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Discussion Starter #1
My ‘91 2wd V8 with 130k miles runs great. This morning my stereo, tachometer, turn signals, and voltmeter did not work on my way to work. Also, the idle was noticeably high. I checked the fuses under the dash and all are intact. Speedometer, fuel gauge etc working fine. Any ideas?
 

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Pull the wiring diagrams and see what's common to all the affected circuits?

Without that, my "from a distance" guess would be the ignition switch; but I don't think they fail as often on the 91+ design as on the 87-90 design.

Idle high could have been due to a vacuum leak that was small enough the ECU could compensate for; or it could be due to a bad signal to the ECU.

Did you check the fuses under the hood also? There's a whole box of them there.

Also, how did you check? With a multi meter or Eyeball Mk I? They can eyeball good and not pass a single electron ... so use a multimeter on them. Or a fuse tester.

RwP
 

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I did only eyeball the fuses and I didn’t check the ones under hood. I’ll go out there on my lunch break and check it with a multimeter. I’ll report back.
 

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I checked fuses under dash and under hood with a multimeter and none were burned. Under hood box only had 8 fuses and a 3 relays. I swapped the two relays that were the same .
 

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Do you have the factory service manual (hint: Is it a Chilton Dakota or a Haynes Dakota? No? Then those aren't FACTORY service manuals) for the wiring diagrams?

I don't have the 1991, so I can't offer much help in specifics.

I would ASSUME (with what that word means! :devilish: ) that it's pretty much the same as my 1992 I have here; but I don't KNOW that it is.

So.

In 1992, the same cartridge fuse (fuse G) feeds several items; the tach and the horn are on the same inside fuse 6 so if the horn works it's not the fuse.

Fuse G also feeds inside fuse 8 which feeds the parking and instrument cluster lights.

The instrument cluster is feed off the ignition switch to fuse 16, which feeds almost all the affected circuits.

I'd start there - do you have a voltmeter? If so, with ignition turned ON, do you get 12V at the input to the fuse? (This is easy to check if you have ATO fuses which have the connecter exposed on the top; ATCs don't. I prefer ATO when possible because it's easier to test with them!)

If so, next stop is to pull the cluster and make sure that cluster pin Red D (Red connector, pin labeled D) gets power when you turn the ignition key ON.

Also, check that you have a good connection from Red F to ground; if IT'S open, you'll have a bunchteen of weird symptoms.

Follow it down to the cross member inside the dash; loosen the lock nut, then retighten it to see if that improves the situation.

But that may not be 100% accurate for you; again, you really need the proper FSM to trace this out in the wiring diagrams.

RwP
 

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I appreciate the guidance. I will attempt to diagnose the problem tomorrow. After work I had to jumpstart the truck because battery was dead. It turned on but sounded rough. I was revving the motor by hand and it sounded like a shotgun went off in my face. Then when revving I felt no power. It died and sounded like it was dieseling. Later I jump started it again and attempted to drive home. I got about a mile away and felt a loss of power and it died. A friend helped me pull it into a nearby parking lot. I’ll trailer it home tomorrow. I need to get a manual. I’ll start by checking what codes it has. And I’ll follow the advice ralphp gave me. I’ll report back tmrw.
 

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My ‘91 2wd V8 with 130k miles runs great. This morning my stereo, tachometer, turn signals, and voltmeter did not work on my way to work. Also, the idle was noticeably high. I checked the fuses under the dash and all are intact. Speedometer, fuel gauge etc working fine. Any ideas?
Check this out. I would guess you may have the same problem.
 

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Since you had to jump the truck it sounds like maybe you have a battery going bad. Low voltage will do all kinds of crazy things. Low voltage won't produce good spark and flasher relays won't work without enough voltage. It also throws off the readings to all the sensors for the fuel injection. Start with the basics like charging the battery overnight and checking that it is 12.6 volts or more after sitting off the charger for 15 minutes or so. Or better yet run it into an auto parts store and have them test the battery that it's holding a good charge. Then turn the switch backwards to the accessory position and see if things work. If so then your switch might be bad if they don't work in the normal run position with a fully charged battery. I also don't remember on the Dakota but on my Ford if you had to jump it from a dead battery you couldn't touch the throttle for a few minutes otherwise the computer wouldn't relearn what it needed to optimize the fuel injection and would run like crap. If it starts and runs with a fresh charged battery make sure you turn on the headlights and see that it;s still charging over 13.5 volts to make sure the alternator is working and you're not discharging the battery while running causing the problems.
 

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Discussion Starter #10
Thanks to the guidance I received, my Dakota is back on the road and running well again. I knew the idle air control motor needed replacing because of the rattling sound it would make. what I did not know is that the alternator was bad. The low voltage must have caused those weird symptoms. It runs strong again. I did notice the temp is on the cool side. It use to be in the middle but now it’s at about 30%.
 
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