chevy 89 c1500 tbi system issues

[leroyd92]

we had a 92 motor put in our 89 truck and it had 80-90k on it compared to our 270k original motor

sometimes, the truck will have to crank over for 3/5 seconds before it starts, when it does start it will act like a carbed motor clearing out from flooding/too much choke...

other times, it wont even start, and you have to hold your foot to the floor to get it to light off. black smoke comes out the pipe and it runs rough for a few minutes.

does anyone know what is misadjusted or maybe failed ? the iac is new, and tps is also... the injectors are clean, and resealed. pump is new along with the fuel regulator

any suggestions are appreciated.

 

[bama7x57]

Flooding symptoms on the TBI system are usually a bad coolant temp sensor. It's located on the intake manifold next to where the thermostat is.

 

[FL_Rob]

How does it run after it's warmed up and out of open loop?
I let the pump prime up for the 3 or so seconds till i hear it shut off(that's my own little fuel check)then i'll crank it over.
The fuel control and all sensors need to be checked out making sure you're getting the reference voltage.Fuel filter i'm sure that was replaced, of course.
Re-check timing and replace all vacuum lines.
Don't discount the tbi unit itself, the throttle plate shaft fitment gets worn over time and require rebuilding.Spray grease around these is a temporary fix.
Make sure the ECU is the proper match for the swap,updates included.
After this it'd be mechanical.

 

[ls1mike]

When you shut it off does it "diesel"?

I had a 1991 S-10 that did something very similar. Turned out to be the oil pressure sending unit/switch. Weirdest thing I have ever had happen on any car I have ever owned. Pump would run for a bit after I shut it off. No one could explain to me how the oil pressure sending unit could do that but I guess it was showing false pressure which allowed the pump to run. At any rate changed it out never had another problem.

My 1989 GMC 1 ton had a bad TBI to adapter gasket that made it run rich and rough as well.

 

[Phishin]

My vote is CTS as well.

When you installed new fuel pressure regulator, did you buy the whole gasket kit and rebuild the entire TBI?

 

[Bud_One]

Originally Posted By: bama7x57
Flooding symptoms on the TBI system are usually a bad coolant temp sensor. It's located on the intake manifold next to where the thermostat is.


+1 - and check your TBI base gasket as well.

 

[leroyd92]

hi guys thank you for all the info. we completely resealed or and or rebuild the TBI system. when we had the guy put the new motor in he said he replaced the coolant temp sensor but I think I'll pick another one up just because. the truck didn't do this before we had the new motor put in (starting issues) once the vehicle is warm and hot and its out of the loop circuit it runs fine. my dad was driving it last weekend when he was coming up a hill it started to pop like if it was lean or the timing was too advanced. so now I'm trying to figure out what the issue is. he doesn't drive it a lot and he's driven at the last week with no issues with it popping or spitting out the throttle body

 

[FL_Rob]

When setting the base spark timing 0*TDC ,did you unplug the tan/black stripe wire to the dist beforehand?
Also the module and pickup coil in the dist are known slap-in-the-forehead problems.

 

[Michael_P]

I have seen a few throttle bodies on the GMT400's where there was excessive shaft play causing vacuum leaks. The condition you describe is definitely a rich mixture and the condition I describe would cause a lean mixture. Just something to look at.

 

[leroyd92]

I'll have to look up those wires and whatnot to set the timing again. I just went and got a new coolant temp sensor and the one that was in there didn't look anything like what orileygave me. after a minute or so it made the idle a lot smoother. another interesting thing to think about the timing tab that is normally on the block is missing on this one. so now I'm going to have to look at my other 350 s and see where the mark on the timing tab roughly is