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Discussion Starter · #1 ·
We recently bought a '97 Dakota 3.9 for my son's first vehicle. Overheated on the way home, so changed the thermostat and attempted to drain radiator (petcock is apparently clogged). Now trying to figure out why it suddenly stopped running while I was revving it at 2,000 RPM to get the engine heated up. Wouldn't restart, so I borrowed a fuel pressure gauge and by the time I got back, it was running again (fuel pressure is a fairly steady 43). Going to pull the plugs and check those next. Anything else I should look at for an issue like this?
 

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Discussion Starter · #3 · (Edited)
Was this a one time episode of shut down & no start, or has this turned into an ongoing issue?
Lately it's an ongoing issue when the engine warms up, it seems like it stalls out after a few minutes. After that, it usually takes a few attempts to get it started again. I'm about to replace the PCV valve, and I have a new radiator ready to install in the next few days.
 

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The PCV Valve & the rad are not the source of your shutting down issue, but from what you typed previously, it does sound like your rad might be clogged up, and, it never hurts to periodically replace your PCV Valve.

You did say that you had used a fuel pressure gauge to read 43PSI when running. Next time it shuts off on you, put the fuel pressure gauge on & see what you read when it is cranking but not starting. If you are getting fuel pressure at the rail, that would eliminate fuel delivery as your issue.

I would think that this would indicate that you are, at intermittent times, not getting getting spark & that's where I would start my trouble shooting.
 

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. . . so when it starts back up for you, how long does it take for it to shut down again?

I am not at all saying that this is your issue, but this kind of makes me think of two problems I had with two other older vehicles (not Dakotas). They would shut down intermittently when warm; with one it turned out to be the ignition module mounted on the distributor, & with the other, it turned out to be that the distributor actually had a hairline crack in it. The module worked fine when things were cold, but it broke down internally when things were hot; with the distributor, the crack expanded when it got hot.

Again, I am not saying that this is what's going on with your Dakota, but then again it may be some ignition component that is failing to operate as advertised as it heats up.
 

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Discussion Starter · #6 ·
Yes, it's getting pressure when running as well as when starting - also when ignition is on but engine is off. Pretty sure it's a spark issue, but suspect it's related to the PCM unit - or perhaps wiring harness. (Really would prefer it's the PCM as the harness would be a lot more challenging to track down and fix.) Because the problem is intermittent when the engine is warm, it's harder to confirm whether it's purely a spark issue or if there's a computer problem at the heart of it - unless you happen to know of a good way to check the PCM that a semi-novice like me could perform 🙂
 

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Discussion Starter · #7 ·
I'm going to check the ignition module to confirm, but I'm pretty sure it's a new unit. That doesn't mean that it can't be messed up, of course, but I suspect the problem lies elsewhere. Bit of a bummer that the distributor is such a pain to access, but I shall persevere.
 

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Discussion Starter · #8 ·
Oh, and to answer your question, it varies on how long it takes to restart, but it generally happens within a minute or two - especially since I replaced the IAC unit, which got stuck in the closed position a few days ago.
 

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To be clear, I wasn't suggesting that either of those were your issue, but I was saying that it sounds possible that as some ignition component is warmed up it breaks down internally. There are a couple of sensors, for example, that the PCM absolutely has to get a signal from or it won't send a signal to your coil; but that typed, I am not suggesting that you start throwing sensors at it just yet. And also, not to beat the dead horse, but just to clarify, you are saying that you are getting fuel pressure when it is cranking but it is NOT starting?

And how long does it take after it restarts before it shut down again?

A combustible mixture of fuel, spark at the right time, & compression is what they used to tell us is what an engine needed to run, & your PCM would be at the front of the spark chain.

I don't have a FSM, & that is really your best resource. I have a Haynes, & it is not the greatest, & mine lists its applicability as from '00 to '04, & not being well versed on these things, I do not know what differences there are in the ignition system from 00 to 04 & your '97. For example, mine does not have an ignition module that can be changed.

BUT, on mine, these are the checks that can be made, & I will paraphrase: "test for battery voltage to the coil by disconnecting the connector from the coil & using a MM to check for volts at the dark green/orange wire with the ignition ON.

No voltage=bad ASD relay.
If volts: use the ohm-meter function of your MM & check primary & 2condary resistance of the coil. My Haynes lists 0.95 to 1.20 ohms & 11,300 to 13,300 ohms respectively, but I believe Haynes is giving me inaccurate specs on that.

If coil ohms out good: check the trigger signal from the PCM. Using an LED test light (inexpensive from Advance or the like) back probe the coil driver terminal (black/gray wire) & check for a flashing light as an assistant cranks the engine.

If no flash: then check the operation of the cam position sensor & the crank position sensor (those are the two sensors I alluded to earlier in this reply).

If those sensors test good: send the PCM out to be diagnosed."

A couple of caveats:
I am paraphrasing from a book that is not inclusive of a '97 & it would probably behoove you make sure you have literature applicable to your year when you troubleshoot, &, #2, it's hard to trouble-shoot an intermittent problem. I had an issue somewhat similar to yours, & when it was intermittent, I threw parts at it. When it devolved to being permanent (as opposed to intermittent) I performed the above checks (with the exception of testing the cam & crank pos sensors because I had already changed them) & as I wasn't getting trigger voltage to the coil (& had already swapped out the ASD relay) I wound up sending my PCM out to a place in Tilden Il. called SIA Electronics. They told me they bench checked it & diagnosed a couple of issues & repaired them & sent it back to me (for about $100 & change as I remember). This is not a plug for that facility, I am simply relating my experience.
 

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Anyway, sorry, but I got ahead of myself by a bit. Since you are saying that you have fuel pressure in the rail when it is in 'crank-but-no-start' I am assuming you are not getting spark. You should verify that before you do any of the above. They make these handy little gadgets you can buy for cheap at the chain auto-parts stores to check for spark. Or, I guess, you can always do it the old fashioned way. Either way, next time you are in a 'crank-but-no-start' condition, verify whether or not you are getting spark.
 

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Discussion Starter · #11 ·
I appreciate all your input. Thought I'd let you know what I found out.

This morning, I had terminal crank-no-start, so I bought a spark tester. Connected it to the coil output and found there was no spark when cranking. Swapped the ASD relay with one that I knew was working, but that had no effect - so I got my son to crank the engine while I jiggled the wires connected to the computer.

Bingo.

Hoping it's just a bad connection that I can fix fairly easily, but knowing where the problem (or at least this problem) is has gone a long way toward easing my frustrations.

Again, thanks for your help.
 

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That's great, it is getting you in the ballpark now.
I would think that this indicates a loose pin on the PCM itself, or something loose/wrong inside the connector that connects to the PCM.
 

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It's been a few years, but it comes to me now, as I think about it, that when the boys from SIA called me to bill me for fixing my PCM, when I asked them what they found wrong, they told me that they replaced the coil transistor (I am pretty sure he said it was a transistor) & also resoldered a loose pin.
 

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Oh, & when you get to changing the radiator, that's a good time to re-hose it. If the previous owner let the rad get gunked up, it's a good bet he never changed any hoses until or unless one sprung a leak. Same with the S-belt. "A stitch in time saves nine", or so they say. Prices on stuff like this are quite reasonable from Rock Auto or CarPartsID. I just read a post where Ralph P. said he goes with CarPartsID if it's Prime shipping.
 

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Oh, & when you get to changing the radiator, that's a good time to re-hose it. If the previous owner let the rad get gunked up, it's a good bet he never changed any hoses until or unless one sprung a leak. Same with the S-belt. "A stitch in time saves nine", or so they say. Prices on stuff like this are quite reasonable from Rock Auto or CarPartsID. I just read a post where Ralph P. said he goes with CarPartsID if it's Prime shipping.
No, I go with Amazon if it's Prime for free shipping. I've never bought from CarPartsID that I'm aware of.

RwP
 

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Sorry about that, Ralph; I misunderstood that post that I was referring to. That makes more sense to me now. Thanks for clarifying.

No, I go with Amazon if it's Prime for free shipping. I've never bought from CarPartsID that I'm aware of.

RwP
 
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