1990 350 TBI no spark question

[68isgreat]

Hi all,

I have a frame off 68 short stepper that I've installed a 1990 tbi 350 in from a Suburban. before I start putting things back on the frame, I'm trying to get it running to no avail. I put on a new painless harness and new rear efi tank and pump. The pump works fine and it gets fuel to the throttle body, but there's no spark t at all to the plugs and the injectors aren't doing anything. It just turns over and nothing happens. I cleaned the cap and rotor and changed the ignition control module, and still nothing. So, what should I try next?

I'm no mechanic, just a guy trying to get his truck running, but there are only a few things it could be that I can think of. Bad coil, bad distributor, or bad computer. Is that correct? I doubt it's the distributor, as it looks like it was replaced a while back, but I could be wrong. The battery is grounded to the block, and the block is grounded to the frame with straps at two locations.

So, not sure what to do next, besides just throw more money at it. Ugh.

Here are a couple pics:







Thanks for your input in advance!

[notsolo]

... not spraying fuel out of the tbi injector pods and no spark. Not the guru on this either, check your battery voltage, ground wires etc...Hopefully, someone will chime in with better info.

[68isgreat]

Originally Posted by notsolo

... not spraying fuel out of the tbi injector pods and no spark. Not the guru on this either, check your battery voltage, ground wires etc...Hopefully, someone will chime in with better info.

Yeah, it has me stumped too. Battery is new last year.

[notsolo]

"Jabo the mechanic" on YouTube has a Tbi no spark no fuel video....bad distributor on his I think.

[bowtie72]

Start by checking for power at coil. If you have it there next check would be the oil pressure switch. If the switch doesn’t see oil pressure it won’t kick on the fuel pump or fire the injectors. The fuel pump should come on for a few seconds when you turn the key on. Then kick on when the engine cranks. They are a pretty simple system.

[60case]

you need a power wire plugged into the coil There should be another 2 wire connector plugged into the coil Pink is 12 volts white is tach lead

[68isgreat]

Originally Posted by bowtie72

Start by checking for power at coil. If you have it there next check would be the oil pressure switch. If the switch doesn’t see oil pressure it won’t kick on the fuel pump or fire the injectors. The fuel pump should come on for a few seconds when you turn the key on. Then kick on when the engine cranks. They are a pretty simple system.

Thanks, I'll check that out. The fuel pump does come on when I turn the key on, but that's as far as it goes.

[68isgreat]

I just checked the circuits, and I'm not seeing any power at all to the coil or distributor with the key on. This is a brand new harness with brand new fuses, etc. I feel like I'm missing something basic. Would a bad computer prevent power going to the distributor/coil with the key turned on?

[RustyPile]

I suggest you start here:

https://www.autozone.com/diy/repair-...96b43f80c90e70

[68isgreat]

Great news! I re-read the instructions from Painless, and I missed the part where it said the hot wire at the coil has to be spliced into the ignition with a fusable link. I thought the power came through the computer from the wire marked ignition, but I guessed wrong. Anyway, I spliced the hot wire in and she runs like a champ!! So excited. I started this project a year ago, and now it's full steam ahead. With the modern powertrain (I'm mating it to a 700r4), I'm considering converting it to 4x4 so I can use it for everything.

[KQQL IT]

I'm about to begin a similar swap on old blue.
Howell harness and a wrecked 90 tbi pickup.
Did you use an tbi adapter to the intake ?

[Rust_never_sleeps]

I hate re-reading the instructions
I hate it even more when there's something I've missed ;-)

[68isgreat]

Originally Posted by KQQL IT

I'm about to begin a similar swap on old blue.
Howell harness and a wrecked 90 tbi pickup.
Did you use an tbi adapter to the intake ?

Not sure what you mean by adapter? My tbi unit is stock.

I found a couple tiny oil leaks at the rear of the manifold once I let it run a bit, so I'll need to put new gaskets on, but that's not surprising.

[68isgreat]

Originally Posted by Rust_never_sleeps

I hate re-reading the instructions
I hate it even more when there's something I've missed ;-)

Yep. Amazing how we gloss over things we don't realize are important until they are.

[KQQL IT]

Originally Posted by 68isgreat

Not sure what you mean by adapter? My tbi unit is stock.

I found a couple tiny oil leaks at the rear of the manifold once I let it run a bit, so I'll need to put new gaskets on, but that's not surprising.

Sorry, I'm swapping tbi onto a 454
I didn't realize you swapped the entire unit.

[roboticjunky]

Originally Posted by KQQL IT

I'm about to begin a similar swap on old blue.
Howell harness and a wrecked 90 tbi pickup.
Did you use an tbi adapter to the intake ?

Trans-Dapt makes a few different adapters depending on if the intake is spread bore or square and if you are using a sbc throttle body or bbc throttle body. They are made n the USA.

One thing to watch out for is how deep the 3 bolts holding the tbi on goes. The bolts might bottom out and you will keep tightening the bolts and then the plate will bend. I did this myself and had a bad vacuum leak.

[KQQL IT]

I've seen several adapters. Why I asked about it.