codes, it may just be bad misfire detection since (to my knowledge) flashing SES usually flashes in tune with a detected misfire.

 

First to answer your question about the distributor gear wear. This is often the fault of using heavier weight oil than the 5w30 the engine calls for, since this gear drives the oil pump. Plus they seem to be a common problem on these Blazers in general.

Flashing SES light indicates misfire, but you need to do a crank sensor relearn when you replace or disturb a crankshaft sensor or it can give a false indication of a misfire. Too bad you messed with it, as crank sensors are very seldom a problem (but often first to be replaced). I would suggest checking the cam sensor retard first, which should be 0° ± 2°. This effectively checks alignment of your rotor to the cap terminal when spark comes across (important for optimal performance and no misfires). There is zero sense in doing a crank sensor relearn on a car that is misfiring in the least (as it will never complete), so this is why I say to check and set the cam sensor retard first.

Not many inexpensive scanners will display the Cam Sensor Retard. For a 2004 I recommend an Android Phone, Car Gauge Pro ($8.99), and the BAFX Bluetooth OBD2 adapter ($22) as sold on Amazon. If it is off more than 2°, you turn the distributor like you was setting timing on an old vehicle. Factory hold down locks distributor in place, so you might have to elongate the bolt hole in the bracket with a Dremel tool to get any rotation.

Once you have the cam sensor retard set - if you do not feel any misfires or sluggishness and the SES light still flashes - then you need to do the crank sensor relearn. This is a function of higher end scanners. I can point you to a stand-alone scanner that will work for around $150, or you will have to take it to someone who has the equipment and pay them to do it.

Be careful not to confuse "cam sensor retard" with "crank sensor relearn" (or CMP vs CKP).

Let me know.