It was running fine, daily driven, driven to work in the morning and wouldn't start when going to leave.

it spins freely but doesn't even start to fire.

It does have spark.

The plugs seem bone dry as far as I can tell.

I hot wired the fuel pump, veryfied it was getting fuel at the shrader valve. I don't have a shrader valve adapter to check the pressure. Doesn't start even with it hot wired.

I stuck a test light on a couple of the injectors, and they are getting voltage. It also flickers reguarly while turning it over so I take it that means they're firing....right? They're down in the manifold (that funky central port SFI the vortec motors use) so I can't stick a finger on them to feel if they are.


What should I check next? I'm not that experienced with fuel infection so I'm kinda stumped. Thanks.

 

Tell your mom to stop driving it

 

lol you ain't kidding. I swear some car manufacturer needs to hire her to have her test drive prototypes and work out the bugs. If it can be broken..she can break it.

 

i'd suspect the fuel pump or regulator, even if you are getting fuel at the valve

 

Nobody can help you on this board w/Vortec information -I already tried. Nothing. lol.

IMO, you HAVE to get your hands on a FP gauge that will fit that schrader fitting. From the minimal info that I have been able to gather, all 8 injectors are in one housing behind the throttle body, above the plenum. Each injector has a line running from it, to a "pop off" valve at it's respective port. These "pop-off" valves exist to prevent fuel from draining out of each cylinders' line, and into the port, between injector pulses.

From what I understand, the pop-off valve needs to see over 50 psi to open. Therefore, if you fuel pump is weak, the injectors can be opening on que, but the fuel presure may not be sufficient to break open the pop-off vavles. These means no fuel to the engine....-If all this patched together information is true. You need to fine out what your fuel presure is. It should be AT LEAST 55 PSI.

There certainly doesn't seem to be much info floating around about this engine. Probably since it only existed for 4 years. But I must say that it is an engine I'm very impressed with. I have one in my '96 Chev 1500, 4x4, and it has thoroughly exceeded my expectations. It has extremely good power, and I get over 20 mpg on the highway with it. I even get over 15 mpg towing my boat (19' ski boat). I wonder why some folks don't throw a scavenged junkyard unit in a car with the injection intact, and headers. It seems like 300 hp out of this motor would be simple. Anyway, how about THAT little tangent. lol.

Hope my little bit of info could be of help.

 

Yeh I love this truck too. Good for anything, anytime. Cept when the fuel infection has problems anyway

If it's supposed to be over 55 psi I don't need a gauge to see it's WAY short, it barely runs out of the the schrader. For some reason I didn't think the operating pressure was nearly that high, but I could certainly be wrong.

Can anyone verify the right fuel pressure? also, how do I dertermine if it's the AFPR or the pump...block off the return line?

 

This exact thing happened to my father's '96 GMC with the 350 Vortec.

It was the fuel pump. His truck has about 110,000 miles.

jms

 

It's confirmed...tis the pump. I picked up a FP gauge and it registers less than 10...even with the return line pinched closed. I looked it up too and you were right tom. S;pposed to be 60-66 psi.

Grr. Gee only about 300 pounds of fuel in the tank too. Gonna take all night to pump out with the pump as dead as it is fun fun fun.


Thanks guys.

 

If you have three good friends that are (fairly) strong it might be easier and quicker to take the bed off.

jms

 

You know..thats not a bad idea. hmm...I wonder.....anyone that sees this happen to know how much a 6' truck bed wieghs?

 

Taking the bed off is a great idea. That is what we do here at work on these trucks, and they have 8' beds.

8 bolts, rear harness weather pack connector, fuel neck and a ground strap an off the bed comes! Good suggestion "jms".

edit: The bed weighs about 400 lbs. Do-able with 3 people, easy with four.

 

I bet its your fuel pump as well. My friend had the exact same problem as you did on his '96 Tahoe. It wouldn't start. I did the same kind of tests as well....unplugged the FP relay and jumped it and fuel came out of the shraeder valve. Checked for spark with a timing light. Had that as well. Poured some gas down the intake and it ran for a second. We suspected it all along and just went ahead and dropped the tank and put in a new pump (its much easier procedure on those trucks than on our f-bodies). Car fired right up. Just because you have fuel coming out of the shraeder valve doesn't mean the pump is pumping the required amount of fuel at the required pressure. At the high fuel pressures that most fuel injection systems are supposed to work at, the fuel should be shooting out of there not trickling.