HELP! 87 300DT Fuel problem - PeachParts Mercedes-Benz Forum

sm0t · #1 11-22-2005, 12:51 PM

I hope you geniuses out there can help me.

Yesterday, I changed the primary (the one between the hard fuel line and the side of the engine) and the secondary fuel filters. After spending 30 minutes of alternately cranking the engine and cycling the key on for 5-7 seconds 4-5 times, I finally got the car started.

After initially running very rough and belching smoke it settled down to a smooth idle. I let it idle for about 10 minutes then manually held the revs at about 3000 rpm for a minute and everything was fine.
This morning I was heading out to visit family for the holiday and I got 1 block before the engine quit.

After 15 minutes of repeating the cranking/priming method above I got the car running and returned home. As I pulled into the driveway the engine died again. I tried the above again and I could not get the engine running. I have put a charger on the battery as it was starting to run down and am now waiting to let it charge a bit.

What did I do wrong? or what have I missed?

Thanks in advance for any help!

Rick
87 300D Turbo

SW · #2 11-22-2005, 01:14 PM

Did you fill the spin on filter with fuel?

sm0t · #3 11-22-2005, 01:27 PM

Quote:

Originally Posted by SW

Did you fill the spin on filter with fuel?

I only had enough to fill it about halfway. That's why I let it idle so long after getting it started the first time. I assumed (yeah, yeah, I know about assuming

) that the filter would fill up during the idle period.

RT
87 300DT

DieselAddict · #4 11-22-2005, 02:54 PM

No it wouldn't have anything to do with filling the filter with fuel before installation. The only thing I can think of right now is perhaps you reversed the input and overflow fuel hoses after changing the prefilter and it's starving the engine of fuel.

Palangi · #5 11-22-2005, 07:27 PM

I don't know anything about 603 engines, but I know there is an o-ring that causes this problem when changing filters.

sm0t · #6 11-23-2005, 01:31 PM

Quote:

Originally Posted by Palangi

I don't know anything about 603 engines, but I know there is an o-ring that causes this problem when changing filters.

Can anyone tell me about this "o-ring" problem?

sm0t · #7 11-23-2005, 01:34 PM

In order to troubleshoot this problem, I bypassed the fuel filter next to the engine block but that has not helped. Is there another way to purge air out of the system or a hand primer?

dieseldiehard · #8 11-23-2005, 01:50 PM

The 603 engine has no manual primer, its operated by the pick up pump when the engine is cranked, so that makes it harder on the starter motor if you installed a empty or half full spin on filter. But since it finally started and ran then priming the pump should be out of the equation, air would have been completely purged unless something else is allowing air into the fuel.
Its also possible the fuel strainer in the tank is getting plugged but I would think you would see some stuff in the primary (see thru) filter - is it clean?
There are two O-rings on the secondary (spin on) filter bolt. If they are leaking I think you will see fuel dripping off the filter somewhere. I have seen them leak and the engine still runs ok.
You may have a bad fuel thermostat. Its a small cylindrical can alongside the IP with four hose fittings coming off at odd directions, it mixes heated fuel with fuel from the tank. It has a big circlip at the front end that holds on a plate underwhich there is a seal that can fail and let air into the fuel, but I don't see how it suddenly went bad coincidentally with changing filters.

dieseldiehard · #9 11-23-2005, 01:53 PM

Quote:

Originally Posted by sm0t

In order to troubleshoot this problem, I bypassed the fuel filter next to the engine block but that has not helped. Is there another way to purge air out of the system or a hand primer?

I'd like to see how you bypassed the secondary filter

BTW, where is R Leo, your neighbor with a SDL? search his member name and Email him for possible look-see.

sm0t · #10 11-23-2005, 02:08 PM

Quote:

Originally Posted by dieseldiehard

I'd like to see how you bypassed the secondary filter

BTW, where is R Leo, your neighbor with a SDL? search his member name and Email him for possible look-see.

To bypass the filter I removed the rubber line coming from the tank to the filter and the the hose from the filter to whatever it is connected to. (small sliver cylinder with three hoses coming out of it. 1 goes to the large secondary filter, and the other two go underneath the intake where I can't see)

sm0t · #11 11-23-2005, 02:14 PM

I am pretty sure I have some bad glow plugs as my light no longer comes on and starting has been getting harder, so I plugged in the block heater (figured it couldn't hurt) and after letting it heat for 1 hour I finally got the car started.

It idles fine and I ran the rpms up to 3000 and held it there for over 1 minute with no stumbling or stalling. I am now letting the car idle. It has been idling for 20 minutes with no problem, but I am hesitant to take it on the road until I can get someone to help in case it quits again.

BTW - the filter I bypassed is brand new ans the fuel in it flowed freely in both directions. The old filter only ran freely in one direction and was completely black although the fuel is quite clean.

Any suggestions? Am I finally OK?

Hatterasguy · #12 11-23-2005, 06:54 PM

You may have bad glow plugs but they won't cause the engine to die. Remember once the engine is started the glow plugs shut down and thats it for them.

It sounds like a fuel issue.

First remove the spin on filter and make sure you didn't fubar the gasket around the threaded hole that the bolt goes in. Also replace the two orings on the bolt.

You can bypass the fuel heater, maybe try running another tank direct to the pump and see if the problem goes away.

I'd almost suspect your lift pump is getting weak, becuase even with an empty filter it shouldn't take a half hour to bleed the air out of the system.

I'd also start splicing in clear lines, look for bubbles you may have an air leak as well.