Tbi, map sensors, and headaches

[Alex guadalupe]

The stories follows me, 24 years old stuck in fort irwin with an 87 k5blazer
350 TBI
To get to the point, I had a wicked loss of power
Hesitation
Then backfire through the tbi
Took the truck to a friend on post amd we found out that the injectors were pissing fuel.
3 days later I rebuilt the tbi with new injectors and gaskets
After that my truck would idle rough
Then just die
We found that my map sensor took a shit
Another week goes by and with help I have a new map sensor
But now she wont even stay on with that new map sensor connected
She dies and when I got to start it back up I get nothing but cranking and the starter whinning that its turning forever

I get spark and fuel deliver
Ive tride everything I know but I just dont have enough experience with TBI
Can anyone help me please

 

[Russell]

First things first, you need to check the basics.

Does your engine have mechanical issues? Even compression in all cylinders? Cam lobes are okay? Valves are set correctly? No burnt valves or holes in your pistons? Do you have any vacuum leaks? What about exhaust leaks? Have you made any mechanical changes to the engine which would affect it's efficiency and pumping characteristics like a cam swap, heads, intake or exhaust?

If your engine is mechanically healthy and appropriately built for EFI, then it's time to look at the electronics.

What is your fuel pressure? Are all your sensors reading accurately? What is your system voltage at? Are all the engine grounds secure? Does your throttle body have any wear? Is your idle air control valve working? Do you have any codes in the ECM?

Shotgunning parts at your system will do nothing but cost you money. Take the time to troubleshoot everything, don't just guess. That means getting some tools to use like an ALDL cable to check data sensors and codes or a fuel pressure gauge and adapters.

 

[bigblock72]

Check the fuel pressure!!! The most common problem I see with a TBI truck is a weak fuel pump. They don't die completely like a normal fuel pump, just wheeze out 3-5 psi of fuel pressure and make you run in circles like you're doing. Most part stores will have a fuel pressure test kit for rent. Remove the fuel filter (it's probably plugged anyway) install the adapter in place of the fuel filter and connect the gauge, should have around 11 psi. If the fuel pressure is good report back and we can tell you what the next step is.