I have a 1994 full size blazer with the 5.7 tbi that is getting fuel and getting fire but not turning over. I am by no means a mechanic so please note ahead of time that the way I know it is getting fuel is while trying to crank it I can smell the fuel. The way I know it is getting fire is I took off the number 1 plug wire and put a screw driver in it and held it next to the steering shaft as my daughter tried to start it. I do not know if it is a fast enough fire or not. I would say about 1 full second between sparks as she was turning it over. The truck ran great driving it home from work. I got home and parked it. Came out the next morning to go to work and it would not start. The truck has always fired right up as soon as you hit the key before. The only symptoms I have noticed is while driving on the interstate heading to work I noticed the service engine soon light comes on and then when I get to my exit it goes off. When I first crank it after work I can smell a strong fuel smell but after a second or two you cant smell it anymore. If for some reason I goose it a couple of times when it is cold it will run real rough and almost die when it goes back to an idle until it is warmed up. I bought the truck almost exactly 1 year ago and due to working 16-18 hours a day I have not done a tune up on it and have no clue when the previous owner has done one. I am going to get a new cap and rotor button and wires and plugs tomorrow when I get off of work and see if the cap and rotor button fixes it but I am not that lucky of a person so I am looking to see if anyone can point in the right direction of things to try. Thank you very much ahead of time for taking the time to help for anyone that does.

 

It turns over...It has fuel...It has spark...And I assume it has Air...

So it either doesn't have spark at the right time , or not enough spark..

To be honest , I think you're on the right track with "new cap and rotor button and wires and plugs"

"but I am not that lucky of a person" ....Hmmm , it's a New Year..Maybe your luck has changed..

I have seen new plugs and wires alone transform an engine from rough running to like almost new..

Stick with your plan, it may just surprise ya and work...

 

Service engine with MIL indicator on highway...

... I would include looking at the sensor inputs.

Temperature sender comes to mind make the engine believe it is still in cold-run mode or EGR.

Maybe somebody on the forum has a service manual for the V8.

 

Okay so now I am really baffled. On my way home I stopped and got the rotor button and cap, came home was getting ready to replace them and something made me decide to have my son turn it over while I checked the number 1 wire for spark again. The truck fired up as soon he hit the key. I plugged the number 1 wire back up and started it and killed it about 30 times and it fired right up every time. So now my question is this. We have had below freezing temperatures the last couple of weeks and yesterday when the truck would not start it was VERY humid. Is it pretty accurate that my problem is a cracked cap and condensation got inside of it and now that it is not humid again it is dry and working properly for the moment?

 

yes, this is possible.

During the tune up or when diagnosing ignition, when disconnecting spark wires, cap etc. always have a very close and thorough look at every single part.
Detach a spark wire and have a close look all along it. Check the insulation for cracks, cuts, rubbing. Look at the terminals for looseness, corrosion, traces of arching with deposits. Also look on the engine along where the cable was routed and check for traces of arching or rubbing.

I check on these things in order to be able to eventually determine a cause for a problem.

Then go on and do the same with the cap. Before cleaning it have a good look outside and inside. Look how the terminals look inside. Again traces of the arching, how does the deposit look how does the cap look inside, deposit of coal on the inside walls, traces of arching along the wall.
Clean it and gently try to pull the cap apart, sometimes when cracked it may be possible to see the crack.

I don't know the 94 full size Blazer and can therefore not give directions about the ignition system and diagnostics. The assumption i can make is that it is pretty much the same as the 94 V6 which means it is a "pre OBD II" vehicle.

Also try to get a hold on the information about reading (or "flashing") the fault codes from the trucks control module.

Stay save! Ignition off, maybe a pair or thin working gloves, a tool to pry caps instead of pulling by hand.