Cold start issues - 617 - Page 3 - PeachParts Mercedes-Benz Forum

ROLLGUY · #31 11-22-2010, 09:17 PM

My experience with adjusting the rack damper is that the idle speed needs to be lowered with the adjusting screw on the back of the IP FIRST, before making any adjustments to the rack bolt. That way the governor is acting on the rack bolt and not the idle speed adjustment. If the idle is too high, adjustments to the rack damper bolt don't change the idle condition. Just my .02
And yes, pulling all the GP's to test with 12 volts is the best way. I hold the GP in the - of a jumper cable clamp while touching the threaded part (that the wire connects to) with the + clamp.

JHZR2 · #32 11-22-2010, 10:11 PM

Thanks, yes, when I adjusted my rack dampener last time, I backed off the idle screw, but it kept dropping so low that the engine would have shut off if I had let it any lower. I did let it out to be as slow as possible before adjusting.

I had the screw way in because I couldnt get the shake to stop at full temp in the summer. I think that now that it isnt the summer (and I dont drive the car all the time), it is just coming to show itself as hard starting. Even if I have to do it again in the real cold of winter, so be it. Im just afraid that letting it out too much is going to make the shake worse again...

I highly doubt that the gold rack damper is shot at 162k, but maybe this is the case... or maybe the PO put a used one in... Perhaps I need to look through all the old receipts...

JHZR2 · #33 11-23-2010, 12:00 AM

After the car sat for a while, we started it because the wife had to take it out.

Same deal... no misfires this time, but still let it glow, cranked to where it seemed to catch, and then instantly dead after I let the key off.

However second try it started beautifully... What gives?!?

Also sounded like it was searching for an idle speed, not really an oscillation on the tachometer, but you can hear a changing pitch associated with a changing engine speed (very slight change).

barry123400 · #34 11-23-2010, 08:36 AM

Well at the risk of suggesting you to do things that may make no difference. Pump the primer pump quite a few times before trying to start. Your situation sounds a little like not enough fuel is available when cold and after sitting quite awhile.

If this produces no results. Check for injection pump overflow fuel when cranking the engine cold after sitting quite awhile. Again. you might be experiencing fuel drainback to some extent.

If the problem is still present after clearing that area I would consider a compresson check.

biopete · #35 11-23-2010, 09:01 AM

Its a hell of a lot of work to pull a glow plug out just to test it. There is a better way i was clued in on in a post somewhere on this forum. And my friend even made it simpler.

First pull the glow plug wire from relay. See if you are getting voltage at all the pins on the relay. Good.

Next if you have a meter, go ahead and check resistance on pins of plug. Should be around .8 ohms , no more than 1.2 or 1.6 or whatever the manual says. My experience is a blown one will be infinite or way above 2 ohms. But regardless, this test is not always one hundred percent accurate so go on to the next test. Its better than nothing if all you have is a ohm meter.

Next *Instead of pulling glow plugs and watching them get hot* , put a jumper wire from battery and touch it to each pin on plug. See if you get a good spark. If it does, its drawing current good and hard which means it should get hot. That's my friend's dead simple way to test glow plugs. He's an electrical engineer.

If you want to get fancy , buy a cheap ammeter that measures 25 amps at least. I got a meter that is for dash mounting at Harbor Freight for like $5.00 or something. I put a long wire with clip that goes to the battery on the B+ term and a wire on the other term. Strip the end of the other wire and stick it in a glow plug pin on the plug harness. A good glow plug draws 20 to 25 amps.

Thats it. No need to pull glow plugs. My understanding is it is physically impossible for plugs to not get hot if they are drawing the right amount of amps. I'm no electrical engineer though.

ROLLGUY · #36 11-23-2010, 11:12 AM

Quote:

Originally Posted by biopete

*Instead of pulling glow plugs and watching them get hot* , put a jumper wire from battery and touch it to each pin on plug. See if you get a good spark. If it does, its drawing current good and hard which means it should get hot. That's my friend's dead simple way to test glow plugs. He's an electrical engineer.

If you want to get fancy , buy a cheap ammeter that measures 25 amps at least. I got a meter that is for dash mounting at Harbor Freight for like $5.00 or something. I put a long wire with clip that goes to the battery on the B+ term and a wire on the other term. Strip the end of the other wire and stick it in a glow plug pin on the plug harness. A good glow plug draws 20 to 25 amps.

Thats it. No need to pull glow plugs. My understanding is it is physically impossible for plugs to not get hot if they are drawing the right amount of amps. I'm no electrical engineer though.

You have a very good point there. That seems like a fool proof way to test the glow plugs, and I will employ it next time I need to test them. If it is not done already, please post the information somewhere on this site so others can benefit from it. Thanks for the great information!!

kerry · #37 11-23-2010, 12:26 PM

That does seem like a reasonably good test. However, I have seen significant differences in how glowplugs glow. Some glow dull orange slowly. Others glow bright orange quickly. I'm pretty sure that makes a difference in the temperature of the combustion chambers.

vwnate1 · #38 11-23-2010, 02:08 PM

And is why I suggested using an infra red thermometer....

It tests with no ambiguity and you don't even get your hands dirty....

These cute little devices are cheap @ Harbor Freight , mine is several years old and still going strong .

JHZR2 · #39 11-27-2010, 09:43 PM

Per my other thread, pulled/replaced the glowplugs, and while I was at it did a cold compression test. I didn't have the time/ timing right to do it hot. I got:

Cyl 1 380
Cyl 2 385
Cyl 3 375
Cyl 4 355
Cyl 5 375

Not sure if I had a slightly poor seal on #4, there is an issue, or it is just a valve adjustment issue...

dieseldan44 · #40 11-27-2010, 10:20 PM

Quote:

Originally Posted by JHZR2

Per my other thread, pulled/replaced the glowplugs, and while I was at it did a cold compression test. I didn't have the time/ timing right to do it hot. I got:

Cyl 1 380
Cyl 2 385
Cyl 3 375
Cyl 4 355
Cyl 5 375

Not sure if I had a slightly poor seal on #4, there is an issue, or it is just a valve adjustment issue...

Either way, at 50 degrees, in my experience a cylinder at 355 shouldn't cause any trouble. My '82 has a cylinder at 240 and another at 220 and it starts OK at 60 degrees after a 15 second glow.

I haven't read your other thread, but I think you should really investigate the possibility of an air leak in your fuel system. A little air leak can cause goofy things at startup. Those of us who deal in WVO do a lot of air leak checking during our installs....

Earlier in the thread it was suggested you park with the nose of the car downhill and see if the problem subsides. Or pump the primer a few times before starting.

Colder temp cause fuel hoses to shrink a little bit more, and allow more pinhole air leaks.

Good luck, these things are annoying to hunt down.

jt20 · #41 11-27-2010, 10:55 PM

Quote:

Originally Posted by JHZR2

Cyl 1 380
Cyl 2 385
Cyl 3 375
Cyl 4 355
Cyl 5 375

Not sure if I had a slightly poor seal on #4, there is an issue, or it is just a valve adjustment issue...

I wouldn't be the slightest bit concerned about those numbers for a cold test.

they are excellent.

#42 11-27-2010, 11:02 PM

I just had an experience with the 240D that might be relevant. For the last couple of mornings it was not wanting to start (about 30F), it would require about 15-20 seconds of cranking to finally start. I checked the glow plugs and they were good, but I noticed a little fuel leakage around the "spin on" fuel filter. I tightened the filter bolt and the issue is gone. I assume the small leak was allowing the fuel to drain back and air was entering the system overnight. You might want to take a look.

funola · #43 11-27-2010, 11:19 PM

It really sounds like you have air in the fuel which is causing the stall from a cold start. Is the clear return line from IP to filter housing brown with age? I think a new line is available. I'd strongly suggest you buy a new one so you can see what's going on and chase down the leak. It's a pain to find air leaks.

JHZR2 · #44 11-28-2010, 09:29 AM

Yes, the plastic lines are brown. How do you crimp them on/remove the old ones? It seems like it is just a friction fit?

BTW, pumping the primer first didnt change anything.

vstech · #45 11-28-2010, 09:40 AM

the new lines come with new fittings... you just bolt it on.