TBI injector problems.
 

I have a 94 S10 with a TBI 4.3L. A while back, we had problems with it misfiring and stalling. So we checked a few things and it looks like the injectors aren't firing. I checked to make sure they were getting power/signal, and they were. They just didn't fire, so I assumed they were clogged. So I pulled the injectors out and soaked them in some B-12 Chemtool, then blew them dry with high pressure air. I broke the gasket between the top/bottom plate, so I used rtv and bolted everything back together. When I went to turn it on, both injectors just poured gas out(not spray). One of them foamed up pretty good, but they both were just spilling gas badly even with the electrical connector removed. Did I ruin the injectors or do I just need to replace that gasket? Any help would be greatly appreciated.

Re: TBI injector problems.
 

Anybody? Well, I ordered the new gasket and I should have it on next week. I'm also going to barrow some injectors from a friend to see if that makes a difference.

Re: TBI injector problems.
 

Now that I think about it, the little o-rings swole up when I dropped them in the b-12. I bet that's why all the fuel is spilling out like that. Good thing I ordered that TBI gasket set.

Re: TBI injector problems.
 

sounds like u ruined the injectors i maded the same mistake on a friends blazer and they just shot fuel out untill i replaced them with new ones

Re: TBI injector problems.
 

Dang it! I hope that's not the case. I'll know next week when I get my gasket kit. I'm not looking forward to getting new injectors. I remember last time I had 2 tbi injectors cleaned it was $87.

Re: TBI injector problems.
 

injectors run about 70 buxs a piece

Re: TBI injector problems.
 

I replaced the gaskets and the gas stayed in the injector pod this time, but the injectors still won't fire. I did hear what I thought was air in the fuel lines. Would that cause the injectors to not fire? I'm gonna swap in some 5.7L injectors tomorrow to see if they spray or not. I tried supplying 12v to the injectors and all it did was click(I think). What do you guys think?

Re: TBI injector problems.
 

sounds like the injectors are fubar'd. i would rather spend the $87 to get them cleaned than $70 each new. as far as the rtv, that was a bad idea. rtv is not fuel resistant and will clog your fuel system. you should have just gotten the gasket set. but try the 5.7 injectors. but if you are going to stay with them then you will need to get an adjustable fuel pressure regulator and dial down the pressure cause they will be too rich for the 4.3.

Re: TBI injector problems.
 

I replaced the injectors and regulator today and it still didn't work. It's definately getting fuel pressure, but it still won't fire. I'm a bit frustrated and I'm tired of this EFI system, so it's getting junked tomorrow.

Re: TBI injector problems.
 

We found a nice rebuilt 4.3L that's already carbureted, so like I said the TBi system will be junked in the morning. I really don't understand what was wrong with it though. We couldn't get the codes to show and everything seemed to be in decent condition...it just wouldn't fire the injectors.

Re: TBI injector problems.
 

Someone correct me, but with that system, voltage should be there when the key is on, the computer grounds the injectors to fire them. Being a 94, it should be a fairly easy circuit, something is not sending the signal to the computer to fire the ground (sensor). Or by what your saying the power circuit is interupted.

Smitty

Re: TBI injector problems.
 

How do you manually fire the injectors? I hooked + and - to one injector and it didn't do anything. I have a TBI system on our tow truck, so I'd like to learn a little more. But the TBI on that S10 is going in the garbage, we can't afford to be chasing that problem all over the place.

Re: TBI injector problems.
 

well have you tried connecting them one way, and then the other?? and are you sure that both sets of injectors are bad? and what about resistance in your ground wires?? if you have a break or a short to ground a continuity and ohm check of the wires will show.

Re: TBI injector problems.
 

I decided to give it another try since I really need this truck running now. I'll try what you said. Thanks.

Re: TBI injector problems.
 

Most computer controlled circuits are given constant power and grounded by the ecu. That way the ecu has less of a load on it and makes less heat.

You said it is getting fuel, but did you check the pressure? A plugged filter or weak pump will cause driveability problems like you described. If I change a fuel filter on a truck I think could have a bad pump, I make sure I have the truck somewhere I can change the pump. I have had TBI trucks run ok, then change the fuel filter and not start again. The fuel pump will loose its prime when the filter is removed and is too weak start it again. On a TBI truck, there is not a schrader valve to connect a gauge, so either you get a fitting with a valve to connect inline at the throttle body or a T fitting that goes in place of the fuel filter.

Also check all of your grounds and electrical connectors for corrosion, starting with the battery cables. Check the connector on the fuel tank too.

I would try to stick with the TBI. It is a great system for a DD.

Re: TBI injector problems.
 

We had normal fuel pressure before I pulled the filter, but I bet the pump is weak...the truck has 217,000 miles on it. I'll get a fuel gauge to put on there and check it again. The pump definately comes on and I know it's getting fuel to the throttlebody since gas streamed out when I removed the regulator and manually activated the fuel pump.

Re: TBI injector problems.
 

well if you removed and didn't replace the regulator then i bet that is your problem. you need a fuel pressure regulator to keep your fuel pressure at a certain pressure. so if you haven't put a fuel pressure regulator back in then get one installed

Re: TBI injector problems.
 

Sorry I wasn't more clear on what I did. I removed the regulator/upper part of the throttlebody and activated the pump to be sure I was getting fuel to the throttlebody in the first place. Then I replaced the regulator and upper part back on the throttlebody. I haven't been able to mess with the truck lately due to the weather, but my next goal is to check to see if the injector connector pulses(on the ground side). They have constant B+, but I didn't check the ground side when I did that test.

Re: TBI injector problems.
 

You can hook up a noid light to the injector plug. This will flash so you can see the injector pulse. I assumed you had done this already.

Re: TBI injector problems.
 

i just had a thought about all the fuel just pouring out of the injectors. did you replace the o-rings when you swapped the injectors back and forth??

Re: TBI injector problems.
 

Yes, I did replace the o-rings and it stopped the fuel leak problem. I did the check with the injector plug and a light. I'm not getting any ground on the one side of the injector plug. I replaced my ignition module with a new one, but now it doesn't have give spark or activate the injectors.

Re: TBI injector problems.
 

You replaced the module and now it does not have spark?
Check all connections. Check for power to the coil. Try the old module again. I'm starting to think the computer may be bad. It ran poorly before the injector problems and now there isn't spark. I think you would be money ahead if either you found someone that can look at it first hand or take it too a shop. It is probably something really dumb causing all of this.

I spent two days trying to figure out what was wrong with a '95 CPI after I replaced the engine. I figured it out when I shot carb cleaner in the throttle body and it popped back. Turned the dist. 180* and the truck fire up as soon as I hit the key.

Re: TBI injector problems.
 

I got the distributor put in correctly(I thought), but it still didn't make a difference. I did get one good backfire though, so I probably put the distributor in wrong.
I checked the injector plug again and I'm still not getting B- on the opposite side. I tried manually firing the injectors, but they didn't work. I'm guessing the fuel pressure is too low to make it fire? I don't have my fuel pressure gauge/fittings right now, so I'll have to check the pressure later. We checked it before it completely went dead on us and it was fine. But maybe the pump died since then? I'll try the old module in a few hours, I just needed a break from all the frustrations...I was ready to remove the regulator and let gas run everywhere and burn this turd to the ground.

Re: TBI injector problems.
 

I have that problem now and i ended up just getting new injecters and replaced the gasket and it works fine but its a big punch to the wallet

Re: TBI injector problems.
 

Damien is correct, that the ECM controls the ground for the injectors.

With the key on there should always be power at the injectors. The ECM grounds the other side of the injector, to make the injector open.

The computer needs to receive a distributor reference pulse from the distributor module to trigger the injectors.

If you have no spark, don’t expect the injectors to work.

Work on the no spark problem.