adjusted valves = hard to start - PeachParts Mercedes-Benz Forum

angst · #1 01-23-2011, 01:24 PM

84 300sd
setting intake 0.1mm
setting exhaust 0.35 mm
I'm no stranger to adjusting them. I've done it many times always with solid benefit to cold starts and more pep.
After meticulously going through them including using a check off chart it will hardly start after my adjustments. It will spin fast and even when you hear some combustion it won't go all the way. It will even start going and with the pedal to the floor stall out.
After I manage to coax a start out of it by plugging in and jumping with an additional battery it runs horrible for 30 to 45 seconds and I get much more white smoke than I usually have.

I pulled everything apart and went through all the valves a second time thinking that I had adjusted them too loose or set one wrong. Still no change.

Is something wrong with my feeler gauge mojo? Could I be using the wrong "feel" for how tight I should feel on the gauge.
I have always understood that its best to err on the side of too loose. My gauge can move in and out without hardly any resistance. Not enough space to wiggle though.

Could outside temps be messing the process up? It is 25f at night and 40f the times I was trying to start. The temp when I was doing the work was in the 35f to 45f neighborhood.

Is there something else that I might have knocked loose that is getting air in the fuel? Could I have changed something inadvertently in the throttle linkage arms? Do I need to re-examine how deep my foot is in the throttle pedal when I am doing a cold start?

Pulling my hair out here because the car was functional and dependable to start down below 30f before all this and I somehow have messed up a routine job.

Plugs test fine. Battery tests as 590cca (of 850) Even if the battery is a factor, jumping it off does not change the symptoms.

79Mercy · #2 01-23-2011, 01:41 PM

Well there is a possibility that it just so happens a GP or 2 burned out recently before you did the valves. You say they test fine, how did you test them? I recommend you pull all 5 and apply voltage to them to be sure, sometimes the OHM test is misleading. Also be sure that your relay is sending about 11V to each GP.

Also, are you sure you didn't reverse the feeler gauge measurements between the intake and exhaust valves?

angst · #3 01-23-2011, 01:58 PM

I used the attached chart that I found around here somewhere.
Confirm that this chart is a match for my car. It would totally make sense if the sequence is different and that is why things are screwy. The sequence matches what is in my Haynes book though.
I only tested the GP's by disconnecting the harness and then an ohm meter from the thread tip of each one to ground. 200amp fuse looked fine. Plugs are all 1 year old. Will dig a bit deeper into that and confirm that there is voltage to them.
The tangibles are too much of a match for electrical to be at the root though it would seem. 1. It was working fine 2. I fiddle with valves. 3. No start
Reversing my gauges isn't impossible but is probably very improbable. I used the print out and went through it all twice. Could the quality of my gauges be enough to take it this far out of whack? What about the outside temps?

billhard · #4 01-23-2011, 02:19 PM

Quote:

Originally Posted by angst

84 300sd
setting intake 0.1mm
setting exhaust 0.35 mm

I am pretty sure those are the correct figures, but you should have a tag in the engine compartment which you could double check on. I attached a picture of one from Diesel Giants tutorial so you know what it looks like, but it doesn't show specs for your car.

79Mercy · #5 01-23-2011, 02:22 PM

That is the correct chart for your engine.

I doubt the accuracy of your feeler gauges are causing the problem...

When you adjusted the valves, did any of the valves turn?? There has been problems in the past with burned valves and when you turn them they no longer seal against the head like they should... This is sort of a rare occurrence, however it could be the issue. To prove my theory to be valid you will need to do a compression test, and then a leak down test on the cylinders with poor compression.

I feel you should dig a bit deeper into the GP system first.... simple things come first.

josha37 · #6 01-23-2011, 03:07 PM

I know it might not be what you want to hear but when rigs come into the shop after being "repaired" and they have a problem now you ALWAYS look at the last thing that was messed with. You need to look at everything you had to remove to do the job but if it is turning over faster than you remember that is because you have less compression now. Start over act like you have done nothing and do everything by the book and fix whatever it was you accidently messed up.

angst · #7 01-23-2011, 04:07 PM

I agree joshua about suspecting the last thing that was messed with.
I will give electrical a once over too since it is a painless process to check that stuff and the battery is at about 80% of what it should be for cranking amps.

I wouldn't say that it is turning over faster at all.
I don't have any reason to believe I have something dire like burned valves since it was starting reasonably well before I messed with it.

Before I pull the valve cover for the third time someone talk to me about proper feeler gauge use. Tutorials always describe getting it to where you can move the feeler in and out with a 'light drag.' I am wondering if I am using the wrong flavor of light drag.

leathermang · #8 01-23-2011, 04:07 PM

Ditto the last posts...
it is easy to get the feeler gauge in the wrong place... just start from scratch and figure the order and the movement of the crank... or cam....and don't take any shortcuts...
probably something very obvious once you see it..

Stevo · #9 01-23-2011, 04:24 PM

It happens now and then that a little chunk of carbon gets between the valve and its mating surface. Its a good idea, before adjusting, to give the valve a couple turns back and forth with the spring exerting enough force to grind up any unwanted bit.

Daman858 · #10 01-23-2011, 04:44 PM

I would respectfully suggest that you make sure that you adjusted the valves by placing the feeler gauge between the cam and the rocker arm pad. There are those that have mistakenly placed the feeler gauge between the lifter and the top of the valve. Don't ask me how I know.
Also, make sure that the cam lobe is pointed to the sky.

See post #22 here Valve adjustment OM615, 616, 617 FYI.

First graphic- NO Second graphic-Correct

tyl604 · #11 01-23-2011, 05:03 PM

Please keep posting. Interested to see what eventually fixes it.

vstech · #12 01-23-2011, 05:46 PM

Quote:

Originally Posted by angst

I used the attached chart that I found around here somewhere.
Confirm that this chart is a match for my car. It would totally make sense if the sequence is different and that is why things are screwy. The sequence matches what is in my Haynes book though.
I only tested the GP's by disconnecting the harness and then an ohm meter from the thread tip of each one to ground. 200amp fuse looked fine. Plugs are all 1 year old. Will dig a bit deeper into that and confirm that there is voltage to them.
The tangibles are too much of a match for electrical to be at the root though it would seem. 1. It was working fine 2. I fiddle with valves. 3. No start
Reversing my gauges isn't impossible but is probably very improbable. I used the print out and went through it all twice. Could the quality of my gauges be enough to take it this far out of whack? What about the outside temps?

?? 200AMP fuse??

layback40 · #13 01-23-2011, 05:54 PM

First thing to realize is that as long as you have some gap the motor will start & run. On a number of occasions i have set valves on a 617 by feel; no feeler gauge. It will have a rattle if they are too loose.
Your problem doesnt sound like valves. The OHM test for GP's is about as useless as an eye test while wearing sun glasses. It will tell you if they are definitely bad, but not if they are good. Pull the GP's & test them properly by watching them heat up. Its the ONLY way to test to see if they are good. If you reconect them while they are out & turn the ignition on you can see if the GP relay etc is good.
You may have disconnected something on the IP when you took the valve cover off.
Good Luck.

angst · #14 01-23-2011, 06:04 PM

Quote:

It happens now and then that a little chunk of carbon gets between the valve and its mating surface. Its a good idea, before adjusting, to give the valve a couple turns back and forth with the spring exerting enough force to grind up any unwanted bit.

Are you saying that prior to adjusting that I should put a wrench on the big nut on top of the spring and wiggle it back and forth a few times to settle things in?

Quote:

make sure that you adjusted the valves by placing the feeler gauge between the cam and the rocker arm pad. There are those that have mistakenly placed the feeler gauge between the lifter and the top of the valve.

Check. Did have the correct spot. Was holding the gauge with my left hand and coming at it from the passenger side and sliding it under the cam lobe.

Quote:

Also, make sure that the cam lobe is pointed to the sky

Hmmm. It wasn't. More like 1 o' clock. Or to describe another way -just to the drivers side of pointing straight up. My Haynes book says... "with the lobe positioned opposite the arm as shown in the accompanying illustration"
All the pics in the manual have it closer to one o clock also.
Some of them I may have had the lobe closer to 12 o clock when adjusting but the cam is going to be dead round on the underside in that neighborhood either way, right? or perhaps this is the problem.

Tonight I put a new filter in my goldenrod big spin on filter. Old one had a fair bit of black on the pleats. Topped off diesel at a known station. Will continue diagnosing in the morn with a cold engine to work on.

Still keen to hear if I may be doing things wrong in terms of "slight drag" with my feeler gauge, or if it feels anything similar to this then it is fine.

layback40 · #15 01-23-2011, 06:10 PM

"4K miles on veggie blends with kero and DinoD no mods. 10K miles on flatplat heat exchanger and various diesel/veg blends."

I think that I have just found the problem.
You probably have stuck rings.
Maybe another case of "Death in a Jug"
There is the alternate fuels sub forum, maybe some one there can help you.