Fuel Pump Nightmare

Good suggestions. I have opened some connectors and reinstalled to foil corrosion, but some connectors I can't get off. I swapped the fuel pump relay with the one next to it with no help.

Have you joined Dakota forum? https://dodgeforum.com/forum/dodge-dakota-21/

Chrysler does some things a great deal differently. Fuel pressure issues are relatively easy, but messy. Do you hear the ASD relay come on. Should run for 3 seconds or so. Then shut off if the engine hasn't started. I don't know why aftermarket fuel pumps don't have rollover switches on them. As I don't intend to roll mine ('99 Cherokee) I left it off. The 9 volts is definitely an issue.

As for the fellow with the fire ants..that certainly seems a very impressive method to stop theft of the cats.

101 K on the clock?? Amazing

Did you buy it new, or did a former owner modify it?

I got the pump new from ebay. I'm the second owner of the truck. Neither the truck nor the pump were modified. I tried the old pump again before I found the voltage was low, bit it didn't work either. The new one is the same size as the old one. I'm wondering if the computer is the reason for the low voltage. Maybe it needs to be reset? Sometimes I can get the truck to run a few seconds at low RPM if I pour gas in the intake manifold if I don't press the gas pedal down. If it starts it's right after I stop cranking the engine.

I would call around to junk yards and see if you can find the exact replacement part. Can one still do that? I would think one could do that on the web now. For used auto parts. I haven’t been out for a while.

If you put in a pump made for a different size, or different orientation tank, The gauge reading might not be correct.

Just looking out for Murphy.

Your truck has achieved beater status, don't throw any time or money at it, just trade it in for another one that is working...

I think you're right. The main reason I didn't get rid of it sooner is that it only has 101, 000 miles on it. I had looked at a truck with 115,000 miles and they wanted $15,000 for it. I hate the idea of trading for one with more miles than what I have. I checked with Carvana a while back and they offered me $200! I had tried WeBuyAnyCar.com and got an estimate of $1370, but they have to see it after I drive it to another city. Now that it doesn't start their offer is $100! That doesn't cover the new spare tire I just bought nor the fee to tow it there. Trading it in as is might be a problem too.

The pump case is all plastic, but the ground idea is good. I ohmed the pump ground pin to the truck bed. It had good continuity. Then I tried the pump supply pin. It had 35 ohms to ground. So there must be a divider or more likely electronics involved. The computer (control unit) is the likely culprit. Is there more than 1? The one in the engine compartment has 3 connectors on it. I removed 1 and checked for codes. No message ever came until I put it back. I have not been able to get the other 2 connectors to come off, so even if I had one I'm out of luck.

Try it back to the battery negative, the truck bed could easily be floating from the rest of the vehicle. A length of any wire will do.

The wires from the pump go back to the engine compartment, so ohming from the wire to the bed and finding ~0.1 ohms verifies that the bed is shorted to the cab and the wire is good. Even if it wasn't it wouldn't matter. The bed is irrelevant.

The battery supplies power referenced to ground. So if you are measuring the 9 volts on the pump motor supply, maybe you should see what each supply lead measures to ground. May give you a clue on the lack of supply.

I can see where a safety circuit might shut off the fuel pump supply power if an open circuit was detected. Sparks near the fuel tank, etc. You could be measuring voltage due to leakage current if you have a nice high impedance volt meter.

The failure of a computer or other microprocessor based component is exceedingly rare. Failure of wiring connections is relatively common across all makes, especially older designs.

Some Dodges have had a reputation for internal failures in the under hood fuse box distribution circuits, the sandwich construction had some problems. Not sure if those problems went back to 1996 tho.

Did the connector that you broke the tabs off of have any other means of orientation?

It could have been plugged in upside down? This would put the wires in the wrong place and cause a many weird problems.

Any wire colors on the wires?

See if you can find a schematic for your vehicle on line. Sometimes a good library will have a professional version of the Chilton manual for pros. It will have the Complete schematic.

I found this on line:

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Maybe little Off topic:

I have a '94 Ford Ranger that was very cold natured, hard to start, ran rough.

Finally it got so hard to start that I decided I had had enough. Troubleshooting revealed low fuel pump pressure. Besides, my fuel gauge had been non functional for a long time.

I tilted the bed back high enough to get to the fuel pump, changed it and WALLA!!

It now starts almost before you can get your hand off of the key, and runs like a new one---and the fuel gauge works.

Good luck. Let us know how things work out.

The pump unexpectedly came with an adapter cable even though other ebay sellers pictures included and adapter but didn't supply one. It fit without modification. I tried them both. Yes the wires are colored. The truck has 6 wires, but the fuel pump only has 4. Your experience was what I expected. My public library used to have a large shelf with Chilton manuals, but they no longer have them and said they got rid of them a long time ago. Thanks.

Truck is now running!

My son was able to get the other 2 connectors off the control unit and another connector apart that I couldn't. The truck still didn't start and there were still no codes. My last idea before giving up was to connect a small 12V battery directly to the pump to see if it would start. It didn't, but we could hear the pump, but could not hear gas in the hoses. So I got the hose and jar and tried again like at first. But this time no gas came out. The miserable plastic ring was not holding the pump in all the way. I had to pound with a hammer and screwdriver over and over again to get the pump down like it should be. I had the minimum amount of gas because of the lowering of the tank. Then it pumped some gas, but I added another gallon or so to make sure.

Then with the pump pumping gas the truck started quickly. I was ready to run another wire, put a switch on the dashboard, or whatever it took. I was surprised that it worked with the normal hookup. Maybe removing the connectors did some good? It had not powered the pump the previous time.

Another mystery is why the old pump didn't work well. I tested the flow and the pressure when powered by a battery, and they were both good. But the new pump has 1.8 ohms and the old pump has 1.0 ohms. Maybe a shorted turn? I found that the old pump lower unit didn't drop all the way to the bottom. The hoses get hung up on the wires. So I suspect that it has a 22 gallon tank instead of the 15 gallon that the manual says it has. I will find out when I fill it up. My '72 Dodge with a V8 had a 25 gallon tank. It was behind the seat so changing the sending unit was a snap.

"If the women don't find you handsome, at least they will find you handy." - Red Green

Thanks everyone for you ideas and help.