TBI with no injector pulse

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Nick_R_23

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This has to be a stupid easy solution that I’m overlooking, someone school me on this please.

Truck is a 1987 (square body), with TBI. Truck ran and drove, transmission and transfer case were worn out, engine ran well but was leaky and dirty. Pulled all three, rebuilt transmission and transfer case, engine was resealed and replaced both oil pressure sensors, CTS for the ECU, and had a close to new distributor from my C1500 so I threw that in. TBI was rebuilt with Napa rebuild kit. Installed everything, finished today and tried to fire up, will just crank, no start.

Injectors are not pulsing, thus engine is not getting fuel. Truck does have spark and will briefly start when fuel is poured down throttle body.

Here‘s what I’ve diagnosed so far:
- Battery fresh off charger.
- Fresh fuel both tanks.
- Checked all fuses.
- Verified both pumps will run and build pressure at relay test port (both sending units work).
- Verified 12v at pump relay.
- Verified 12v at both injectors.
- Verified 12v at coil and at ignition module from coil.
- All engine harness grounds are connected at proper locations and clean.
- Cab to head, block to frame, frame to core support grounds are intact.
- Verified that injectors will pulse and spray fuel when ground is added.
- Verified that injector wires and ignition module wires all have continuity to ECM.
- Verified that all ECM grounds are good.
- Swapped ignition module with known good unit, no change.
- Wired in second distributor and spun with key on. Will spark, but no injector pulse.
- Checked ECU for damage, burnt components, bad solder joints, none visible.
- Swapped in known good ECU from my 1988 TBI Suburban, no change.


What the hell am I overlooking?
 

PlayingWithTBI

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When you turn the key on, engine off, do you hear the fuel pump run for 2 seconds? If not, your fuel pump relay, or wiring, may be bad. There's an oil pressure switch on the china rail near the distributor which will turn on the fuel pump when it sees ~4 PSI and bypass the fuel pump relay. This is from an 88 but s/b the same as yours.

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Nick_R_23

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That’s too funny, I was actually looking at the same diagram. So I realized that although I had checked for grounds at the ECU, I hadn’t actually checked for power, I just assumed it was there. The orange 12v wire that feeds both ECU connectors, the oil pressure switch, and the fuel pump relay only show 0.5v, so I definitely have an issue there. Tracking it down now to see what I find - the wire runs inside the cab and appears to go to the fuse block, so I’m curious what the issue actually is.
 

Rustjunky67

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Well it sure is nice to read yet another thread that just stops mid stroke as if the wife walked in and caught ya.... it's no wonder the same issues keep having new threads made
 

Levman74

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I usually think the OP accidently set it ablaze and no longer needs help.
 

Rustjunky67

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I usually think the OP accidently set it ablaze and no longer needs help.
I can understand that..... I'm at that point right now..... told my buddy if he could get here before the scrap man, he can have it
 
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