1980Merc. 300D engine install

I have a Metallic-Blue, 1980 M 300D. The engine's compression was low in 2 cylinders, and would now start, so I replaced the engine with a 1979 issue 300D M. engine. The 79 engine has different spark plugs(big) & relay harness & relay, also vacuum module on top of the fuel injector. I have both harnesses, and relay boxes, and injectors. How should I resolve these problems, especially, the glowplug-harness, relay problems. Thanks in Advance. Sure could use some help with this! James

[Stevo]

James

Just get the glow plug upgrade kit for the "78" which will be the 18mm plugs, wires, and a new relay. I think you could just get the 18mm plugs, make up the wires, and use the "80" relay but the price is not that much more for the kit. you would be going to the new series plugs so you must DISCONNECT the ground strap at #1. Dont know about the vacuum module. Good luck

No, the simplest thing for the glow plugs would be to just get the bushings to adapt the pin type glow plugs, then use the wiring harness, relay, et al in the later model car. Use whatever engine components from the old engine that are not the same as the new. This way, the long block is the same but the accessories stay with the original car in which you are putting the engine.

One more thing, the early and late models have a slightly different starter. Use the starter that is on the '79 engine to be sure.

Good luck,

[Fisherman]

The vaccum module ion the IP is a bleed valve.

Are you changing out the motor and tranny or just the motor?

if just the motor and your 80 does not use the vacuum module then no big deal. If your 80 is like mine you need this bleed valve for the tranny to shift correctly.
If the IP's are the same mw style then it is fairly easy to convert the top plate on the IP to match teh one that was in the 80. Issues may come up if the throttle shaft does not have teh fitting for the push rod that connects to the vacuum bleed valve.

I just did a conversion on a pump that was not so equiped and it was no big deal but if the two pumps are in fact both MW's then you can just switch teh pumps and be done with it. If you need to switch the shafts also I can walk you through how I did mine but be prepared to go inside the back cover and r&r parts between the two pumps. I was nervous when I did it but it turned out to not be a big deal once I finished... Oh, and it worked

If you need more info let me know.

The 79 M engine that I installed in my 80 has the fast acting 18mm, pencil type glowplugs already in it. I got the conversion kit yesterday, and found that the 79 did not have the filament type, loop style glowplugs. I was told that these fast acting glowplugs can be used in the 1980 as it is, and may not need installation of the other parts in the kit, so my focus turned to the fuel injector. The ip on the 79 does not have the fitting for the push rod that connects to the vacuum bleed valve. I am debating switching ip's vs r&r parts. (the throttle linkage shaft that goes thru the ip looks like it is removed form the rear of the ip engine side, necessitating ip removal, to switch linkages & vac. bleed valve assy. on top. What do you guys think? I appreciate your info. I think I was told right, that the guys on this site have a wealth of information on the diesel. There is some light from the end of the tunnel! James

[Fisherman]

The change you are referencing on the IP does require access though the back of the pump. If you can pull the one off the 80 then just switch them.
I have done the change you are thinking about and managed to pull it off without losing any parts but if you can just pull one and replace the other with that it is by far easier and less stressful.

I managed to do my changeover without the oil filter housing removed but it takes patience. The biggest pain is the rear bracket that holds the pump. It cannot be in place when you fit the IP and you cannot get the bolt in the back of the IP after installing the pump with the oil housing in place.

I solved this problem by cutting the top off the bracket. I then let it hang from the spring as I put the pump into place (with the rear bolt threaded in the pump) and then I was able to climb under the car and refit the bracket to the bolt with some twisting and turning... BTW - I made an 14 inch extension on a 13mm box end to tighten this bolt after mounting, this really helped too.

It's not fun but it works!

Make sure that your pumps are both of the same model (MW) before switching them, although I have no idea if it really makes a difference. Supposedly all parts in the 79 are interchangeable with the 80 according to my dealer.
However, I make no warranties expressed or implied....

[Stevo]

"the simplest thing for the glow plugs would be to just get the bushings to adapt the pin type glow plugs"

Larry

Do you know where to get this 18mm to 12mm bushing? I looked all over for them and was told they dont exist. I also talked to a mechanist friend about making them. That would indeed be the way to go as those 18mm GPs are about twice as expansive as the 12s.

James... I have switched IPs between 78 & 80 but I dont know about this vacuum bleed valve. I thought both IPs were just about the same. These guys will know whats going on. It sounds like you are doing ok.

I dont know how to get the 18mm to 12mm bushings, I will look around this area for them though. This evening I am going to take a closer look at the problem of switching the ip's. I appreciate the information. I'll let you know how it turns out. James

I've never bought any, but they are part of what is called a Bosch Quick Glow kit. Maybe if you search for the Quick Glow kit, you can find a source for the bushings.

Good luck,

[Stevo]

Larry

I have bought a couple of these "kits" and the Bosch ones I bought included relay, wires, nuts, and 18mm series GPs. It made a BIG difference and I would never go back to the loop style, anyway if anyone knows about these bushings I would interested, someone around here made them from an old plug.

Stevo

I switched the ip's and used the relay & 18mm pin type gp's, and wiring on the car (80). 79 engine had 18mm pin type gp's already. I got the conversion kit also but found the gp's to be the same as already on the car. Repaired broken wires to the neutral safety sw., causing no power to the starter sol. and got the starter to crank the engine, but no start yet. I also bled the ip

I think I'll revisit the gp's, and then its wiring. Its been good reading through the threads. Thanks, real good discussions, guys. James 80M 300D Metallic Blue (I'm closer than ever, now, to starting)

ATTENTION!!!!!!!!!!!!!!!!!!!!!!!!!!!!

If you are going to go into the IP, MAKE SURE!!!!!!!!!!!! that you check the shut off BEFORE STARTING THE ENGINE.

To do this, before starting the engine, remove the shut off vacuum line from the shut off diaphragm at the very back of the IP. Put in its place an auxilliary vacuum source and apply vacuum. The STOP lever should move freely. IF IT DOES NOT, DO NOT START THE ENGINE!!!!!!!!!!!!!!!!!!!!!!!

If you do, it will very likely runaway (go to max RPM with no easy way to shut it down.)

Even after checking the shut off, have a 17MM wrench in your hand before starting the engine. If it does runaway, loosen the injector line nuts quickly one at a time. It will make a mess, but you will save the engine.

Been there, done that!

Good luck,

[P.E.Haiges]

James,

Easiest way to make the bushings is from the 18mm glow plugs (GP). I made a set that way for an 190D so I could put the fast GP in it. It worked great. The hardest thing is to get the porciline out of the 18mm GP but this can done with carbide tools on a lathe.

For runaways: Take the input hose off the air cleaner. If the engine should run away, just put something over the air cleaner input and engine will stop without spraying fuel like Larry's method.

P E H

Larry, I hear you loud, and clear & I did have a 13mm wrench in my hand when I cranked the engine. I did the vacuum test, and the stop lever did not move. I did not open the ip, as of yet, but now that I remember, the mechanic that serviced the car may have. P. E. H. - I will also be ready to block the air intake, if needed. Guys, I checked the gp's & they were ok at .9ohms. How do you check the injectors. I'll look closely at the gp wiring before I wrestle with the ip again though. Im also wondering about adjusting the timing degree from 19d btdc. Thanks James