Hello, I started my truck just a little while ago and moved it around in the driveway. I turned it off and got out and smelled plastic burning. I looked at the front of the truck and there was smoke coming from under the hood. I popped the hood and opened it to see fire coming from the passenger side of the engine near the head. I got a hose and put it out. Then looked closely to see what was burning. It was a black plastic plug with 2 wires that melted. It connected to a one prong sensor in the back of the head on the left side of the last glow plug wire. I think this is a temperature sensor. Why would it have 2 wires and only one prong? Could this be something else? Thanks in advance.

Eric

Sounds like your thermostat control unit in the right rear head. A wire goes from the glow plug controller in the left rear head to the thernostat. When the engine is cold then it passes current to the glow plug relay which energizes the glow plug solenoind sending current to the glow plugs. When the engine is warm then the thermostat opens preventing current from going to the glow plug relay thereby preventing the glow plugs from being turned on. You must have a short in the wire at the thermostat control unit.

I looked closer at the wire today. One metal conector was fine and the other metal conector was discentagrated. Could they have just touched or arched? If i get a new wire connecter and a temperature sender do you think it will fix it?

Check out the circuit first with a multi-meter before you buy anything. The connector probably developed a short.

I will check it with a multimeter. I just found a little puddle of diesel fuel on the ground today. Apparently it is leaking from the 2 high pressure hoses (rubber/metal) that go into the fuel tank. Can the two be related? I know that if you have a fuel leak air can get into the lines and cause trouble.

Are you talking about the fuel return hoses/line from the fuel injectors to the fuel tank? They would have nothing to do with your electrical problem.

I saw them from under the truck. They are two high pressure hoses coming from the fuel tank that travel together then go into steel lines along the frame. One goes through the electric fuel pump thats mounted on the frame then they go into high pressure hoses again and up to the engine compartment. I will look under the hood tomorrow and see what they connect to.

As far as the fuel lines go, they go close to the transmission and end up behind the rear engine. I cannot see them. They tuck them in there good. However i am convinced that the other problem (engine fire) was cause by the temperature sender in the head. It went bad internally and melted one of the metal prongs and wire causing the plastic around the two wires to catch on fire and then the insulation on the fire wall ( it must have had grease or something on it). I checked the wiring for shorts and there were none. I also installed a fire extinguisher incase this happened again. It's odd that when this part went bad that it caused a fire. If i hadn't been home when it happened the truck would have went up in smoke. That part should have definatly been recalled.

If you are handy it is possible to easily bypass that switch. A wire runs into that unit and one runs out. It is an "always on" switch - that shuts off as the temp gets hot - it sends current to allow the glow plugs to come on when the engine is cold.

Bypass that switch by running a wire to by the steering column, by a "momentary" switch (that is one that is only ON when you push it). Then run the wire out to the other wire that came out of that temp control switch.

To start a cold engine hold that switch in (at the steering wheel) and hold it on until the engine starts (for 10 - 15 seconds at a time at the most - to keep the starter from getting too hot).

You can keep pushing that switch as the engine warms up for a minute or so - the glow plug light will keep cyclying on and off.

To the fellow with the engine that won't go fast - before anything else, run a can or two of SeaFoam (NAPA, etc) through the fuel. It cleans infectors, the filter temporarily - maybe - and conditions the fuel. Used by the big refinerys in Washington state on all diesel engines. It is good stuff. About $6.00 a ca.

Now, my problem. '86 Surburban, 6.2. Keep blowing head gaskets - usually #8 cylinder - tho' also #1 (if I remember right) My fourth head gasket in two years. Last time he even put in a "special" waffled head gasket set (at $135 a set). Cost each head gasket replacement- about $600

Probably warped block - but, anyone with suggestions on this 4th repair so it will last past a year?

Dennis

On my '86 that switch is right under the firewall mounted fuel filter. A "rubber" hose goes from there to the injector pump. If the hose or filter or injector is leaking at all, it can puddle in there - and is fuel for the fire. Look between the "spider" intake (do your have that system?) to see if there is fuel.

The throttle axle (?) that goes through the injector pump wears oblong from lots of use/abuse - and fuel will drip out of the injector pump down into there. If you park on an "up" hill, it may run back toward that switch.

Dennis

I checked for fuel leaks in the engine compartment. There is none. It was definatly the switch that went bad inside and burned off one of the posts then melted the plastic and the insulation went up ( probably old dried up engine degreaser) I took the insulation off there.

Eric