Give it the full glow - PeachParts Mercedes-Benz Forum

fruitcakesa · #1 10-11-2009, 10:05 AM

Always a 1 crank morning starter, in the the past few months, my 81 has gotten progressively harder to start.
I began to suspect a glow plug, but did nothing other than letting it crank more times until it caught, which it always has.
Time passed and then just this week, it would start after 6 or so cranks,
and idle more lumpily than normal with no power for a minute before I could drive off.
A little history. I think my tank vent is plugged and have done nothing about that other than vent the fuel cap now and then. But it has stopped me more than once on the road where I had to vent the tank and prime it to restart. I know, very lazy
2 nights ago, in rain and fog, I drove to my daughters soccer game about 50 miles away.the
It is a very hilly and curvy route, quite a pleasureable ride on a sunny fall day. As I rolled into Manchester I decided to get a creemee before the game. As I turned into a lot to get back to the store, the engine quit.
I hopped out, vented the tank and restarted lumpily but then it ran ok so I just went straight to game.
After the game , which we lost 4-3, it restarted lumpily but got me back home...whew.
Last night another game, this one close by.
Started the Benz lumpily, began to drive off but it slowly lost all power in about a minute and then quit on my steep driveway.
I backed down, refired it but it would not power up or idle. I tried a tank revent and got it to run barely so I parked it.
We went to game in the TDI and won that 3 zip.
This morning, the coldest yet about 32* , I had been reading glowplug threads and decided to take some advice from them.
I went out switched on and let the GP's cycle fully. Turned the key and it fired in 2 cranks and idled up within a minute!
So, methinks my glows are working but I will pull and test them all to be sure how well they actually work.
Also both fuel filters will get changed since it has been about 6 months and 4k miles since last change.
And lastly, the tank vent will be checked and cleared if need be.
I guess this rant is simply a reminder of how little things can sneak up on us if we don't listen to our car and check it out now.
And the full GP cycling for easier starting
I will post results.

aaa · #2 10-11-2009, 10:20 AM

Valves. When was the last time you did them?

fruitcakesa · #3 10-11-2009, 11:18 AM

<4k ago.

fruitcakesa · #4 10-11-2009, 10:07 PM

Replaced both fuel filters after noting that I did not change them when I bought the car so they have unknown miles and time on them.
Still have not checked the tank vent...tomorrow.
Definite leakage around the primer pump which I replaced with the new style 2 months back.
Full glow cycle tonight and it started with 2 cranks and idled much better with power to drive.
Supposed to be sub freezing tomorrow morn so I can give it a good cold start test.

Cr from Texas · #5 10-11-2009, 11:13 PM

Why would you not always give it the full glow?

Brandon_SLC · #6 10-12-2009, 01:59 AM

Quote:

Originally Posted by Cr from Texas

Why would you not always give it the full glow?

Exactly! You're supposed to be having a moment of silence in honor of Rudolph Diesel.

aaa · #7 10-12-2009, 07:07 AM

So, what exactly is a "full gp cycle"? They keep going for an entire minute. I just wait for the light to go out.

fruitcakesa · #8 10-12-2009, 08:05 AM

Quote:

Originally Posted by Cr from Texas

Why would you not always give it the full glow?

I do now!

Oldwolf · #9 10-12-2009, 09:29 AM

Quote:

Originally Posted by aaa

So, what exactly is a "full gp cycle"? They keep going for an entire minute. I just wait for the light to go out.

I want to know too.

#10 10-12-2009, 09:33 AM

In reasonable temperatures I use the light. If it's very cold (below 10-15F) I let it glow for the full 40 seconds before cranking. That seems to work for my cars (with good GPs and adjusted valves).

curtludwig · #11 10-12-2009, 10:54 AM

The fuel tank vent is pretty easy to deal with, I've been around the bend on this one before too (including one 50 mile drive at 45mph).
Under the car just aft under the driver's seat (IIRC, might be farther back) you'll find a plastic trumpet thing pointing down. It'll be clamped to a hard line, remove that and backflush with compressed air. If its really buggered run some water through. I'm always hesitant to use solvent on plastic... Easy peasy. I now do this every other oil change as a regular preventative.

In theory there might be a clog farther along the line and it might be worth blowing the line but I'm nervous about shooting whatever the clog is back into the tank...

fruitcakesa · #12 10-12-2009, 02:21 PM

Quote:

Originally Posted by curtludwig

The fuel tank vent is pretty easy to deal with, I've been around the bend on this one before too (including one 50 mile drive at 45mph).
Under the car just aft under the driver's seat (IIRC, might be farther back) you'll find a plastic trumpet thing pointing down. It'll be clamped to a hard line, remove that and backflush with compressed air. If its really buggered run some water through. I'm always hesitant to use solvent on plastic... Easy peasy. I now do this every other oil change as a regular preventative.

In theory there might be a clog farther along the line and it might be worth blowing the line but I'm nervous about shooting whatever the clog is back into the tank...

That was my first thought.
I crawled under today, but it was darkish and I really could not see much, and found a rubber hose sticking down just aft and to the inside of the rt rear wheel. It seems to be clamped to a hard line. I stuck a thin metal wand up it and it slid up the 18" length unobstructed. Is that the tank vent or is that the overflow tube for the filler neck?

Brandon_SLC · #13 10-12-2009, 03:56 PM

Those of us with the older systems have more time for paying respect. When the light goes out, so do the glow plugs. In extreme cold I let the plugs glow through 2 cycles. I did a diesel purge this spring, so I'll be curious to see how much easier the car starts this winter. Shortly before I bought my 240D, I know the valves were adjusted, and 2 injectors were replaced with rebuilt ones. (about 4k miles ago) I know that seems odd, but evidently 2 injectors were still within specs. Engine runs smooth and quiet now that I've performed the Diesel purge.

tangofox007 · #14 10-12-2009, 04:13 PM

Quote:

Originally Posted by Brandon_SLC

Those of us with the older systems have more time for paying respect. When the light goes out, so do the glow plugs.

It might be worthwhile to define "older."

Brandon_SLC · #15 10-12-2009, 04:37 PM

Older 123's had series conected loop style glow plugs up until sometime in late 79, I think. They were very slow to heat up enough to start your car. My car is an early 79 and has the series style slow plugs.

The newer "Pencile style" are wired in parallel, heat up much faster, and as far as I know, they keep glowing for some time after your engine starts, to help smooth out the lumps.