(solved) Tbi injector not pulsing on startup

[andrewgasc]

Hello all, Recently bought a 91 crewcab square with a 454 TBI with a 4l80e behind it, after vehicle has been shut off, after more then 30 seconds it won't restart, found injectors to not be pulsing on startup/spraying fuel. If vehicle is started with starting fluid it will stumble to life slowly, then idle fine, will run as long as you please after that, runs good.

Just replaced ICM after following someone's testing that using a simple test light connected to a battery source, touching the purple wire on the 4 wire connector of the ICM would pulse the injector, did that, injector would pulse. So per that troubleshooting one should replace the ICM, no change. Have pulled the upper TBI housing off to check regulator diaphragm, not torn, no debris.

When I changed ICM noticed like rust or dust powder that seemed excessive around ICM.

Using extension leads from injector connector to injector terminals I remove the injector, sat in cab with door closed, cranked, no pulsing. Connected battery to one side of injector, then would tap ground against other pin, injector would pulse in my hand. I do have 12v on one side of each injector clip. Both injectors acted the same. Both injectors ohm at 1.2 ohms. Have checked all fuses in cab, none blown, replaced all with new anyway.

Just looking for insight in to this, owned a 350 TBI before, never experienced an issue like this.

 

[andrewgasc]

Also worth noting, have no check engine light with key on, haven't pulled dash to confirm bulb voltage yet, but.

 

[Ricko1966]

Are you sure you have fuel pressure when this is happening? Looks like a and e orange and grey are power to and power from the fuel pump relay. Make a fused jumper to short the fuel pump relay next time,see what happen. If the fuel pump relay fails your fuelnpump will not turn on until you have oil pressure. There's a redundant circuit through the O P. Switch.

 

[gmbellew]

the injectors are pulse grounded by the ECM.

 

[andrewgasc]

Are you sure you have fuel pressure when this is happening?

I have fuel pressure, cracked the input fuel line, good stream/spray.

the injectors are pulse grounded by the ECM.

ECM fuses are good

 

[gmbellew]

I have fuel pressure, cracked the input fuel line, good stream/spray.

ECM fuses are good

find the drivability and emissions manual for your rig and follow chart A-4 for injector diagnosis. in the reference library of this website

 

[Ricko1966]

I don't know about tbi injectors,I do know that the vortec injectors will not work with low pressure,40 psi will spray fuel everywhere but it will not start a vortec truck. Check pulse with a noid light .

 

[andrewgasc]

find the drivability and emissions manual for your rig and follow chart A-4 for injector diagnosis. in the reference library of this website

Thanks found it, looks like I'm starting with the check engine light being off and going from there, never knew about these manuals, a wealth of knowledge! Thank you so much. Will post an answer when I find it.

 

[andrewgasc]

find the drivability and emissions manual for your rig and follow chart A-4 for injector diagnosis. in the reference library of this website

Are the terms ECM and pcm in the manual, used to reference the ECM behind the glovebox? Or are these two different modules that I need to locate.

 

[gmbellew]

Are the terms ECM and pcm in the manual, used to reference the ECM behind the glovebox? Or are these two different modules that I need to locate.

I believe they use ECM and PCM interchangeably. and yes behind the glove box is where it is located.

 

[andrewgasc]

Thanks, wanted to make sure I wasn't chasing something that didn't exist.

I believe they use ECM and PCM interchangeably. and yes behind the glove box is where it is located.

 

[gmbellew]

Thanks, wanted to make sure I wasn't chasing something that didn't exist.

might be PCM because of the 4L80e transmission and it also controls the transmission. P - powertrain? the ECM only controls the engine. so yours is a PCM. my 1990 suburban with 350tbi amd 4l60 is an ECM. E - engine?

 

[andrewgasc]

Have a resolution, when I had the ECM down from the glovebox, I opened it to inspect the board for any damaged components, or traces that looked odd, found non, the ECM did have a hyper tech adapter and chip dated 1995 installed in it, I removed the hyper tech components and installed only the OEM prom back into the ECM.

I regained pulse on crank, injectors would spray roughly 5 times then dribble, priming the fuel pump with key would create the same thing again.

From there I decided on a fuel pump and filter, changed filter, no change, pulled bed and tank for pump replacement, found a previous owner had installed longer hoses from chassis to tank resulting in the pressure hose being completely kinked over touching itself. Removed tank and replaced pump, reinstalled with shorter lines on the tank.

Now hop in, turn the key to start, fires up in about three revolutions. I have no clue how my wife's father was able to drive it 60 miles home like that.

 

[squaredeal91]

Now. Will it work with the hyper tech chip?