Need wisdom - PeachParts Mercedes-Benz Forum

DeltaDave · #1 11-04-2005, 05:11 PM

Okay, here is the deal , the 240D I've had since May doesn't like to start when it is cool (less than 50F) outside. It seens to spin slower than my 300D. I replaced the alternator and the battery checked good. I haven't adjusted the valves yet. Also even when warm it smokes a little, makes me think injectors are a little mucked up. I did check the glow plugs earlier and their resistances check OK. What are the odds that it is the valves or starter or maybe injectors with bad spray pattern ?

TX76513 · #2 11-04-2005, 05:13 PM

How is your compression Dave?

DeltaDave · #3 11-04-2005, 05:24 PM

I haven't checked it yet. But if it was low the engine should turn over faster right ? Wonder if the 240D starter is less powerful than the 300D starter proportionally. My 300D really spins fast, the 240D maybe spins at 2/3 the speed.

t walgamuth · #4 11-04-2005, 05:29 PM

plugs are working? when it does start does it buck and smoke light blue?

then the starter... it should spin faster. as fast as your 300. i would check the grounds. check and clean battery cables, ground to chassis and engine to chassis grounds. then if still not sure, sometimes an extra ground from bat to a starter bolt will do the trick.

yeah if the starter is ok then low comp will let it spin a littel faster.

tom w

Brian Carlton · #5 11-04-2005, 05:35 PM

Firstly, please describe on how the battery was checked............was it done under a proper simulated load?

Then, if the battery is definitely OK, it's time to check all the cables from the battery to the starter and from the engine block to the frame. After 20 years they get a bit of corrosion behind them and this increases the resistance to current flow.

If you are sure the battery and cables are all OK, then the starter itself becomes the culprit. Some starters have a lower output after 20 years of use. Just can't convert the juice to torque as efficiently as when they were new.

With regard to the injectors, it would be a benefit for you to send them to a fellow and have him check them. One of our members does this for $3.00 each. It's a heck of a deal and you will know, for sure, what the status is. Four of mine were perfect. One was NG. He's listed under "tool rental program" at the top of the first page of DD.

DeltaDave · #6 11-04-2005, 05:36 PM

It bucks a little when it starts, mostly whitish/ slightly blue smoke I think. Would tight valve clearances make it hard to spin ? The starter connections are oily looking. I'm just trying to decide if I should go after starter stuff or valves first :-)

DeltaDave · #7 11-04-2005, 05:39 PM

I had the battery checked at an Advance Auto. Their tester puts some kind of load on it.

Brian Carlton · #8 11-04-2005, 05:45 PM

Quote:

Originally Posted by DeltaDave

I had the battery checked at an Advance Auto. Their tester puts some kind of load on it.

They have a decent unit AFAIK. If the battery passed that check, then the cables should now be removed, cleaned, and reinstalled. Don't forget the ground strap.

Brian Carlton · #9 11-04-2005, 05:47 PM

Quote:

Originally Posted by DeltaDave

It bucks a little when it starts, mostly whitish/ slightly blue smoke I think. Would tight valve clearances make it hard to spin ? The starter connections are oily looking. I'm just trying to decide if I should go after starter stuff or valves first :-)

Tight valves won't affect the cranking speed. I don't think it will affect the capability to start, either. The risk of tight valves is burning one of them if they fail to fully close when the engine is very hot.

RAYMOND485 · #10 11-04-2005, 07:09 PM

1984 300d Turbo
Replace Your Starter Easy Diy On 240d Replaced The 300d Starter
Have To Lower The Trans 2-3 In It Will Spin Faster And Fast
Start

t walgamuth · #11 11-04-2005, 07:24 PM

and bucking for a while on startup= glow plug issues....usually.

you may also have the starter issue though.

tom w

boneheaddoctor · #12 11-04-2005, 08:49 PM

Cranking the engine way too long without allowing the starter time to cool of is a leading casue for starter failures...

MS Fowler · #13 11-05-2005, 05:42 AM

After reading all this, I would still suspect the glow plugs. I have read posts from other members that even though the resistances looked good, the engine started better after replacing them.
The other item is the starter. A diesel needs to spin quickly to create the heat required for combustion. If its not the battery, then check every connection and finally the starter, itself.
Valve adjust can affect starting. If they are too tight, they will leak pressure which will lower the temperature of the compressed air and make it harder to start.
You may have a situation where each of these is just a little marginal. The combined effect is greater than any one of them would be.
My (former) 240 would start without any problem, or use of the block heater, until the temps dropped below freezing.

Brian Carlton · #14 11-05-2005, 07:40 AM

Quote:

Originally Posted by MS Fowler

If they are too tight, they will leak pressure which will lower the temperature of the compressed air and make it harder to start.

Kindly explain this in more detail.

If the valves are too tight............let's say an exhaust valve has a clearance of .007" when the spec is .014"...............the valve will fully close. In fact, there must be some warming of the valve stem before the .007" goes to .000" and the valve then begins to remain open.

So, I'm not following how a tight valve would affect start. Naturally, I make the assumption that the valves still have some clearance............they are not neglected to the point where the valves have zero clearance when cold.

bullwinkle · #15 11-05-2005, 09:55 AM

I can testify from personal experience that cranking speed is EVERYTHING on starting these cars-my 300D has had a gradually failing battery that I replaced just this past week-it would start fine if warmed up or driven every day-but let it sit and cool off below 55 deg F, it would have to run multiple glow cycles or it just wouldn't get up enough speed to start. I took it to an AutoZone-they initially tried a handheld tester(thought it was OK) but the big computerized one said it was bad. Bought a new Duralast with a 7yr prorated/2 yr free replacement 925 CCA battery, and now she starts like my Dodge Cummins-its been going bad the whole time I've had the car! Only $65.99 too-the old A.Z. saves the day again(just don't ask them to troubleshoot anything difficult).