Spider injection issues

[BLACK&chrome]

Alright folks I've got a problem noone can seem to track. Front side injectors work intermittently. Can fire all through scanner. Fuel pressure good, filter good, pump good, ecm fuses good. I hooked up 3 more grounds and tried 2 different spiders, new plugs, wires, distributor and all sensors are new still no difference. Anyone have any ideas what else it could be?

 

[BLACK&chrome]

2000 5.7 with 4L80E

 

[stutaeng]

You tried 2 different new spiders? Oh, I see where you said new...

Take a look at a wiring diagram. I found one here for a 96, but I think they are all the same: The ECU grounds the individual injectors to pulse them. The 12V+ looks like is a pink wire: https://www.scannerdanner.com/forum...l-vortec-engine-2wd-crank-no-start-issue.html

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Do they act up when you are driving? Or even at idle? Only under load? If you are in the states where rust is a problem, you may have a wire(s) that probably corroded and not making good contact. How do you know they are failing intermittently?

I've watched videos on guys using a long screwdriver and a cut plastic jug/bottle over the screwdriver handle as a low-tech, stethoscope. It's supposed to work really well to see if an injector is not pulsing, just put the blade of the screwdriver of the suspect injector. Obviously, can only do this in Park, and can't do this with the spiders living under that plenum.

 

[stutaeng]

Like this...and looks like it has other uses, LOL.

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[1998_K1500_Sub]

I'm really confused...

You said "Front side injectors work intermittently."

Which are the "Front side injectors"? How did you identify them?

Define "intermittent"... and explain the conditions. At idle? Cruise? Light / heavy acceleration? During power enrichment?

 

[BLACK&chrome]

You tried 2 different new spiders? Oh, I see where you said new...

Take a look at a wiring diagram. I found one here for a 96, but I think they are all the same: The ECU grounds the individual injectors to pulse them. The 12V+ looks like is a pink wire: https://www.scannerdanner.com/forum...l-vortec-engine-2wd-crank-no-start-issue.html

You must be registered for see images attach

Do they act up when you are driving? Or even at idle? Only under load? If you are in the states where rust is a problem, you may have a wire(s) that probably corroded and not making good contact. How do you know they are failing intermittently?

I've watched videos on guys using a long screwdriver and a cut plastic jug/bottle over the screwdriver handle as a low-tech, stethoscope. It's supposed to work really well to see if an injector is not pulsing, just put the blade of the screwdriver of the suspect injector. Obviously, can only do this in Park, and can't do this with the spiders living under that plenum.

Yes I tried 2 new spiders, miss fire 1-4. 5-8 are over loading with fuel when 1-4 quit. So basically front half motor runs lean back half runs rich. No codes at all. Hooked up to snap on scanner is how we were able to determine miss fire and check injectors. All injectors work properly when controlled by scanner. However without the 1-4 seem to fire at random if at all. You can tell both by surging of power and the amount of raw fuel smell and "smoke" when they are not firing. This is at all time they randomly start working and shut down. Which is why grounds were added incase some sucked.i haven't probed the wires yet but all connections look good. Nothing melted or discolored. All are clean as they come new. All original rust free truck.

 

[stutaeng]

Yes I tried 2 new spiders, miss fire 1-4. 5-8 are over loading with fuel when 1-4 quit. So basically front half motor runs lean back half runs rich. No codes at all. Hooked up to snap on scanner is how we were able to determine miss fire and check injectors. All injectors work properly when controlled by scanner. However without the 1-4 seem to fire at random if at all. You can tell both by surging of power and the amount of raw fuel smell and "smoke" when they are not firing. This is at all time they randomly start working and shut down. Which is why grounds were added incase some sucked.i haven't probed the wires yet but all connections look good. Nothing melted or discolored. All are clean as they come new. All original rust free truck.

Very strange indeed. Seems odd that 1,2,3,4 are missing, while 5,6,7,8 are okay. How do know that 5 through 8 are overloaded with fuel?

I think the way the injectors work is the ECU pulses them in milliseconds. The fact that a few are missing wouldn't necessarily cause the "good" ones to somehow start flowing more fuel. You get my point? Regardless, that's not the problem, I don't think. The ECU will command a bit more fuel via fuel trims if lean condition is detected, but only to a certain point.

I would go directly to the ECU pinout and hook up a noid light there. That would rule out any wiring faults. I suppose focus on the first 4 injectors, since those are the problem.

Did you just buy this truck? Was it running well before? Do you know any history on it?

 

[1998_K1500_Sub]

Might you happen to have a vacuum leak, driving the fuel trims whacky on one cylinder bank vs. the other? Perhaps a temperature-sensitive gap between the head / intake / gasket that causes variable air bleed depending on, e.g., engine temperature or similar factors, and therefore wandering fuel trims.... leading to the behavior you're seeing?

Has anything been done to the engine that might have precipitated a vacuum leak to your knowledge?

I assume you've looked at the fuel trims. Do you make note of their values?

 

[1998_K1500_Sub]

I'm grasping at straws quite a bit here (in my prev post and here too).

I'm stuck on this idea that something's driving your fuel trims too far one way or the other...

- Vacuum leak from... anywhere
- Intake manifold gasket vacuum leak (e.g., into one or more cylinders on one bank)
- Stuck injector (but you've tried multiple spiders, so...)
- Misbehaving O2 sensor
- Blocked cat converter on one bank
- Head gasket leak (e.g., between two cylinders)


Also, I've been assuming that when you say "1-4" or "5-8" it actually means you're referring to one of the two cylinder banks (cyls 1,3,5,7 or 2,4,6,8). Your terminology "front side injectors" meant nothing to me so I have to infer...

 

[BLACK&chrome]

Very strange indeed. Seems odd that 1,2,3,4 are missing, while 5,6,7,8 are okay. How do know that 5 through 8 are overloaded with fuel?

I think the way the injectors work is the ECU pulses them in milliseconds. The fact that a few are missing wouldn't necessarily cause the "good" ones to somehow start flowing more fuel. You get my point? Regardless, that's not the problem, I don't think. The ECU will command a bit more fuel via fuel trims if lean condition is detected, but only to a certain point.

I would go directly to the ECU pinout and hook up a noid light there. That would rule out any wiring faults. I suppose focus on the first 4 injectors, since those are the problem.

Did you just buy this truck? Was it running well before? Do you know any history on it?

No vacuum leak has been found, well what leads me to think that is the front 4 cyl spark plugs tell me they are lean and rear four are rich and very wet . Unplug egr(also new) and it runs even more lean plug it back in vapor from rich 4 hits front for and it runs a little better. Front half literally cyl 1324 are the ones not getting fuel and have misfire. Your spider sits sideways in the intake so literally there is a front half and back half as they are spit both physically and electronically. Take it how you want it I suppose. Oh and compression checks were golden also so yeah... oh and this just happened out of no where drove home one day shut it down got about half way to work the next day and I felt it dog and start misfiring.

I'm grasping at straws quite a bit here (in my prev post and here too).

I'm stuck on this idea that something's driving your fuel trims too far one way or the other...

- Vacuum leak from... anywhere
- Intake manifold gasket vacuum leak (e.g., into one or more cylinders on one bank)
- Stuck injector (but you've tried multiple spiders, so...)
- Misbehaving O2 sensor
- Blocked cat converter on one bank
- Head gasket leak (e.g., between two cylinders)


Also, I've been assuming that when you say "1-4" or "5-8" it actually means you're referring to one of the two cylinder banks (cyls 1,3,5,7 or 2,4,6,8). Your terminology "front side injectors" meant nothing to me so I have to infer...