300SD Not Starting, Need Expert Help - Page 2 - PeachParts Mercedes-Benz Forum

Lew · #16 02-27-2008, 02:35 PM

Thanks for the suggestions! I'll run it out of a bottle again with some more cleaner, see what that does - and this time I'll disconnect the vac line to the shutoff valve. The filters are two days old at this point, but you're right, Jim - the WVO has really loosened up stuff and my filters must be changed regularly.

Lew · #17 02-27-2008, 02:46 PM

Thank you very much for the suggestions. I'll run it out of a bottle with the shutoff vac disconnected and see what I get.

ptwheatstraw · #18 02-27-2008, 02:51 PM

if the valves were not cked in 70k after engine overhaul this is where i whould start.

Lew · #19 02-27-2008, 03:00 PM

It's been approximately 30k since I last adjusted the valves.

JimSmith · #20 02-27-2008, 03:08 PM

Given the pretty sudden no-start or start with ether and no idle affliction so soon after the incident with fuel types, I would not suspect something like valve adjustments right off the bat. Not that the valves shouldn't be checked, but I would be surprised if the combination of events needed to bring about the reported behavior depended on something that has such a gradual rate of degradation, and that it would affect nearly all the cylinders at the same time. But that doesn't mean don't check and adjust the valves. But, even if they are out of adjustment, don't be surprised if that doesn't fix things, unless the gaps are huge, meaning the all the valves open late and close early or tiny meaning they all open early and close late. Even one being significantly off doesn't explain this behavior.

Jim

Lew · #21 02-27-2008, 04:46 PM

OK, pulled the vac line off the shutoff valve, adjusted the idle up a bit (just in case a low idle was affecting things), set up a jug with good fuel, and she started and ran great and held an idle ... until the temp neared 80, then it became hard to keep running unless I kept the RPMs and kept my foot on the pedal to keep her going.

I noticed that, although the idle was around 800 cold, the warmer it got the lower the idle speed until it finally wouldn't hold an idle.

My WVO heaters are still installed and, therefore, the fuel is getting warmed as the car warms up. Could the resulting reduction in fuel viscosity be a key clue?

I really need to take all the WVO stuff off this car and get it back to factory setup. Anyone need a nice 26-plate heat exchanger, or injector lines with heaters installed (in exchange for replacement lines, of course)?

JimSmith · #22 02-27-2008, 05:47 PM

I am unfamiliar with the idle speed adjustment on the OM617 engined cars equipped with automatic transmissions and turbochargers, mainly because I have never owned one. On the 240D and Euro manual transmission, non-turbo 300D's there is a knob on the dash you turn to adjust the engine idle speed. Up when starting and then down when the engine is warm.

Your idle control sounds kaput. There must be something that looks at your engine temperature to set the idle speed. It may look at some other things too. On a car without an idle speed adjusting knob, something has to take care of this function, and it seems yours is not doing it correctly once the engine warms up - Diesel fuel changes density and therefore energy content more than gasoline does with temperature. It may be that your fuel heater controls are out of whack and they are confusing what controls your idle speed. Or set too high and causing an air leak after time... Pure speculation on my part so don't put much credence in the suggestion - but try the same experiment with the fuse for the fuel line heater disabled. Maybe that will help. Grasping at straws. Sorry. Jim

kerry · #23 02-27-2008, 06:01 PM

Some of the early 617 turbo's had the manual idle control knob but I think onthis one, the only idle control is the screw on the IP.
I'd check the lift pump and see if it is failing when the fuel is less viscous. I can't think of anything else to check.

patbob · #24 02-27-2008, 07:28 PM

If you leave it set for a few minutes, but not long enough to cool all the way down, will it restart? If it won't, then it is probably engine temp related.

I think there's only a temp sensor for the AC and another for the EGR on that vintage if I recall. Try plugging the EGR line and unplugging the AC clutch. If the tmep sensors for either is causing problemd, that should eliminate them.

Lew · #25 02-27-2008, 08:46 PM

The EGR has been plugged since about day two of my ownership. I'll unplug the AC clutch thing - AC doesn't currently work anyway. I'll also disable my fuel heaters to eliminate them as culprits.

As far as the lift pump goes, it has been off the car for some time. I recently reinstalled it and have kept in place the electric pump that I used with WVO - so I actually have an electric pump feeding the lift pump. Just to be sure, we're talking about the thing on the side of the IP that has the manual purge pump on it, right?

The only idle adjustment I know of is on the "engine" side of the IP, held in place by a lock nut. Loosen the lock nut, and turn the screw clockwise for faster idle, counter clockwise for slower. This is what I've been doing, anyway.

Today, it would always crank back up after cutting out. In the recent past, it didn't do so until the next day or much later in the day (I usually have to wait overnight 'cause I gotta sleep sometime in order to deal with my high school students with some amount of decorum the next day ...).

FYI - This issue didn't happen suddenly. For a long while (perhaps 3-4 months), it would stumble at an idle, particularly if my fuel blend was thinner than usual (a higher percentage of diesel). I blamed it on clogged filters, air in the lines, etc., and didn't think too much more about it. It eventually got worse, then one day after a secondary filter change (filling with Sea Foam, as was my custom) it didn't start back up.

Great improvements have been made recently. Perhaps another diesel purge or some other cleaner will continue to improve the situation.

Keep up the suggestions, and I'll keep working on it until she's reliably back on the road. Thank you so much for your help!

Lew · #26 02-28-2008, 07:07 AM

How do you change the title of the thread; this one is currently misleading. Should I start a new thread?

doxland · #27 02-28-2008, 05:38 PM

Once you have verified that the lift pump is good;
Connect up an independent fuel supply with a head(gravity feed), reliably suspended with a cord from the hood so it'll be hands free, unattended.
Take what you know to be a good injector and connect it to #1 injection pump pipe,
bleed air by cranking and close up tight but injecting into free air or catch can(not installed in it's cylinder.
Have someone crank while you watch and see it the IP can push fuel through the injector. Crank with accelerator part way down.
Repeat with all the other injector cylinder pumps.
Alternatively you could remove all your injectors from their holes and connect to the injection pump and crank after bleeding while watching their performance. This will be messy but gives you a good one shot trial.

This would remove your suspicions about to much wear in the pump.

There are classic tales of Marine Diesels running on heavy fuel getting along just fine on an ocean crossing then switching over to light fuel, stopping for a reverse test, and failing to start again because of wear in the IP cylinders. All pumps had to be rebuilt before ship could proceed. The wear had occured because of the rotten fuel they burn but it's viscosity was high enough that it could be pumped, but the light fuel replacing it couldn't.

Possible too, I suppose, is Lube Oil dilution for some reason or other. Make up a simple viscosimeter and compare to new oil.

Lew · #28 02-28-2008, 06:49 PM

I ran her today with the fuel heaters off and she ran like a champ. Took it for a spin around the block and back, got the engine good and warmed up, and all was well. This is with what was in the tank, which is, if I remember correctly, about 15% WVO.

I was shocked when I turned the key off and it kept running ... then remembered that I'd disconnected the vac to the shutoff valve. hooked it back up and it shut off right away.

So ... it appears that fuel viscosity is critical to this thing running. My next move is going to be running some more cleaner through it. It did improve dramatically with the Diesel Purge. I have half a gallon of "silver" Power Service Diesel Kleen that I'll run straight through after I add half a gallon of diesel to it, see what that does.

For what it's worth, while I put 35k on this with a veggie blend my commute was a long one - 45 miles each way. The commute, however, changed to only 12 miles each way, and that's when I started having trouble, and I suspect that the short trips caused some gunking.

Lew · #29 03-02-2008, 10:07 PM

Well, I guess I need an IP. I tried running off diesel, and once the diesel hit, she died and wouldn't crank again. I've got the batter on a charger and have pumped and pumped trying to get my "thick" fuel back up to it. If it starts on the thick stuff but won't run on the thin, then I guess it's time to pull the IP and get her built or replaced, right?

I recently read the humongous thread where the 15-year-old young man went through the ringer to get his $300 ride going. I guess if he can do it, I can do it - truly an inspiration that fellow was/is! I'll search the threads and see what I can find on pulling IPs. Wish me luck!