2.8 tbi just quit-injector signal?

[johnc]

I have an 86 s10 with 2.8 tbi. It just quit. It is getting fuel. It will also run with fuel sprayed down the intake, so I must have spark. I checked for voltage at the injectors while cranking and got a very small reading (maybe 1 volt or less) What are the chances the brain box is having problems? Should I try a scanner? I don't want to dump money into a new brain and not fix it.
thanks,
johnc

[johnc]

I found a site dealing with getting the codes out- I am getting a "33"

[bszopi]

DTC 13 Bank 1 (Left) Oxygen Sensor (O2S) Circuit (Open Circuit)
DTC 14 Engine Coolant Temperature (ECT) Sensor Circuit (High Temp. Indicated)
DTC 15 Engine Coolant Temperature (ECT) Sensor Circuit (Low Temp. Indicated)
DTC 16 Distributor Ignition System (Low Resolution Pulse)
DTC 21 Throttle Position (TP) Sensor Circuit (Signal Voltage High)
DTC 22 Throttle Position (TP) Sensor Circuit (Signal Voltage Low)
DTC 23 Intake Air Temperature (IAT) Sensor Circuit (Low Temp. Indicated)
DTC 24 Vehicle Speed Sensor (VSS) Circuit
DTC 25 Intake Air Temperature (IAT) Sensor Circuit (High Temp. Indicated)
DTC 26 EVAP Canister Purge Soleniod
DTC 27 EGR Vacuum
DTC 28 Transmission Range Pressure Switch
DTC 32 Exhaust Gas Recirculation (EGR) Circuit
DTC 33 Manifold Absolute Pressure (MAP) Sensor Circuit (Signal Voltage High-Low Vacuum)
DTC 34 Manifold Absolute Pressure (MAP) Sensor Circuit (Signal Voltage Low-High Vacuum)
DTC 36 Distributor Ignition System
(Faulty High Resolution Pulse or Extra Low Resolution Pulse Detected)
DTC 41 Ignition Control (IC) Circuit (Open Circuit)
DTC 42 Ignition Control (IC) Circuit (Grounded or Shorted Circuit)
DTC 43 Knock Sensor (KS) Circuit
DTC 44 Bank l (Left) Oxygen Sensor (O2S) Circuit (Lean Exhaust Indicated)
DTC 45 Bank l (Left) Oxygen Sensor (O2S) Circuit (Rich Exhaust Indicated)
DTC 46 Personal Automotive Security System (PASS-Key 11) Circuit
DTC 48 MASS Air Flow (MAF)
DTC 50 System Voltage Low
DTC 51 PROM Error (Faulty or Incorrect PROM)
DTC 53 System Voltage High
DTC 55 Fuel Lean Monitor
DTC 61 A/C System Performance
DTC 63 Bank 2 (Right) Oxygen Sensor (O2S) Circuit (Open Circuit)
DTC 64 Bank 2 (Right) Oxygen Sensor (O2S) Circuit (Lean Exhaust Indicated)
DTC 65 Bank 2 (Right) Oxygen Sensor (O2S) Circuit (Rich Exhaust Indicated)
DTC 66 A/C Refrigerant Pressure Sensor Circuit (Open or Shorted)
DTC 67 A/C Refrigerant Pressure Sensor Circuit
(Pressure Sensor or A/C Clutch Circuit Problem)
DTC 68 A/C Relay Circuit (Shorted Circuit)
DTC 69 A/C Clutch Circuit
DTC 71 A/C Evaporator Temperature Sensor Circuit (Open or Shorted)
DTC 72 Vehicle Speed Sensor Loss
DTC 73 Pressure Control Soleniod (PCS) Circuit
DTC 74 Traction Control System (TCS) Circuit Low
DTC 75 Transmission System Voltage Low
DTC 77 Cooling Fan Relay Control
DTC 79 Transmission Fluid Overtemp
DTC 81 Transmission 2-3 Shift Solenoid Circuit
DTC 82 Transmission 1-2 Shift Solenoid Circuit

[johnc]

Thanks,
now the big question: would the MAP circuit cause the vehicle to quit?

[bszopi]

Oh yeah, quite easily. If the ECM thinks there is no vacuum or different vacuum than actual, then it will adjust the fuel and spark accordingly. If it doesn't get a signal, then it can't adjust the parameters.

[johnc]

OK, still plugging along. Turns out the injectors are getting a full 12v. A shop says they are meant to stay hot, and the ground is cycled to pulse them. No grounding is happening. Next step is to chase those wires and see where they go. This vehicle was meant as a donor for a carb'd vehicle. Might go that route if I can plumb in a proper electric pump set-up with tank return.

[johnc]

I chased the wires. They connect to the computer. The "33" code is not happeniing now. I might have counted a quick "12" (flash, pause. flash flash) as a "3". All I get now is the "12" continuosly. The computer must get a trigger reference from somewhere. I read somewhere that the ref signal is from a tachometer signal. The only thing that looks close is the dist. sensor. Seems if that went out, the spark would quit too.
johnc

[johnc]

just a thought. I pulled the leads to the ECM when I was checking connections. Did I erase the stored codes by pulling the power?

[geoffinbc]

Yea codes will go if power is lost. Ther needs to be ignition power and and ignition pulse tot he ECM so make sure to check out the ignition module in the dizzy and be sure there are no ECM fuses blown out.

[johnc]

BTY,
I checked all the fuses on the fuse block. They were all good. Is the ECM fuse somewhere else? I borrowed another dizzy module, and it still will not start. I think I borrowed MAP sensors too (one on aircleaner, and another in firewall above distributor? ).I can run a 12v wire to the injectors and pulse them with a ground wire. I might try keeping it going this way for a minute, then check codes again.

[johnc]

Pulsing the injectors will keep the engine going, WITHOUT THE COMPUTER PLUGGED IN. What is this all about? This blows all my troubleshooting.

[johnc]

After conferring with a shop, the conclusion was the pickup coil was no good. I pulled the dist. and replaced the coil. I get fuel pulsing, and spark, but no start. I have tried turning the dist. while cranking, but not even a backfire. One of the ECM fuses blew on the first try, but is OK now. Can the module in the dist. be screwy and throw the timing so far out that it cannot fire?

[geoffinbc]

Fuel and spark but no start? That is weird you should at least hear some sort of effort comming from the engine even if the timing is out.

Remove the timing wire under the dash and then try and start the truck.

Your engine should be set up like this when Cylinder 1 is on TDC COMPRESSION

http://members.shaw.ca/betterthanyoutoo/ignition2.8l.gif

[johnc]

bty,
what timing wire under the dash? Is it part of the 4 wire connector that joins the main computer harness on the passenger side?

[geoffinbc]

No there is a brown wire under the dash board and behind the carpet on the passenger side. You MUST disconnect this wire and ONLY this wire when timing the engine. If you have not been doing this while timing it is no wonder its way of. Unplug the wire (it has a quick disconnect) and time to 10* BTDC. Dont forget to reconnect it when done.

It will turn the check engine light on. This is Normal it is the ECM saying "Hey I do not have timing control anymore" and this is exactally what you need to do. It removes timing function from the ECM so you can manually set the base tming for the ignition system. Once set the ECM will take control from there.