hi all, i recently purchased a 1994 blazer with the CPI 4.3 motor in it from one of my friends, in a non running state, for $400. anyway, i've been doing some diagnosing as to what the problem may be, and i'm led to believe it could be the fuel injector unit (spider valve or whatever its called). here's what i've done so far:

-when the blazer stopped running for my friend, we didnt hear the fuel pump running anymore, so we replaced it. we then heard the fuel pump operating normally, but it still wouldnt start.

-i've confirmed it is a fuel problem, because it will run fine off of starter fluid.

-i haven't put an actual gauge on it yet, but i have confirmed fuel pressure by pressing in the valve on the fuel line with a screwdriver (got a gush of fuel), letting the pressure bleed off, then repriming the system by turning the key to on. the pressure at the valve on the fuel line was back again.

thats about where i stand as of now. i've done a lot of reading up on this issue, and my next plan is to remove the upper plenum and do a visual check of the fuel injector, but i would like to know if there is an actual way to check and see if that fuel injector is bad.

thanks for any info or help on the subject

 

Most of them I have run into will at least run with a bad injector so you may need to do more diags. Don’t drop your fight with the fuel pressure either. I would test this before you crack the plenum. Fuel pressure testers are cheap ($14.00 at harbor freight Chinese tools). I just replaced my fuel pump that was giving me starting problems but still reading close to normal (like 51 I think). While testing it repeatedly in the drive way it stopped dead and never pumped another PSI again (man was I lucky). You may also have a filter problem if you didn’t change it. A clogged filter will kill a fuel pump over time. The screw driver into the Schrader valve is like the worst thing I could ever think of doing for your safety (both fire and eye damage) as well as for the health of the valve.
A pressure gauge may also tell you if the CPI is bad. If the pressure bleeds off after you charge the fuel system it may be a leaking “nut kit” or CPI. It should stay charged for 5+ minutes.

Starting fluid can deceive you! It contains Ether and may just detonate the thing to life (old history). The best way to test is to simply spray a little gas with a cleaning product spray bottle past the air valve (being very careful obviously). Double check you are getting spark (fast test).

But CPI testing. You can remove the variable butterfly at the top of the manifold and peak into the plenum. If the passenger side is Clean it is bad. If you see gas pools it is bad. But this won’t tell you if the “nut kit” is leaking. This is another potential you will want to look at. The best advice is to just crank off the top of the plenum. I have gotten it down to less than 10 minutes as I have done this so many times. This is the quickest way to see if it is the nut kit or the CPI. If I knew how many miles you had it would also help. I think the typical failure curve of the original unit is 90-120K.

Lastly see if you have any stored codes (you probably killed this when you changed the fuel pump) to make sure it isn’t the EGR valve sticking open (but this too usually at least starts).