1987 300sdl won't start after sitting overnight - PeachParts Mercedes-Benz Forum

JustJim · #1 12-28-2016, 08:46 AM

My 1987 300 SDL quit running after being parked at the airport overnight. It may not be related, but on the way to the airport it began losing power and wouldn't run over 60 mph. When trying to start it, it acted like it was starved for fuel. Replaced the lift pump (with used pump from running 300 D), purged the injector lines, started the car, but it sputtered and quit. Had the car towed home, tried to start it again, and it started and seemed to drive fine. Next morning wouldn't start again. Again purged the lines and she started and ran fine. Next morning wouldn't start again...

Any suggestions?

Thanks

psaboic · #2 12-28-2016, 10:06 AM

Change both the spin on and in line fuel filters, and check all fuel lines for cracks and fuel line conections for tightness....

Diseasel300 · #3 12-28-2016, 10:09 AM

Sure sounds like you have an air leak somewhere.

JustJim · #4 12-28-2016, 10:13 AM

Probably should have mentioned that I changed all filters, connected a small electric low pressure pump to the lines, got good fuel flow, disconnected the electric pump and fuel continued to run out of the line from the tank until the line was connected to the lift pump. Got the car started and with car running had good fuel flow at all 6 injector lines even without the electric pump, but still won't start after sitting over night.

Diseasel300 · #5 12-28-2016, 10:22 AM

So you say that you got the car started and had good flow from all 6 injector lines, but the car won't start after sitting overnight.

Did you crack the injector lines and determine if you have good fuel flow the next morning during the no-start condition? Just because you had good flow the night before doesn't mean you do now. If air leaked into the system while it sat, you're not gonna have a good time restarting.

JustJim · #6 12-28-2016, 10:34 AM

All of the lines are tight, but no, I didn't check the lines for air before trying to start in the morning. I agree that there may be air getting into the system, but since I don't find any signs of fuel leaks, running or not, don't know where to start looking. It would have to be fairly significant to cause all of the fuel to leak out of the lines in just a few hours. Where would be the likely source of such a leak?

Fulcrum525 · #7 12-28-2016, 11:51 AM

I'm going to second air getting into the system. You mentioned that you replaced the filters so this would be the first place that I would check. The same thing happened to me with my 617 and it just turned out to be one loose clamp. (I had been playing around with them a few days earlier)

sixto · #8 12-28-2016, 12:49 PM

A loose line upstream of the lift pump can draw air without leaking fuel.

Keep the injector lines cracked while cranking to see if fuel spews out of each line. If you have fuel at the injectors, it's unlikely to be a fuel problem. Does fuel flow easily from the tank? It's not gelled?

Is the glow system working?

Sixto
83 300SD (yes, babymog, I'm still at it)

JustJim · #9 12-28-2016, 01:32 PM

Checked all clamps and fittings, none loose. Purged the lines again, got the car started again. Still no signs of leaks...

This all started after leaving the car overnight at the airport in the parking garage. So far I have been able to get it started again after purging, but after replacing the lift pump and all filters and verifying continued good flow from the tank the problem persists. Could the injector pump be leaking internally and causing this problem?

barry12345 · #10 12-29-2016, 11:10 AM

Relief valve not remaining pretty much open?

JustJim · #11 12-29-2016, 12:42 PM

How do I check this (and where is it located)? BTW, tried to start it this morning, it started normal, but quit after 10 seconds then had to have injector lines purged...

sixto · #12 12-29-2016, 12:57 PM

It's built into the banjo bolt that holds the [used to be] clear return line from the engine side of the IP to the big filter. Most 603 relief valves are sealed, most 617 relief valves can be disassembled. They're physically interchangeable. A temporary fix is to stretch the spring. I don't know how to check it without a gauge but maybe lightly clamp the return hose from the big filter to the tank to see if that buys more running time.

Sixto
83 300SD

tiger64 · #13 12-29-2016, 01:44 PM

You might have 2 root causes. Eliminate your glow plugs, relay, and fuse as one of the potential problems. Then you can be sure it is just a fuel problem

psaboic · #14 12-29-2016, 10:29 PM

Well, if it started normal and ran for 10 seconds before quitting, it is not likely a glow plug problem......I'm sure it is a fuel delivery issue. I'm starting to think you might have bad fuel or a clogged pick up scren in the fuel tank. One way to check it is to get it started and see how long it will run before dying. Then try starting it from an alternate fuel source (such as a five gallon can with the fuel hose and return line in the can) and see if it runs longer. If it does, you either got bad fuel, someone added something to your fuel tank when the car was parked at the airport, or your tank strainer is clogged.

Diesel911 · #15 12-29-2016, 11:04 PM

I think both of these have been mentioned previously.

I believe the Fuel Pressure Relief/Overflow Valve has a plastic piece in it that people have said warps and or falls apart.

The Fuel Supply/Lift Pump Valve could be allowing fuel to leak back to the fuel tank overnight. There is a couple of threads on how to rebuid it.