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Tbi help, no pulse

stockk5

stockk5

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Hey everyone, I feel like I am typing the same problems I had a bunch of years ago and I feel like I am well diversed in tbi issues. I recently swapped a new to me motor into my 87 k5. I used all the same parts from my old motor that blew and oil line and bleed out till it froze the crank bearings.

I was having some starting issues and couldn't get any injector nod lights to work, simple I'll put a new ignition mod in and it will run. I put a new one in, fires right up no problem, time it, clean up n call it a night.

Next day no start, lots of cranking over, lots of spark and no injection pulse. I am pissd, put another ignition mod in I had and nothing. Put a brand new napa expensive one in, nothing. Luckily I was able to return it.

The injectors themselves have 1.7ohms, when I spray starter fluid in it, starts. I have my oil pressure sensor hooked up, never did in the old truck, no pulse. I use the ignition node and no light still. I am really confused and this brings me back to why I hate tbi sometimes.

Any idea where to go? Could the coil not send the right signal to the ignition mod?
 
No ideas here, sorry, but I'm having the same issues with my '89, unfortunately, I can't work on it regularly as it's like 1900 miles away stuck at the parents place.

Mine seems more intermittent though, brand new ICM's a few, brand new distributor, (not reman'd).. new fuel pump, injectors are not that old, starts and runs when it feels like it and just shuts off when it feels like it. Completely random and very unreliable.

I even swapped out the computer box, had to reuse the old chip though, thinking I may just swap the whole computer out with a new chip as well on the next try. Also just going to change out the complete engine management wiring harness as well as it's pretty beat up.

Please keep things updated as to what you find, I would, but you obviously have yours available to work on it. :D
 
The pick-up coil inside the distributor could be bad and it is a good idea to replace it at the same time you change the ignition module. Either the ignition module and or the pick-up coil could be bad.
 
Injector fuse! Do you have power to injectors?

Usually if you have spark you have the DRP needed to fire injectors...
 
Mine was a bad wire in the 2 wire plug from the ICM. Intermittent, persistant and baffling. 3 weeks to figure it out.
 
eagle mark said:
Injector fuse! Do you have power to injectors?

Usually if you have spark you have the DRP needed to fire injectors...
Click to expand...

Like he said. Check the ECM fuse. Remember, the injectors are one side hot all the time when in run or crank.

The computer grounds one leg to fire them.
 
ktmoutfront said:
Mine was a bad wire in the 2 wire plug from the ICM. Intermittent, persistant and baffling. 3 weeks to figure it out.
Click to expand...
And when you loose the signal you loose the injector firing.

Fordum said:
Like he said. Check the ECM fuse. Remember, the injectors are one side hot all the time when in run or crank.

The computer grounds one leg to fire them.
Click to expand...
Exactly!

Check power to injectors!
 
FWIW, here is a chart for crank no start http://www.fullsizechevy.com/forum/...-start-troubleshooting-101-a.html#post2640793

Odd, they kinda missed the whole "check fuse" didn't they? It should be step 1. Other than that, I think it looks pretty thorough. That chart will keep you from chasing your tail. IMO I'd ignore the ECT/TPS testing unless the other tests don't resolve the issue because it's fairly tough to do those without a scanner. I'm sure they CAN cause problems, but the likelihood of them causing a no-start is probably about 1% compared to all other potential causes.
 
dyeager535 said:
FWIW, here is a chart for crank no start http://www.fullsizechevy.com/forum/...-start-troubleshooting-101-a.html#post2640793

Odd, they kinda missed the whole "check fuse" didn't they? It should be step 1. Other than that, I think it looks pretty thorough. That chart will keep you from chasing your tail. IMO I'd ignore the ECT/TPS testing unless the other tests don't resolve the issue because it's fairly tough to do those without a scanner. I'm sure they CAN cause problems, but the likelihood of them causing a no-start is probably about 1% compared to all other potential causes.
Click to expand...

thanks guys, I will use that chart, and once again check the fuse, maybe swap in a new coil and go from there. Now.. if it would just stop snowing...
 
If you've got spark, what would the problem be with the coil?

If there is spark, but no injector pulse, more than likely its either something with power to the injectors or the ECM is not getting a signal that the engine is turning over from the ignition system.

I assume the check engine light works properly?
 
Also, can have spark and faultu coil but it will not effect injectors, just weak spark.

Do you have 12 volt Batt power to injectors with Key On?
 
We'll after using the chart you guys posted I was getting either bad ignition module or bad connection. We'll the 4 prong on the ignition module had all the pins screwed up and pushed in, I replaced that connection and it fired up! Timing is still a little off but getting close. I still cannot locate that tan and black wire you are supposed to disconnect to time it. Any help on its location?
 
It's should be over near the brake booster (passenger side of booster). It's the only wire with a black single prong connector inline.

I *think* it's supposed to be sticking out of the wire loom.
 
ok, i think i have found that... but i have NO idea where it would actually plug into. Anyone have a picture?
 
It SHOULD already be plugged into the other end of the connector.

It's a single pin weatherpack connector. This Camaro picture is not quite up close enough to see what the connector looks like exactly, but it's the only single pin connector on the truck I can think, so the idea is exactly the same, and pretty sure the connector is identical: http://i3.photobucket.com/albums/y94/paulo57509/camaro/estbypassconnector.jpg
 
My wiring has been redone over the last 12 years... Did this connect to the coil?
 
No, I *think* it goes to the module. I'm not certain, I'd have to look at the wiring schematic. Definitely not to the coil, as it's a timing deal, not spark.
 
My 87 has a terminated wire in that same area. The one you are looking for should be plugged together during normal operation. The Jimmy one was in the split loom.
 
to give you guys a little update, turns out that my 4 prong plug for the ignition module was bad... simple fix!



 
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