Can't start! - Page 2 - PeachParts Mercedes-Benz Forum

kerry · #16 01-13-2012, 09:57 PM

You want to do the compression test to determine whether or not the adjusted valves improve compression.

whunter · #17 01-13-2012, 10:04 PM

If you can reach it with extension cords?

Get two of these.
Attach one to the oil pan, and the other to the passenger side cylinder block for two hours.
Then try to start it.

magnet block heaters.
https://www.google.com/search?q=magnet+block+heater&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US

fficial&client=firefox-a

Cold weather starting links

Emergency (starter failure) tow starting a gas or diesel engine with automatic trans
.

Brian Carlton · #18 01-13-2012, 10:15 PM

Quote:

Originally Posted by kerry

You want to do the compression test to determine whether or not the adjusted valves improve compression.

You'd need to do a compression test before the adjustment...........and after.

Why bother?

If the valves are really tight, you can bet the intakes are not allowing a complete seat in very cold temps...........and the odds are............nobody has checked them in years.

kerry · #19 01-13-2012, 10:18 PM

Quote:

Originally Posted by Brian Carlton

You'd need to do a compression test before the adjustment...........and after.

Why bother?

To answer the question, "Did I do anything or not?"

katja · #20 01-13-2012, 11:29 PM

What effect does injection pump timing (start-of-delivery) have on cold starting? I've read comments here & there that indicate that it would - for example, if you have over 200,000 miles on the engine & the timing chain is the original one and is somewhat "elongated" so fuel is injected too late in the cycle....I also remember seeing someone demonstrate a "timing advance" knob on an older VW diesel that would be pulled out for cold starting assist, so that makes me think that retarded timing would be bad for cold starts.

I know in my engine the compression is a bit low, but it started at 17 degrees a few winters ago with no problems, but it starts the same way at 40 degrees too - it turns over for a second or two (doesn't light off on the first rotation like it used to), the remaining cylinders start to fire within a few more seconds and needs about half throttle to stay running for about 15 seconds & misses, shakes & smokes a lot. Then it runs perfectly. I should also say that it will no longer start at 100 degrees (partly warmed engine) without the glow plugs connected, but all glow plugs do glow visibly orange when powered.

I have also heard worn injectors can cause cold starting difficulties. True?

Brian Carlton · #21 01-13-2012, 11:33 PM

Quote:

Originally Posted by kerry

To answer the question, "Did I do anything or not?"

Seems like a lot of work...........

If the intake valves are at 0..........you probably did help yourself a bit.

Brian Carlton · #22 01-13-2012, 11:37 PM

Quote:

Originally Posted by katja

What effect does injection pump timing (start-of-delivery) have on cold starting? I've read comments here & there that indicate that it would - for example, if you have over 200,000 miles on the engine & the timing chain is the original one and is somewhat "elongated" so fuel is injected too late in the cycle....I also remember seeing someone demonstrate a "timing advance" knob on an older VW diesel that would be pulled out for cold starting assist, so that makes me think that retarded timing would be bad for cold starts.

I believe the IP timing matters not in the slightest to effect a cold start. Even if the timing was very late, and the engine couldn't use the fuel, quite a bit of it will be still in the cylinder during the next compression cycle.

Many of the engines on the forum are running very late (6-10 degrees late) and the owners don't see any difference in day to day operations. They were not even aware of the late IP timing.

There was a fellow who started the engine with the timing 360 degrees out of phase with the crankshaft. The IP was injecting fuel at the top of the exhaust stroke. No real problem in starting it............but, wouldn't make any power and smoked violently.

whunter · #23 01-14-2012, 01:50 AM

Quote:

Originally Posted by KaiserChief

Long time reader, first time poster--but I know there are plenty of sagacious folks on this forum...

A cold snap just hit, and I forgot to plug in my block heater. Previously, my Benz didn't like to start when it was under about 40 degrees (had to hold the accelerator down after ignition to keep it running for 30 seconds) but now it's 15 out, and I can't get any ignition at all.

Battery is good, starter cranks fine (as far as I can tell). I plugged in my block heater about 6 hours ago, so that should've helped by now...?

I also tested the glow plugs and the relay--I'm getting 12v at the plugs, and the relay works fine. I even jerry-rigged a straight line from 12V+ to the glow plugs, bypassing the relay, and that didn't help either. The glow plug indicator light hasn't been working for a few days--I assumed it was a bad bulb, but maybe there's a systemic issue.

Finally, since I know fuel leaks can be an issue, I used the hand primer pump, and then loosened the bolt on injector 1 and cranked away--no luck. Frankly, I think less fuel was spurting after I tried this then when I used the same trick after replacing the fuel filter a few months ago.

I have not yet pulled the plugs...but again, it feels like 15F thanks to the wind, and the plugs check out electrically, so I'm hoping I don't have to.

Tips, pointers, complaints, or suggestions? Call our hotline at, er...here.

I disagree with the ohm testing theory, as anything but a vague (possible) indicator.

A new glow plug at 70° F is 0.7 ohm.
A marginal or bad glow plug can have any reading.
I have boxes full of used glow plugs that read correctly, but either do not glow or have random dull glow.
NOTE: I have many new glow plugs damaged by owners over torquing the 8 MM electrode nut.

Here is a simple graphic showing why the TIP must glow as hot as possible, NOT the element body.

READ THIS BEFORE TESTING.
Never Touch Hot Diesel Glow Plugs!!!

The pencil type are easy to test:
#1. Just pull each one.
#2. Trap the hex wrench flats with the heat element pointed inside the vice jaws.
#3. Use a car battery or charger to apply power.
#4. Attach ground to the vice body.
#5. Hold the positive to the threaded glow plug power pole.
#6. Fifteen seconds is more than enough for maximum visual display.
#7. If it glows like this, it's good.

#8. Use pliers or channel locks to handle HOT glow plugs, and have a METAL tray or can to put them in for cooling.
NOTE: Never quench hot glow plugs in water, it can cause a steam explosion and/or damage the glow plug. Other liquids (soap, oils, etc) can flash fire.
#9. Half an hour of cooling time, and you should be totally safe to reinstall any good used glow plugs.

My personal rule of thumb:
If it has difficulty starting 32° F and lower:
* Check the valve adjustment, and reset as needed.
* Remove the glow plugs.
* Ream the holes.
* Install new glow plugs.
* Glow test the old units.
* Junk the bad glow plugs.
* Give away any usable glow plugs to economic hardship customers.

Don't always trust your glow plug indicator light!

.

Yumeko-chan · #24 01-14-2012, 02:09 AM

Hmm, this would certainly explain why my car has a harder time starting in the cold than it used to. Good to know! One more thing for the list!