Strange glow plugs

[david85]

They may have failed from a bad controller. The system for 1986 and older uses a thermal switch assembly that the reads into the head at the rear Driver's side corner of the engine. That will then control the glow plug relay, which is mounted on the Passenger side inner wheel well (among the mess of wires behind the battery).

The thermal switch might as well be 1930s technology because it's little more than a bimetal switch set up like a timer. They can fail in various ways, and they fail often. Mine failed in such a way that it would not switch off. Instant set of glow plugs burned out in one shot! Another way they can fail is simply not coming on at all. Or they can start cycling while driving down the road. Or they can sometimes glow for only a few seconds instead of the full 10 seconds. 1987 and up uses a solid state controller that calculates glow time based on a simple ohm's law calculation in the integrated circuit (glow plug resistance increases with temperature). Much more reliable.

Oddly enough, I replaced mine with a set of Bosch before I realized the controller was the problem all along. The tips ruptured but none of them broke off. The failure appearance was very similar to Beru when they burned out (from excess heating).

I still have the 1986 style system, but also run a three position OFF/AUTO/ON switch, with ON being momentary.

Figure if im gonna turbo it down the road ill pull the whole block and do the bottem end too

Hehe, that's how my saga started too. Although that was a separate incident with dual coil wellman glow plugs. Thinking back, it sure took a while for me to learn

 

[Ethan Smith]

**** yeah its a helluva learning experience. I told myself i was gonna pull those basterds when the block was hot, but i got a hair up and pulled it cold. At least this way i get to redo the heads. On my way to my buddies to pick up the spare set ive had for a while. Know how to make sure my spares will match up?

 

[david85]

Just compare the threads to the old one you pulled out. Then compare the length of the body (GM IDI glow plugs have the same thread but are different length). The good brand is will say BERU on it with a part number ZD1A (ZD9 for the 1987 and newer style).

And for what it's worth, hot or cold likely wouldn't have made much difference. Just make sure you check that glow plug control system when you get it all back together. Anything longer than 10 seconds glow time and you must switch off the power to prevent killing the new set. This is why most of us use a manual bypass switch

 

[Ethan Smith]

Ima go with the manual when its all said and done. Thanks for the imput bud i appreciate it. I found some motorcraft zd1 plugs on rockauto, they the ones or will they say beru? Got any 2 cents on what to do to the top end of the motor while ive got the heads off? I wouldnt mind getting it right and running this build for the next 200k or so until im a rich man and can do it all over again.

 

[Golden Helmet]

Ima go with the manual when its all said and done. Thanks for the imput bud i appreciate it. I found some motorcraft zd1 plugs on rockauto, they the ones or will they say beru? Got any 2 cents on what to do to the top end of the motor while ive got the heads off? I wouldnt mind getting it right and running this build for the next 200k or so until im a rich man and can do it all over again.

Motorcraft and Beru are the same thing, so you're safe there. I don't know much about engine rebuilding so I can't comment much there, but iirc once the heads are off you should be able to put an upgraded camshaft in if you wanted, throw studs in there too and you'll have the perfect foundation for making power later with a turbo kit

 

[david85]

You can do a simple head gasket job and be done with it. That would be the fastest and cheapest solution especially if time or cost are factors right now.

Next up is to have the heads checked and any issues dealt with. New guides might be needed, or they might not. Depends on the age and condition. If you had the heads rebuilt with proper guides installed, they would last well for however long you wanted to run the engine. And it would be one less thing to deal with if and when you did a full overhaul.

Head studs are also a good idea because they will only improve reliability and can be reused. They are not easy to install with the engine in the truck though.

Whatever you decide, I would suggest pulling the engine to do the head gasket job. It can be done in-frame but it isn't fun. You can do a much better job with the engine out, and it wouldn't take much longer (if at all).

 

[Macrobb]

I've gotten tips out before using the old "crank it over" method. It'll create a lot of pressure doing that and often knock it straight out. I've even fired it up before to try to knock the tip out.
Remember, there's no vacuum really on the downstroke, so it isn't going to go down, and it would still be inside the precup. Looks like that's a pretty large chunk missing too, so I doubt it could come out of the precup even if it did somehow go downward instead of come out.

Obviously YMMV, but I've done it.

On the other ones, a lot of spinning helps. And using some WD-40 down the hole. And warm engine.

 

[Ethan Smith]

Shoot. Hell ima turn it over in the am tommorow. I hope it ***** that thing out otherwise not only am i out a work truck when everybody needs hauling but im out money time and patience. I really appreciate the help you guys, if your ever in springfield oregon come find chainsaw smith and youve got a friend.

 

[Ethan Smith]

Well its warming up right now to pull the rest of them. The tip coulda shot out when i was turning it with the gp hole open, i fished around for the better part of an hour with some neodymium magnets and some saw files and wires and whatnot to poke around playing wheres the tip, but i didnt find anything. Either it shot out or she ate it. I may as get a compression gauge and check out any kinda damage it may have done.