Fuel Pressure and spark.. but no ignition!!!

Hi All!

Here's one for you...

my Blazer (1995 vin W 4.3L CPI V6 4x4) isn't starting..
(starter cranks engine fine... fuel pump kicks in and gives pressure) but never get ignition...

I've got good values on the following:

- fuel pressure (60psi at the shcrader valve)
- compression (avg 180 psi on each cyl.)
- spark (or at least I'm getting spark.. according to an inline spark indicator)

back history part...
3 months ago I had problem with misfire.. replaced everything electrical:
-spark plugs
-spark plug wires
-distributor
-distributor cap & rotor
-coil and ECM
Still was misfiring on cyl 6.. turns out it was the cpi fuel injector.. the poppet on cyl 6 was stuck or plugged.. Replaced fuel injector and misfire went away... blazer ran wonderfully..

Then 1 week later the car wouldn't start.. couldn't get it to start for 4 days..
poked and prodded.. thinking loose connection somewhere.. tried to start it every day.. then on the 4th day it just started.. and has run fine since then!!
until 2 days ago..

so..

my question is.. what could be causing it to not start given that I have good fuel pressure.. good cylinder pressure.. and getting spark on all the cylinders..
????

a friend said maybe I flooded the engine.. I didn't think you could flood a fuel injected engine... is that possible??

I could take out the spark plugs and let the cylinders 'dry out'.. but wanted to see if anyone else had some ideas as well...

Thanks,

Tim

Yes, EFI systems can flood. You can remove a couple of the more easily accessible plugs and see if they are fuel fouled. Any liquid fuel means you need to completely dry out the plugs or replace them with dry plugs.

Another problem I see is the fuel pressure. The system should really be producing at least 62 PSIG for reliable poppet injector operation. 60 is slightly below the specified minimum.

Yes, EFI systems can flood. You can remove a couple of the more easily accessible plugs and see if they are fuel fouled. Any liquid fuel means you need to completely dry out the plugs or replace them with dry plugs.

Another problem I see is the fuel pressure. The system should really be producing at least 62 PSIG for reliable poppet injector operation. 60 is slightly below the specified minimum.

Yea when I get a chance to get back to the truck I was going to remove a few of the plugs and check them out..

fuel pressure was actually higher than 60.. I just rounded to the nearest 5's place.. maybe 61 or 62 will have to check it again to be sure.


What (if it is flooding) would cause that to occur? I've driven the truck for 12 years (275K miles on it) and never had this symptom.. and now (possibly) twice in two months..

It is a new injector spider from autozone.. (since the previous one was misfiring on cyl 6).. could it either not be injecting.. or ocasionally 'over injecting'? bad regulator? how can you tell if a poppet is 'spraying'?

Is it 'safe' to undo the intake manifold and release the poppets from their seating and 'watch' them while someone turns over the engine?

thanks,

Tim

You've replaced a bunch of parts, what brand name did you use? These engines are very "fussy" with certain parts, especially the spark plugs. Fuel delivery is critical on these engines also. When checking fuel pressure: key on, engine off, fuel pump running, must be 60psi to 66psi. After the pump shuts off, the pressure must remain above 55psi for 3 to 5 minutes.

I don't remember all the brand names of the parts I've replaced.. I don know it was ACDelco sparkplugs.. and sparkplug cables...

But that's not the reason I'm posting today...

I'd been trying to start the blazer every other day since last Wednesday when it failed to start (basically whenever I got a moment of free time to drive to where it was stranded) (thank goodness the grocery store people know I'm a loyal customer.. they hadn't towed it yet)

So last time I tried I left my parking lights on by accident. So the battery was totally drained. Couldn't even pop the back hatch to get to the jumper cables I keep in the back. After climbing over everything to grab them, I hooked them up.. waited a few minutes.. and BAM, she started -right- up..

So.. while I'm happy the blazer is starting again.. I still don't know why it failed to start for a week, unless it was flooded, which I didn't get a chance to check the sparkplugs.. or something computer related was keeping it from 'injecting' (since the battery died the computer had to have reset).

But now it is starting.. and running fine..

at least.. until next time it decides to strand me someplace..

:headshake: & :confused: