>1979 Mercedes 300 SD. The engine would idle rough and a little smokey (but good) and
>would run fine. During about a 1 hour period, while driving on the highway the car hesitated a few
>times (semi dying) but then would go right back to running fine. It
>then really started to "bog" down untill it finally stalled.
>
>I tried starting a couple of times, semi turns over but then dies as
>quickly as it starts. It also FEELS like the engine is having difficulty turn over. (new battery but turns slower as if there is a load on the engine).
>
>Any ideas?
>
>I just tried replacing the fuel injectors with no luck.
>
>I do notice when I try starting it, I get that diesel fumecoming fromthe muffler (there is ahole in themufflerby the muffler header). I have verified all glow plugs are working (I took them all out, hooked them up ALL up and grounded them and watch them all glow at the same time).

Does anyone have any ideas?

Is it possible that the Valves break?
(I ask cause almost as if oil is coming out from the lid on the oil filter like maybe the engine is getting unercompression.... just not sure).

 

You need a diesel purge if you're idling rough. Check the motor mounts as well

It could be the fuel filters and not enough fuel getting to the engine.

 

Hi,
Whatdoes a diesel purge mean?

 

odd that it runs an hour. Does it heat up at all? Any of the gauges show anything? lights? do you have to wait a period of time for it to kick over?

good luck -

 

It is odd that after it was hesitating (as if lack of fuel), it went back to normal, and later on just died. In other words, doesn't sound like a major failure at first. Now it barely acts like it wants to start and I get the diesel fumes coming up.

I never got any bad signals on the dash. I think I had good oil pressure.....

I did order the device to check for engine compression.

The only other thing I can think of is if the actual whole Fuel injector is bad. I took out the back plug and the oil at the bottom of the injector looks fine (someone had told me that when fuel injectors go bad sometimes they drop diesel in the lower oil (pan) of the injector unit.

Is there an easy way to check to see if the fuel injector is sending out adequate pressure on all 5 pistons. Can I take the glow plugs out, and look in the hole to see if I am getting a fuel spray?

 

It could be a bad fuel filter....

 

If your fuel filter isn't clogged find a shop that repairs big rigs. They can pop test your injectors... On the other hand you can buy new nozzles for less than $100. .It's very easy toopen and clean the injectors with brake cleaner, then replace the nozzles.A pictorial at http://www.dieselgiant.com is a big help....Butwhen clamping the injectors, turn the injectors oppositethan the pics.... so you won't crack the chambers...After you've replaced the nozzles, have them pop tested, or make your own pop tester and do it yourself..... You can find plans for making your own pop tester at some old man .com
If you remove the injectors you must always replace the heat shields!

Still, the fuel strainer, which is located in the fuel tank, may be clogged. Check it by switching the fuel lines, i. e., remove the incoming line from the I.P and place it on the fuel return line coming from the top of the fuel filter... Then put the fuel return line that was connected to the top of the fuel filter, onto the incoming line on the IP... It only takes a minute or so and it by passes the fuel tank strainer.

Ifthe engine runs well, then most probablythe strainer is clogged. The other way to check is by doing the diesel purge system ( litre plastic bottle full of diesel with connecting incoming and return fuel lines ) , only instead of a diesel purge, use regular diesel. Again, if the engine performs well, then it's probably your fuel strainer... In which case you'll need to drain the fuel tank and replace the strainer.... I think diesel purge also has a pictorial for that.....

When I drained my tank I used a pella.... which is a hand vacuum pump that sucked out most of the fuel so I had to drain less than a litre of fuel... Which is a big help... Those vacuum pumps are also sold at harborfreight.com for half the price of the pella.. The harborfieight vacuum pump is metal and the pella is plastic...I suspect harborfreight has the best pump.

When you remove the fuel strainer, look into the tank. If it'sfull of algae, you need to remove it and havecleaned at a radiator shop. If it looks okay, but the strainer is clogged, then after youclean and replace the strainer and fill the tank, you should usea good anti algae additive... It seems the bestbrand is startron ( that may be mis-spelled) which is sold at marine supply stores...

 

Thanks for the REply!!!! But fuel is not the problem. When I disconnect the primary fuel filter from the fuel pump, diesel flows out (I put car on rear stands and fill tank complely full).
When I push the hand pump I can watch and hear the fuel get pumped back the return line.

Does anyone have any Experience with the Diesel fuel injector iteself going bad? Is there any way to test to see if the fuel injectors are actually pumping out the required pressure?

Just still no idea of why I would get diesel fumes coming out of the exhaust pipe, the glow plugs are hot, and it wouldn't start. This one really has me stumped. Any other ideas out there?

 

As I said, in order to test the injectors, they need to be pop tested. That particular test measures the pressure in each injector. You can have them pop tested, or build a simple pop tester and check them yourself. It could be that the injectors are dirty, etc... It's all in my last post.
Since fuel filters are relatively cheap, I'd still, regardlless of flow, first change the fuel filter.

When changing the nozzles in my fuel injectors, I noticeed one injector that didn't seem to have a load on it. I took it to a shop, had it pop tested and it had next to zero pressure. A shim was added, it was again pop tested and up to specs....

 

Thanks, I did put brand new bosh injectors in and still the same thing... I also tried both fuel filters. Hmmm. I just ordered the compression check (to measure the compression on the cylinders). That is the only other thing I can figure it could be.
Only other thing is if it is the actual injector pump on the side of the engine. Does this ever go bad? What is the sypmtoms when the pump goes bad. I know they contain little pistons that pressurize the fuel to like 4,000 psi. Is there any way to test the pump?