Glow plug wear question

I am sure this is an easy question for most of you, but I am here to learn, so that hopefully if I can ever retire, I will be able to work on diesels:

With regard to glow plug 'wear', what actually causes the wear--the starting cycle (my understanding is this is the only time they 'glow')? Is this why truckers, ect...leave their diesels running while at rest areas? More miles doesn't necesarily translate to glow plug wear does it?

Just want to know so that I can stretch the plugs' life as long as possible, as it seems to be an ordeal to change them on my car.

[P.E.Haiges]

Glow plugs (GP) are like lightbulbs, they get a little dimmer with age and eventually burn out.

Most trucks don't have GP because they have direct injection but some do have manifold heaters for cold starts.

I thought the truckers left the engines running to get heat in the sleeper cab.

The only way to increase the life of a GP would to use it less, as with a light bulb. But it would be a false economy to let the engine idle for long periods to try to increase the life of the GP.

I've driven MB Diesels for about 30 years and 1/2 million miles and only had to replace about 8 GP. The cost was miniscule.

Some here recommend replacing all the GP if one goes bad. I do not agree with theory. If I had done that, over the time I have driven MB Diesels I would have had to purchase about 35 new GP which would have cost more than $400.

I just replaced a GP yesterday because 300SD wouldn't start. Actually 2 were bad and they were in sequence in the firing order. But replacing one corrected the starting problem so I will wait until it gets warmer to replace the other one. I have some used GP in a parts engine that I will transfer for the other bad GP.

I learned here that there is some analysis that the GP circuitry does on the GP in #1 cylinder. So I put the new GP in #1 and moved that GP to replace the bad GP in #5. I suggest this be done if only one GP is replaced.

P E H

[sixto]

Originally posted by P.E.Haiges
I just replaced a GP yesterday because 300SD wouldn't start. Actually 2 were bad and they were in sequence in the firing order. But replacing one corrected the starting problem so I will wait until it gets warmer to replace the other one.

Why not wait until it gets cold again to replace the last glow plug?

In the case of the 606, I think what accelerates wear is the after glow feature or continuing the glow process after the engine has started. It might be possible to disable the after glow timer relay but I don't know how the engine will perform until it warms up.

Compared to the earlier Diesels, I understand the 606s have a ridiculously short glow plug life. Something like 40K miles in some cases.

Sixto
91 300SE
87 300SDL
83 300SD

[leathermang]

"I thought the truckers left the engines running to get heat in the sleeper cab."

LOL... yes , when cold that certainly works.... when hot you can run the ac.... but I think other factors are more important ....

1. Diesels use an amazingly small amount of fuel to idle... like 1/80th what a gas engine does... so it is very cheap to let them idle...

2. A big percentage of wear on internal combustion engines happens when the engines are started, because there is more tolerance before the parts are the correct temperature....

3. It would not be uncommon for a big engine starter to cost more than $250.... so the less you use it the better....

4. If it is cold you take away the chance you won't get the engine started in the morning and don't make your deliveries on time.

5. I take this one out because it has been since 1975 since I worled for the Katy Railroad.... LOL....looks like they are more adaptable to fuel prices now....

[Wasuchi]

The Diesels in locomotives are shut down when fuel prices are this high, at least when they are going to sit somewhere for a while. Many of them have a small engine now to keep them warm because they automatically dump their water (coolant) when they reach a certain temp. (45 I think) Of course this solves the problem of them getting cold too. Some of the older ones will start puking their oil out the exhaust if the idle long enough to cool down much (ever seen one that's gunked up with oil, nasty).

[P.E.Haiges]

Sixto,

I noticed the '79 300SD ran rougher than the '80 when cold. Probably because it had one bad GP. The glow plug light only workes intermittantly but I did notice it would blink once in a while when I was away from home. So I will replace the 2nd dead GP to see if the rough cold idle smoothes out. Also that way I won't have a no start condition if another GP goes dead.

The GP are much easier to change on the 5 cylinder compared to the 6 cylinder engines. I looked at my 300SDL engine and I couldn't even see some of the GP buried under the intake manifold. Those are some GP I might replace with new ones even if not bad, if I ever had the intake manifold off.

What surprised me was the 2 dead GP causing a no start condition and replacing one of them made the engine start almost instantly. I would think it would still start if 3 GP were working.

P E H

Thank you all for the responses. $250 for a starter for a big rig? I bet one for mine is more

[sixto]

Originally posted by P.E.Haiges
What surprised me was the 2 dead GP causing a no start condition and replacing one of them made the engine start almost instantly. I would think it would still start if 3 GP were working.

The glow plug wiring isn't straight forward parallel. There's a dependency on #1 or #5 such that if that one isn't drawing the right current the others don't work properly. I don't remember where I read it but it was very confusing to me.

Sixto
91 300SE
87 300SDL
83 300SD

[P.E.Haiges]

Sixto,

It was the #5 GP that was bad that stopped the engine from starting. As soon as I replaced #5 the engine started immediately (with GP warmup). I couldn't believe how much difference replacing 1 GP could make. So maybe it is #5 that is anaylyzed by the GP circuitry.

Since it was warm on SAT, I replaced the bad GP in cylinder#3 and it does run smoother at startup.

P E H

[R Leo]

Fuel prices are certainly a shutdown driver but earlier large diesel powerplants such as the EMD 567 and 643 series engines were notorious coolant leakers. So much so that if they were shut down any length of time they would invaribly fill one or two cylinders with water.

From the EMDs Operation Guide for the F-3 (a 1940s-50s era loco equipped with a 567) freight locomotive (check out step #7):

Starting Engines

1. Close all switches in distribution panel.
2. At engineer's station close "control" and "Fuel Pump" switches.
3. Place independent brake in full "application" position.
4. Set "PC" switch.
5. BE SURE REVERSER LEVER IS REMOVED FROM CONTROL STAND.
6. Check engine lube oil and water levels and oil level in governor and air compressor.
7. If engine has been shut down more than 2 hours, open cylinder test valves, pull layshaft closed and press "START" button on engine control panel. Crank engine over a few revolutions and release. If water was discharged from cylinders investigate, if not, close test valves and proceed.
8. Turn on fuel pump switch and check for fuel flow through sight glass on fuel filter nearest engine (mounted on right front of engine).
9. Check setting of overspeed trip (Pull to set).
10. Check governor oil alarm trip button.
11. Hold layshaft 1/4 open.
12. Press engine start button until engine starts (Not more than 15 seconds).
13. Place isolation switch in "Run" position (Down).
14. Check oil pressure
15. Check ground relay.
16. Check starting contactor interlocks.
17. Allow engine to idle until water temperature comes up to green area on gauge before working the engine.
18. For Starting troubles (see Art. 1110).

Later 645s and now the 710 series primemovers have solved coolant leakege to the point that they can be shut down and restarted with relative ease.

Regards all,
Randy Leo