Vortech Fuel Injectors

Hey,

Can you guys talk to me about the 1996-1998 350 Vortech fuel injection system?

My pickup seems to shudder at idle and sometimes even has a hard miss now and then. All the ignition components are new about a month ago. Delco 41-993 plugs, denso cap and rotor, and delphi wires.

When I pulled the plugs, maybe you remember a couple had some considerable depositis on them and all smelled like gas. I assumed the deposits was oil buildup from valve stem seals. Now I am wondering if maybe an injector is sticking or a bunch of them are sticking.

What can I do to diagnose the shudder at idle? The truck runs good and starts good otherwise, and it accellerates and drives just fine.

I am thinking one of two things, possibly a leaky fuel pressure regulator, and or one or more sticking fuel injectors.

What is the best way to diagnose rather than to throw parts at it? (cause the spider injector assembly is expensive).

And I see there is an upgraded spider injector for sale. Anyone have good luck with them?

My info is that the SCPI injector (and also CPI) is very sensitive to proper fuel pressure.

Change fuel filter is an easy one, if there was an aftermarket/non Delco fuel pump installed at one time I'd change it.

SCPI is a screwy interim design that probably shouldn't have been done. I suppose the money to develop the Gen 2 small block V8 into a SFI fuel system design with proper port fuel injection was more than GM wanted to spend knowing the Gen 3 was already headed for production already with above hardware.

Keeping the injectors up high resolves a lot of hot-fuel handling (vapor lock) conditions while the "feed tubes" keep the manifold "dry" to resolve hydrocarbon emission issues. But you end up with the oddball hardware that doesn't match up with the trouble-free durability of the TBI and the newer SFI systems.

Yeah, I think I am going to rent a fuel pressure guage and see what the pressure is. Any onw know the spec for key on engine off and key on engine running?

They are particular about having enough fuel pressure...60 psi minimum to start and not much less to run well. If you find it is low, try changing the fuel pressure regulator located on the back of the spider assembly. Good luck!

There is two types of injection systems used on the 97 K-1500 5.7 engine.

CSI specs 60/66 lbs fuel pressure.
SFI specs 56/62 lbs fuel pressure.

Fuel pressure and fuel pump should be tested for up to specs.

Also most good engine capable scanners have a fuel pressure/injector test for each injector proper operation and bleed off.

Also will shoud each cylinder no of missfires..
Cam shaft retard should also be checked and set.

Fuel pump testing.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

Thanks guys, I have not had a chance to check fuel pressure yet. Plus it has been -20 degree windchills in MN recently. So as soon as I have a chance I will get my fuel pressure specs. How do I know if my truck has SFI or CSI?

Hello guys, I am new to this site and have always driven chevy trucks. Have the exact same problem with my 1997 chevy 5.7L that t blake is having. The idle has a constant tremble warm or cold and sometimes in gear at idle a shudder will occur. The trucks runs great at all rpms, does not hesitate, nor has any starting issues warm or cold. All new wires, plugs, K&N air filter plus B-12 fuel cleaner. I suspect that it is the injectors but am not for sure. Any and all help on my problem will be appreciated. I don't know if there is a thread on here about removing the deflector on the throttle blade, but my truck is more responsive after doing so.

Hi Truckerred! Glad you joined the forums. Sorry to say this, but its nice to know someone else has the same issue as me! HAHA! (sarcasm aside)....Removing the Defelctor on the throttle blade? I am intrueged! Can you ellaborate?

Also on my pickup, I somehow fear that my issue is a bad lower intake gasket. I think maybe one of the port runners sucked the gasket in causing a vacuum leak into the crankcase. That would explain the shudder at idle, possibly the oil fouled plug (if the vacuum leak is large enough) and will also explain the uneven plug conditions. 2468 bank was fine, 1357 bank, 3 was fouled with oil, and 1357 all were dripping with gas almost as if the computer was compensating that bank for a vacuum leak. I will have a little bit of time tomorrow afternoon. I will rent a fuel pressure guage and do some checks on the LIM gaskets and let everyone know.

Sucks that this sort of stuff always crops up when its so darn cold out. I will report back with what I find out.

The lower intake gasket is a required fix on these truck. Had mine fixed last year with felpro gaskets-not factory, was leaking coolant outside the front of the engine. If you remove the quick disconnect heater hose, it will disintergrate and break off at the threads-be forewarned. The throttle blade has a delfector on the underside, who knows what it's there for? I removed the throttlebody and throttle blade then with tinsnips cut the flimsy metal away close to the rivets. Then I gently hammered the remaining metal flat level to the throttle blade and reassembled. It was free and I can tell the difference. Use lock-tite on the throttle blade screws.

Sounds good, thanks for the info. (on the throttle body and the quick disconnect in the LIM.

My problem is #3 and #5 plugs fouling out. I pulled the new ones I put in a couple months ago out, and they were coverd in this lighter colored residue. I replaced them with a could cheapo autolite 605's and it ran good again. I think I will just keep swapping them out until it gets warm in MN, and then try replacing the valve stem seals.

try a vial of the Lucas Fuel Injection cleaner (or any brand of your choice) seems to work well on my previous vehicles took care of the shudders, remember its that time of year so the oil and other fluids thicken thus retaining more impurities.

Problem turned out to be multiple issues.

-FPR was leaky
-2 Injectors were leaky (stuck open)
-LIM gaskets were sucked in in #3 and #5 ports

New upgraded MPFI injection unit solved the injector and FPR issue. At the same time I replaced the LIM gaskets with the fel-pro brand. After all that, fuel pressure would not hold so it also got a new fuel pump. All is good now.