Was wondering if anyone has ran into something like this before. I know it's an electrical problem but wanted to ask for some pointers if it's ever been seen by someone.

Here we go. I have a 1988 F150 with a 300 6cly and a 5 speed.

For about a year the fuel gauge on the front tank only, stays on full until it hits about a 1/4 tank. Then it drops to a 1/4 and just goes nuts all over the place. Empty - full - half, you name it it does it within 15 seconds. Never gave it a thought beyond bad sending unit in the tank.

About 4 months ago the oil pressure gauge started jumping all around and then would go back to normal and be fine for a while. Last week I noticed the gauge would go nuts every time I got it on a hard pull over 2200rpm and put my foot into it. Let out and the oil gauge settles down. Stomp on it again and off to whack nuts goes the gauge. Added a mechanical gauge to it to keep an eye on things and it sits steady at 50psi while all this stupidity is going on around it.

Now today the tachometer decided it needed a turn to be a pain in my @#! and it's flying around from 700 to 3000 at an idle.

Volt meter and temp never act up. Speedo is mechanical.

The grand finale is that twice today it stumbled like you shut it off and switched the key back on.

Has anyone seen something like this?

Maybe a hey Jeff, check the so and so right here and you'll find a bad plug or corrosion.

Maybe a diagram or word of advice as to where all this stuff crosses in the harness and maybe melted together?

Does anyone know where the tach gets it's signal? I'm guessing the distributor but since this is a TFI ignition I don't know which wire I'm looking for. Not like the old ones that had a bolt labled Tach.

Now that you are all laughing, I do have a 2015 6.7 and can not bring myself to another payment for a work ride. Gotta fix old Black.

 

Wish I could help, but for what it's worth, I'm overheating every time I hit a bump, and when I top off fuel it only reads 3/4 and it runs out showing 1/4 lol, I only have 1/2 tank that reads

 

I wouldn't be able to afford another ride either, if I had a 2015 6.7.

I personally have never had an issue like yours where everything was going nuts on my dash. If it isn't sensor related, I'd bet it's ground related...or something is shorted in the cluster itself.

It's also very possible that your senders/sensors are bad individually. The pip is what is inside the distributor that feeds tach signal and also gives cam/crank position to the eec. If you're stalling and your tach is jacked up, that's definitely the conventional culprit.

 

Sounds like you may have a failing body ground somewhere, or perhaps the cluster is just dying?

I'd start by chasing grounds.

 

Going to get in the garage in the morning and start chasing grounds around. figured I'd take apart everything I can find and clean them up. Probably going to add a few new ones to in case I miss a hidden one.

I'll let you guys know what happens.

 

Sorry it's been a while for a reply.

Got the thing in the garage last week and went over every ground I could find. Buffed them up bare, added a little Grote pigtail dope and put everything back together. I definately got improvement on the oil pressure gauge. It went from running on the N of Normal to the R with no fluctuation.

The tach on the other hand, not so much. The stumble has gotten worse pretty quickly. It almost quit completely on me a couple of times. When it finally did that I thought this is starting to really act like plug wires or a cracked cap. Nursed it home and took a hose to the wires. It quit almost instantly and would not start again that nite.

Did some digging the next day and found what looks like a leaking wire and a suspicious crack on the bottom of the coil.

She's getting an entirely new high voltage side of the ignition system everything from the coil to the plugs. I learned a long time ago to grin and bear it as you flop down the Benjamins on Motorcraft ignition parts. They always seem to work much better than aftermarket.

Just waiting on my Rock Auto order since it was about $40 cheaper than the dealer.

I'll check back when the parts are in.

 

For the fuel gauge, the sending unit can develop bad spots if you keep the fuel within a certain level most of the time. They act up by swinging the needle around.

 

Yeah I figured the fuel gauge is a sending unit problem but with a second tank I run the bad one out first.

The last time I checked the sending unit runs $80+ because it now comes with a fuel pump. Heck the fuel pump is still good.

 

RockAuto does show the sending unit available by itself but you are almost at the price of the whole assembly. I have another vehicle to drive so if it was me I would drop the tank and test the sending unit with a multimeter. Actually I'd have the part on hand just in case it is bad.

 

Well Guys I got everything changed.

Truck started and ran fine on 20 mile test drive. The tach still was acting up though. Got home and went to move it into the garage and it stalled on restart twice. The third time it missed, stumbled, popped, and quit. Tried to restart and cancel Christmas it's dead. Grab a timing light and not even a flicker.

Off to Advance as now I need the truck and no time to wait on a Motorcraft ignition module. New BW module and the thing starts better than it has in years. The tach seems to have cured itself too.

I have never had an ignition module act up like this one apparently did. Everyone I have had let go just quit dead. I'm thinking the tach issue was caused by the module going bad. Never heard or seen that one before.

Don't know what caused what to go first but I'm guessing it all started with a bad ground and that got the module as well as the gauge. It had 60K on the plugs, cap and wires and they looked poor so it needed them anyway.

Any Guesses?