TBI No injector pulse

[elks]

So it has been years since I set it up and had a problem. I have an after market TBI set up on my 72 blazer with a 350. My blazer sat for months due to carnage… Got that fixed but this last week I jumped the battery, it fired right up and I let it sit out and idle since it had not been ran for a long time. Ran for a bit then stopped. Have fuel pressure, have injectors are clicking, but no pulse. Has spark as it will fire on starting fluid. When I crank no mood light at all…

Remind me of my next steps? Test signal to EFI or is it a bad ECM? Like I said been 8-10 years without an issue…

 

[Wes Harden]

Who's after market tbi? What model ?

 

[dyeager535]

You are using a 12V test light across the leads?

Odd you are getting any sound if they aren't being pulsed, since the only sound they should make is when they are being pulsed.

You should have constant 12V on one wire to each injector, the ground (if a GM based system) will be pulsed by the ECM based on the ICM indicating the engine is being cranked.

 

[elks]

Who's after market tbi? What model ?

This is an older kit that came from Howell or Holley. It is using all GM stuff…

 

[elks]

You are using a 12V test light across the leads?

Odd you are getting any sound if they aren't being pulsed, since the only sound they should make is when they are being pulsed.

You should have constant 12V on one wire to each injector, the ground (if a GM based system) will be pulsed by the ECM based on the ICM indicating the engine is being cranked.

I have a set of the noir lights that are designed to show injector pulse. No flash from the light no power etc. I have used the 9v battery truck and both injector click when hit with voltage.

So I kind of figure it has to be either the ecm or the signal from
The distributor to the ecm.

 

[elks]

Also to add. I have good spark and when it died the blazer was running. I tried another ecm and same effect. I think it must be the signal from the distributor to the ecm. I have an after market tach, could it have went bad and caused an issue?

Again tried with a separate ecm from
Affordable fuel injection. Get 12 v power to the injector but no pulse, good bright white spark at plugs. When cranking my tach is wave surging from 0 to 1200 rpm on the dial, I seem to remember it always went to 0 hard on crank?

 

[dyeager535]

Tach signal comes from the ignition module, but it's on its own wire. No clue if a bad module can cause the tach to act squirrelly. I would assume yes.

If considering swapping any distributor components and you dont already have a spare, I consider getting a complete cheapy aftermarket as a decent option.

 

[1-ton]

Injector pulse starts at the distributor pick-up. Then goes to the control module...out the control module to the ECM, and then from the ECM to the injectors. There are electrical circuits that supply power to the fuel circuit such as relay and oil pressure sensor/sender.

 

[elks]

Injector pulse starts at the distributor pick-up. Then goes to the control module...out the control module to the ECM, and then from the ECM to the injectors. There are electrical circuits that supply power to the fuel circuit such as relay and oil pressure sensor/sender.

So I have an hei. I am trying to figure out if I could possibly be getting spark and no tach signal out? I have fuel pressure, I have certified spark… I am wondering if it is possible to have have spark and no tach from an hei? My gut is telling me my tach itself went bad and as a result the aftermarket ECM/TBI…

Just trying to figure out if I am getting spark if somehow the hei will not send each signal…

 

[Wes Harden]

for sure a ground tach can kill spark not sure about injector signal.

 

[1-ton]

When you say HEI distributor...you are talking about an ECM controlled HEI, and not an older non computer controlled HEI distributor?

 

[elks]

When you say HEI distributor...you are talking about an ECM controlled HEI, and not an older non computer controlled HEI distributor?

When you say HEI distributor...you are talking about an ECM controlled HEI, and not an older non computer controlled HEI distributor?

It is an older vacuum advanced HEI. I can’t figure out why I am getting spark and no injector pulse. I did have a second ECM I put in and even with it no injector pulse. I checked the white wire from the distributor to the ECM it look ok. I have a hard time believing 2 bad ECMs. Unfortunately I don’t have access to another HEI to test. But maybe I can find one this weekend…

 

[1-ton]

It is an older vacuum advanced HEI. I can’t figure out why I am getting spark and no injector pulse. I did have a second ECM I put in and even with it no injector pulse. I checked the white wire from the distributor to the ECM it look ok. I have a hard time believing 2 bad ECMs. Unfortunately I don’t have access to another HEI to test. But maybe I can find one this weekend…

If you have an aftermarket TBI, then who's ECM are you using.

 

[elks]

If you have an aftermarket TBI, then who's ECM are you using.

I believe it is a Howell. The sticker on it is missing. I bought the set up used off Craigslist like 10 years ago. The second ECM I had laying in my parts pile
Is from and affordable fuel injection after market system as well. This is in a 72 blazer.

Thanks for the help… I might have another hei in storage but I have to shovel out a drift to get into it..

 

[1-ton]

As far as I know, in order to communicate with an OBDI/ECM you need an HEI distributor from a 1988 to 1991 TBI equipped GM vehicle. The terminal ends for the control module will be different from an HEI distributor for a carbureted engine than an HEI for a TBI engine.

 

[elks]

As far as I know, in order to communicate with an OBDI/ECM you need an HEI distributor from a 1988 to 1991 TBI equipped GM vehicle. The terminal ends for the control module will be different from an HEI distributor for a carbureted engine than an HEI for a TBI engine.

Yep. I got another hei hooked it up
With the white wire to the tach signal and spun the grounded distributor and no pulse
For the injector that I could see… so either a
Continuity issue or an ecm
Issue…