97 blazer wont start

[agcneo]

i just swapped my motor into my blazer, its the same 4.3 vortec. everything is connected, and we set the timing, or so we thought and tried cranking the motor over. it sparks here and there, turns over smothly, then stops all of a sudden, then jerks around a little bit, then continues turnin smothly. and that sequence is completely random. we thought we had it 180 off, so we corrected it, and it still just wont fire up. u can hear it combust, suck air in, back fire, everything but just start. all new wires, plugs.. rotor and cap is maybe 4 months old. i dont think im missing a sensor connection, that i know of. is there any connection that would prevent the motor from starting. the motor also sounds awful when it tries starting, nothing like it did with the old motor, almost like a smoker coughing. im gettin quite frusterated with this blazer, almost ready to give up. any help please?!

[DelCoch]

Are you trying to use the old vcm/ecm that was dunked in the pond?? Unless you have the vcm that was with the new engine it will have to be reprogramed.

[agcneo]

as a matter of fact yes. im supprise you rememberd i did that. but that motor ran for 2-3 months before it blew up. so i figured the old ecm is fine. never showed any signs of problems

[DelCoch]

You need to get the ecm that was on the new engine. Unless both ecm's have the same numbers the engine won't even start. Are both engines the same year? If not you will probably need the wiring harness that was with the new engine.

[agcneo]

the guy at the yard told me that it was the same year motor, how do i check this number on the ecm and motor?! i was not aware of this. wire harness seems to fit everything perfectly. now im startin to get a lil worried, how much does the typical yard charge for the ecm

[DelCoch]

Originally Posted by agcneo

. . . how much does the typical yard charge for the ecm

I got a vcm for my '95 for 40 bucks, but the price will probably depend on what part of the country you're in. The long set of numbers on the ecm's have to be the same, even then you won't get anything other than a start without reprogramming the ecm, as it has to be set up with the transmission, etc.

I don't have a book to check engine numbers, but as I recall there's a big article about engine types in the "How To/Tech Info" section of the FAQ's section of this Blazer forum.

[agcneo]

i didnt think it would be a problem since they are both identical motors taken out of "supposedly" 97 ls blazers and its still the same tranny. everything is the same, i just never saw the vehicle. i guess im gonna give that a shot and take a look into it, anyone else have any ideas bout it? anyway to tripple check my timing?

[DelCoch]

Here's a link to the article I was talking about, it gives the casting numbers for engines up through '98. Check the casting numbers on both your blocks, if the casting numbers are not the same, then they are different years.

The timing should not be adjustable on a '97, as that function is handled by info supplied to the ecm by the crankshaft sensor and the camshaft sensor. To set the time, bring #1 cylinder up on compression, align the timing marks on the damper pulley and put the distributor in with the rotor pointing towards #1 spark plug wire in the cap, or as close as you can get it to point to #1 spark plug, as it may point between #1 & #3 or between 5 & 1. Make sure you know which cylinder is #1.

[agcneo]

thanks, i appreciate it lots. if this doesnt solve it, is there anything else i should know

[DelCoch]

The firing order is 1-6-5-4-3-2 - so, set your distributer with rotor pointing as close as possible to #1 in the cap. Make sure you have the spark plug wires on the right spark plugs as it's easy to get them on wrong.

[Jari]

Originally Posted by agcneo

thanks, i appreciate it lots. if this doesnt solve it, is there anything else i should know

There are actually two timing marks on the damper pulley ('98). When you are timing the engine, make sure to use the latter timing mark. If you use the other, engine won't start.

[agcneo]

the latter one?! i know theres 2, but what one is the later one. after the compression? by buddy, who is also my mechanic, set it to top dead center, droped the dist in, and it still sounded like timing was off a bit. so we should use the other timing mark?

[Jari]

First mark is before TDC and the second one is TDC. When you rotate engine, don't use the first mark but the second. In TDC other mark is pointing 3 o'clock, not 12 o'clock. You can try both of those it doesn't harm the engine.

[BlazerLT]

Hold up guys, it is a 1997, he needs to replace the ignition switch.

[DelCoch]

Originally Posted by BlazerLT

Hold up guys, it is a 1997, he needs to replace the ignition switch.

Maybe, but I doubt it at this point - he has a compatibility problem - probably should just divorce the whole thing.