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94 C1500 won't start

dji1
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dji1 Enthusiast

dji1

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The original problem was the injector wiring harness. OBD1, I will clean the IAC.  I have had some issues with it over the years. Replaced the IAC and wiring 10 years ago. 

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dji1
dji1

I was thinking about doing both. After I take the tbi apart I will clean and look things over. I am still undecided on redoing the fuel regulator. Normally I would just replace everything. Now I just

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dji1 Enthusiast

dji1

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I removed and cleaned the IAC. Disconnected the battery to reset. Same problem. I will drive it around tomorrow and see what happens. I didn't think there was too much carbon built up? The throttle top side plate is clean. When I was trying to figure out why it wouldn't fire, we sprayed quite a bit of throttle cleaner. Also, that is when we checked the injectors spray. All that seems fine. 

 

See attached photo's

 

image.jpeg.43fa9aaebba277ec37955e477d0dcbc7.jpegimage.jpeg.f19fa5d97bbedb07f92d166a9cf4d5e9.jpeg

tpi1.jpeg

richard wysong Senior Enthusiast

richard wysong

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There is an idle relearn procedure, Google 94 Chevy pickup idle relearn procedure. It sounds like the IAC is working where you have a higher idle when cold. Also the TBI system had problems with vacuum leaks at the TB gasket and spacer plate so check that before trying the reset also check that the EGR valve is fully closed

Edited by richard wysong
asilverblazer Senior Enthusiast

asilverblazer

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On 5/12/2026 at 5:32 PM, dji1 said:

I did adjust the throttle cable

Did you or did you NOT adjust the throttle cables?

 

Was the throttle body removed during the repairs to the injectors?

 

Don't go looking for new problems in new places - stay where you are working and messing with stuff.

dji1 Enthusiast

dji1

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No, the throttle body was not removed. Just replaced the electrical connectors. Ten years ago, when I replaced the tpi base gasket. I did adjust the kickdown cable then.

 

I think someone told me on a 94 the kickdown cable was there but it did not control anything anymore. The sensors do all the tpi adjustments.

 

I did notice that the kickdown cable was tight and had no slack in it like usual. Not sure why or if it even makes a difference on my 94? I did loosen it a 1/4 turn this morning. 

 

 

richard wysong Senior Enthusiast

richard wysong

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The kickdown cable controls the transmission, it has nothing to do with idle speed. Proper adjustment is critical to transmission operation. Consult the service manual for adjustment procedure

dji1 Enthusiast

dji1

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I reset the kickdown cable back 1/4 turn. While I was driving around today, I finally got an error code 44 (lean exhaust) The truck was warmed up, and I was idling at a stop sign.  

 

I am going to re-check for vacuum leaks. I did replace the hose for the brake booster. I am going to check the wiring to the O2 sensor and remove and clean the EGR valve hopefully tonight.  

 

I have been thinking about buying a fuel tester at Harbor Freight just to eliminate pressure issues. Any comments?

 

Thanks again.

 

richard wysong Senior Enthusiast

richard wysong

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Unless it is a tool you may use frequently the parts store tool loaner plan may be a better option. I don't know the price or quality of the H F tester. I have a Snap-On and the hose is getting stiff from the gas and lack of use. With the loaner if it has an issue it's not your problem

dji1 Enthusiast

dji1

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Yea that is the 2 reasons I haven't bought one before. I am sure I would use it once and have no need for it again. The only reason I thought about it was that it was only about $20 and I have never tested fuel pressure before and I am not sure if 1 person could, do it? I bought a brake bleeder kit years ago that I forgot I had. Found it in the garage the other day. Brand new never used it. When I was checking it out to use all the nipple attachments broke in my hand.

 

I may try the loner tool at the parts store. Never had in the past. I don't think the fuel pump is the problem this time. When I drive down the road the truck runs okay.

 

I re-checked for vacuum leaks again last night and I don't hear any. I also checked the wiring to the o2. It looks excellent. I am going to re-check the injector patten in a few minutes to make sure. I didn't remove and clean the EGR valve last night. I replaced the gasket and cleaned it less than 10 years ago that is only less than 50k mile for me. I still may do it. 

 

Should I start a new thread for the idling problem? It is no longer a won't start issue.

 

Thanks

dji1 Enthusiast

dji1

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It looks like the passenger side injector is not flowing much at idle. I think. It is hard for me to see for sure. I may just pull a plug on that side to see what it looks like.

 

When I give it gas, I can see the flow on both ejectors. The driver side looks okay.

 

Can I swap the connectors from 1 injector to the other side injector? There is a very small chance that when we soldered the new connectors on something went wrong.

 

I took a video with the truck running. 

 

 

richard wysong Senior Enthusiast

richard wysong

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A timing light hooked to the coil wire or any fast strobe light shining on the injector spray will help you see the spray clearly. An injector not spraying at idle will indeed cause  erratic idle rpm. The way the tool loaner program works is you pay for whatever tool you want to borrow and they refund your $ when you return it. Great for tools you may only use occasionally. You should be able to switch the wires between injectors as long as the polarity is the same. 1 wire is 12v+ with the key on, the other is a pulsed ground from the ECM to fire the injector. If it sprays under open throttle the injector is at least partially operational. I'm not sure if the injectors are polarity sensitive so you might want to consult a wiring diagram. (Charmli,free service manual download with wiring diagrams)

dji1 Enthusiast

dji1

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I am going to try the timing light suggestion. I purchased my timing light in the early 70's. It has a spring that you attach one end to the plug and the other end to the wire. It's not user for sure but it works so I have never upgraded. I also will try and set-up more lights so I can get a good look. The shadows under the carport were not good this afternoon. I can also move the truck to a better position if I need to.

 

I will check the polarity of the connectors before I swap them.

 

Thanks

richard wysong Senior Enthusiast

richard wysong

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Another obsolete tool, the timing light, I have a top of the line Snap-On that hasn't been used in at least 5 years. I think I have more obsolete tools than useful 1s

dji1 Enthusiast

dji1

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The passenger side injector is not working at all. It is getting 12 volts. I couldn't test to see if the ECM is sending a signal to the injector. No one around to help crank the truck today. 

 

I was going to buy a Noid light at AutoZone $5.99 but they don't stock it. They just advertise it online. I'm going to modify my test light and see if that will work. 

 

Didn't have a problem today seeing the injector (no) flow. The natural light was perfect.

 

If the ecm is the problem, would it affect both injectors?

 

Or if 1 injector is working then the other injector has a problem.  

 

 

 

 

 

 

richard wysong Senior Enthusiast

richard wysong

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Posted

I'm pretty sure the ECM has separate drivers for each injector so a bad ECM is a remote possibility. You should be able to test the ground pulse with a test light with the engine idling, just hook the clamp to the positive post. If no pulse check it at the ECM before condemning it

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