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Discussion Starter · #21 ·
I do not understand which wire you think you need to move in the bulkhead of the firewall?

In post #14 I gave references to 2 wiring diagrams; one for 1989 and one for 1990 - 91. You need to print out both diagrams. Start with the 1990 - 91 diagram and check and find the counterpart pin with the same color wire and description on the 1989 diagram. It will be in a different pin location. Check all pins on the 1990 - 91 diagram. You will find one on the 1990 - 91 diagram that is NOT on the 1989 diagram. Identify that pin. It may be the solution to a no spark condition.

To create spark in this throttle body injection, the PCM must receive a timed pulse signal from the distributor. When the PCM receives this pulse, it interrupts the current flow (removes the ground) from the primary circuit in the ignition coil. Interrupting the electrical current flow in the primary winding causes the collapsing magnetic field to induce a high voltage current in the secondary ignition coil winding. This high voltage current then travels through the spark plug tower, to the distributor center port, onto the rotor coil under the distributor cap and to the appropriate spark plug tower which carries high voltage charge to the appropriate cylinder spark plug. The high voltage arcs across the spark plug tip and fires the air - fuel mixture.

You need to check the wiring and distributor pickup and make sure it is generating proper pulses. No pulses from the distributor then there will be no spark. It is also possible that the distributor pickup sensor is generating pulses but internal circuitry has failed in the PCM and it cannot control the ground for the coil.
I find in my haynes book , jumping the hall effect sensor to make spark on coil , a try and nothing !??
 

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. . . .I find in my haynes book , jumping the hall effect sensor to make spark on coil , a try and nothing !?? . . .
You will not get a spark from the coil with igntion key in the ON / RUN position and the engine crankshaft not rotating. Go back to my post #19. Crankshaft must rotate which means distributor shaft is turning. With distributor rotating pulses sent to the PCM. If the PCM receives these pulses then it will ground the ASD relay and provide power to the coil, electric fuel pump.

I will assume you have the battery postive and negative cables connected and posts and clamps (inside and outside) are shiny, free of corrosion? Do you have interior lamps with open door? Do you have any working lamps on the vehicle; ie, headlamps, tail lamps brake lamps? If the answer is NO then you probably have an open circuit somewhere in the positive battery cable to the fuse box. This will need to be fixed before proceeding.

Once you have working lamps on the vehicle test for 12 volt power traveling to the PCM from the ignition key switch. Go back to my post #14 dated jul 12, 2021. There is a link to a discussion about wiring diagram for a 1990 Dodge. Scroll until you find a file named scan.pdf. Download that file which is the wiring diagram for 1990 - 91 V8 TBI.

Once downloaded look at pdf page #2. It shows all 60 pin connections at the PCM. Note pin #9 which is the ignition feed. The PCM receives power on the DB wire when the igntion key switch is in the ON / RUN position. Do these checks and report ;your findings. See attached image.

PCM Wiring Ignition Feed partial.gif
 

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Discussion Starter · #23 ·
You will not get a spark from the coil with igntion key in the ON / RUN position and the engine crankshaft not rotating. Go back to my post #19. Crankshaft must rotate which means distributor shaft is turning. With distributor rotating pulses sent to the PCM. If the PCM receives these pulses then it will ground the ASD relay and provide power to the coil, electric fuel pump.

I will assume you have the battery postive and negative cables connected and posts and clamps (inside and outside) are shiny, free of corrosion? Do you have interior lamps with open door? Do you have any working lamps on the vehicle; ie, headlamps, tail lamps brake lamps? If the answer is NO then you probably have an open circuit somewhere in the positive battery cable to the fuse box. This will need to be fixed before proceeding.

Once you have working lamps on the vehicle test for 12 volt power traveling to the PCM from the ignition key switch. Go back to my post #14 dated jul 12, 2021. There is a link to a discussion about wiring diagram for a 1990 Dodge. Scroll until you find a file named scan.pdf. Download that file which is the wiring diagram for 1990 - 91 V8 TBI.

Once downloaded look at pdf page #2. It shows all 60 pin connections at the PCM. Note pin #9 which is the ignition feed. The PCM receives power on the DB wire when the igntion key switch is in the ON / RUN position. Do these checks and report ;your findings. See attached image.

View attachment 81591
Have 12v on pin#9 on PCM
Oil pressure light alway ON on cluster , anti-lock on message center is alway ON.
Working light : headlamp low/high , brake light , roof light
Not working light : reverse , left flasher don’t work when headlight switch is actived ( left flasher indicator on cluster is lightly illuminate)
 

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Discussion Starter · #24 ·
You will not get a spark from the coil with igntion key in the ON / RUN position and the engine crankshaft not rotating. Go back to my post #19. Crankshaft must rotate which means distributor shaft is turning. With distributor rotating pulses sent to the PCM. If the PCM receives these pulses then it will ground the ASD relay power to the coil, electric fuel pump.



I will assume you have the battery postive and negative cables connected and posts and clamps (inside and outside) are shiny, free of corrosion? Do you have interior lamps with open door? Do you have any working lamps on the vehicle; ie, headlamps, tail lamps brake lamps? If the answer is NO then you probably have an open circuit somewhere in the positive battery cable to the fuse box. This will need to be fixed before proceeding.

Once you have working lamps on the vehicle test for 12 volt power traveling to the PCM from the ignition key switch. Go back to my post #14 dated jul 12, 2021. There is a link to a discussion about wiring diagram for a 1990 Dodge. Scroll until you find a file named scan.pdf. Download that file which is the wiring diagram for 1990 - 91 V8 TBI.

Once downloaded look at pdf page #2. It shows all 60 pin connections at the PCM. Note pin #9 which is the ignition feed. The PCM receives power on the DB wire when the igntion key switch is in the ON / RUN position. Do these checks and report ;your findings. See attached image.

View attachment 81591
You will not get a spark from the coil with igntion key in the ON / RUN position and the engine crankshaft not rotating. Go back to my post #19. Crankshaft must rotate which means distributor shaft is turning. With distributor rotating pulses sent to the PCM. If the PCM receives these pulses then it will ground the ASD relay and provide power to the coil, electric fuel pump.

this is the verification procedure in the Haynes book for the Hall effect sensor! is this true?
81600

I will assume you have the battery postive and negative cables connected and posts and clamps (inside and outside) are shiny, free of corrosion? Do you have interior lamps with open door? Do you have any working lamps on the vehicle; ie, headlamps, tail lamps brake lamps? If the answer is NO then you probably have an open circuit somewhere in the positive battery cable to the fuse box. This will need to be fixed before proceeding.

Once you have working lamps on the vehicle test for 12 volt power traveling to the PCM from the ignition key switch. Go back to my post #14 dated jul 12, 2021. There is a link to a discussion about wiring diagram for a 1990 Dodge. Scroll until you find a file named scan.pdf. Download that file which is the wiring diagram for 1990 - 91 V8 TBI.

Once downloaded look at pdf page #2. It shows all 60 pin connections at the PCM. Note pin #9 which is the ignition feed. The PCM receives power on the DB wire when the igntion key switch is in the ON / RUN position. Do these checks and report ;your findings. See attached image.

View attachment 81591
 

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. . . Have 12v on pin#9 on PCM
Oil pressure light alway ON on cluster , anti-lock on message center is alway ON.
Working light : headlamp low/high , brake light , roof light
Not working light : reverse , left flasher don’t work when headlight switch is actived ( left flasher indicator on cluster is lightly illuminate) . . .
This indicates fuseable link between battery and PCM is good and passing electrical current. Check and test for 8 volt at pin #7 at PCM. Check and test for 8 volt at terminal #1 of 3 pin connector at distributor. See attached image.

Distributor Hall Effect Power.gif
 

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. . . . yes a have 8 volt on terminal #1 . . .
Check terminal #3 at PCM. This should have constant 12 volt power regardless of ignition key switch position.

Disconnect negative battery cable. Disconnect 60 pathway connector at PCM. Check for continuity to ground on signal ground #5 terminal at PCM to negative battery cable. Check for continuity to ground for power ground terminals #11 & #12 to negative battery cable. See attached image.

PCM Wiring Ignition Feed Grounds.gif
 

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Discussion Starter · #28 ·
Check terminal #3 at PCM. This should have constant 12 volt power regardless of ignition key switch position.

Disconnect negative battery cable. Disconnect 60 pathway connector at PCM. Check for continuity to ground on signal ground #5 terminal at PCM to negative battery cable. Check for continuity to ground for power ground terminals #11 & #12 to negative battery cable. See attached image.

View attachment 81603
Yess a have 12v on pin3
Continuity between negative cable and pin 5-11-12
 

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. . . Yess a have 12v on pin3. . . . . Continuity between negative cable and pin 5-11-12 . . .
Power and ground connections good at PCM. Next step is to test the distributor pickup coil and determine if it is pulsing between 5 volts and 0 volts.

Follow the instructions in this link for testing distributor coil pickup. Note that you must use a back probe wire on the 3 wire connector at the distributor. Disconnect secondary spark wire from coil tower to distributor tower.


If you see the volt meter change from 5 to 0 to 5 to 0 . . . then the distributor pickup is pulsing correctly. If you get this pulsing voltage change from 5 to 0 to 5 and so forth, do you hear the ASD relay close momentarily and the electric fuel pump run?
 

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I have an 1889 B250
Earlier this year, the day after completing a 2500 x country journey, I had a stall right after putting it in reverse in a grocery store parking lot, and a no Spark situation.

The relatively new coil was within spec.

I had been having weird issues with my tachometer being intermittent on the eastbound cross country journey and found the ground wire for tachometer was having issues. I repaired it, and no more intermittent tachometer issues on the 2500 miles westbound.

I noticed when cranking my engine, my tachometer needle, which usually bounced when cranking the engine, did not move at all and I assumed the coil driver on the ECM had failed.

This No spark situation occurred Within my 7 mile free towing AAA radius, It was the first time i ever used it in the now 20+ year ownership of this vehicle.

Ordered a reman engine computer, it fired right up, and I recently passed a CA smog test.
Old ECM the pin for the Ignition coil driver was burnt looking at the base.

The ignition driver component on my ECM failed. Perhaps due to the missing/failed ground on my aftermarket tach and its weird intermittent operation 2500+ miles earlier. The specific part number looks to be unobtanium and would require more soldering skills and tools than I have.

I want a back up computer not only for peace of mind, but as it seems the easiest way to test some theories, is a known good ECM.

Your ECM coil driver could have failed to, and its not just that it is not getting the expected signals on the other wires in order for the ECM to fire it. Perhaps closely inspect that pin's base. If it looks like it has melted the plastic immediately surrounding it I would say bingo, but not definitively rule it out if it looks fine.
 

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Discussion Starter · #31 ·
Power and ground connections good at PCM. Next step is to test the distributor pickup coil and determine if it is pulsing between 5 volts and 0 volts.

Follow the instructions in this link for testing distributor coil pickup. Note that you must use a back probe wire on the 3 wire connector at the distributor. Disconnect secondary spark wire from coil tower to distributor tower.


If you see the volt meter change from 5 to 0 to 5 to 0 . . . then the distributor pickup is pulsing correctly. If you get this pulsing voltage change from 5 to 0 to 5 and so forth, do you hear the ASD relay close momentarily and the electric fuel pump run?
I check your link to check the pick up plate ( Hall effect sensor ) and all is OK
8-9v on orange
0 to 5v when a turn the engine manually
And good ground
 

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. . . I check your link to check the pick up plate ( Hall effect sensor ) and all is OK
8-9v on orange
0 to 5v when a turn the engine manually
And good ground . . .
Good. So you know that the hall effect device is functioning properly and generating a 0 - 5 V square wave signal.

. . . Dont hear the Asd relay click . . .
Not so good news. Pulsing signal from the distributor should cause the PCM to ground the ASD relay. Need to check that the pulsing signal is traveling to the PCM.

Back probe pin #24 at the PCM. This is the end of the GRY signal wire from the Hall effect device in the distributor. With ignition key switch in the ON / RUN position turn the crankshaft slowly Do you see a pulsing 0 - 5 V signal at pin #24?

Another test to try. When you initially turn the ignition key switch from the OFF to the ON / RUN position do you hear the ASD relay engage momentarily (1 - 2 seconds) and the electric fuel pump run for a short burst and then stop?
 

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Discussion Starter · #34 ·
Good. So you know that the hall effect device is functioning properly and generating a 0 - 5 V square wave signal.



Not so good news. Pulsing signal from the distributor should cause the PCM to ground the ASD relay. Need to check that the pulsing signal is traveling to the PCM.

Back probe pin #24 at the PCM. This is the end of the GRY signal wire from the Hall effect device in the distributor. With ignition key switch in the ON / RUN position turn the crankshaft slowly Do you see a pulsing 0 - 5 V signal at pin #24?

Another test to try. When you initially turn the ignition key switch from the OFF to the ON / RUN position do you hear the ASD relay engage momentarily (1 - 2 seconds) and the electric fuel pump run for a short burst and then stop?
Yes on pin#24 on pcm have 0 to 5 v !
No don’t hear the pump ( no click )
 

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. . . .Yes on pin#24 on pcm have 0 to 5 v ! No don’t hear the pump ( no click ) . . .
When you turn the ignition key switch to the ON / RUN position from OFF, do you hear the ASD relay click and fuel pump run for 1 - 2 seconds?
 

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. . . No . . .
Review. At this point you know the Hall effect has good power, good ground. When crankshaft rotates it generates a pulsing signal that fluctuates between 0 - 5 V. This same pulsing signal is present at pin #24 of the PCM.

From your post #16, July 12, 2021 there is 12 volts present at reference point #86 (control side) of the ASD relay. Reference point #85 (control side) of the ASD relay should be grounded by the PCM to engage the ASD relay. This is not happening. This is further evidenced by the fact that the PCM should energize the ASD relay for 1 - 2 seconds (without distributor pulses) when ignition key switch is turned to the ON / RUN position but the ASD relay does not energize and run the electric fuel pump. This points to a possible failure of the PCM to ground. the ASD control circuit from reference point #85 of the relay.

Final test on the control circuit ground to the ASD relay.
Back probe pin #51 at the ASD relay. It should have a DB / YL wire. With ignition key switch in the ON / RUN position you need to effect a ground on that wire. Grounded the electric fuel pump should run. That means the ASD relay is functioning properly and it can control and energize all devices attached electrcially to the load side of the relay. Question is a process to do this safely without damaging any components.

At first one would think to connect a jumper wire from pin #51 to ground. If ASD relay engaged and electric pump runs you know the ASD control side and load side wiring are good and functiional. Danger is that wiring diagrams could be incorrect and so the information that I have given you. Wiring connectors are very close together and it is all too easy to touch an adjacent power wire. With a jumper wire you create a direct short and can cause excess current flow and damage.

I use a 12 volt test lamp with LED bulb (not incandescent). 12 volt LED bulbs draw just a few milliamps of current so if you inadvertently ground a power wire, the test lamp illuminates but no damage. Not so with a straight jumper wire.

So I will leave you with the final test. Pin #51 at the PCM needs to be grounded with key switch ON / RUN to verify ASD is functioning. How you do it is up to you. I have warned about using a straight jumper wire on a PCM circuit. Safer to use an LED test lamp in the circuit. If you "smoke something" or damage a circuit, I am not responsible.
 

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Discussion Starter · #38 ·
Review. At this point you know the Hall effect has good power, good ground. When crankshaft rotates it generates a pulsing signal that fluctuates between 0 - 5 V. This same pulsing signal is present at pin #24 of the PCM.

From your post #16, July 12, 2021 there is 12 volts present at reference point #86 (control side) of the ASD relay. Reference point #85 (control side) of the ASD relay should be grounded by the PCM to engage the ASD relay. This is not happening. This is further evidenced by the fact that the PCM should energize the ASD relay for 1 - 2 seconds (without distributor pulses) when ignition key switch is turned to the ON / RUN position but the ASD relay does not energize and run the electric fuel pump. This points to a possible failure of the PCM to ground. the ASD control circuit from reference point #85 of the relay.

Final test on the control circuit ground to the ASD relay.
Back probe pin #51 at the ASD relay. It should have a DB / YL wire. With ignition key switch in the ON / RUN position you need to effect a ground on that wire. Grounded the electric fuel pump should run. That means the ASD relay is functioning properly and it can control and energize all devices attached electrcially to the load side of the relay. Question is a process to do this safely without damaging any components.

At first one would think to connect a jumper wire from pin #51 to ground. If ASD relay engaged and electric pump runs you know the ASD control side and load side wiring are good and functiional. Danger is that wiring diagrams could be incorrect and so the information that I have given you. Wiring connectors are very close together and it is all too easy to touch an adjacent power wire. With a jumper wire you create a direct short and can cause excess current flow and damage.

I use a 12 volt test lamp with LED bulb (not incandescent). 12 volt LED bulbs draw just a few milliamps of current so if you inadvertently ground a power wire, the test lamp illuminates but no damage. Not so with a straight jumper wire.

So I will leave you with the final test. Pin #51 at the PCM needs to be grounded with key switch ON / RUN to verify ASD is functioning. How you do it is up to you. I have warned about using a straight jumper wire on a PCM circuit. Safer to use an LED test lamp in the circuit. If you "smoke something" or damage a circuit, I am not responsible.
When a jump pin#51 to ground , the fuel pump working
 

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When a jump pin#51 to ground , the fuel pump working
At this point, I'd be checking the connector for both the Hall effect sensor into the PCM, and the ASD out of the PCM.

If you jump pin #51 to ground, will the motor then start?

If the connectors are good in the housing (not loose on the pins!), I'd have to say you've just about beat it down to the PCM, as rare as PCM failures actually are.

But one more thing I'd suggest.

With the negative battery cable disconnected from the battery, remove/reinstall both connectors on the ECU three to four times.

Then reconnect the negative battery cable to the battery, and see if it runs.

RwP
 

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. . . .When a jump pin#51 to ground , the fuel pump working . . . .
OK. You have narrowed the issue to a failed PCM. I like the suggestion by contributor RalphP. Check all connections at the PCM and make sure all pins and receptacles are clean.
 
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