300SDL - IP Issues? - PeachParts Mercedes-Benz Forum

Diseasel300 · #1 09-25-2016, 03:07 PM

The car in question is an '86 and sat for nearly a decade. Bought as a long term project car since the car itself is solid, drivetrain was questionable from sitting. Last on the road in '07.

Block has cleaned up well, head got new valve guides and stem seals this past winter, and overall the engine seems relatively "healthy" other than the fact that it runs poorly.

Had a couple of leaky hard injection lines and replaced with a new set from another member on this forum. No fuel leaks with the new lines installed. Injectors are all good and pop-test 1950-2000 PSI.

Compression (taken stone-cold on 9/18/16) is good:
1: 385 PSI
2: 375 PSI
3: 380 PSI
4: 370 PSI
5: 375 PSI
6: 370 PSI

The issue is a random loping/missing idle, very rough running, extremely reluctant to rev, grey acrid smoke, and an extremely difficult time restarting when just shut off. Simply shutting the engine off and immediately restarting requires 3-4 attempts, and the final startup is very rough.

Another observation is the amount of diesel spurted out when the nuts are loosened on the injectors. 1, 2, and 3 will squirt hard enough to shoot you in the face if you aren't careful. 4, 5, and 6 barely dribble out of the nuts. The engine will run solely on cylinders 1, 2, and 3, but not 4, 5, and 6.

When running on all 6 cylinders, it behaves like a governor hunting....250-300 RPM up and down all over the place. If left alone to idle, will eventually stall. If the engine is revved, it will stall when the throttle is returned to idle 100% of the time. If the throttle is slowly returned to idle, it will continue to run. Once stalled, it requires 5-10 seconds of cranking to restart as if the hard lines are airlocked or lacking pressure.

As checked in an earlier thread, the lift pump seems to be ok, supply pressure is ~12PSI. Fuel filters have been changed, fuel returning through return line is clear (no foam).

Have also done delivery valves, with no change in behavior.

Previous thread also dealt with IP base timing. IP was originally badly out of time. Was retimed and helped *some* but didn't cure the loping/missing issues. Have rechecked the timing, and it is still where it was set previously. Someone had clearly tinkered with the engine at some point in the past before I got it.

At this point I just have to wonder....is the IP my issue here? Diesels seem so simple....fuel, air, and compression. Compression is good, air is available, all that really leaves (in my mind at least) is fuel...

sixto · #2 09-25-2016, 03:57 PM

Make sure the shutoff actuator is releasing completely. Tie the stop lever in the upright position if necessary.

Make sure the idle actuator is working. Does idle respond to the numbered dial by the brake master cylinder? Does idle get worse if you disconnect the plug at the round thing on the tail end of the IP?

I assume you're not running on 10 year old fuel. Have you run a bottle or two of Diesel purge directly into the IP? Maybe clean the pressure relief valve but you'd be complaining of low power under load if that were an issue.

Yes, these Diesels don't need much but IP tuning is a bear to restore when it goes off and there isn't much appreciation for prechambers which are about the only thing you haven't investigated.

Sixto
83 300SD

Diseasel300 · #3 09-25-2016, 04:27 PM

The shutoff lever seems to be releasing completely. For giggles I tied it up with a piece of wire and made no difference. That's not to say something inside isn't gummed up.

The idle actuator does seem to be working. Lowest idle speed is ~450 @ 1 and around 750 @ 7. With the harness unplugged from the IP, idle is very low and the car wants to stall.

I did run diesel purge back in January before really working on the car much. I don't suppose it would hurt to run it again. The PRV was original and definitely bad. I forgot to mention in the original post that it was replaced recently. The original one rattled and had no resistance at all when blown into. The car has no power at all, it's reluctant to even rev the engine.

I'm definitely not running 10 year old green diesel. I have the car running from a 2L bottle as a "redneck gas can".

You mention prechambers. I have not pulled them, however when the head was off all the holes were clear in the piston area and all of the little "balls" were present internally. Is there anything else that should be checked?

babymog · #4 09-25-2016, 08:10 PM

You didn't mention whether you have bypassed the fuel heater, I agree it sounds like fuel stervation more than air infiltration though.

Diseasel300 · #5 09-25-2016, 08:42 PM

The fuel heater has been bypassed. It was dripping coolant and it never gets cold enough here to warrant its use anyway.

Right now it has a 2L bottle mounted near the filter-dryer for the A/C, short piece of 5/16" diesel hose going to a filter, then another piece of 5/16" diesel hose going straight to the lift pump. Return line is another piece of 5/16" diesel hose going straight back from the filter housing to the 2L bottle.

babymog · #6 09-26-2016, 08:38 AM

The IP is pretty robust, the only thing I can think of that could affect just the back three consistently is rust in the elements from moisture in the fuel while parked for so long. I'd like to be wrong this time.

Try swapping injectors around and see if the symptoms follow the injector, would indicate weeping nozzles.

dude99 · #7 09-26-2016, 09:21 AM

Maybe try running a can of diesel purge through it? Could be gummed up. Also, is the pump installed correctly. I see to remember Simone installing a pump 180 deg. Out, it ran, but was very hard to start, ran like crap, and smoked like crazy.

Diseasel300 · #8 09-26-2016, 09:36 AM

I have played "musical injectors" and 4, 5, and 6 are consistently the problem regardless of what injector is installed.

This pump *WAS* installed 360˚ out. It was 15˚ ATDC on #6 instead of #1. It ran.....poorly. So much white smoke it would fog out the neighborhood and wouldn't even attempt to rev. Very loud diesel knocking. After being retimed the engine is much quieter (amazing really), but still runs very poorly and still doesn't want to rev, although it will if you wait long enough.

I've got some Diesel Purge on order (surprisingly nobody carries it here despite selling other products from the same brand) and I'll try running that through. I do wonder if when I ran it the first time it didn't do much due to the PRV being wide open.

Another dangerous thought is I have to wonder if someone in the past changed the delivery valve seals and O-rings and pulled the injection elements up out of the IP body. I've read over and over never to remove them and I just have to wonder if that's what someone did in the past. Could that be enough to cause what's going on here?

funola · #9 09-26-2016, 09:58 AM

Sounds like time to try a good used IP.

Diseasel300 · #10 09-26-2016, 12:20 PM

I'm still willing to try just about anything before sinking money into an IP, but I'm slowly resolving the fact that the IP may just be toast.

Found some references on this site to doing an in-place solvent soak in the IP, and that is looking like my next step. Pump it full of solvent (lacquer thinner), let it sit, turn it over a couple times in a 24 hour period to cycle the pumping elements, flush, and try with fuel again. If there's any varnish or gummed up crap in there, seems like a pretty solid way of getting it cleaned out. If not, oh well....at least I tried.

funola · #11 09-26-2016, 12:34 PM

If the elements has been disturbed as you suspected, it is very difficult to get them right without a Bosch test bench and the knowledge to calibrate it. If you are willing to try anything before replacing the IP, try setting the 3 element positions that are low on fuel yourself and see if you can increase fuel output.

Diseasel300 · #12 09-26-2016, 12:36 PM

Quote:

Originally Posted by funola

If the elements has been disturbed as you suspected, it is very difficult to get them right without a Bosch test bench and the knowledge to calibrate it. If you are willing to try anything before replacing the IP, try setting the 3 element positions that are low on fuel yourself and see if you can increase fuel output.

Do you have a forum link or other reference on how to do this? If the solvent bath doesn't help, it may be worth trying, if only to concretely diagnose the IP as being the culprit.

funola · #13 09-26-2016, 12:44 PM

Quote:

Originally Posted by Diseasel300

Do you have a forum link or other reference on how to do this? If the solvent bath doesn't help, it may be worth trying, if only to concretely diagnose the IP as being the culprit.

I don't have any specific links but google "Bosch inline IP theory" , there are a few training pdf's from Bosch that are pretty good. Also look on youtube for Dieselmeken, I have seen videos from him replacing elements.

funola · #14 09-26-2016, 01:01 PM

Quick search found this one http://www.superturbodiesel.com/std/attachment.php?aid=870

Diseasel300 · #15 09-26-2016, 01:42 PM

I found that one too. Not the same pump (pretty sure it's the right pump for the 617 tho), but close enough for the theory to be applicable. Will read when I have some free time.