Engine will crank. but will not start. any help is much appreciated
 

My blazer was down for about a month while doing starter repairs. Changed out spark plug wires and added a k&n air filter. It has a new starter now. Before it was down it started good. Fired right up. Now i cant get it to start unless i spray starter fluid into the air intake. Any suggestions on what this could be? Ive been told to test fuel pressure. Map sensor. Ciuld these things cause it not to fire up?

If the engine will "run" with starter spray, then air and spark are present, fuel is missing; so to answer your question, Yes...if there is no fuel pressure, the engine is not going to run.

Check the fuel pump fuse and try applying +12V to the fuel pump test terminal and listen for the fuel pump running.

+1^ Lanny181

another thing to check is the fuel pump relay and it's connecter... can even switch with another relay with same number, maybe A/C one.

if all looks good there maybe possible fuel pressure regulator could be bad and located under intake

Checked fuel pressure. Was 40 psi and dropped slowly. Omh'ed out IAT sensor, read good, checked voltage at MAP sensor,it checked out good. not for sure on where to go from here. Changing out water pump tomorrow. Any help much appreciated.

What exactly do you have under the hood? size motor and year? Why are you replacing water pump? Is it leaking or overheating or something?... Once I get further info, I or others as well, should be able to guide you bit better

40 PSI is not enough, when you say dropped slowly, how slowly? Your fuel pressure should be in the 60ish range and hold to around 55 for several minutes.

like tempest said. 40 is way too low. 60 minimum at key on and it has to hold over 55 for 10 min.

Was the fuel pressure checked with the engine off?....needs to be. If so, then 40psi is not going to work and likely time to replace the fuel pump. ONLY use a Delco pump or you will be doing this job again in a few months..at best.

I had the same issue a couple weeks a ago. Thought it was the ignition but took my ECM in to A zone and they tested it was fine.. Got it to fire with starter fluid. determined it was the fuel pump.. had to take it in to get replaced along with the fuel filter and now is all better..

Yes I totally agree there.... If it's not the earlier throttle body type.... since this section cover '95 to '05, I didn't want to just assume.