my 1988 trans am 5.7 tpi auto will not start

about a week ago it would barely start and using 1/4 throttle helped it start and then it would idle really rough on about 5 cylinders and slowly clean up and run ok.

now it just wont start, it winds over and over and will not fire up. at first I could hear it fire one or two cylidners but it got worse trying to crank it, and now no hint, it's like I have no spark, yet I have spark at the spark plugs?

I've replaced ECM, distributor module, spark control module, new coil, has new cap and rotor button, over the last 2 years it's had new starter motor, new iac, tps coolant temp sensor, oil pressure sensor, oxygen sensor, new plugs and leads.

when winding engine over it has spark at the spark plug. and fuel pump primes and his 41psi rail pressure, I even tried spraying extra fuel into the intake manifold to be sure but still no start. it's so strange to have spark and fuel and no start... when I wind it over I start to smell a bit of a fuel smell but no start. normally I've been able to figure these kind of things out, but I'm lost. there are no check engine codes as the engine wont run to even throw a code. I've also checked fuses. my only other thought is, pickup coil? or some wire has come off something and preventing it from running? any help is greatly appreciated.

 

I'm having the same issues with a NEW motor !!

 

What does the ECM think engine temp is?

 

Seeing a spark on a plug out of the engine and it being strong enough to the fuel mixture in the cyl are two different things.
The fact it wouldn't fire with fuel squirted is a dead giveaway your spark is weak or missing

Run these tests
http://easyautodiagnostics.com/gm_ic...n_module_1.php


Past codes seen are stored in the ECM ; engine dosen't have to run to see them

 

thanks for that vetteoz, I'll read through that and see how things go.

 

Did u do a compression test?

 

FIXED! previously I had cleaned the spark plugs and no change. I checked them for spark outside of the engine and they sparked. it turned out spark was dead under compression. a new set of spark plugs and it fired up and runs great again. I guess the lesson there is, don't think the plugs are working because you cleaned them and they spark outside of the car. try a new set of plugs. I can't believe it lol. but there we go. very happy. thanks guys.

 

Similar situation occurs if your plug wires are old.
Spark will take the path of least resistance so even if the plug is seen to spark out of the engine as soon as it is subjected to cyl pressure,
the spark will escape from a deteriorated plug wire or cracked dist cap

 

Im having the same problem with my car now, ive just done a 5.0 to 5.7 swap, and my 5.0 was doing the same thing before i pulled it out, just cranking over and over

the 5.7 fired up first time but felt like it was running on like 3 cylinders, i was getting spark, good fuel pressure but it was just missing and ran terrible. And now it wont start at all, it just cranks continuously.

Im using the same NGK plugs from the 5.0 engine in the 5.7 so ive got a new set of plugs on the way, if it turns out to just be the plus i will be so happy.

So if just one of your plugs crapped out would it cause the car to just crank over all the time without even trying to fire up ?

 

If its not the plugs. Did you see if the injectors are firing?

 

They are pulsing fine, and they are also brand new injectors from southbay

 

all this sounds like timing???