Glow plug bypass - tell me why this won't work
 

On the old torn up 300D I think I have some glow plug relay issues or other possible electric gremlins. The previous owners have not been gentle with this car and the wiring harnesses are cut in several places. Car runs rough, mostly I think due to no glow function. But, I'm not really complaining it was only $400.

What I want to do is go with the pencil plugs on the '78 300D and basically hook up a switched line direct from positive on battery to glow plugs. I'll re-wire them to run parallel rather than series and let them ground out on the block. If I wire it such and turn the switch for 10-20 seconds or so I should get glow in the cylinders. Right?

So tell me, why won't this or why it's a really bad idea?

well say it does work, what about after the car is started? ur just gonna let the GPs keep running?

nope, once started I'll turn the switch off. Essentially I become the timer relay without the accompanying flow of electricity (I hope).

If you go with the pencil type, they are self grounding. All you need is the + side. A relay is a must, they have 80A of current flowing through the circut.

See THIS post on how I control mine.

Sure it will work. I would use a older style ford starter solenoid and a pushbutton myself. The starter solenoid can easily handle the 80 amps and the push button you will never leave on accidentally.

Instead of all that why dont you just do this

http://dieselgiant.com/mercedesdieselloopglowplugrepair.htm

peragro,

Using a started relay and switch will work . Make sure U use a momentary switch or push button so U don't forget to turn the GP off.

After a while U will be able to estimate how long to leave the GP energized for easy starting depending on the temperature. I essentially do the same thing on my automatic system because the GP light doesn't stay on long enough for easy starting.

Thats just what I did several years ago on my 79. The push button switch (15 amp) is located under the dash (just above the left knee) so I can glow and turn the key at the same time . Its wired through the GP light on the dash. Works great

At this point an old ford starter relay is less expensive and less work than re-doing the original glow plug circuit. My relay doesn't click at all when power is applied and I can't get any voltage readings from it - thus I assume that it's dead.

Glow plugs in parallel should handle the 12V directly, especially the pencil type ones, and I'm still keeping the 80A strip fuse in the circuit just because.

That's a really nice write up though, and I've been looking at your site. I'm sure if I can find an old 300TD that I'll be looking into some of the kits that you have...

does anyone know what to ask for at the parts store with regard to the solenoid? I tried autozone and asked for a ford starter solenoid and they just gave me a blank stare. If you guys could tell me where to look on an old ford I could just head to the junkyard.

I'm assuming that any pushbutton switch would do?

Pretty sad to walk into a parts supply place and not be able to get a Ford solenoid, maybe you should ask for the manager. The push button switches should be available there too, I used a 15 amp one.

If you go back to autozone tell them 1987 ford f-150 2wd auto 351cid V8. starter solenoid
without all that info those jackasses wont be able to find parts for their own cars.
I wonder how many autozoners ride bikes to work?

The junkyard up the road has complete, or near complete, GP harnesses and its ancillary items. There has got to be a yard in your area with the same; and for way less money.


(although rumor has it that MB diesels come to Fla to retire, so I could be wrong)

I ended up popping back in to Autozone later in the evening on the way to rent some movies. I found a different guy and told him that I wanted the cheapest starter solenoid that was switch activated that he had and then told him what I wanted to do with it. He seemed to know what he was doing and went right to the part, so I'm all set with parts.

The town where I live is pretty small and very remote. I've already picked through the 3 old Benzes that we have in the local boneyard. All had the more modern GP relay. There is a yard about 120 miles south that has half-price weekends for you to pick and pull. My buddy and I are seriously contemplating a ride down there next weekend (which is the half-price weekend). Reportedly they have and old 300D still. I'm just not real excited about spending the day in the junkyard when it's 110F. I'll just wear a big floppy hat and about a gallon of sunscreen...

Try this source for several different kits !
 

At:
http://www.**************.com/
you can put " glow relay manual " in the Search Box and you will see the several kits they have to do what you want... although a bit pricey! But hey, they include a good set of instructions too if that means anything to you. You should have done away with that old series system as soon as you got the car! The normal amps for the new system is 50 to 60 amps and the fuse is 80 amps. I think the old one was only a 50 amp fuse which mean the glow plugs were drawing ~40A and much of that was used to heat up those large series wires on the outside of the engine. Very inefficient!!!
Sam