Hello, I have lurked here for a while and always found this forum to possess an extremely valuable base of knowledge, but my blazer has recently died and I cannot quite find a similar situation that is already answered. Mine is a 1998, 4-door, 4wd Blazer, 4.3 L V6, vin W, and with approximately 170k miles. The problem began a few days ago, when it started up fine and after pulling out onto the road, it sputtered as I pressed the gas to accelerate and promptly died. The trip did not take half a mile. It cranks fine, but will not fire.


A buddy towed the blazer up the hill and into a barn for diagnostics. The check engine light never came on, nor has the security light. Everything visually appears to be in working order and all fuses are fine. The fuel pump primes for a couple seconds when the key is moved to the on position, before rotating through to start. It does not prime when the fuel pump relay is removed. Fuel pressure measured 60-62 PSI, which initially ruled out the fuel pump. However, we checked sparked and it was good, pushing the blame back to the fuel system.


Starting fluid initially did nothing. First sprayed into the air cleaner, then directly into the throttle body. Finally, pressing the gas pedal approximately halfway and spraying under the butterfly was enough to finally get the engine to fire. I let it run, parked, for a moment and then turned it off. It started up again without any problems. I drove it around a little bit at approximately 10 mph and then up and down a little hill and did not encounter any problems. I brake loaded (drove with feet on both the brake and gas) as a test and may have heard a slight sputter. Then I drove down a large hill to return a loaned tool and shut it off. It started up fine, but sputtered again climbing the hill and died. It has not restarted since.


These symptoms seemed to indicate a faulty fuel pump, and others have found a failed fuel pump to give the specified pressure. I replaced the fuel filter first and, without success, proceeded to replace the fuel pump. However it still does not fire.


I will get help and observe whether the injector is firing or not tomorrow, but am really running out of ideas. This is really baffling as it has spark, certainly has air, and appears to have fuel, but it will not start. Does anybody have any ideas? Thank you in advance!

 

well at 172k mine did the same, the fuel pump was going bad on mine.. one time it would work until i shut it off then wouldnt work.. replaced it, fired up but then would surge under gas.. come to find out that the caps that snap onto the spark plugs 2 of the right angle ones.. cyl 2 and 3, had cracked and it was shorting out also. new plugs and wires later and all was good. visually though the wires looked good until i tried to take them off the plugs and they fell apart. jsut food for thought.. good luck and keep us posted on your finds.

 

Did the pressure bleed off at all after the pump shut off?

When was the last time a tune up was performed & what brand were the parts that were used?

 

James1965. Thank you for the suggestions. I checked and pulled at all the spark plug caps and they were properly connected and in good condition.


Swartlkk, the pressure slowly bled off to about 58 psi after a long time (at least 20 minutes, probably an hour). The blazer has not had any major tune ups, although I replaced the spark plugs with AC Delco's about 20k miles ago.


Today someone suggested looking at fuses and the crank position sensor. I tested all fuses in both the the underhood and cabin fuse boxes with a test lamp. I pulled some out, but did not replace any as none were blown. I also located the crank position sensor; it was dirty, but appeared fine.


Even before poking around the spark plug wires, I tried to start the engine and it did not fire. After playing around with all this stuff, I tried to start it again and it fired up first try without any problems. I let it idle for a minute, then took the rpm up to 2000 and held it for a short while. It was very smooth.


Each time it restarted fine and was idling smoothly. I drove it less than a tenth of a mile and up and down a small hill. As I returned to the barn, it began sputtering and died. I restarted it (this time it took a couple tries) and parked it in the barn. Now when it starts, it idles smooth but will begin to sputter and eventually die with the slightest touch of the gas pedal.


Still no check engine light. If the crank position sensor was out, would it give an error code? I might try unplugging it to see if that triggers the light. Although it refused to start when cold before, this bears some resemblance to ignition control module problems. I might take that in to be tested. Thank you for the help so far. Is there anything else to look at?

 

Not sure if you've seen these two threads, but they may help in ruling out certain things:
Engine Cranks But Does Not Run
No-Start - Engine Cranks OK - Ignition System Diagnosis

Also, concerning the CKP sensor & codes, it should trigger a code, but not always from my experience:
P0336 - CKP (crankshaft position) Sensor Circuit A Range/Performance
P0339 - CKP (crankshaft position) Sensor Circuit Intermittent

 

Well, it starts and runs now. It even idles smoothly, but it will sputter and die if the gas pedal is touched, rendering it impossible to drive. It does idle in park, neutral, reverse, and drive though. After dying it will start again, although a little roughly.

Swartlkk, thank you for the links. The second link was initially ruled out because it has spark, but I no longer know whether to pursue the fuel or ignition system. I will give a go at the first link. I do not have an OBD scanner and do not trust the blazer as it is to drive to a scanner. Is this important enough to tow it to a shop? The P0339 diagnostic looks promising, so I will try that as well. Especially after replacing the fuel pump, I am trying to avoid replacing good parts, but I cannot find any specific part that is broken.

 

Updates:

I am in the process of eliminating potentially malfunctioning parts. First I unplugged the mass air flow sensor; it ran a little rough and still was not stable above idle. This triggered the service engine light, but that went away after a couple restarts.

I finally gained access to a scanner. The only code listed the mass airflow sensor, but this did not reappear after restarting. Other than when I unplug something, there are no trouble codes.

The throttle position sensor has been ruled out as well. Closed measured 0.6 V and it increased smoothly up to 4.5 V at wide open. While I was doing this, the ignition was on but the engine was not running. I heard something faint like a solenoid intermittently moving for a few seconds deep in the manifold . Could this be a clue?

I have delayed it, but I will test the crank position sensor and take the ignition control module in tomorrow. Now that the blazer starts, I almost need to change the title to 'unstable above idle'. It has certainly changed the diagnostic path.

https://blazerforum.com/forum/engine.../?ref=esp-link

If the engine idles smoothly, why would the CKP malfunction above idle?

On the P0336 diagnostic that swartlkk linked above,
https://blazerforum.com/forum/diagno...plained-35150/
In step 3, is the ignition positive voltage circuit just the pink wire at terminal 'A' in the schematic?
Likewise is CKP ground the purple wire at terminal 'B'?


Edit: Sep 18 21:03

It was fixed yesterday. I will detail the solution in a couple days; hopefully it may help someone else. Thank you everyone!

 

After cranking so much with little run time, the battery drained. After charging, it would not start any more. I started checking everything accessible: TPS, IAS, MAP, ICM, and even the CKS, but I did not have a duty cycle meter to finish. I pulled the #2 spark plug (easiest to access) and it was black and smelled of gasoline. It definitely had fuel then, so the problem must be with the spark despite it previously had some.

After putting everything back together I wiggled the spark plug wires again and then it started. There was a clicking sound like a solenoid or relay so I ran around to the front of the vehicle. The coil wire that I had just inspected and reinstalled was arching through the corrugated plastic to the radiator hoses to the heater core. I shut it off and replaced the coil wire and have not had a single problem since.

James1965 and swartlkk, you guys were both right. This was extremely hard to find until it started throwing sparks. All the spark plug wires looked to be in good condition and all the boots were still supple. Before finding the problem, I had unplugged the coil wire at least twice. On the occasions it was idling, I had manipulated the throttle right next to the coil wire, and did not witness any arching or current leakage. The malfunctioning coil wire showed no signs of damage and measured a resistance of 800 ohms. Although it did have some white dust near the section that was arching.

In conclusion, a broken coil wire can prevent a Blazer from starting or running above idle and it is very cheap to replace. Now that mine is running, it is getting a tuneup with a set of AC Delco wires, rotor, and cap. The plugs are newish enough to not warrant replacing, especially that #3.

Thank you everyone!