93 Dakota 3.9 fuel pump issues
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Joined: Jul 2006
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93 Dakota 3.9 fuel pump issues
I have a 3.9 with 212,000 miles. I had the fuel pump replaced about 5 years ago, but only drove the truck about 15,000 miles and it died, seemingly from no fuel.
We tried "testing the pump". We couldn't hear the pump run, so I disconnected the inline filter and cranked the engine. No fuel came from the lines. We tested the 5-pin connector. The two black, ground connectors had good ground. The center connector (to computer?) read about 12 volts and connector #2 read about 8 volts. I couldn't get voltage on the dark green line with the black stripe (which should be the power line. We checked continuity good on the dark green line with black stripe from the pump connector to the fuel pump relay. To confuse things, I read on the Autozone site that the fuel pump gets it's power from the Auto Shutdown relay. Is this true? Anyway, we took the pump out, and it worked after applying a wire with 12v to pin one (dark green/black) and the other pin to ground. It seems like the pump is good. I had disagreement with my partner on when 12v should be available on pin one (dark green/black). Should that pin on the connector have 12v when the key is turned to on? Does this 12v come from the fuel pump relay or from the Auto Shutdown relay? I'm a bit confused.
Also, when we pulled the pump. 2 pieces fell out. They were light brown. One piece was half-oval with a straight piece on top with a metal ball inside the piece, and the second piece that fell out was the same color and looked like it worked with the first piece. Would the displacement of these pieces cause the pump to not work properly, or would it cause some danger? Any help would be appreciated. The truck usually runs like a champ.
We tried "testing the pump". We couldn't hear the pump run, so I disconnected the inline filter and cranked the engine. No fuel came from the lines. We tested the 5-pin connector. The two black, ground connectors had good ground. The center connector (to computer?) read about 12 volts and connector #2 read about 8 volts. I couldn't get voltage on the dark green line with the black stripe (which should be the power line. We checked continuity good on the dark green line with black stripe from the pump connector to the fuel pump relay. To confuse things, I read on the Autozone site that the fuel pump gets it's power from the Auto Shutdown relay. Is this true? Anyway, we took the pump out, and it worked after applying a wire with 12v to pin one (dark green/black) and the other pin to ground. It seems like the pump is good. I had disagreement with my partner on when 12v should be available on pin one (dark green/black). Should that pin on the connector have 12v when the key is turned to on? Does this 12v come from the fuel pump relay or from the Auto Shutdown relay? I'm a bit confused.
Also, when we pulled the pump. 2 pieces fell out. They were light brown. One piece was half-oval with a straight piece on top with a metal ball inside the piece, and the second piece that fell out was the same color and looked like it worked with the first piece. Would the displacement of these pieces cause the pump to not work properly, or would it cause some danger? Any help would be appreciated. The truck usually runs like a champ.
Joined: Jul 2006
Posts: 45
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RE: 93 Dakota 3.9 fuel pump issues
Its too bad you pulled the pump already, I doubt its bad.
Power to the fuel pump goes through both the ASD (Auto Shut Down) Relay and the fuel pump relay. You can test both of these relays by swapping them (one at a time) into the starter relay spot and try to turn truck over. If it wont turn over on one of those relays replace that relay. If that doesn't get your problem solved then you want to invistigate a few solder joints in the wire harness that goes from teh relay box to the computer (PCM) on the passenger side. These soldered together 4 wire joints corrode after time and need repaired, very common. To do a quick check if this is your problem, when you turn key to on, not start the check engine light should go on for 4 seconds then off. If it doesn't come on at all then your PCM (computer) is not getting power and the solder joints I mention have failed. There are 3 of these splices, two are just in front of or just underneath the relay box. The third is right above the steering column. To repair you unwrap tape from harness and look for where 4 wires come together and also have tape around them. Unwrap and you might find green powder on the solder splice. I fixed all three on mine. They were a set of 4 blue wires, a set of red with stripe (could be orange or white) and last set was 2 black and two gray (maybe white) wires. I cut the splices out, added a short (3-4 inch) wire and used two wirenuts per splice to tie em back together. A better fix would be to re-solder them and tape em but I didn't have a solder iron handy on the side of the highway when I fixed mine (dont ask, miserable experience). If this still doesn't fix your trouble your PCM may have been destroyed by the shorting. Oh be sure to have negative battery disconnected when playing wtih these wires. You can destroy your PCM if its not already bad. If all else fails above then turn key to on (not start) when problem is apparent then go to computer and give it a fairly firm whack with your hand and listen for sounds of fuel rail charging and sensors clicking. If you hear noises try start truck. If truck starts, buy a new PCM for about $200. Easy to replace.
I sure wish I had found out about the bad splices earlier, in my case my PCM was ruined by the shorting. If I had fixed the splices earlier I would have saved $200. So even if your problem isn't the splices I'd fix em anyway.
Power to the fuel pump goes through both the ASD (Auto Shut Down) Relay and the fuel pump relay. You can test both of these relays by swapping them (one at a time) into the starter relay spot and try to turn truck over. If it wont turn over on one of those relays replace that relay. If that doesn't get your problem solved then you want to invistigate a few solder joints in the wire harness that goes from teh relay box to the computer (PCM) on the passenger side. These soldered together 4 wire joints corrode after time and need repaired, very common. To do a quick check if this is your problem, when you turn key to on, not start the check engine light should go on for 4 seconds then off. If it doesn't come on at all then your PCM (computer) is not getting power and the solder joints I mention have failed. There are 3 of these splices, two are just in front of or just underneath the relay box. The third is right above the steering column. To repair you unwrap tape from harness and look for where 4 wires come together and also have tape around them. Unwrap and you might find green powder on the solder splice. I fixed all three on mine. They were a set of 4 blue wires, a set of red with stripe (could be orange or white) and last set was 2 black and two gray (maybe white) wires. I cut the splices out, added a short (3-4 inch) wire and used two wirenuts per splice to tie em back together. A better fix would be to re-solder them and tape em but I didn't have a solder iron handy on the side of the highway when I fixed mine (dont ask, miserable experience). If this still doesn't fix your trouble your PCM may have been destroyed by the shorting. Oh be sure to have negative battery disconnected when playing wtih these wires. You can destroy your PCM if its not already bad. If all else fails above then turn key to on (not start) when problem is apparent then go to computer and give it a fairly firm whack with your hand and listen for sounds of fuel rail charging and sensors clicking. If you hear noises try start truck. If truck starts, buy a new PCM for about $200. Easy to replace.
I sure wish I had found out about the bad splices earlier, in my case my PCM was ruined by the shorting. If I had fixed the splices earlier I would have saved $200. So even if your problem isn't the splices I'd fix em anyway.