Trouble with 1993 White/GMC

Early series 60 detroit. 11.1

I have a local yard with a parts cab, but it is an 04 or newer, different cluster. Oil pressure is mechanical. All other sensors are there. It must be a loose connection, or a bad card, because it will work ever once in awhile and then go back out with the buzzer. It must be a ground issue as when it doesn't work the dash lights go out too. If I pull the fuse the dash lights come back on.

 

I have a friend who drives for UPS, and he checked a junk yard near him. They have 3 gauge clusters that are the same as mine on a shelf. I'm debating shelling out the money to buy one and install it, just to see what happens. If it is a bad one as well though, I think I will be out the purchase cost.

All the wiring and sensors look good under the hood.

 

Ok- I got the diagnositic tests out of the owners manual, and it keeps flashing 3, 4, 5, and 6.
Which are:
(3) brake check not carried out or faulty brake switches,
(4) No engine speed signal (engine switched off)
(5) Faulty engine speed signal form injection pump
(6) faulty engine speed signal (auxiliary)

I replaced the engine speed sensor on the bellhousing. I also replaced the speedo sensor. I replaced the coolant temp sensor as well.

Now the temp sensor works- I drove it to work this morning and got the same buzzer, no dash lights, and no tach or speedo. When I got here, I pulled the fuse and put it back just for grins and giggles. To my surprise, everything worked. I drove it around, had way more power, tach and speedo worked fine. Spun it back around, and parked it. After a minute or two, it went back out and buzzed at me again.

SO- I'm leaning towards something with the ECU, or a loose connection somewhere. I don't have time to track all this down, I need the rig to start hauling loads- they are backing up.

So I'm going to cut off my right arm, and left nut, and take it to a shop and let them hook the computer to it, and tell me what's wrong.

I hate electronics! if everything on this truck was mechanical I'd be better off.

 

I'm getting ready to drive it to the dealer, I'll let you know what they find. (besides the bottom of my checking account, lol)

 

I took it to the deal, and told them JUST to tell me what is wrong- they went and put a new dash in, called and told me to come get it, $2300!!!

I told them I would pay the labor, but pull the dash. Bought the one from the wrecking yard for $100, and it works great!

Now if I can just figure out why it runs like crap. I put new filters on, have flushed the fuel system. Will hardly pull itself up a hill bobtail. I think after sitting for years, some of the hydraulic lifters (does the detroit have those?) are stuck.

Thanks for you guys help!