Help diagnosing multiple engine issues - PeachParts Mercedes-Benz Forum

michael_j_brown · #1 12-13-2017, 10:57 PM

Hey guys,

I purchased an 85 300 D that set under a tree for 10 years. I’ve spent months getting it to run. I know some of you reading this are familiar with this car already.

First of all, I don’t want to junk this car, I’ve spent too much time and money on it, but at the same time it’s becoming a real problem around my house. It’s been in the garage now for four months and it’s created a huge oily mess.

The biggest issue I have at the moment is the turbo is producing zero boost. I have a pressure gauge, it’s hooked up to the test port on the manifold and even driving the car under load produces zero boost pressure. In addition, you do not hear the turbo spool up at all. The blades are spinning and you can freely turn them with your finger.

I had the turbo re-built. When I installed the rebuilt turbo and got the engine to crank, I did hear the turbo spool up and it sounded normal, that was the one and only time I heard the turbo. All seals and gaskets are brand new

Tonight after work I pulled the wastegate cover and checked the rubber diaphragm and it looks perfect. Took me over two hours to get the spring on and off, it was a nightmare.

The pressure gauge I’m using is brand new, I have not tested it and I have no way to test it as far as I know, unless someone can point me in the right direction of what I need to do to test a pressure gauge.

I did hook a vacuum pump up to the pressure gauge to see if by chance it was leaking and there are no leaks it held a vacuum perfectly.

I don’t know if this has to do with the turbo, but when you floor the car, it just seems like it’s not revving like it should, it’s just weak. The car does seem to idle just fine and it starts just fine.

If someone would be so kind as to tell me what I need to do to figure out why the turbo is not working so that I can move onto the other issues that this car has I would greatly appreciate it

dieselmania · #2 12-13-2017, 11:18 PM

It is possible you have a fuel delivery issue preventing the engine from building enough RPM to spool the turbo. Have you checked your filters? Crap/Algae in the fuel?

Diseasel300 · #3 12-13-2017, 11:19 PM

Will the engine rev freely with the transmission in neutral or park? Does putting the pedal to the floor move the injection pump linkage against the hard stop?

Not sure why you checked the diaphragm on the wastegate. The wastegate is a valve, not unlike the valves in the engine, that bypasses the turbine wheel. If it is stuck or hung open you will have no boost.

If the car sat that long, the IP may have issues. The rod that the ALDA acts on could be stuck, or the internal guts of the IP could be gummed up. If the turbo doesn't build boost, and the IP doesn't enrich the mixture to build more boost, the car will be a SLUG.

Try physically removing the ALDA and go for a drive, see if there's any difference. If there is, you know the ALDA or it's sensing circuit are at fault. If there isn't, you know it is the turbo or the IP at fault.

michael_j_brown · #4 12-13-2017, 11:31 PM

Yes, brand new primary and secondary fuel filters were installed. Also, I drive an 83 300 D almost every day so I’m very familiar with the way they operate and sound and how the turbo reacts . I actually resurrected that one too, it sat in a field for years but it was nowhere near the problem this one has been

Quote:

Originally Posted by dieselmania

It is possible you have a fuel delivery issue preventing the engine from building enough RPM to spool the turbo. Have you checked your filters? Crap/Algae in the fuel?

michael_j_brown · #5 12-13-2017, 11:40 PM

Yes, the engine will rev freely while in park or neutral. I actually adjusted the IP timing to factory spec, one drip per second and that seems to be working perfectly.

I took the cover off of the wastegate trying to figure out how I could tell if it was stuck open or closed but I just don’t have the experience so I had no idea what I was looking for so I put the cover back on.

I can remove the ALDA and try that route to see if it makes a difference

Quote:

Originally Posted by Diseasel300

Will the engine rev freely with the transmission in neutral or park? Does putting the pedal to the floor move the injection pump linkage against the hard stop?

Not sure why you checked the diaphragm on the wastegate. The wastegate is a valve, not unlike the valves in the engine, that bypasses the turbine wheel. If it is stuck or hung open you will have no boost.

If the car sat that long, the IP may have issues. The rod that the ALDA acts on could be stuck, or the internal guts of the IP could be gummed up. If the turbo doesn't build boost, and the IP doesn't enrich the mixture to build more boost, the car will be a SLUG.

Try physically removing the ALDA and go for a drive, see if there's any difference. If there is, you know the ALDA or it's sensing circuit are at fault. If there isn't, you know it is the turbo or the IP at fault.

michael_j_brown · #6 12-13-2017, 11:47 PM

Wastegate diaphragm photo I took this evening

okyoureabeast · #7 12-14-2017, 12:09 AM

This might seem counterintuitive, but hear me out.

When I first got my 300D, it had been sitting in storage for many many years.

When I first got the car, it was a slug. Turbo wasn't spooling and I thought this was going to be it.

Instead, I decided to just drive it until I got time around to futzing with it.

Oddly enough, about 2 weeks in it eventually just started working on its own. Turbo spooled and everything worked as it was supposed to.

Diseasel300 · #8 12-14-2017, 12:15 AM

Quote:

Originally Posted by michael_j_brown

Yes, the engine will rev freely while in park or neutral. I actually adjusted the IP timing to factory spec, one drip per second and that seems to be working perfectly.

I took the cover off of the wastegate trying to figure out how I could tell if it was stuck open or closed but I just don’t have the experience so I had no idea what I was looking for so I put the cover back on.

I can remove the ALDA and try that route to see if it makes a difference

The diaphragm tells you nothing about the health of the wastegate, other than if it is torn, it will never open the wastegate and you can have an overboost condition.

Under that diaphragm is a spring that keeps the wastegate closed. Had you pushed on the nut exposed in your picture, you could have seen if the wastegate moves freely. If it drags, or takes excessive force (it will require some force to overcome the spring pressure), it is likely bound up. Given that the turbo was rebuilt, I'd be more focused on fuelling problems.

Alec300SD · #9 12-14-2017, 12:51 AM

These diesels definitely thrive on being run regularly.
Have you run a diesel purge with LubroMoly or ATF yet?

Years ago I ressurected a W126 300SD that had been sitting at least two years that was scary slow by first making sure the fuel delivery system was up to snuff.

I ran it with ATF (from an under hood mini tank), as the fuel source for about an hour every night (to hide the prodigious smoke) for a week and that really helped in cleaning out the IP.

In the meantime I dosed the tank with BioBor and StarTron to rehabiltate the old fuel and clean the residue in the fuel tank.

The BioBor and StarTron treament regimen is currerntly being applied to "Stormcloud' as part of the process to get her roadworthy.
She's on her second fillup of high cetane Propel Diesel HPR.

dkr · #10 12-14-2017, 01:01 AM

What about the strainers in the tank?

Have you tried cutting or replacing them or running temporarily off a tank in the engine bay?

Dkr.

t walgamuth · #11 12-14-2017, 07:21 AM

There is a small plastic line about 1/8" d which feeds boost to the
Alda, IIRC, which runs from the injection pump around to the intake manifold somewhere.

I don't know what its called but if it is cracked or loose your injection pump does not get the signal that more fuel is needed as boost comes on.

If it happens you'll feel like you are towing a ships anchor when you try to drive the car.

...No performance but you'll have excellent fuel economy.

michael_j_brown · #12 12-14-2017, 08:01 AM

I read that it takes very little pressure about 10 psi to move or open that wastegate And that you can hear it open. I was messing around with that angle and was never able to hear anything coming from the Wastegate.

Let’s say for the sake of argument that I pull the cover off the wastegate again and I discover that there is an issue with it being stuck… What then? Will turning the adjustment free it up or am I going to have to take the turbo off the car and rebuild the waistegate?

A few of you have mentioned the fuel. I drained the fuel tank and put 10 gallons of brand new diesel in the car I just don’t think that it’s a fuel related issue, however I suppose it’s possible. I will look into the suggestion of cleaning out the lines.

Quote:

Originally Posted by Diseasel300

The diaphragm tells you nothing about the health of the wastegate, other than if it is torn, it will never open the wastegate and you can have an overboost condition.

Under that diaphragm is a spring that keeps the wastegate closed. Had you pushed on the nut exposed in your picture, you could have seen if the wastegate moves freely. If it drags, or takes excessive force (it will require some force to overcome the spring pressure), it is likely bound up. Given that the turbo was rebuilt, I'd be more focused on fuelling problems.

Alec300SD · #13 12-14-2017, 09:35 AM

Don't give up yet.

My best guess is that you have one or more problems in your ALDA boost circuit if indeed you have no fuel starvation issues from filters, lift pump, strainer, etc.

Have you ruled out pressure leaks in the boost sense lines?

Previously you had one critical boost line from the switchover valve to the ALDA missing, that has since been replaced.

Are both sealing washers present on the banjo bolt on the back of the intake manifold?

Are there hidden cracks in the first hard boost sense line coming off the back of the intake manifold?

Is the rubber connector from the first hard boost sense line to the swichover valve in good condition?

With your MityVac set on pressure mode, and connected to the previously mentioned rubber connector on the switchover valve (to emulate boost conditions) does the system hold 10psi or does it leak down?

Has the switchover valve electrical input failed allowing boost to vent to the atmosphere?

Has the 'Blue flying saucer' diaphragm failed allowing boost to leak down?

As suggested earlier as a temporary test, physically removing the ALDA from the injection pump (and putting a solid bolt in place of the banjo bolt on the back of the air intake manifold) should allow the turbo to spool up (because you removed any boost leaks that prevent fueling of the turbo).

Let us know what you find.

Diseasel300 · #14 12-14-2017, 09:40 AM

The pressure to open the wastegate depends on where the spring tension is set. It can be as low as a couple of PSI, or it can be as high as 20 or more if it's really cranked tight.

Factory setting for the 617 was somewhere around 9-10PSI, the 603's took it to 12-14PSI.

Not sure who said you can hear the wastegate open. If you're trying to operate it manually, you'll never hear it. If the exhaust on the car is hooked up, you'll never hear it either. Gas engines have a blowoff valve in their intakes for an overboost condition, you definitely hear that as a "BWOOF" when they operate and a lot of people mistake that as the "wastegate".

It's easy enough to test the fuel angle. Run from a bucket or some sort of external tank/bottle and see if it behaves the same way. Change your secondary fuel filter for good measure just in case it's clogged up. If the engine runs the same way, it isn't a fuel supply issue, it'll be fuel delivery (including enrichment) or turbo.

Taking a systematic approach and doing the most basic things one thing at a time to rule them out first will save your sanity. Don't fall in the trap of trying to tackle everything at once, it'll drive you to drinking very quickly.

michael_j_brown · #15 12-14-2017, 10:49 AM

This is excellent information!!!! Some of this has been done but there are specific steps here that have not and I will take tonight.

Sorry about my attitude when I posted this last night...I was beyond frustrated, mainly because I spent 2 hours messing with the spring around the the waistgate cover.

Quote:

Originally Posted by Alec300SD

Don't give up yet.

My best guess is that you have one or more problems in your ALDA boost circuit if indeed you have no fuel starvation issues from fliters, lift pump, strainer, etc.

Have you ruled out pressure leaks in the boost sense lines?

Previously you had one critical boost line from the switchover valve to the ALDA missing, that has since been replaced.

Are both sealing washers present on the banjo bolt on the back of the intake manifold?

Are there hidden cracks in the first hard boost sense line coming off the back of the intake manifold?

Is the rubber connector from the first hard boost sense line to the swichover valve in good condition?

With your MityVac set on pressure mode, and connected to the previously mentioned rubber connector on the switchover valve (to emulate boost conditions) does the system hold 10psi or does it leak down?

Has the switchover valve electrical input failed allowing boost to vent to the atmosphere?

Has the 'Blue flying saucer' diaphragm failed allowing boost to leak down?

As suggested earlier as a temporary test, physically removing the ALDA from the injection pump (and putting a solid bolt in place of the banjo bolt on the back of the air intake manifold) should allow the turbo to spool up (because you removed any boost leaks that prevent fueling of the turbo).

Let us know what you find.