Cold start issues - 617 - Page 2 - PeachParts Mercedes-Benz Forum

layback40 · #16 11-21-2010, 07:07 PM

You have 5 parallel paths to earth. They are all joined at the relay, you should have got the same reading on each. Just pull them out & test them properly.
There is nothing special about the .8 ohm reading, it is not proof that the GP's are good. They can have that resistance but not be heating the tip. I have 1 that did that .

#17 11-21-2010, 07:09 PM

Quote:

Originally Posted by layback40

You have 5 parallel paths to earth. They are all joined at the relay, you should have got the same reading on each. Just pull them out & test them properly.

That's probably the best way to do it, but I don't bother unless I'm still having a problem after checking the individual resistance (separately) and replacing any bad GPs.

kerry · #18 11-21-2010, 07:15 PM

Quote:

Originally Posted by Craig

That's probably the best way to do it, but I don't bother unless I'm still having a problem after checking the individual resistance (separately) and replacing any bad GPs.

That's my practice also.

JHZR2 · #19 11-21-2010, 07:46 PM

Yeah, I'll try it at the relay tomorrow and see what I get. I have a few beru gps in the basement that I could use, even if I don't swap them all. I'd like to pull all and ream, but we will see what the weather does...

Biodiesel300TD · #20 11-21-2010, 07:57 PM

If you decide you need one or two new ones, I have a couple of new in the box pencil styles that I don't have a car for anymore. I'll make you a deal.

I've also never had luck reading the ohms on the GPs. I pull them and give 'em 12v.

#21 11-21-2010, 08:23 PM

My good ones usually read between about 0.5 and 1.0 with a cheap digital meter. The bad ones usually read infinity. If you are unsure of the readings, pull them out and test them.

vwnate1 · #22 11-21-2010, 11:07 PM

Quote:

Originally Posted by JHZR2

Mentioned it at the top. Valves adjusted within last 2k, injectors pop balanced and cleaned within 500. Starting funniness and shaky idle existed before injector job - had hoped it would help...

So you did ~ this is what I get for ' skimming ' your original post before replying , I'm sorry .

Anyways , I cheat and use my cheapo $19.95 Harbor Freight infra-red thermometer to test them as that beats touching them and getting 2nd. degree burns on your fingertips

.

If even one heats less than any of the others , I toss in a full set as they're all the same age (except in junkers , Barrio Bombers , Ghetto Hoopty rides and veggie-oil freak cheapo wagons) , this has worked out fine for me so far .

Interestingly , the ones I watched being bench tested with a good battery , glowed white not just red or orange .

I cold started my Coupe to-day and , barely touching the throttle , it lit off *instantly* but wouldn't idle even after I'd held it @ 1,800 RPM's for 35 ~ 40 seconds , I let off the throttle to open the gate and it shook like a paint mixer
SO badly , I was afraid it'd shear off the air cleaner rubbers again (I just replaced them and the 'T' bracket last time I drove it) so I killed the engine and opened the gate then re-started it and backed out , keeping the RPM's to 1,000 by gently touching the throttle with one foot whilst t'other worked the brakes .

Old tech cars ~ whatter' ya gonna do ?

.

I still love this old Mercedes more than anything else I've ever owned and so flexing my habits to make it happy & run well , is a no brainer trade off to me ~ just like waiting 15 seconds for the tranny to fully take up before revving it up to move .

JHZR2 · #23 11-22-2010, 10:14 AM

Did the go test via the harness... All are 0.6 ohm except one which read 0.5 ohm.

Seems that I'll need to pull them.

I'm going to adjust the rack dampener a bit to aide in starting...

#24 11-22-2010, 10:26 AM

Quote:

Originally Posted by JHZR2

Did the go test via the harness... All are 0.6 ohm except one which read 0.5 ohm.

Seems that I'll need to pull them.

I'm going to adjust the rack dampener a bit to aide in starting...

That sounds good, I would pull them for a test anyway. If you are confident that your valves are properly adjusted; how are your fuel filters, air filter, and injectors?

JHZR2 · #25 11-22-2010, 11:11 AM

Valves are properly adjusted, car runs like a top and returns 29 MPG fairly easily. Filters are all good. No issues with power or operation once it is running... It is just the 30 seconds before the stable idle and operation is established...

#26 11-22-2010, 11:20 AM

The rack damper might be an idea, I believe having it turned in too far can cause hard starting but I've never had that issue.

Do you know if your compression is OK?

ConnClark · #27 11-22-2010, 11:51 AM

Glowplugs can fail in a short mode too. This should blow the fuse but if it doesn't the one that shorts can hog current from the others by dropping the voltage across them. Try replacing the 0.5 Ohm one.

DieselGiant has a good write up on glowplugs

JHZR2 · #28 11-22-2010, 11:55 AM

Yeah, I just know that I messed with it to get rid of a subtle engine shake at idle, which didnt really go away anyway... Even after changing engine shocks...

JHZR2 · #29 11-22-2010, 08:10 PM

Well I did an experiment and backed out the rack damper cold by maybe 1/2 turn. Started and after just glowing through the light, it caught first cylinder like I'd expect, though it shook hard and stopped after a few seconds.

I backed it out a bit more and it started right up, much less shake, though it had already been glowed once (did it a shorter time the second try).

So I'm thinking it may be rack damper.

More to note in a few minutes...

JHZR2 · #30 11-22-2010, 08:30 PM

One thing of interest is that I have a gold damper bolt head, but my startup characteristics can be expressed very simarly to this:

http://www.peachparts.com/shopforum/showthread.php?t=136219&highlight=Rack+dampener+start+idle

Post number 13 especially.

Also, I noted that my car really stinks when starting. Now, I've had w123 cars for almost 10 years now and at least 100k miles. I know diesels stink, but what I get is no consistent appreciable smoke, just really bad smell...

Which I'd think would relate back to a bad GP, though they all test ok via the harness.

I'm going to pull all and test/replace. Any suggestion what size drillbit to use since I'll not be able to get the tool before the weekend, when I'm hoping to do it... Or Wednesday if I find time...

Thanks!