This is for a 99 blazer 4.3. The replacement engine was a 2001.
After an engine swap the replacement engine will not start.
Here is what was done.
The replacement engine had all of the gaskets replaced, we did remove the
distributor when the intake manifold was removed.
The knox sensor was moved from the old engine.
The engine cranks, but will not start.
What has been checked.
1) have fuel pressure at the intake.
2) have spark
3) have oil pressure
4) have check the timing
5) have sprayed intake cleaner into the intake and the engine will fire
6) No codes
Any thoughts no what I am missing........

Thanks

 

Do you have injector voltage pulse while your tring to start it?

 

Are all of the fuses good?

What was the fuel pressure with the key-on/engine-off? Did it exceed 55psi? Did it remain above 50psi for 10 minutes after the pump shut off?

Have you read either of these two DIY articles?
Engine Cranks But Does Not Run
No-Start - Engine Cranks OK - Ignition System Diagnosis

 

hertz20
Do you have injector voltage pulse while your tring to start it?

Yes.

swartlkk
Are all of the fuses good? Yes

What was the fuel pressure with the key-on/engine-off? Did it exceed 55psi? Did it remain above 50psi for 10 minutes after the pump shut off?

I see 50 PSI when the key is on/engine-off. And yes it keeps the 50 psi after the key is turned off.

 

50psi is not high enough for these engines. The lowest I have seen from a running engine on an accurate gauge is 55psi. GM states 60psi as the proper low limit.

Sounds like the fuel pump is weak.

 

Just replaced it last year. I will have to recheck when I get home.

 

I had some time and checked it and its at 62 psi.

 

Any thoughts on this. When I pull the #1 plug to check for TDC.
The plug does not have any gas smell.
Should I smell gas after tring to start it?

 

I found my problem. It was the spider. Put the one in from the old engine.