Jump to content

Gm Tbi No Injector Pulse While Cranking

camaro_thunder92

By camaro_thunder92
in Ask A GM Technician

Recommended Posts

camaro_thunder92 New Member

camaro_thunder92

Posted
Posted

I am helping out a co-worker on this one. He swapped a 91 TBI 350 into an 85 chevy truck. The engine will run if you either spray starting fluid down the throttle body or hook up a remote start switch. If you use the key, there is no injector pulse while cranking. As you let go of the key and return it to the run position, the injectors give one squirt. Here is the checklist:

 

Painless wiring harness

Fuel pressure: good

Fuel pump primes when key is turned to run position

Plenty of spark under crank position

12v to injectors at run and crank position

No pulse while in crank

 

Like I said, the truck will start and run if we use a remote starter switch and injectors pulse. It will also start and run with the key if we use starter fluid or gasoline through the throttle body.

 

Thanks in advance for any help you are able to provide.

Heavy Cruiser Enthusiast

Heavy Cruiser

Posted
Posted

No START pulse to the ECM?

See if the colored injector wires are pulsing during crank - view the analog scale of the DMM - it reacts faster than the readout- or a bulb across the disconnected inj connector - one lead on the black wire, the other lead on other wire, watch the filament for pulsing.

camaro_thunder92 New Member

camaro_thunder92

Posted
  • Author
Posted

There is no injector pulse while cranking. I used a Noid Light while cranking, and nothing. We do get pulse if we use a remote starter. For some reason, the ECM is not sending the injector pulse signal while the ignition switch is in the crank position.

  • 10 months later...
GMTBI350 New Member

GMTBI350

Posted
Posted
BTT...

 

Any luck finding the problem? I'm having the same with my parents Suburban 5.7 TBI. It never started on the first try, but does on the second, or if you crank the engine for about 8 to 10 seconds on the first attempt. Everything is working great except there's no negative Injector pulse for the first 8 to 10 seconds. People have mentioned a "Injector Driver Module" between the injectors and the ECM. Not sure if this model year has one though or if there refering to the Ignition control module which leads me back to the Distributer and the Magnets again during start. I've seen a schematic showing the EST/ECM with a note "Above 600rpm after 5-15 seconds". Not sure what that Diagram is trying to tell me though. All I need is 1 second of negative injector pulse before I hit the starter and the truck fires up instantly.

post-70172-1260476456_thumb.png

post-70172-1260476456_thumb.png

post-70172-1260476456_thumb.png

post-70172-1260476456_thumb.png

  • 1 year later...
chuckyou New Member

chuckyou

Posted
Posted

Having the same issue with my truck 88 gmc 1500 and I see all these places where people are having it but no one says what they did to fix it.. Please help

wrencher New Member

wrencher

Posted
Posted

Check for a high throttle position sensor voltage, high TPS voltage at start can stop the injectors when cranking. It's used as a clear flood function when the throttle is held open during cranking. A quick test is to just unplug the TPS, that will set a fault code and the clear flood mode would be inhibited. :sigh:

Archived

This topic is now archived and is closed to further replies.

Go to topic listing

  • Latest Articles

  • Posts

    • Black02Silverado
      Missing thrust bearing? And oil selection

      By Black02Silverado · Posted

      Maybe, but it seems he is the only one that has backed up data to prove what he is stating. I think he is doing this more because he enjoys it and wants to get the information out to us. He's got the knowledge and access to the proper equipment and having the funds doesn't hurt.  I would love to do what he is doing and would do it if and when I hit the Powerball.  I'm not a Tribologist by any means but love to learn what I can.   I would bet there would be doubting people out there if a completely independent lab with high quality work and highly respected in the automotive industry, put out information like this.  The world can't be pleased, one just has to take the information that they are given, do more of their own research to find actual lab data to back up what they are trying to figure/find out.  Most don't bother, they just want to believe what they first see.     I don't have the minimax but my 6.2 in my 2019 Silverado with 64k miles shows excellent UOA results with 0w-20 and for my own purposes 5w-20.  Since not much of a change using 5w. I liked the data sheet information on the SS 5w-20 and figured I would give it a try.  Still the same viscosity at 100℃.   In the end we all just do what makes us happy, life is too short to get upset over trivial social media.   On a side note, I do feel GM has dropped the ball and just cares about the bottom dollar and not quality anymore.  "Like a Rock" has been long gone.  Seems "Built Ford Tough" has as well.
    • Tyler Gibbs
      Thoughts on these wheels?

      By Tyler Gibbs · Posted

      Better than stock but that's like putting lipstick on a pig
    • flattop
      2026 sierra bad brake controller

      By flattop · Posted

      Hello, my 3 month old Sierra Elevation wont recognize a trailer with electric brakes? All the lights work correctly, but no power to the brakes?   This is the factory installed brake controller. If you manually push the knob, the display shows the power % but does not light up like my 2022 silverado.   I have an appointment with the dealer, but was checking to see if anyone else has seen this issue.    Thanks, 
    • Black02Silverado
      Post your latest oil change.

      By Black02Silverado · Posted

      Been using SS 0w-20 from new, but wanted to change to the 5w-20 because I liked the data on the data sheet, to me it seems like a little better product. But as you can see, not much difference. This is also with running a mix of 10 gallons E85 to a tank topped with 93. It isn't a flex fuel vehicle so any higher I get a CEL for running lean on both banks. Yes my mileage takes a hit. Instead of 20 mpg I normally get on trips I get 17mpg. This is also using EaO17 filter.  What is amazing is I have the AMSOIL cone filter on it since I have the GM Performance intake installed and that air filter has 44k miles on it.  I just take it out and shop vac it off once a year.  I use the upholstery tool on my shop vac.  Works well.   
    • revmanii
      Starting a new thread regarding mounting my 2014 OEM wheels to my 2026

      By revmanii · Posted

      So, lot's of googling and reading, and a trial fit found, that indeed they hit the newer fatter caliper. I did some re-testing today, and found just 3/16" worth of washers was enough for the wheel to spin freely. I added 2 more on each, and again it spun freely. Tested lock to lock with the 4 washers, about 5/16" not quite the 3/8" Im considering, but pretty close. No issues. I've been looking at the BORA .375" spacers and using extended lugnuts to get back lost thread due to the spacer. All the ET lugs I've seen are all .33" reach inside the wheel lug holes. For those that don't like spacers or think they're unsafe, I think it depends on what type of spacers you're using and making sure you get good quality hubcentric ones, and if you're using bolt on ones, regular mainenance, checking the spacer lugs. Not wanting or needing that much spread. Looking for the minimum that will let me run these rims and tires.  it does look to stick out a little, but I really want put these on. and use the stock all-terrains in the winter. 

  • GM-Trucks.com Clubs

  • Popular Contributors

×
×
  • Create New...