Another (still) no start woes - PeachParts Mercedes-Benz Forum

coachgeo · #1 02-12-2009, 02:01 PM

Won't start in temps below 40 deg. (85 300sd)
Car often sits alot waiting for a day warm enough to drive it.

. Battery checked by CheapoZone and said it showed to be fine.
. New Glow plugs. All checked to get red at tip when powered before install. (well one is old but while in car it showed normal resistance. All others showed no resistance as in DEAD no contact) Now all show normal resitance when on car.
. Relay fuse shows power on both sides

Do not have an amp meter yet.

Wondering if something else Im not thinking about that would cause no start that the cold helps create such as cold temps can worsen poor contact in electrical connections

Since car often sits alot waiting for a day warm enough to drive it, I thought maybe it leaks in air. So other day it was warm but got same no start. Using 12v pump I put by tank... I primed the system at the filter. It started. BUTTTT...... on cold day..... this does not help; I tried.

Im baffled and desperate. This is my only legal transportation

UriahT · #2 02-12-2009, 02:06 PM

Did you ream your glow plug holes when you put in new injectors?
Sometimes there's enough carbon in there to kill GP in short order.

Could also be a starter spinning too slow, low compression, poor injector spray pattern, bag GP relay or a host of other issues. I was lucky enough to replace my glow plugs only twice... after not reaming the first time.

tangofox007 · #3 02-12-2009, 02:13 PM

Sometimes the glow plug timer malfunctions and does not run for the proper length of time. When you turn the key from "Off" to "Run," how long does it take for your relay to open?

coachgeo · #4 02-12-2009, 02:14 PM

No did not ream them. Did not have time but.... they all came out easy indicating to me the thread area is clean. Also have checked resistance several times since and they all still show normal.

That and the additional miles on the car since the new plugs is less than 200 miles.

rrgrassi · #5 02-12-2009, 02:18 PM

Reaming the GP's is not for the threaded area, it's to clear the area for the tip.

coachgeo · #6 02-12-2009, 02:18 PM

I'm beginning to doubt it is glow plugs issue.

since it appears I had only one or two old glow plug working previously.. and car was starting ok at warm temps..... then even if a few new ones went out now... thats still more glow plugs than before and newer ones at that so at only 40deg it should still start. Lower than 40 sure... maybe not..... but at 40?? it should.

But they all show good resistance in the car. No they are not Autolights etc. Good new German plugs

Graplr · #7 02-12-2009, 02:30 PM

Maybe you can describe what happens when it does not start.

On my 'new' engine, it started fine this fall. Then when the temp started getting close to freezing it was having problems starting. It was fairly easy to diagnose it as the starter since it would start spinning and then stop with just a whhrrrrrrr noise. I replaced the starter and have had no problems since, even a completely cold start at -4F earlier this winter.

So, describe what happens when you try to start it both successfully and unsuccessfully.

Do you have a block heater? If so, have you tried it?

Things to consider when it has problems starting cold-
Glow plugs
Valve clearance
Oil weight
Starter
Battery
Fuel (air, clogged filters, gelling, etc)
Block heater
Compression

You seem to have ruled out GP and battery.

When was the last time you checked/adjusted the valves? The first winter I had mine my valves were adjusted improperly and I couldn't start it cold unless it was above 25F. I doubt this is your issue but worth checking.

My money is on the starter/wiring to the starter.

Once you have exhausted all options it is time to check the compression.

coachgeo · #8 02-12-2009, 02:33 PM

It is in the mid sixties right now. Car started with out flenching.

Tried it last night as it dipped below 40. NO START. It tried to but no go. Primed the fuel filter with the 12v last night too.. still no start

Might go home tonight instead of sleeping on the floor here at the office. Weather says lows just above freezing tonight though but warm to mid 50's by 9am. ........ hmmmmmmm...... nahhhhhh.... better not. I got to unlock and start projects here at the biz; and let the cleaning crew in by 10am...... tommorow morning..... dont think I'll risk getting stranded at home again. Home is 30 min drive from the biz.

coachgeo · #9 02-12-2009, 02:38 PM

Stater spins fine though at freezing and below it is a bit slower. Last night at 40 or tad below it was spinning nice and fast.

Oil weight hmmmmmm.... I use regular diesel rotella though nothing out of ordinary.

Valves. Adjusted them about 1500 miles ago or so. Car gets little to no use till the last 6 months when my daily driver went down. It just suppose to be for occasional use and eventually as a parts car for another project.

Block heater. To my suprise.... no block heater on this one.

coachgeo · #10 02-12-2009, 02:38 PM

BTW- thanks for the thoughts you folk are putting into this.

Graplr · #11 02-12-2009, 03:08 PM

So it spins and spins but won't start at 40F? How long do you let it try to start for? Does the battery die and need recharging?

If it spins and spins but won't start, I would think that would point to a glow plug, fuel, or compression issue.

Many have stated that the switch from dino to syn oil adds 15-20F of lower cold start point. I can't verify because I have only ran syn. But at 40F, oil should not be the limiting factor in keeping you from starting the car.

Since you seem to have ruled out GP and fuel, perhaps it is time to check compression. You can get a cheap kit at Harbor Freight-
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=93644

Although I would go back and double, triple, perhaps even quadruple check the GP system. Have you verified voltage at the glow plug itself?

coachgeo · #12 02-12-2009, 03:58 PM

Quote:

Originally Posted by Graplr

So it spins and spins but won't start at 40F? How long do you let it try to start for? Does the battery die and need recharging?...

Although I would go back and double, triple, perhaps even quadruple check the GP system. Have you verified voltage at the glow plug itself?

It tries to start.... does not just spin freely. Colder it gets the more it begins to kill the battery. I do let it spin while cranking while it tries to start but don't over due it so not to kill the starter.

coachgeo · #13 02-12-2009, 04:01 PM

next time its cold out........ think I'll try the bypass the relay again just as a diagnosis test. What I do for this is wire the harness to the glow plugs with jumpers tied together strait to the battery. Tried this earlier before switching out to the newer plugs. Think this might have killed some of the weak older GP's that were in there at the time though.

kerry · #14 02-12-2009, 04:44 PM

I'd do the compression test to rule out any low compression problems. Feeling the glow plugs can sometimes confirm if they are glowing. You can also detect their warmth with a non-contact thermometer. If compression and hot glow plugs are confirmed, I think fuel would be the next thing to test.
If you can video your cold start attempts and post them on youtube, someone may come up with a better diagnosis for the visual and audio experience.

moon161 · #15 02-12-2009, 05:09 PM

TDC temp depends on inlet air temp and TDC pressure, head temp. Consider your favorite cold start shenanigans: Hair dryers, block heaters, WD-40, inlet air heating w/ a blow drier, torpedo heater.

Check valve lash, can't take more than an hour to check each one. May as well take your tools to work, something to do while you spend the nite. Could be your problem. Once done, do a compression test. Do a leakdown test, your valves may be burned, or seats thrashed that would tell you.

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