Wont start

[PlayingWithTBI]

12 - 14 LBS for 87-95 TBI, 60+ LBS for 96+ Vortec. You need to get your pressure back to ~13 PSI. Maybe the injectors are jammed now with that much pressure? I've run them at 28 PSI but never that high!

the injectors are pulsing, I probed them with a multimeter and while in the run position they were getting power and while cranking they would raise and lower

Voltage was probably raising and lowering due to starter draw. Use a noid light to ensure they're getting pulses.

xc_hide_links_from_guests_guests_error_hide_media

 

[Schurkey]

I have no idea how you could jack-up the fuel pressure to ~40 psi without using an aftermarket pressure regulator, or a fuel pump so big that it overpowers the return system. The TBI regulator won't go that high even if you have an OEM-style fuel pump rated for 40--60 psi.

My '88 has an AC-Delco EP241 pump rated for 40+ psi, but I actually have about 11 psi due to the TBI regulator.

 

[Christian ojeda]

I have no idea how you could jack-up the fuel pressure to ~40 psi without using an aftermarket pressure regulator, or a fuel pump so big that it overpowers the return system. The TBI regulator won't go that high even if you have an OEM-style fuel pump rated for 40--60 psi.

My '88 has an AC-Delco EP241 pump rated for 40+ psi, but I actually have about 11 psi due to the TBI regulator.

Well then I'll have to hook a fuel pressure gauge up to it myself, his shop told him he's running over 40 now right at the back of the throttle body so I guess I'll have to see when I get the chance to hook it up

 

[Schurkey]

Well then I'll have to hook a fuel pressure gauge up to it myself, his shop told him he's running over 40 now right at the back of the throttle body so I guess I'll have to see when I get the chance to hook it up

Good plan

 

[Michael Oliveira]

The ECM grounds the injectors, they're always fed 12V with key on. You should use a Noid light to test that.

I'm having the same issue. 88 TBI spark no pulse with noid light. Truck runs if I spray starter fluid. Checked grounds. I'm obviously missing something. Now looking at ECU control wire to injector pulse pin A6 have constant 12V
I changed out the entire distributor assembly to eliminate ICM and pick up coil. Have voltage from ICM on purple wire to ECU. also from what I understand this TBI is a bypass system so I disconnected the timing advance wire to force bypass mode. So it should get pulse signal directly from ICM. Any thoughts would be greatly appreciated

 

[PlayingWithTBI]

When you turn the key on, engine off, does the fuel pump run for 2 seconds? The ECM turns on the fuel pump for 2 seconds and shuts off if it doesn't see any DRP (Distributor Reference Pulses). Once you start cranking it'll see DRPs and turn on the fuel pump. Otherwise, when the oil pressure switch on the back of the block near the distributor, sees pressure it'll turn on the fuel pump.

If the fuel pump doesn't come on with KOEO, you need to troubleshoot that 1st. You may also have an issue with your Oil Pressure switch.

 

[Schurkey]

Check the injector fuse(s)

 

[Michael Oliveira]

When you turn the key on, engine off, does the fuel pump run for 2 seconds? The ECM turns on the fuel pump for 2 seconds and shuts off if it doesn't see any DRP (Distributor Reference Pulses). Once you start cranking it'll see DRPs and turn on the fuel pump. Otherwise, when the oil pressure switch on the back of the block near the distributor, sees pressure it'll turn on the fuel pump.

If the fuel pump doesn't come on with KOEO, you need to troubleshoot that 1st. You may also have an issue with your Oil Pressure switch.

Problem fixed, tracked back good distributor reference pulse. Tracked back injector ground pulse wires to ECM pin 14 and pin 16. No ground pulse. Fix was the PROM in the ECM
Replaced prom truck started

 

[Schurkey]

Glad you found it. The PROM is not the first thing I'd have expected.

You done good.

 

[PlayingWithTBI]

No ground pulse. Fix was the PROM in the ECM
Replaced prom truck started

Congrats! Maybe the PROM wasn't seated properly? I've heard of these old chips losing their memory but, rarely.