This is a "real" vortec 350, w/all the original vortec intake, injection ("Central Fuel Injection"), etc. -as opposed to a "Vortec" longblock w/some other type of induction.

It developed the common Vortec intake gasket leak and leaked coolant into the valley/oil pan. I removed the intake tonight to replace the intake gasket, and #3 roller lifter which was ticking on start up. When all the parts were off, I threw everything in the aqueous parts cleaner (like a big dishwasher). The intake manifold and injection, the plenum lid, and the valve cover.

Reassembled everything, and was pleased w/my work. Changed the oil and filter, unplugged the primary plug on the coil and cranked until I had oil presure. Plugged the primary ignition back into the coil, and....it wouldn't start.

It has spark

It will run on gas that is manually fed into the plenum.

It has 55 - 57 PSI of fuel presure.

The plugs are bone dry.

Why aren't the injectors firing?? HELP!

 

sounds like a clogged fuel system...
Eric

 

Which part? All eight injectors? At the same time?

The fuel filter is not clogged. Again, 55+ PSI.

 

Doesn't sound like enough fuel pressure.... those things take ALOT, like 60 psi +. And when they don't have enough, it's not a gradual taper off in performance, like with port FI or traditional TBI; they simply stop running. That "poppet" thing won't open at all if there's not enough FP.

 

I think that the 55psi of fuel pressure is enough to pop of the vortec injectors, however check all of your electrical conections, especially the big one on top of the manifold. also, do you know about setting the CMP retard after doing an intake job on these?

 

RB, althought you are correct about the manor in which these engiens die rather than "fade" as the FP drops, GTA Matt is correct about the pressure. It takes ~45 - 50 PSI to pop the "poppets" and I have more than that.

Matt, I did double check (Tripkle checked actually) ALL connections, and I even unplugged and re-plugged some of the critical ones, including the 16 pin injector plug ontop of the manifold that you're talking about.

CMP Retard? I don't know anything about this. What is this?

Is it possible that the aqeuous parts cleaner ruined the injuctors or the poppets?

 

While the pressure is too high (43psi with the vacuum hose disconnected from the fuel pressure regulator, or the engine off) it's not preventing the injectors from flowing.

Have you checked for codes? If the ECM doesn't flash at all it's dead and the injectors will not fire. I assume you've checked the fuses?
If ECM, and Fuses are good, then
Use a Noid light to check for ECM signal (bright pulsing light) to injectors.
If SIgnal is good, then
Check injector resistance (14-16ohms.) one injector at 4ohms will hog the current and keep the others from opening.
If resistance is good, then
Disconnect the coil, raise the fuel rails put glass jars underneath each pair of injectors, crank engine and check for flow.

 

rgarcia63, you're thinking of a conventional EFI system. This one is different and 55+ PSI is not too much.

I have checked fuses, codes (none), etc.

I have pretty much figured it out; the "Port Poppets" are clogged by the residue from the soap left by the aqueous parts cleaner. now I just need to figure out how to get them unclogged/flowing again. :/

-Tom

 

Every single no-start I've ever run across in those CPFIs, without one exception yet, was from inadequate fuel pressure.

It would be nice if there was some other way to test it besides replacing the pump. But, I think that's where your problem is going to turn out to lie.

 

RB, thanks for the reply again. I agree that with these things 99% of the time it's the fuel pump. We have 25 of them here at the ski resort and we probably change a pump a month. But as per our GM technical service manual, the FP spec is 55-61 PSI (just looked it up to verify). I'm at 55-58 ish. I should be O.K. FP wise. We see these things all the time in here w/ FP issues, and I've seen them run as low as 49 PSI. After that though, nothing.

I've got it firing on one cylinder now. I'm going to try to push about 70 - 80 PSI through the injectors and see if that clears out the poppets.

Edit. I also just read in the service manual;
"Also since the injectors are electrical components, these injectors should never be immersed in any type of liquid solvent or cleaner as damage may occur."

Uh-Oh....

 

Thanks, my WOT fuel pressure would barely be enough to open those poppet nozzles.
I think I'll stick with the conventional.

Good Luck!!

 

Lol. Conventional is better.

So, it WAS the poppets. They were all stuck, and I'm sure it's from the parts washer soap.

I took the plenum lid off, and re-attached the fuel lines to the injector "pod". I pullet all eight poppet tips from the ports and pointed them up in the air. Cranking the engine resulted in spray from exactly ZERO poppets. I gave all eight of the poppets a light, but sharp "rap" w/a tiny hammer, holding them in my hand...just enought to jostle them smartly. Tried the key again, and pow-pow-pow-pow-pow-pow-pow-pow-pow! All eight of them shot a plume for gas into the air in a nice sequential order! (cool looking) Woo-hoo!

Re assembled and fired her up. Thanks for all the input everyone. I can now drive home from work!

-Tom

P.S. Pushing 90 PSI though the injectors didn't get them going, but tapping on them(the poppets) did!

 

CMP retard is setting the timing in the distributer. on those motors, you don't do it the conventional way. you need a scan tool where you can see the CMP retard. Make sure the motor is warm, then quickly rev it to about 2k, then let off. turn the distributer and rev it up everytime you move it. you want it to be set between 0 and +2. if it is way off it will set the SES light after a while.

 

Huh. That's interesting. I just marked the dist body, intake, and rotor, and then put it back in the same orientation as it was when it came out. That's fine isn't it?

 

Cool! Glad it was a cheap fix at least, if not real intuitive or easy.