1987 300D no start - PeachParts Mercedes-Benz Forum

300DTurboWV · #1 08-21-2013, 09:54 PM

The car was run low on fuel after sitting for several years and it appears that the tank strainer partially plugged. The car then must have ran out of fuel due to the strainer not passing much. This all happened in my Dads driveway and he has given me the car(my first Mercedes and the first diesel I have worked on). I have changed all the filters (tank screen, pre and main filters). Cranked the car off an on for several days and it still won't start. I have fuel to the injectors but it doesn't seem like I have enough pressure. When I crack the nut on the hardline it gets wet but doesn't squirt the way I have seen in some videos.

My question is, can the pressure relief valve on the back of the injection pump cause reduced pressure at the pump and not allow the engine to start if it has failed? The reason I ask is Dad told me the car ran rough for a while and then just died and wouldn't restart. I am wondering if I am fighting more than just a "out of fuel/repriming" issue. I am really hoping this isn't a injection pump issue.

NJ300sdl · #2 08-22-2013, 11:28 AM

Believe you can pinch off the return to build up pressure if the relief valve fails.

Lift pump bad?

Try running it off a small container of diesel. An ouboard tank with a pump ball is nice to use.

300DTurboWV · #3 08-22-2013, 08:10 PM

Pinching the return hose was going to be my next little test as soon as the rain stops here.

I forgot to add that when I did the tank strainer I did replace the lift pump with a new one. I don't think that was the issue though, I did it just so I didn't have to worry about it later.

Thanks for your help!

vstech · #4 08-22-2013, 11:37 PM

use this method to test out the vehicle. use a kerosene siphon hose with a squeeze ball as the supply line, and just use diesel instead of DP...

mkrazy1 · #5 08-23-2013, 04:35 PM

Maybe a dumb question but, are the glow plugs working?

300DTurboWV · #6 08-26-2013, 08:52 PM

Dad replaced the glow plugs before he ran it out of fuel...... I know that doesn't mean for sure they are good but I am assuming they are at this point. He didn't ream the passageways out when he changed them though. That could be a consideration.

I had a mechanic buddy of mine looking at it with me this evening and he believes there is still air in the system. He advised me to make a temp tank and run off of it to assure there isn't a blockage or air leak in the lines coming to the engine just to be sure. That is what I am going to try next.

My battery is about shot now, I have been using a large charger when cranking but the battery doesn't hold up well. I am hoping that it goes instead of the starter.

I am not gonna give up. I think I would have a very hard time finding an 87 this nice inside and without a spot of rust on it. It has 169K on it right now.

rrgrassi · #7 08-26-2013, 09:53 PM

Sound like lots of air in the system, still.

You can also use a mity vac to pull fuel from the tank to the lift pump

Skippy · #8 08-27-2013, 05:13 AM

I agree there's still air in the system. Does the '87 have a primer pump? If so, use it. If not, as I'm guessing, keep charging and cranking with the injector nuts cracked. Once you get good fuel flow at a given injector, tighten it back up. I've done this on Hummvees many many times (no primer pump on them either), and they will usually fire up on four cylinders. Once it fires, that will almost instantly bleed any injectors still cracked in the time it takes you to shut the engine off. Then just tighten the remaining injector nuts and you're good to go.

This of course assumes glow plugs are functioning and everything else is working properly.

mkrazy1 · #9 08-27-2013, 11:29 AM

This one doesn't have a lift pump. The "temp tank" is a good idea, but no matter what you do, you should at least remove the large filter and prefill that with fuel, then as Skippy said, use a mity vac or whatever to get all the air out of the lines to the injector pump. Then crack a couple of the injector lines and verify when cranking that fuel is coming through.

You could also use some WD40 as starting fluid to verify it will at least fire and run. This would also help prime it faster instead of just using the starter.

300DTurboWV · #10 08-27-2013, 12:31 PM

WD40 as a starting fluid, would have never thought of that but that sounds like something I want to give a shot! I will pick some up on the way home from work!

The car acts like is is just about to run all the time, at points it fires and runs for a second or two and then dies.

Skippy · #11 08-27-2013, 05:17 PM

I would be very reluctant to use any kind of starting fluid, including WD40, in any diesel vehicle I owned. If you're getting it to the point of running and it still dies, you may be sucking air somewhere in the fuel system.

300DTurboWV · #12 08-27-2013, 05:32 PM

That was why I was considering the temp tank approach. I could bypass the line from the tank and even the fuel thermostat and hopefully eliminate an air leak if there is one.

Wouldn't WD40 be a much safer alternative to normal starting fluid? Maybe it's that I don't understand what normal starting fluid lacks that causes damage. I always assumed the problem was it was a very dry fuel. Wouldn't be the first time I was wrong and it sure wont be the last.

mkrazy1 · #13 09-04-2013, 11:25 AM

You don't want to use standard starting fluid because the glow plugs may/will cause it to "explode" at the wrong time.

300DTurboWV · #14 12-27-2013, 08:40 PM

Been creeping along with this project. Still haven't got it running but haven't had much time the last few months. Did a few things to it that I figured I would end up doing eventually and have checked a few things. This car has been sitting for a few years, but was running about 6 months ago until it was starved for fuel by what I believe was a plugged tank strainer. After replacing all the filters and the lift pump I spent quite a few days bleeding the lines to the injectors and cranking. The car would fire and run for a very short time then die.

I had friends that know more than I about diesels tell me that the injectors were most likely gummed up by the fuel which was at least 3 years old before the car crapped out last summer on my dad. I decided that since the car has just short of 170k on it that the injectors were probably worn anyway so I replaced them with remanufactured Bosch units. I have a spare set of injectors to rebuild myself sometime if I ever want another project.

I have checked the resistance of each glow plug and each measured if I recall just below 1 ohm and all were about the same. I have not yet checked the glow plug relay to see if it is keeping power on to them long enough though.

I bypassed the fuel thermostat/fuel tank and installed a temporary tank that I purchased from ************** this fall. In the tank I used Diesel purge rather than just fuel. I spent a short while trying to bleed the air and start the car last weekend since the weather was warm. No luck. I did use the block heater and can say that I am surprised at how warm that got the engine.

I have a feeling that the old fuel (probably algae probs too) that was in the car last spring caused a great deal of this no start issue. I have diesel biocide coming from Amazon as I write this. I probably will use the old fuel and added fuel to burn a stump or something but I doubt it will ever let it get to the prefilter again.

Anyone have any hints or tips that I could try to help this thing going again?

jay_bob · #15 12-27-2013, 11:13 PM

That's the beauty of a Diesel engine - you just need fuel, air, and compression. Well you do need glow plugs to get the chambers hot and ready to fire.

Let's think about what we might be missing.

Glow plugs, good that you measured 1 ohm on each. That's a start, but not a guarantee of a good glow plug. Does the glow light come on for about 10 seconds (temperature dependent) and then turn off? I would let it continue glowing (yes it keeps on going after the light goes out, the light is just a guideline for when you should attempt to crank) for about 10 more seconds, then try to crank it. Double check you actually have 12 V dc at one of the glow plug terminals, (whichever one you can reach the easiest), that verifies your GP fuse is good and the relay is pulling in.

Fuel: Whenever you changed the main (canister) filter, did you put it on dry or pre-fill it with clean fuel (or Diesel Purge) first? If you put it on dry you will have to pass a ton of air through the system before it will run. Did you change the seals on the stem when changing the filter? Hose clamps good and tight on the in-line filter and the other rubber hoses?

Diesel fuel normally will remain stable for a long time. As long as it does not get algae growing in it. However if it does get infected then Startron or Biobor will clean it up and make it usable again. I don't think your injectors got gummed up from sitting, that just doesn't normally happen on Diesel engines running on straight #2 fuel. (Veg oil, that's another story...)

Injector line nut cracking is important, if you don't do this it won't release the trapped air caught between the delivery valve and the injector.

Air: Double check you don't have a mouse nest in the air filter, from sitting so long.

Compression: Let's make sure the rest of the story is in place before going there. But since the car ran up until a few months ago, hopefully you are ok in this department.