1987 300d starts fine then dies after a few seconds - PeachParts Mercedes-Benz Forum

hawk · #1 03-21-2015, 02:46 PM

I bought this car about 3 weeks ago. It has around 180,000 miles on it. I'm new to diesels, but when I was checking out the car everything looked and ran good( no blowby with oil cap removed). The seller lived about an hour from me drove it all the way home no problems at all. Temp Guage stayed steady around 90, oil pressure was good, great highway cruiser.

I have a lease car that this will hopefully be replacing so for the next week after I get it home I would take it around the neighborhood on short trips. This way I could work out any issues that might be present before it's my daily driver. Well an issue definitely appeared. I went down to my garage one day to start it and it's started right up like normal ran fine for a few seconds then stalled out. I tried it again same thing. I tried starting it and giving gas right away and it would just bog down and stall. I should mention this started during a very cold stretch, however my garage is below ground so it rarely gets below 32 degrees. This issue has continued unchanged even with the warm up in temperature.

I'll list the things I have done and tried including the one that has me really stumped.

-1st thing I did when this happened was look around the engine for anything loose. I did find a line from the alda was disconnected. Could have been before because it was hard to see. I hooked that back up.
- pulled gas cap no change
-pulled oil cap no change
-looked for fuel line leaks and didn't see anything(still could be of course)
This lead me to try a diesel purge so I could isolate a fuel leak if there was one. This is where it gets weird first few tries it did the same start then stall but then It would idle a little longer then stall. Finally no stall running good. I run the engine at different speeds like your suppose to and everything sounds great (actually sounds even better the longer the purge runs) I shut it down after the purge was almost gone. Bottle was filthy! So I think this might have solved it.
-I wait a couple days for new fuel filters
When fuel lines were off I used low pressure air to blow back into tank. In case it was a plugged line or strainer.
-hooked everything up with new filters
Fired it up and it does the same thing starts then stalls
-switched fuel lines so supply was on return and return on supply same thing happens at the same time. If the was a leak in one of lines going to tank wouldn't it stall a a different time with the lines switched?
-now I'm thinking bad fuel so I get some fresh diesel from a busy station and hook up a bottle in the engine compartment and hook it up exactly the way I did withe purge. Fire it up and it does the same start stall thing. So is there a reason diesel purge will run in this set up but not diesel fuel? ??
-so at this point I'm really stumped. To eliminate any other possible air leaks I removed the fuel thermostat from the system by connecting the supply line straight to the lift pump. And of course no change same start stall.

any guidance you could give would be greatly appreciated!
Thanks

rob300SD · #2 03-21-2015, 10:28 PM

Disconnect the shutoff vacuum switch at the back of the injection pump. Maybe the valve on the ignition steering lock is leaking and shutting the car off? I'm assuming your 87 still works the same way mine does but I could be wrong.

NJ300sdl · #3 03-21-2015, 10:54 PM

Also could be excessive exhaust back pressure. Remove plug in manifold located around #1 and #2 cylinders to test.

vstech · #4 03-21-2015, 11:48 PM

my first thought was the vacuum line somehow got directly connected to the shutoff valve.

next I'd check the exhaust by pulling the brass plug in the exhaust manifold between the front two cylinders.

if the vacuum line is unplugged from the shutoff valve, and the brass plug is pulled, and chugging... and the car STILL shuts down in a few seconds report back.

hawk · #5 03-22-2015, 04:38 PM

I pulled the vacuum line from the shut off valve. No change still starts right up then dies after a few seconds.

Pulled brass plug from the exhaust and still no change.

Is it possibly the lift pump? It ran off a bottle of purge but not off a bottle of diesel. Is diesel fuel heavier than purge? And the lift pump isn't pumping the diesel as easily?

TnBob · #6 03-22-2015, 05:37 PM

You did say the purge was pretty dirty. Id be running purge thru it again and go from there.

rob300SD · #7 03-22-2015, 06:11 PM

Could be the lift pump. Maybe the IP has enough fuel to start up bit then goes empty.

rob300SD · #8 03-22-2015, 06:39 PM

weird the purge would work and not the deisel when running from the same bottle and setup.

JimFreeh · #9 03-22-2015, 07:03 PM

Any chance you've got enough water in the tank to pull it into the engine?

Bad fuel is possible. A weak pump might also be sufficient with the bottle of purge, but not enough to get through to the tank and possible clogged strainers/filters.

I've seen some pretty old diesel fuel that sat in some of farm tractors for years, and those engines would still light off an old fuel without a problem. I don't think projecting a gasoline issue onto diesel fuel is correct.

Jim

JimFreeh · #10 03-22-2015, 07:07 PM

...one more thought.

Check the air filter. Might be something in the housing that flips up when the airflow is sufficient, blocking the air to the engine.

I actually saw this happen. Owner installed the air filter in the dark, and forgot to remove the instructions. Car ran until the airflow was enough to suck the paper into the filter and stall the engine.... Shut it off and the paper dropped down, enabling the car to restart, until.....

Jim

rob300SD · #11 03-22-2015, 08:17 PM

Any oil in your coolant reservoir?
Did you change the oil after you bought the car?

rob300SD · #12 03-22-2015, 08:18 PM

Remember that cars always run good until they don't. So the problem could really be anything.

rob300SD · #13 03-22-2015, 08:19 PM

Does it sputter and slowly die or does it just cut off like when you turn the key off?

sixto · #14 03-22-2015, 09:26 PM

Does it stay running with the fuel filler cap off? Might you have reversed the fuel supply and return lines?

Sixto
MB-less

hawk · #15 03-22-2015, 09:31 PM

So I setup the bottle tank with diesel purge and it took awhile but after about 10 tries it stayed running. It was running rough at first, but the longer it ran the better it got. Once the purge was almost gone I filled the bottle with diesel and it kept running. I ran that down and then I added more diesel. Now it's running on straight diesel. Once that was almost gone I shut it down and reconnected it to run from the tank. It started right up, revved it up everything seemed fine. Let it just idle for awhile and then I tried revving it up again. It would hesitate and so the previous symptoms of being starved of fuel. Once it hit 2000 rpms it would go away and act normal. When it dropped to idle it would act like it was going to stall, but it would catch itself and level off. I tried shifting it into reverse and it would stall out. The inline filter was only a quarter full at idle and when I revved it up it would go almost completely empty.
So I'm thinking there most be an air leak from the filter back to the tank, right? Or possibly bad fuel
The idle speed also seems to be really low around 580-620 and this was even with purge running.

I want to say thanks to everyone was has helped me to this point. Let me know if I'm on the right track. Thanks