Hello i'm robert first time here, what i have is a 95 blazer vin w, obd ii, cpi injected. Bought with a bad motor and i heard it run w bad mains so i got a new motor went threw it and refreshed it completely. After installing it it fired right up ran good for 20 mon than started to stumble run rough under light load not wot so investigated with my snap on mt2500 scanner. Found bad knock sensors so replaced them and also found a puddle of coolant on floor, installed new heater core fired it up and it run for a few now won't start has spark, has 61lbs of fuel pressure now after pump and line change, good compression everything checks out and timing is right or it would of never started and ran good before it also has a new spider inj. Unit now i'm stumped. Owned and worked as a mechanic for years. I know these trucks are tempermental the only thing that has not been replaced is the vcm. Which is on top of coolant bottle. So what gives sounds like timing but it's preset by timing marks and the #6 imprinted on distributor and balancer is good not spun. Likes to foul plugs and barely fire but has good spark i'm clueless so did i screw something up on the heater core change or is the computer bad? Never looked for help on any vehicle since i was in my teens,25 years ago! Any help would ne appreciated again this vehicle ran great for the first 20 min of it's life and nothing in this new motor broke or moved, positive! I've have spent 4 days trying to be thurow.

Anybody got some ideas. This vehicle is for my son and I've got a lot of time and money invested

 

Check this:
https://blazerforum.com/forum/engine...32/#post432930
I had a problem - I could start an engine only with big stationar starting booster - after that run was good. That problem was random - sometimes engine start well. Try to check fuel pressure when U can't start the engine - it must be 60-66 lbs, by the way, fuel pressure becomes lower after the ignition is turned off, but little bit. If pressure goes to zero after ignition off - look for some holes or disconnections in fuel system. Sorry for bad english.

 

Your English is fine I've got 61 lbs when cranking then it goes to 58 after I let go of key and holds there no bleed down. Starting to think spark could be stronger. It acts as if fuel delivery and spark are off time. How much of a draw should I see cranking should everything stay at 12 volts? I'm in the high 11s while cranking.

I would love to put an msd on this it would rule out spark

 

does anyone have an answer or clues that i might be overlooking.

 

not sure but dont these have the wire you have to unplug under the dash near the heater core for timing. possibly still unpluged

 

It would idle ok with it unplugged.

 

I wish I could unplug a wire its obd ii and computer is on the coolant bottle that's for the years prior.

Where's all the big knowledge people at? I was hopeing for some good info since this site was about blazers or is it cause I'm a newbie here!

 

EDI Engine Timing - procedure for setting the timing on the EDI engines (horizontal wire terminals on the distributor cap)

Another issue that has cropped up from time to time and proves to be quite a hassle to diagnose is a faulty electrical connection at the CPI spider. I recommend replacing the connection whenever the spider is replaced for this very reason. It's cheap enough. To test this theory, gently pull on the wires (2 wires that exit the front of the lower intake manifold below and slightly to the driver side of the throttle body). If the engine fires, the connector needs to be replaced. You can also test this by doing an injector test with a compatible scan tool and watching the fuel pressure.

 

I agree with what you say for some strange reason I can do all functions like set cam retard and everything else on my 96 Chevy 1500 4x4 and everybody else's vehicles but this 95 blazer and it's 1st gen obd ii you can't get into I've tried tricking it into 96 with no luck but even with that all set aside it should still start just throw a code(I say this laughing because what was I thinking its a 95 blazer the pickiest truck of them all). As for the injection wire I could replace it but Im getting a flood issue like spark can't ignite the brand new 93 octane that's in there,11.8 v at wire and brand new msd coil.. boy I really wish I could make this thing relearn though my scanner is not a programmer and I have a feeling that's where I'm at!

 

Your scan tool may not have the proper programming for the early implementation of OBD2 with the '95 model year trucks. But you are correct that even if the CMP Retard and CKP/CMP Correlations were off, the truck should still fire & run. I simply posted the procedure so that you could verify that the base timing was correct.

Are you sure that it is a spark timing issue? Maybe compression is off? Are the plugs getting wet?