Electrical help!

[Alan Jones]

96 FJ80: On the way home earlier this week, dash lights go a bit crazy (blinking then back on, battery light on intermittently), and throttle stops working correctly (no more ability to accelerate, but would continue at idle). Limped home and now it won't start but definitely turns over. Newer battery, newer starter, and alternator. I will begin diagnosing tonight, weather permitting, but thought I would ask for any advice before digging in. I doubt the alt, starter, or battery and am thinking fusible link, fuse, ground, etc...
Thanks to anyone with advice.

 

[Marine7]

Really sounds like a ground breaking contact. Definetly sounds like a simple fix....... but we all know how them go! Good luck!

 

[jonheld]

Multiple dash lights (christmas tree effect) usually point to the charging system. Suspects are alternator and related cabling, battery and related cabling.
Put a meter across the battery terminals with the engine running. You should see 14.4 volts or so if the alternator is charging.

 

[Marine7]

Sorry.... I missed the dash lights going crazy part.... long night! I thought your battery light was coming and going..... good luck!

 

[Jorgito]

I would also check the fusible links

 

[Mandrake]

With the ignition off...
Check battery voltage.
Disconnect positive lead from battery amd check continuity from the negative terminal to a good ground such as the intake manifold or frame.
Inspect the ground cables between the battery and wherever they go. Look for corrosion, fraying or chafing.

If the battery voltage is enough to start (about 11.5v or more) and the ground lead shows zero resistance and has no visible signs of damage or corrosion...
Start the truck and measure voltage between the battery + terminal and a good ground.

Let us know what you come up with for all that.

 

[Alan Jones]

As of now, battery at rest is 12.5 and once cranked running about 14. So alt is good, battery is good, and starter fires right up. There seems to be two main ground wires coming right of the battery terminal, one immediately to the body and one back into the harness. the harness ground seems to be solid. Retightening and securing the body ground now. Is there a fuse or link that seems to be indicated or is it just a random wiring issue probably. thanks again everyone

 

[Alan Jones]

And after cranking, it still tries to stall under load. Idles fine, but dies under acceleration.

 

[Alan Jones]

Fusible links seem to be good. Will crank but stalls under load. No headlights, but all other lights, hi-beams, radio, hazards, parking lights, etc. work.

 

[-Spike-]

I would also check the fusible links

This. Problems with fusible links are often difficult to diagnose because they break inside the wire insulation. The torque of the motor can be enough to separate the break in the wire, causing the symptoms you describe. With the truck idling, give the fusible links a few tugs and see if the engine dies or misses. They may not be the issue, but it makes sense to make absolutely sure.

 

[Alan Jones]

I'll check them again when I get home...

 

[Alan Jones]

Just to clarify, here is what I ran through last night: LC cranks and runs fine in idle. In any gear (even park), any acceleration and it tries to stall. Put it in drive and don't touch the accelerator and it will creep down the road. Grounds are all good, battery tests out, alt. and starter are good. Tested the fusible links and they all had continuity, but will tug on them while running this evening. All vacuum hoses, etc. appear good after tugging and checking. The headlights will not come on, but parking lights and hi-beams work fine. All interior lighting is working fine. Electrically, is there anything connecting the headlights and the throttle?? A fuse, a link, a sensor?? I think this is a minor electrical fault but could use more guidance on where to dig when I get in tonight. I will definitely check the fusible links again through the tug method...

Thanks again to all who have more electrical knowledge than me!

 

[jonheld]

I'm going to say that the headlights are a separate issue. Both the headlights and EFI system have the same power source (FL MAIN). If that was defective this engine would not run.

Are you still getting the dash light christmas tree effect?
Have you verified that your battery cables are tight?
Have you verified that the alternator cable is tight?

Always check the simple things first.

 

[Alan Jones]

Battery cables are tight. Will check alt. cable tonight. No more crazy acting dash lights, but that was at road speed which I cannot attain at this point.

 

[Alan Jones]

As of this morning, battery cables are tight, alt cable is tight. Tugged on fusible links and got nothing. Still doing same thing, cranks and runs but dies as accelerator is pressed. i am going out to do some diagnostics on the TPS and will report back when my hands warm again.

 

[Alan Jones]

BTW, replaced a headlight and they are working. So whatever may have failed caused both headlights to blow if that helps anyone with thoughts...

 

[Alan Jones]

TPS is working fine. Any chance the fuel pump is related some how. i fired it up cold this morning and it idled fine. Now won't crank unless I'm on the throttle. I am ordering a set of fusible links just to see if that solves it. any thoughts would be appreciated...

 

[blkprj80]

If you blew a headlight, you may have had an alternator surge. How old is the alternator? The wacky dash lights is apparently a common issue with a bad alternator.

 

[gummycarbs]

Have the alternator tested, or swap in a known good one. The regulator may be going out.

 

[ppc]

TPS is working fine. Any chance the fuel pump is related some how. i fired it up cold this morning and it idled fine. Now won't crank unless I'm on the throttle. I am ordering a set of fusible links just to see if that solves it. any thoughts would be appreciated...

Are you sure that you mean "no crank" and not "no start"? The throttle position has nothing to do with the engagement of the starter.