79 300 sd, hard to start..HELP - PeachParts Mercedes-Benz Forum

linda ann · #1 09-17-2007, 06:50 PM

hi all! please help. my 79 300 sd, 116 has glow plugs about 1 1/2 years old (life expectancy?) and will only start with a shot of "quick start" even though it is 80 degrees here. after it starts and runs for a while it will continue to start for maybe up to 2 hours, after that it's back to the "quick start Stuff" which can't be good. any ideas as to the problem, as i am really bummed not being able to drive my baby and leave it sit for any length of time due to fear of being stranded. thanks to all in advance linda ann

Wodnek · #2 09-17-2007, 06:54 PM

Does the glow plug light seem to function correctly? (no flashing) If the light flashes try replacing just number one glow plug. (front one) If you have to replace them be sure to get bosch, not champion.

linda ann · #3 09-17-2007, 07:31 PM

no flashing on glow plug, seem functioning, thanks

hangit · #4 09-17-2007, 07:44 PM

Here's a link to Diesel Giant and glowplugs. http://www.dieselgiant.com/glowplugrepair.htm.

Hope this will help diagnose your problem.

John

fahrgewehr2 · #5 09-17-2007, 07:53 PM

Even without glow plugs that car should start up with extra cranking in 80 degree weather. If the engine is healthy. I would think a little extra cranking would be preferable to 'quick start'.

linda ann · #6 09-18-2007, 11:09 PM

thanks to all, and thanks for the link... extra cranking does not help, have tried till battery gets weak and it's a new battery. someone told me it could be the fuel distributor, would that be the next step? thanks in advance, linda ann

rs899 · #7 09-19-2007, 08:49 AM

I would thouroughly check out the glow system first.

Is the fuse intact on the glow plug relay? ( pull the cover on the black plastic box on the front side of the driver's inner fender) I would check this and do the diagnosis on all the gps first before looking anywhere else.

Bosch glowplugs have a very long life ( no so with Champions) and if you changed them last year enough of them are probably good enough to start. Relay is next most likely failure.

Rick

Mike D · #8 09-19-2007, 09:36 AM

Diesel engines require three things to start and run. Compression, fuel and air, in THAT order.

First things first. What are the compression readings?

Should be a MINIMUM of 275 p.s.i!!! A "good" engine will have apx 300 p.s.i. If you don't have sufficient compression no amount of "glowing" or cranking will make any difference.

Without knowing the compression of your engine (and I'm guessing it is on the low end of the scale due to the "compression in a can" starts) any advice we give you is worthless.

Wodnek · #9 09-19-2007, 10:22 AM

If you dont have a way to check compression, then pull each glowplug and use an oil can to squirt some motor oil in each cylinder. Reinstall glow plugs and try to start. The oil will help the rings seat to build compression. This is the only way I can get mine to start for the first time each year.

Whiskeydan · #10 09-19-2007, 11:27 AM

Linda Ann, Do you have a voltmeter or, even a 12 volt test light to perform some very simple test?

Get one of these and we can do some testing of the Glow circuit.

http://www.autozone.com/az/cds/en_us/0900823d/80/17/3b/bc/0900823d80173bbc/repairInfoPages.htm

t walgamuth · #11 09-19-2007, 02:16 PM

Quote:

Originally Posted by Mike D

Diesel engines require three things to start and run. Compression, fuel and air, in THAT order.

First things first. What are the compression readings?

Should be a MINIMUM of 275 p.s.i!!! A "good" engine will have apx 300 p.s.i. If you don't have sufficient compression no amount of "glowing" or cranking will make any difference.

Without knowing the compression of your engine (and I'm guessing it is on the low end of the scale due to the "compression in a can" starts) any advice we give you is worthless.

Actually compression readings as low as around 220 are acceptable. I don't think linda has glow function.

Linda, you need to get this fixed. Using ether is very not recommended. YOu can blow your head gasket or break a piston!

Tom W

linda ann · #12 09-19-2007, 11:51 PM

ok... glow plugs are fine..compression is the problem, where do i start, how costly is this and is it a diy project? or is it time to start parting out my baby???

thanks to all!!!!

linda ann · #13 09-20-2007, 12:38 AM

also.. one more thing and i'm probably answering my own question here... but i DO have a slight oil leak and need a oil pan gasket, could this be enough to throw my compression off ??? thanks again!!!

rs899 · #14 09-20-2007, 06:49 AM

No, oil pan gasket and oil leaks have nothing to do with this.

You are giving us tidbits of information. It is a lot easier to help if we know the whole picture.

1. How many miles are on this engine? Does the car burn a lot of oil ( a lot of blue smoke)? What has been the history of the starting problem? Has the car gotten progressively harder to start over time, or was this a sudden problem? Is the starter spinning quickly?

2. How did you test the glow plug system? What did you check? In an earlier post you noted problems with what seemed to be the relay....

3. What are the compression readings? How did you test ? Have you adjusted your valves to make sure they are in spec ( and closing at the proper time increasing compression)?

4. How many times have you had to use ether to start the car?

Rick

Whiskeydan · #15 09-20-2007, 09:22 AM

Quote:

Originally Posted by linda ann

also.. one more thing and i'm probably answering my own question here... but i DO have a slight oil leak and need a oil pan gasket, could this be enough to throw my compression off ??? thanks again!!!

Only if you've let her run with little or no oil.

How dd you determine the glow plugs are working?

When was the last valve adjustment performed?