I have tried to diagnose this thing, but it has me beat. Hopefully one of you experts can set be back on the right track. Thanks in advance.

I have a 98 blazer that cranks and wont start. I have tested fuel pressure and leakdown (I read the sticky), and that looks good.

I started checking spark and found that there was no spark to at least some of the plugs. Checking at the distributor cap doesn't work too well with my tester, so I skipped that and checked for spark at the coil. The coil produced proper spark (It should because it is pretty new,) so I decided to take off the distributor cap and rotor. They were full of carbon, so I replaced them and retested for spark at the plug end of the ignition wires. Still no spark. I then replaced the wires, but I still have no spark. I'm pretty much stumped. I have spark at the coil, but it doesn't make it to the plugs, but everything in-between is new, so what am I missing? I have seen new parts fail, but how would I test it? My spark tester is the old school type that plugs in like a spark plug and adjusts by screwing in the other end (I would post a link to showing what kind it is, but I don't know if that is allowed on this forum.)

 

Did you install AC Delco cap & rotor? Aftermarket stuff doesn't cut it on this engine. The white crusty stuff on the cap terminals is normal. Silicone dielectric grease must be applied to the terminals of the cap to reduce/prevent corrosion. When voltage goes through, it crystalizes.

 

Unfortunately the AutoZone where I live does not have the AC Delco brand so I got what they had. I'm guessing the problem is either the new wires, or the new cap and rotor. Is there a good way for me to test which one? They are new so if I can show they are bad I can return them

 

If it says "Duralast" on the box, they're bad. They are the worst offenders. Look through the forum, you'll find countless times people put that stuff on, and then went with AC Delco and the problem was solved.

 

Thanks for the input, and sorry it has taken so long for me to reply (I have been working lots of overtime.) I have tried switching to acdelco, and still no luck. I thought maybe I had a ground problem so I tried using a set of jumper cables to ground the engine straight to the battery, and it fired right up. I continued to get it to start about a dozen times that night. I drove it several miles and even filled the gas tank. Unfortunately it wouldn't start the next morning, or at all since. Since then I have replaced the distributor because it had a lot of play (and I figured that it was getting spark to the distributor but not after, so it was a likely problem.) No luck. Still no start. Although there is a new symptom: It will diesel for several seconds after you crank it and get no start. It also had exhaust come out of the air filter once. The only other thing is I tested the map sensor and it seems to work correctly (voltage is in range and changes when I suck on a hose connected to the sensor.) I also am getting a reading from the tps and maf when I try to start it.

I have to admit I'm pretty stumped. I retested the spark and I still get weak intermittent spark at the plugs (I only tested one, because I have done this several times already.) I still have what looks like good spark at the coil.

So far I have replaced the coil, cap rotor, distributor, ignition wires, plugs, and fuel filter.

It intermittently ran once, when it did run it had an issue of being sluggish when going slow sometimes.

I have tested the fuel pressure and checked for leak down and that all looks good.
It seems to have weak spark, or maybe my tester is junk.

Also battery voltage seems to be 14

 

clean all your grounds - battery posts, where the main ground cable attaches at the block, there is several on the back of the heads, there is a few on the fire wall ect - where you grounded the engine too the battery with cables and it ran my best guess is that's where your problem lays - if nothing else a good place too start and it's free

 

If you can`t atleast find ac delco where you live?look up summit racing.com.My blazer has aftermarket dist.cap,plugs ,plug wires,aftermarket o2 sensors.Guess what it runs like a charm.Some guys swair the blazer only runs with ac delco parts.That`s a myth.

 

I think I may have found the issue. Following the write-up on https://blazerforum.com/forum/tech-a...anks-ok-45942/ it appears that I have a short in the wiring between the coil and the ICM (see steps 6 and 28.) I cut the tape off the wires between the two, but instead of connecting directly, the wires disappear in to a larger bundle of wires. Any idea of where they go? I really don't want to tear up all the wiring under the hood chasing this thing.

 

So I rewired the connectors for the coil and the icm and the short is gone. Unfortunately there still is no spark to the plugs. I do get spark at the coil, but not when the tester is set at 30. It does produce a good blue spark when the tester is set at about 20. Before testing the spark, I tried starting it and obviously it did not run, but It will diesel for several seconds after you turn the key off.

I'm pretty stumped at this point, and very frustrated. Does anyone have a clue as to what I should try next?

 

#1. The pink wire at the ignition coil, and at the ignition control module, must both show battery voltage with the ignition in the "RUN" and "START" positions.


#2. Disconnect the electrical connector at the ignition control module. The black with white stripe wire must show less than 5 ohms resistance to ground.


#3. Disconnect the electrical connector at the ignition control module. Using a test light, (not a volt meter, and not a DVOM) connect the test light ground wire to battery positive. Touch the test light probe to the white wire and crank the engine. The test light must blink.


#4. Reconnect the ignition control module electrical connector. Using a test light, (not a volt meter, and not a DVOM) connect the test light ground wire to battery positive. Touch the test light probe to the white with black stripe wire at the module connector, and then at the ignition coil. The test light must blink at both connectors while cranking.


Notice there is a black wire with white stripe, AND a white wire with a black stripe.


Post your readings/results to each of the tests.