1990 5.7 TBI fuel delivery??

[jake15]

Ok, in order to fully understand my predicament it's probably best to provide a full back story. About two weeks ago i finally decided to dive in and fix problems that had been goin on for two years. My truck would idle extremely erratically like it start at 800 then would go to about 1800 then 2100 the 900 and just wherever it wanted whenever it wanted. I Checked SES light and it was saying TPS and Coolant Temp Sensor. Replaced both to no avail. Got a multimeter and both sensors checked out fine. Replaced computer, Swapped PROM and Calpak, replaced with new parts the distributor, ign module, ign switch and TPS. Problems were seemingly fixed, engine was still burning extremely rich and the new computer was giving a code for the knock sensor. Before i could replace it i had about a two hour drive ahead of me. twice during that drive the truck just died going down the highway. after a few minutes of sitting i was able to get the truck started (holding pedal all the way down). I replaced the knock sensor but my haynes manual says to remove both the distributor and oil pressure sending unit. now i probably should have but i didnt remove the distributor or the Oil Pressure sending unit (looked and looked for the Oil pressure sending unit but never could find it). ran great for the 5 minute drive i took. Now i have this Problem, Still burns extremely rich and the smell is horrible, but driving down the road the truck still just dies but without being able to restart it. If I park the truck and shut it off before it dies, I can start it right back up but if it dies, no joy. I did notice that when it dies, the injectors arent spraying. with a lil help from some starting fluid it would start and low and behold the injectors would start spraying again. the fuel pump is working normally, even when the injectors arent firing. smells as though its flooded but no matter how long it sits, even overnite, it wont start back up once it's died. Please someone with hoards of knowledge give me a simple solution to this growingly annoying situation im in. oh and the SES light is still on for the Knock sensor.

[jake15]

And I did check the connectors on the injectors and everything checked out fine no melted wires, fuel pump relay and everything is good as far as I can tell.

[maxwedge]

You need to check fuel pressure 10-13 psi. Running rich can be the map sensor,also stuck egr, clogged cat, or high fuel pressure.

[jake15]

Ok will do. But the fuel pressure wouldn't cause the injectors to randomly just stop spraying would it? I mean when i try to restart the truck after dying they won't spray at all. The pump will run but no spray from the injectors

[jake15]

Ok I got the throttle body apart tonight. Fuel pressure is fine, getting fuel all the way to the injectors but not through them. Now not getting spark either. All fuses and relays are good. I guess tomorrow I'm goin to take the ign system back off and have what i can tested. It's all brand new so still under warranty. Now what is the possibility that the old PROM chip went bad when placed in the new computer? Don't sound feasible but I'm not sure. I did check the wires leading to the injectors with my multimeter and they seemed to be in operating order so prolly just old wore out injectors. Hmmm...

[2000CAYukon]

Have you checked if the MAP sensor can hold a vacuum? Also check the vacuum hose between the MAP and TBI. I don't have my 90 anymore or the manuals but a bad MAP can cause it to run rich.

//2000CAYukon

[maxwedge]

Do you have 12v to the injectors, start there.

[jake15]

I am getting voltage but not 12. I'm on my way home now to double check and dive into this thing again. What would cause the injectors and the ign system to all stop at once? There arent any blown fuses.

[jake15]

Ok the ign system and the fuel delivery system are working fine. There's something that's keeping them both from running

[jake15]

Haha. What I meant was all components in each system are in working order. There's just something keeping the injectors from receiving the correct voltage and something keeping the ign coil from receiving voltage as well

[maxwedge]

If no power to the components which recieve 12v from the ign switch, possible the fusible links down at the starter have failed.

[jake15]

Hmm. Just finished checking all the fusible links and still nothing. If tha MAP sensor failed could that cause this? It should still start though right?

[maxwedge]

No magic answer her here, you need to trace why you don't have 12v from the ign to the required circuits.

[carrfixr]

with the key on and a fully charged battery what are your voltage readings at the injectors and ignition coil. with them unplugged its the red wires at the injectors.

[jake15]

Ok so I checked it all over again and from what I can tell and have been told its more than likely the electronic spark control module. But before I just replace it is there a way to test it?