I have a 77 300d that I bought about 6 months ago. The engine needed some work(valve adjustment, filters changes, ect.) and I updated the out of style loop plugs for the pencil ones and that made a huge difference in start up time. However, over the past month or two it has become progressively harder to start where now it takes sever extended cranks (30 seconds or more) to get her started. Furthermore, once the engine has started and allowed to run/ get warm, restarting it is no problem. I live in San Diego so cold weather is not a factor, it can be 80 degrees out and this still happens. I replaced two injectors with the other three on their way, which made no difference, the glow plugs are new as stated above and I even went to far as to do a voltage drop over each one and they all draw a current, and Im assuming the compression is good since Im starting the car with it....

Please help!!

Also, i was thinking maybe its carbon build up in the pre-fire chamber where the glow plug sits? thinking about getting a reamer just to see.

 

You could use an Ohm Meter to check the Glow Plugs but you need to remove the Jumper Wires and check each individual one.

People have said that if the Previous Owner had neglected the Valve adjustment for an extended period and you adjust them after a few hunderd Miles they sort of wear/seat through the old deposits you need to recheck the Valve Adjustment.

It could be that the Valves in the Fuel Supply/Lift Pump or an Air leak is allowing Fuel to migrate back to the Fuel Tank when the car sits. Sort of losing its prime.

If you have the Old Style Hand Primer with the Shiny Aluminum body they are noted for causing Air Leaks when they get older.

 

The adjustment is fine i just rechecked it the other day. The new injectors seem to help the starting issue but I did notice when I was replacing the old injectors that the crushwashers had oil on them. I know that this is a symptom of worn piston rings, could this also be contributing to the starting issue?

 

Yes poor or marginal compression contributes to poor starting. Maybe it is time for a Compression Check.

Harbor Freight used to sell a Cheap Diesel Compression Tester but the price has gone up and they have more than one tester set to pic from. While most have done OK with this tester once in a while the quality control issues catch up with them.
I have one but have never used it so I cannot comment on the quality issue.

Also I don't remember if the Kit had a Fitting for the Glow Loop type Glow Plugs. That would mean that you would need to remove the Injectors and that would mean new Injector Heat Sheilds when the Injectors go back in.

Another way Oil can get into the Cylinder is through worn Valve Guides/Stems and Worn Valve Guide Seals.
The VG Seals don't cost much but there is some labor to the job. If you change them get good quality ones.

Another thing that can effect starting is if the Camshaf Timing is late due to Timing Chain Stretch/Gear Wear.
You can get a rough check of this by lining up the Timing Mark at the Rear of the Camshaft Gear with the Timing Mark on the Front Camshaft Bearing Tower; but do that exactly.
Then look down at the Crankdamper Degree Marks and see what the Pointer points to.

When your Engine was new it was liked up on OT (that is top dead center).
As an example at a little over tewnty thousand Miles My Engine as 2.5 degrees of late Camshaft Timing. That is normal for that amount of miles.
If you have 4 degrees or more there is offset Woodruff Keys to restore the Camshaft Timing. However, at that point you need to do what is called the 2mm Method to determine the exact amount and what Woodruff Key to use.
But, the rough check will give you some idea what is going on.

The below pic is a split one. The left is the Camshaft Gear lined up with the Timing Mark and the right side is a pic of the Crankdamper degree marks and Pointer. The Pointer is somewhere between OT (top dead center) and 2.5 degrees.

 

When using that offset key, keep in mind that chains only stretch so far before they break. Make sure that your chain isn't too loose in the links, and also make sure that the sprockets aren't worn so far that they are starting to "hook". A "hooked" sprocket will cause the chain to hang, and eventually break.

 

Concerning the Timing Chain Stretch issue and Timing Gear Wear.

There is no specs in the Manual on either to go buy.

The Majority of the People who Replace the Timing Chain (and the large Timing Chain Tensioner/Guide Rail) do nothing about the Crankshaft Sprocket or the Camshaft Drive Sprocket at all.

In theory it is not good to install a New Chain on worn Sprockets. The problem is there is no spec as to what is the wear limit other than a Visual Check and the Crankshaft Sprocket is the one that does the most work and is not easily seen like the Camshaft Sprocket is.

When I ask the question on another Forum what people though caused the Timing Chain failure most thought it was the drive end of the Vacuum Pump failed and the Pieces fell into the Timing Chain/Gears causing the Chain to Fail.
I also ask what they though caused the Vacuum Pump to Fail and they said it was either the Vacuum Pump had the old Bearing with unshielded ***** failed or the Timer had too much End Play (this actually killed a brand new Piston type Vacuum Pump). Or somtimes the Vacuum Pump bearing just failed.

 

Just another idea you may or may not have looked at is the starter and charging system. Given the high compression in a diesel ,especially when cold, if it's not spinning fast enough to compress the fuel she won't start.

 

Slow cranking speed can indeed be a cause of poor starting. However, where the Guy live in the Morning it is likely in the low 60 degree F range.

If I had not mention it He might want to check and see if His Fuel Supply System is putting out enough pressure during Cranking.