Alright, I went on a search yesterday and specifically kept track of my route to calculate my MPG from google maps. (My speed/odo don't work)

So I went 112 miles on 10.181 gallons of 87. Ouch.

Now to clarify, I don't drive like a bat out of hell. I drive like an old man, and the vast majority of it was highway. My trans is skipping second, but I hardly had to do any stop and go.

11 seemed WAY too low for that type of driving, especially on the highway around 60mph the whole time.

This is on a 1990 K1500.


So I went out this morning to check out my injectors after doing a bit of reading. I couldn't find any great info on TBI spraying, so here I am!

I took 2 good pictures of the injectors spraying. I've also got a video on youtube for reference. Notice during one picture I've got a solid cone while the other is like particles flying out.

Watching the video you can see they have the minor stutter, and I think that's when I snapped those pictures. They both run almost identical if you sit and watch them.

Up close


Little bit back. You can see the normal full cone here.


For reference, here is the youtube link:
K1500 TBI fuel spray - YouTube

My issue here is that I don't know how heavy the fuel should be running out of the injectors. I don't have an O2 sensor, so one theory is that it's dumping all of the fuel it can because it's not getting a readout.

Any educated advice on this issue would be greatly appreciated. I'm just looking for possible reasons for this exact issue, mostly for learning. I may be doing a swap in the future, so lets not discuss that right now.

 

Wow your picture is Huge. If you could please try and make them a little smaller in future post.

As to your issue, it looks like your injection is not functioning right.I don't want to steer you wrong so check this link out. If your wanting to do it your self this will show you how to go through it. I found this on You tube. chevy tbi rebuild and injector testing - YouTube

chevy tbi rebuild and injector testing - YouTube

 

Okay...... Now are you saying you don't have an aftermarket wideband for verification...... or are you saying that truck itself no longer has a factory O2 sensor installed..... thus it's running in open loop all the time. That would be one of your problems if that is the case. Your injector spray really doesn't look that out of the ordinary in the video especially.

Try adding an oxygen sensor and hooking it back up ( yes it would have had one, either in the Y pipe towards the cat or the drivers side exhaust manifold) and see how that helps.

 

Damn, the pictures were so huge I missed the actual link of it running.

I also agree we need more info about the setup and what you posted sounds correct.

 

No kidding on the pics..... I lost the video in there for a bit too, lol. I am fairly certain I had every conceivable problem someone could have with a TBI truck with my last one. Not something to be proud of, lol.

 

No, but at least you can share the knowledge you gained from it.

Just like with any system they need to be maintained and as you pointed out all the other components need to be installed and working correctly.

I don't think they were the most fuel efficient set up, but I think If the bugs are worked out he could at least get better mileage out of what he has for the time being.

 

Biggest reason for bad mpg on a TBI SBC is neglected tune up. The absolutely require new plugs, cap, rotor, fuel filter, and set timing every 30,000 miles.

The next most common problem is a bad ECT sensor. When the ECM thinks engine temp is -30*F, fuel mileage goes to ****. Won't throw a DTC either. You need to moniter the sensor values while you're driving, as they can fail intermittently.

Oxygen sensors can crap out also, and you should verify that the truck actually is going into closed loop. Hope this helps. That truck should be able to achieve 16-17 hwy when not towing a trailer.

 

Yeah they weren't terrible on fuel. I get 18 + U.S. mpg on the highway out of my 92 350 powered regular cab long box 4X4 with 3.73 gears. It worked at the time..... but that is approaching 20 years ago, lol.

 

Wow. Apparently my subscription hasn't been sending me the emails.

Okay, to clarify. I purchased this truck stock, minus a butchered K&N/Airraid intake setup. I changed out to all new plugs and wires, as well as Long Tube wrapped headers. The O2 sensor was pulled from the truck. NO O2 at all.

If I have to put an O2 sesor and bung back on to fix it I will... but I'll go ahead and get an AFR gauge while I'm at it.

I've read the temperature thing other places as well, but how would I go about fixing that?

 

Now that I think about it. My ECT is probably bad. I forgot my temp gauge isn't work. Uh oh. I'll swap it today and see what happens.