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Engine does crank, will not start.

20447 Views 4 Replies 3 Participants Last post by  carverman
Replacing the parts has turned out to be very beneficial to my truck, because now all the sensor lights on the dash are off.

A relay is a switch which controls a larger voltage with a smaller voltage.

Fuel pump relay has both switch power and power for the fuel pump present, yet the larger power for the fuel pump never comes out the other side of the relay, even if you put in a new relay.
So I am thinking that a ground is missing.

What is a PDC?
A search for that brought back a starter.

I am quite sure that my ECM does have power, as long as you are talking about the black box on the right fenderwall under the hood.

I was driving across a bumpy road, torn up by road construction. When I got across the road the truck started running rough and died.

I thought I needed to get spark back, there is not any voltage at the coil.

Later I found out that you cannot get spark if there is no fuel pump working. I was able to feed power through a jumper wire from the battery to the wire under the hood for the electric fuel pump, which then operated correctly.

Power does go from the ignition through both the ASD relay and the fuel pump relay, but it does not go from the relays to the ignition or the fuel system.

Power is present at pin 51 of the ECM under the hood on the passenger side fender.

There is no spark.
I have replaced, crank position sensor, camshaft position sensor, electric fuel pump, auto shutdown relay, fuel pump relay.
Signal power is being sent to switch the relays closed.
Power is going through both relays from the ignition and onto the computer alongside the fenderwall on the passenger side.
I can feed power to the electric fuel pump.
So why will the engine not start?
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There is no spark.
I have replaced, crank position sensor, camshaft position sensor, electric fuel pump, auto shutdown relay, fuel pump relay.
Signal power is being sent to switch the relays closed.
Power is going through both relays from the ignition and onto the computer alongside the fenderwall on the passenger side.
I can feed power to the electric fuel pump.
So why will the engine not start?
What was the original symptom before you changed all those parts?
On the dakota (not entirely sure on the first gen '92) there is an
ASD (auto shutdown relay that gets operated by the ECM, if it detects
a serious timing issue with a sensor.

First of all, the power for the ECM does not come through any relays.
It gets it's power directly from the PDC.
The auto shutdown relay is operated by the ECM/PCM and will shut
down the ignition coil driver, +12 volt to the coil and the injectors solenoids
The fuel pump relay is controlled directly by the ECM and it can shut it
down as well.

Please explain what you mean by "poweris going through both relays from the
ignition and the computer..that is NOT how it works.

The ECM always controls the low side of :
1: the ignition coil through the coil driver in the ECM
2. the injector solenoids by individual injector drivers in the ECM
3. The fuel pump relay.

The ASD relay supplies B+ to the high side of the ignition coil and individual
injector solenoids.
The fuel pump relay supplie B+ to the fuel pump.

All of this is directly controlled by the ECM

I don't know what the original problem was that you decided to "throw
a bunch of parts: at the symptom..so perhaps you should go back a bit
and explain why you changed those parts. :D
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would a 92 have that splice below the junction box that corrodes and breaks off?
would a 92 have that splice below the junction box that corrodes and breaks off?
I don't know what you are referring to as "splice below the junction box'..
do you mean the PDC (power distribution center) ..the black box with
with the cover you remove..where most of the heavy fuses and relays are located?

The PCM should have 3 connectors on it. C1/C2/C3

C1 (connector towards front of vehicle) (taken from a 20001 dodge ram
shop manual) is a 32 pin connector

Pin 1. ignition coil driver #4 (8.0L)
Pin 2. fused ignition switch output (run/start)
Pin 3 ignition coil driver #3 (8.0L)
Pin 4 sensor ground
Pin 5 ignition coil driver #5
pin 6 Prk/Neutral position switch
pin 7 3.9L/5.2L/5.9L ignition coil #1 driver ***
pin 8 crankshaft position sensor
pin 9 ignition coil #2 driver (8.0L)
pin 10 idle air control #2 driver
pin 11 idle air control #3 driver
pin 12 n/c
pin 13 PTO switch sense
pin 14 n/c
pin 15 intake air temp (IAT sensor) signal
pin 16 engine coolant temp (ECT sensor) signal
[B]pin 17 +5V supply to sensors[/B]
pin 18 Camshaft position sensor signal
pin 19 idle air control #1 driver
pin 20 idle air control #4 driver
pin 21 n/c
pin 22 Fused B+
pin 23 Throttle position (TPS) sensor signal
pin 24 3.9/5.2/5.9L Oxygen sensor 1/1 signal
pin 25 3.9/5.2/5.9 Oxygen sensor 1/2 (CALIFORNIA) signal
pin 25 oxygen sensor 8.0L signal
pin 26 oxygen sensor 2/1 signal
pin 27 map sensor signal (MAP)
pin 28 n/c
pin 29 Oxygen sensor 2/2 signal
pin 30 Oxgen sensor 1/2 signal
pin 31 Ground
pin 32 Ground

C2 (middle connector)
pin 1 Transmission temp signal
pin 2 Fuel injector #7 driver
pin 3 fuel injector #9 driver (8.0L V10)
pin 4 fuel injector #1 driver
pin 5 fuel injector #3 driver
pin 6 fuel injector #5 driver
pin 7 n/c
pin 8 govern pressure solenoid control (to transmission)
pin 9 n/c
pin 10 Generator field winding driver
pin 11 Torque convertor clutch solenoid control (TCC)
pin 12 Fuel injector #6 driver
pin 13 fuel injector #8 driver
pin 14 fuel injector #10 driver (8.0L V10)
pin 15 fuel injector #2 driver
pin 16 fuel injector #4 driver
pin 17 (n/c)
pin 18 (n/c)
pin 19 (n/c)
pin 20 n/c)
pin 21 3-4 shift control solenoid (Overdrive)
pin 22 n/c
pin 23 engine oil pressure sensors signal
pin 24 n/c
pin 25 Output speed sensor GROUND (AUTOMATIC TRANSMISSION)
pin 26 n/c
pin 27 Vehicle speed sensor (VSS)
pin 28 Output speed sensor SIGNAL
pin 29 Governor pressure sensor signal (Automatic transmission)
pin 30 Transmission relay control
pin 31 + 5 v supply (to sensors)
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PCM connector pin out
C3 (connector towards firewall of vehicle)

pin 1 A/C compressor clutch relay control
pin 2 n/c
pin 3 Auto shut down (ASD) relay control
pin 4 Speed control (cruise) vacumn solenoid control
pin 5 Speed control (cruise) vent solenoid control
pin 6 n/c
pin 7 n/c
pin 8 Oxygen sensor 1/1 heater control
pin 9 Oxygen sensor downstream relay control
pin 10 leak detection pump solenoid control
pin 11 Speed control (cruise) power supply (to cruise switches)
pin 12 Automatic shutdown (ASD) relay output
pin 13 Overdrive OFF switch sense
pin 14 Leak detection pump sense
pin 15 Battery temp sensor signal
pin 16 oxygen sensor 2/1 heater control
pin 17 n/c
pin 18 n/c
pin 19 fuel pump relay control
pin 20 Evap Emission solenoid control
pin 21 n/c
pin 22 A/C switch sense
pin 23 A/C select input
pin 24 Brake switch sense
pin 25 Generator source ( current source for field winding of alternator)
pin 26 Fuel level sensor signal
pin 27 SCI transmit
pin 28 CCD bus (-)
pin 29 SCI receive
pin 30 CCD Bus (+)
pin 31 n/c
pin 32 Speed control (cruise) switch sense signal
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