94 dodge Dakota starting and running problems
Champion
Joined: Sep 2013
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You sound like you are doing what I do when trying to run down a problem I have no clue how to run down like a pro. Take a break then write down on paper what you think you know and what you have done in order. That should help you regain perspective. It sounded like you had it for a minute then you went on a tangent and tried something that probably came to you for good reason, which gave you new data that confused what you thought you knew. .
Record Breaker
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https://drive.google.com/file/d/0BzA...lCaF84MnM/view
Okay, so I pulled up the 94 drawings above (not the FSM drawings, but hopefully accurate enough)....a little different than my 90 for the ASD but basically the same. Whereas my 90, the ASD goes to the fuel pump, your 94 has a separate fuel pump relay. The ASD in your truck controls the hot side of the fuel injectors, ignition coil and power to the o2 sensor.
From the fig 8 of the drawings, you can see the ASD relay...it has four wires:
Dk Blue - This wire comes from the ignition switch and powers both the ASD and fuel pump relay. It's the 12VDC supply.
Dk Blue/Yellow - This is the ground of the relay supplied by the PCM
These two signals are required to energize the relay.
Red/White - This wire is all the time 12VDC and is the supply to the injectors/O2/ignition coil through the relay
Dk Grn/orange - This is the wire to the O2 sensor, ignition coil and injectors and gets 12VDC from the Red/White wire when the Relay is energized
Now, on that same diagram, the ignition coil Dk Grn/Orange is spliced to the injectors.
So, if you are doing continuity tests, you can see that the Dk Grn/orange wire should ONLY have continuity when the relay is closed. And it would have continuity with the Red/White wire as well as Dk Blue wire because they are tied back together ahead of the fuses from the 12VDC supply. You may also read continuity to the Dk Blue/Yellow wire through the small resistance of the ASD relay coil. That's why continuity is not really a good test here.
With the truck off, pull the connector to the ASD relay. Put your meter on continuity and one lead on where the Dk Grn/Orange wire would connect and one lead on where the Red/Whit wire would connect. This is on the relay terminals, NOT the connector. You should read OPEN or infinite ohms.
Now run a temporary jumper wire from the battery POS terminal to where the DK Blue wire would connect on the relay. Then with another jumper tied to ground, briefly touch the terminal on the relay where the Dk Blue/Yellow wire would go. You should hear the relay click, and your meter should now read CLOSED or 0 ohms.
If the above works, then your ASD relay is fine.
If the relay is fine, and your coil is not getting voltage, then the Red/White wire at the relay could be missing 12VDC. That comes from fuse D in the power dist block. Check it with your meter. You can pull the relay connector and turn the ignition on. With your meter set for VDC, check the pin on the connector that has the red/white wire and see if you have 12VDC to ground (one lead on red/white wire, one lead on a good ground or NEG of battery). You should also have 12VDC on the DK Blue wire at the same time. Check it too. If you have 12VDC on both these, plug the relay back in. You should hear/feel the relay click on. If you do not, then you are missing the ground signal from the PCM. I'm not sure if this ground from the PCM is timed, so turn the ignition off then back on and feel/hear if you get a click. If all this checks out and the relay clicks on, and you have 12VDC at the red/white wire and you've checked that the contact on the ASD relay is good with the earlier continuity check, then you have a broken wire from the relay to the splice, or a broken wire from the splice to the coil. You can check this by pulling any injector connector. With the ASD relay on, you should have 12VDC at the DK Orange/Green wire on any injector. Again, check this to ground. ALL your voltage checks should be with meter on VDC and the black lead of your meter secured to a good ground or the NEG post of your battery. If your injectors don't have voltage then the main wire to the splice is broken. If the injectors have voltage but the coil does not then the wire from the splice to the coil is broken. If you have voltage to the coil, but the spark is weak, then bad coil or bad ground at the injector.
Okay, so I pulled up the 94 drawings above (not the FSM drawings, but hopefully accurate enough)....a little different than my 90 for the ASD but basically the same. Whereas my 90, the ASD goes to the fuel pump, your 94 has a separate fuel pump relay. The ASD in your truck controls the hot side of the fuel injectors, ignition coil and power to the o2 sensor.
From the fig 8 of the drawings, you can see the ASD relay...it has four wires:
Dk Blue - This wire comes from the ignition switch and powers both the ASD and fuel pump relay. It's the 12VDC supply.
Dk Blue/Yellow - This is the ground of the relay supplied by the PCM
These two signals are required to energize the relay.
Red/White - This wire is all the time 12VDC and is the supply to the injectors/O2/ignition coil through the relay
Dk Grn/orange - This is the wire to the O2 sensor, ignition coil and injectors and gets 12VDC from the Red/White wire when the Relay is energized
Now, on that same diagram, the ignition coil Dk Grn/Orange is spliced to the injectors.
So, if you are doing continuity tests, you can see that the Dk Grn/orange wire should ONLY have continuity when the relay is closed. And it would have continuity with the Red/White wire as well as Dk Blue wire because they are tied back together ahead of the fuses from the 12VDC supply. You may also read continuity to the Dk Blue/Yellow wire through the small resistance of the ASD relay coil. That's why continuity is not really a good test here.
With the truck off, pull the connector to the ASD relay. Put your meter on continuity and one lead on where the Dk Grn/Orange wire would connect and one lead on where the Red/Whit wire would connect. This is on the relay terminals, NOT the connector. You should read OPEN or infinite ohms.
Now run a temporary jumper wire from the battery POS terminal to where the DK Blue wire would connect on the relay. Then with another jumper tied to ground, briefly touch the terminal on the relay where the Dk Blue/Yellow wire would go. You should hear the relay click, and your meter should now read CLOSED or 0 ohms.
If the above works, then your ASD relay is fine.
If the relay is fine, and your coil is not getting voltage, then the Red/White wire at the relay could be missing 12VDC. That comes from fuse D in the power dist block. Check it with your meter. You can pull the relay connector and turn the ignition on. With your meter set for VDC, check the pin on the connector that has the red/white wire and see if you have 12VDC to ground (one lead on red/white wire, one lead on a good ground or NEG of battery). You should also have 12VDC on the DK Blue wire at the same time. Check it too. If you have 12VDC on both these, plug the relay back in. You should hear/feel the relay click on. If you do not, then you are missing the ground signal from the PCM. I'm not sure if this ground from the PCM is timed, so turn the ignition off then back on and feel/hear if you get a click. If all this checks out and the relay clicks on, and you have 12VDC at the red/white wire and you've checked that the contact on the ASD relay is good with the earlier continuity check, then you have a broken wire from the relay to the splice, or a broken wire from the splice to the coil. You can check this by pulling any injector connector. With the ASD relay on, you should have 12VDC at the DK Orange/Green wire on any injector. Again, check this to ground. ALL your voltage checks should be with meter on VDC and the black lead of your meter secured to a good ground or the NEG post of your battery. If your injectors don't have voltage then the main wire to the splice is broken. If the injectors have voltage but the coil does not then the wire from the splice to the coil is broken. If you have voltage to the coil, but the spark is weak, then bad coil or bad ground at the injector.
Administrator
Joined: Apr 2010
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From: Clayton MI
The way the system works, you will only see 12 volts at the coil for about three seconds, if the PCM doesn't see the engine turning.
If you have continuity to several wires at the ASD relay socket, you have a short somewhere. That ain't right.
If you have continuity to several wires at the ASD relay socket, you have a short somewhere. That ain't right.
Record Breaker
Joined: Aug 2013
Posts: 1,033
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However, I caution against using continuity check on any wires fed from the ECM. I believe these are grounds fed through switching transistors. You can have continuity through the transistors, as the diode on the transistor is one way. Depending on which way the leads of your meter are oriented you can read continuity through different circuits as your meter applies a small current, and that current will go 'backwards' through the emitter leg of the transistor. See here as an example: https://www.allaboutcircuits.com/tex...ransistor-bjt/
To get a true continuity measurement at the ASD, I would advise pulling the ECM connector when doing so. That will eliminate any chance of backfeeding through the ECM circuitry. With the relay pulled and the ECM connector pulled, if you read continuity on more than 2 legs of the connector, then yes, you have a short somewhere.
Administrator
Joined: Apr 2010
Posts: 87,479
Likes: 4,223
From: Clayton MI
Define several....he will actually see continuity between three of the four wires if he's measuring with the relay attached. With the relay attached, the impedance of the relay coil is small, and a cheap meter will read read through the two legs of the coil. Granted, I doubt he's doing that, as it would be difficult without some jumpers. If he's pulling the relay and just measuring the connector, then he would see continuity between two of the wires as they originate from the same hot through 2 different fuses (the relay power and the feed to the injectors/coil).
However, I caution against using continuity check on any wires fed from the ECM. I believe these are grounds fed through switching transistors. You can have continuity through the transistors, as the diode on the transistor is one way. Depending on which way the leads of your meter are oriented you can read continuity through different circuits as your meter applies a small current, and that current will go 'backwards' through the emitter leg of the transistor. See here as an example: https://www.allaboutcircuits.com/tex...ransistor-bjt/
To get a true continuity measurement at the ASD, I would advise pulling the ECM connector when doing so. That will eliminate any chance of backfeeding through the ECM circuitry. With the relay pulled and the ECM connector pulled, if you read continuity on more than 2 legs of the connector, then yes, you have a short somewhere.
However, I caution against using continuity check on any wires fed from the ECM. I believe these are grounds fed through switching transistors. You can have continuity through the transistors, as the diode on the transistor is one way. Depending on which way the leads of your meter are oriented you can read continuity through different circuits as your meter applies a small current, and that current will go 'backwards' through the emitter leg of the transistor. See here as an example: https://www.allaboutcircuits.com/tex...ransistor-bjt/
To get a true continuity measurement at the ASD, I would advise pulling the ECM connector when doing so. That will eliminate any chance of backfeeding through the ECM circuitry. With the relay pulled and the ECM connector pulled, if you read continuity on more than 2 legs of the connector, then yes, you have a short somewhere.
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Professional
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https://drive.google.com/file/d/0BzA...lCaF84MnM/view
Okay, so I pulled up the 94 drawings above (not the FSM drawings, but hopefully accurate enough)....a little different than my 90 for the ASD but basically the same. Whereas my 90, the ASD goes to the fuel pump, your 94 has a separate fuel pump relay. The ASD in your truck controls the hot side of the fuel injectors, ignition coil and power to the o2 sensor.
From the fig 8 of the drawings, you can see the ASD relay...it has four wires:
Dk Blue - This wire comes from the ignition switch and powers both the ASD and fuel pump relay. It's the 12VDC supply.
Dk Blue/Yellow - This is the ground of the relay supplied by the PCM
These two signals are required to energize the relay.
Red/White - This wire is all the time 12VDC and is the supply to the injectors/O2/ignition coil through the relay
Dk Grn/orange - This is the wire to the O2 sensor, ignition coil and injectors and gets 12VDC from the Red/White wire when the Relay is energized
Now, on that same diagram, the ignition coil Dk Grn/Orange is spliced to the injectors.
So, if you are doing continuity tests, you can see that the Dk Grn/orange wire should ONLY have continuity when the relay is closed. And it would have continuity with the Red/White wire as well as Dk Blue wire because they are tied back together ahead of the fuses from the 12VDC supply. You may also read continuity to the Dk Blue/Yellow wire through the small resistance of the ASD relay coil. That's why continuity is not really a good test here.
With the truck off, pull the connector to the ASD relay. Put your meter on continuity and one lead on where the Dk Grn/Orange wire would connect and one lead on where the Red/Whit wire would connect. This is on the relay terminals, NOT the connector. You should read OPEN or infinite ohms.
Now run a temporary jumper wire from the battery POS terminal to where the DK Blue wire would connect on the relay. Then with another jumper tied to ground, briefly touch the terminal on the relay where the Dk Blue/Yellow wire would go. You should hear the relay click, and your meter should now read CLOSED or 0 ohms.
If the above works, then your ASD relay is fine.
If the relay is fine, and your coil is not getting voltage, then the Red/White wire at the relay could be missing 12VDC. That comes from fuse D in the power dist block. Check it with your meter. You can pull the relay connector and turn the ignition on. With your meter set for VDC, check the pin on the connector that has the red/white wire and see if you have 12VDC to ground (one lead on red/white wire, one lead on a good ground or NEG of battery). You should also have 12VDC on the DK Blue wire at the same time. Check it too. If you have 12VDC on both these, plug the relay back in. You should hear/feel the relay click on. If you do not, then you are missing the ground signal from the PCM. I'm not sure if this ground from the PCM is timed, so turn the ignition off then back on and feel/hear if you get a click. If all this checks out and the relay clicks on, and you have 12VDC at the red/white wire and you've checked that the contact on the ASD relay is good with the earlier continuity check, then you have a broken wire from the relay to the splice, or a broken wire from the splice to the coil. You can check this by pulling any injector connector. With the ASD relay on, you should have 12VDC at the DK Orange/Green wire on any injector. Again, check this to ground. ALL your voltage checks should be with meter on VDC and the black lead of your meter secured to a good ground or the NEG post of your battery. If your injectors don't have voltage then the main wire to the splice is broken. If the injectors have voltage but the coil does not then the wire from the splice to the coil is broken. If you have voltage to the coil, but the spark is weak, then bad coil or bad ground at the injector.
Okay, so I pulled up the 94 drawings above (not the FSM drawings, but hopefully accurate enough)....a little different than my 90 for the ASD but basically the same. Whereas my 90, the ASD goes to the fuel pump, your 94 has a separate fuel pump relay. The ASD in your truck controls the hot side of the fuel injectors, ignition coil and power to the o2 sensor.
From the fig 8 of the drawings, you can see the ASD relay...it has four wires:
Dk Blue - This wire comes from the ignition switch and powers both the ASD and fuel pump relay. It's the 12VDC supply.
Dk Blue/Yellow - This is the ground of the relay supplied by the PCM
These two signals are required to energize the relay.
Red/White - This wire is all the time 12VDC and is the supply to the injectors/O2/ignition coil through the relay
Dk Grn/orange - This is the wire to the O2 sensor, ignition coil and injectors and gets 12VDC from the Red/White wire when the Relay is energized
Now, on that same diagram, the ignition coil Dk Grn/Orange is spliced to the injectors.
So, if you are doing continuity tests, you can see that the Dk Grn/orange wire should ONLY have continuity when the relay is closed. And it would have continuity with the Red/White wire as well as Dk Blue wire because they are tied back together ahead of the fuses from the 12VDC supply. You may also read continuity to the Dk Blue/Yellow wire through the small resistance of the ASD relay coil. That's why continuity is not really a good test here.
With the truck off, pull the connector to the ASD relay. Put your meter on continuity and one lead on where the Dk Grn/Orange wire would connect and one lead on where the Red/Whit wire would connect. This is on the relay terminals, NOT the connector. You should read OPEN or infinite ohms.
Now run a temporary jumper wire from the battery POS terminal to where the DK Blue wire would connect on the relay. Then with another jumper tied to ground, briefly touch the terminal on the relay where the Dk Blue/Yellow wire would go. You should hear the relay click, and your meter should now read CLOSED or 0 ohms.
If the above works, then your ASD relay is fine.
If the relay is fine, and your coil is not getting voltage, then the Red/White wire at the relay could be missing 12VDC. That comes from fuse D in the power dist block. Check it with your meter. You can pull the relay connector and turn the ignition on. With your meter set for VDC, check the pin on the connector that has the red/white wire and see if you have 12VDC to ground (one lead on red/white wire, one lead on a good ground or NEG of battery). You should also have 12VDC on the DK Blue wire at the same time. Check it too. If you have 12VDC on both these, plug the relay back in. You should hear/feel the relay click on. If you do not, then you are missing the ground signal from the PCM. I'm not sure if this ground from the PCM is timed, so turn the ignition off then back on and feel/hear if you get a click. If all this checks out and the relay clicks on, and you have 12VDC at the red/white wire and you've checked that the contact on the ASD relay is good with the earlier continuity check, then you have a broken wire from the relay to the splice, or a broken wire from the splice to the coil. You can check this by pulling any injector connector. With the ASD relay on, you should have 12VDC at the DK Orange/Green wire on any injector. Again, check this to ground. ALL your voltage checks should be with meter on VDC and the black lead of your meter secured to a good ground or the NEG post of your battery. If your injectors don't have voltage then the main wire to the splice is broken. If the injectors have voltage but the coil does not then the wire from the splice to the coil is broken. If you have voltage to the coil, but the spark is weak, then bad coil or bad ground at the injector.
Record Breaker
Joined: Aug 2013
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but no matter....sounds like the asd relay is fine as I suspected and an issue with the connector at the pcm.
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Professional
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When I first started messing with this truck the pcm connector did look pretty dirty so it's possible is has dirty connection. Looked like really old dried up dielectric Grease and such. I sprayed it with electronic cleaner but is there a better way to clean it up?
Record Breaker
Joined: Aug 2013
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I soaked my connectors in vinegar and salt bath...then neutralize with baking soda...then air dry well and cost with new dielectric
Administrator
Joined: Apr 2010
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From: Clayton MI
Yeah, cleaning it out would be the first step....... I have some little tiny brushes for just such an occasion, but, there are a LOT of pins there....... it's a career move to clean them all. 