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Discussion Starter · #1 ·
I have a '96 Dakota Sport with just over 100k. 2 years ago I installed new front timing gears, chain and tensioner. About 6 mos. ago I was driving down the road and the truck died and wouldn't restart. Waited for a while and it restarted and ran for 30 seconds and died again. Had it towed home and replaced the fuel pump relay and the truck started and ran. A week later, the same thing. This time I installed a new fuel pump. Truck started and ran. 2 months later it does again. Over the past 6 months these events I have driven the truck on a 500 mile trip and numerous jaunts of 100 miles with no starting issues. Sometimes it will run rough but straighten out on it's own. A couple of times it has quit running at 70 mph on the interstate, coasted for 1/4 mile but I restarted it before coming to a stop. A couple of times in the morning it has refused to start on the first attempt, but fired after a 2nd or 3rd attempt. This morning it won't fire at all after numerous attempts.
It acts like an electrical problem because priming the TBI with fuel doesn't help, however the tach registers as I crank it which I assume indicates that the crank sensor isn't the problem.
Any ideas?
Stumped in Tampa Bay
 

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Yah, the tach indicates the ECU is seeing tach pulses from the CPS; OTOH, if it's a bad signal, it may get some but not the right ones.

Since it's a 1996, I'd grab a ELM327 Bluetooth/OBDII adapter and datalog with Torque on my Android phone (or tablet with Bluetooth capability); keep it running and see what it thinks is happening.

But for a quick "Let's eyeball it", check the splices from where the battery is to up towards the firewall in the wiring harness. On the older Magnum Dakotas, there's a 1-to-3 splice that likes to corrode and start failing with an intermittent at first.

(I'd also, because of my experience with connectors, a) disconnect the negative cable from the battery, b) pull and reseat all three ECU connectors three or four times, c) reconnect the battery cable, and d) see if that made it happier.)

RwP
 

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Discussion Starter · #3 ·
Rep, Thanks for the info. Quick questions.
1. Does the truck have to be running for the OBDII diagnostic to work?
2. Is the ECU a large shiny metal box.
3. Where is the ECU located so that I can check the 3 connections? In the cabin or engine compartment?
 

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Well, for a 1st Gen, the ECUs were all on the inside passenger side fender; being a 1996, you'll have to do three connectors.

I don't know if it's shiny or not, being, well, 25 years of under hood "weathering" on it.

It has to have the ignition ON, but not running, for OBDII diagnostics to talk to the ECU. But the datalogging would be done while driving around minding your business to see what changes when it quits running.

RwP
 

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Discussion Starter · #6 ·
Ralph,

I found the ECU - no problem. shiny metal box under a black plastic cover. 3 connectors as you said. Unhooked the battery cable, unplugged the 3 connectors. All looked clean and dry. Replaced them and traced the wires to the firewall. There were about 6 other connector junctions that I couldn't get apart without fear of breaking them, however, I wiggled and pushed them together as best I could. Reconnected the battery, jumped into the front seat, turned the key and VOILA! The truck fired immediately.

The bad connection makes perfect sense and correlates to the behavior of the truck - intermittent running with no rhyme or reason for failure. I sure hope that it is the FIX. I will get some contact cleaner and some advice on how to get the other connectors apart. I might even try some grease to prevent future corrosion.

If I find this is the solution, I will pass it on to other owners whose symptoms imitate mine.

Thanks for your help, Ralph. I appreciate you and this forum.
 

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Ralph is the bomb on these things!

There was a thread started not all that long ago by someone who isolated his intermittent crank-but-no-start issue down to wiggling the connector to his ECU. He was thinking that he needed to either replace or repair the connector, but then his intermittent issue devolved into a terminal issue that wiggling the connector no longer resolved. Turned out to be a loose pin in the ECU & he wound up fixing his with a remanufactured ECU.

Hopefully you have resolved your problems with nothing further needed, but just something to keep in the back of your mind. Just in case.
 

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Discussion Starter · #8 ·
Ralph is the bomb on these things!

There was a thread started not all that long ago by someone who isolated his intermittent crank-but-no-start issue down to wiggling the connector to his ECU. He was thinking that he needed to either replace or repair the connector, but then his intermittent issue devolved into a terminal issue that wiggling the connector no longer resolved. Turned out to be a loose pin in the ECU & he would up fixing his with a remanufactured ECU.

Hopefully you have resolved your problems with nothing further needed, but just something to keep in the back of your mind. Just in case.
The fear rolling around in the back of my head has been ECU replacement. 25 year old parts are getting a bit hard to come by and not cheap, either unless you catch something being discontinued at Rock Auto.
 

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I'll see if I can find that thread. I am pretty sure that he went through some place called computerexchange.com. I actually had mine repaired (in 2018) at a place called SIA Electronics in Tilden, Il. due to an intermittent crank-but-no-start that devolved to terminal. As I remember, the price wasn't way crazy at the time.
 

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Here is one of the threads that came from that:

 
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