Engine stalled when coasting 20MPH - finally started after 5 minutes

[wayneesch]

I was driving my 1968 280SL coasting down from 40 MPH and at 20 MPH the engine stopped running, alternator light came on. Moved transmission to neutral and tried to start, did not fire. Parked at side of road, and tried to start several times, no success.
Waited 4-5 minutes, pressed accelerator down 3/4, and it started. I searched forum for solutions: I checked the fuel filter into the fuel pump, it is clean; checked output fuel pump pressure into injector and it is 15psi; checked the evaporative fuel canister emissions vent lines in trunk, all clear. Any other ideas? 
 
Less than 1000 miles ago, I rebuilt the engine and fuel injector, new fuel pump, changed all three fuel filters and cleaned the gas tank.
Details that day, temps in 70's, I drove 15 miles in city, encountered heavy rains for 10 miles on highway, then 10 more highway miles. Parked for about 1 hour.  Then 15 minutes city driving, 5 minutes highway 65MPH, 5 minutes at 40 MPH. then coasted to stop ahead when engine quit running at 20MPH. Appears to be fuel related. I wish I had let the fuel pump run for 30+ seconds before trying to start each time. Have driven 20 miles city/highway no problem again yet.

[Bonnyboy]

That really sounds like it could be fuel starvation -  can you shine a light into the fuel tank to see if something was missed during the tank cleaning which has migrated down to the flowerpot -  could be something like a flake of crud that eluded the cleaning process (stuck to the top of the tank)  which found a new home when driving.

[Cees Klumper]

Did the engine cut out like you turned off the ignition, or more slowly started to sputter/run rough and then die? I ask because although you say it seems fuel related, it could also be electrical/spark.

[wayneesch]

I was coasting and engine was idling down. It quit suddenly, I quickly noticed because the alternator light came on. I'm thinking if there was a loss of electrical connection, alternator light would not be on. I previously replaced the points with Magnetic sensor when engine was rebuilt. If it was a loss of spark, don't understand where it would fail and why it would come back. Thank you for ideas!

[Cees Klumper]

Thanks, I asked because a few years ago I had an intermittent fault where the engine would just cut out suddenly, then restart after some effort, or quickly, only to do it again days later. It turned out to be a badly crimped (courtesy yours truly ...) connector to the small signal wire going to the ignition coil. Only the spark stopped, all other electrics (including alternator light) kept working, just not the engine.

[ctaylor738]

Unless you can find an obvious culprit like a loose wire, you will need to catch it in the act.  I suggest you carry something like the Faded Star Garage breakdown kit to check for fuel or spark problems.  See picture.

Cheers and good luck,

CT

[BHap]

Does your car have a fuel shutoff solenoid on the injection pump? There is a series of tests to determine when it should be activated - coasting in 3rd or 4th gear will shut fuel off in my 1970 280SL with manual trans. I think automatics have the shutoff too.

[wayneesch]

Thank you for the idea. My 280SL with automatic trans does have this shutoff solenoid, however, the wires were disconnected 100,000+ miles ago. My mechanic and I are still checking for why it stalled.  We have only driven another 30 miles since it occurred - concerned it may fail in busy intersection or other unsafe location. Mechanic has not had time to examine the flowerpot yet for floating debris in fuel. We also plan to setup to monitor fuel pump pressure while driving.

[teahead]

" encountered heavy rains for 10 miles on highway, then 10 more highway miles. "


Maybe a little water got on/in your distributor?

[wayneesch]

Failed more than 1 hour after heavy rains - does not seem likely.

[dirkbalter]

If you haven't done already,  I would insure that the fuse controlling fuel pump is seated properly amd has no contact or corrosion issues.

[stickandrudderman]

Always check fuel delivery rate as well as pressure, preferably when engine has run for 30 to 40 minutes.

[wayneesch]

Thanks for all the suggestions. Finally found a problem. Took out the fuel gauge sending unit from the trunk and looked in with a flashlight. In the flowerpot on the bottom of the tank around the fuel screen are many fine light brown particles which probably clogged the screen while driving ang and then slowly fell off when the engine stopped running allowing the fuel to flow again. Found these particles on the bottom of the tank all over and particles drained out of fuel gauge canister.

Reminder, this car sat in storage for nearly 20 years (power washed inside of tank before filling with gas to clean - apparently did not completely clean the inside of tank). The fuel looks nice and clean.  Is this residue from old fuel?

Drained the fuel tank. See photos attached. Placed some particles on my index finger and rubbed with my thumb. The fine particles are not gritty. Rubbing turned to black paste. When dried the paste turned light gray.

Considering replacing the tank with new tank if I can find.  Also going to try spraying in mineral spirits, agitate with compress air and drain out the bottom. Hopefully mineral spirits will dissolve the particles. 

Any other ideas?

[ctaylor738]

Glad you found the problem.

Repro tanks by Dansk are widely available.  I have installed several with no problems.  They do not have a flower pot.  I believe you can still get a tank from Mercedes if that's important to you.

Don't forget the collar and escutcheon for the filler neck.

Cheers,

CT

[BaronYoungman]

Dont forget about the small filter on the pump 27mm (see picture) But Napa or Kent (mercedes source) sells a kit to put a clear inline fuel filter between the tank and fuel pump. Nice part about having a clear filter is you can check it once a year to get and idea of fuel tank.
Bob
Baronyoungman@hotmail.com

[wayneesch]

The small filter in the fuel pump is clean as a whistle just like when we put it in new. I took an external fuel pump wuth a filter and Pumped Fuel from the output line back into the gas tank but it wasn't really moving the sentiment from the tank into the flower pot and out. So I reverse the process and hooked up the external fuel pump to take the gas from inside the tank using a metal wane and filtering it and then dumping it back into the gas tank. After 6 hours of this very tedious work 1/4" wide each swpie and using a camera to watch the end of the wane, I've completely filled up four filters and making good progress at cleaning the tank. Problem is it's hard to get maneuvering around the flower pot area to grab the particles off the bottom of the tank. Photo of my setup attached