[ccrobin]

OK, I've been tuning up the newly acquired 1987 300SDL. All has been going OK, but this one has me stumped.

Background - The car has 275K Miles. It has been starting great for me every day in the week since I bought it. I know the fuel has some contaminants in it (i've changed the primary filter 5 times - also changed the large secondary filter yesterday just before the seafoam procedure). The sediment seems to be less and less the last few days so I think most of it is gone. Not sure if this is contributing to the problem or not - but thought I would mention it.

Yesterday, I removed the vacuum line from the top of the blue flying saucer looking thingie (located on the driver-side fender well area under the hood). I placed the vacuum line in the bottle of seafoam and allowed it to slowly take-up the liquid into the system. After about 20 seconds it sounded as though the engine began running much smoother. I didn't see much smoke out the back of the car - but could smell the seafoam from exhaust so I know it was getting to the engine.

After emptying the bottle into the system, I let the car run for a few minutes and shut it off. About 5 minutes later I restarted it (started great) and went for a little spin. Seemed a bit peppier (but still a bit of lag). At any rate, I parked the car and went in to have a celebratory beer. About 2 hours later I was going to take the car for another longer drive and it wouldn't start. It turned over fine (even started and ran very rough for a few seconds - exhaust smelled very rich or perhaps more seafoam?). It tries to start but sounds like it is starved for fuel. I cranked for about 30 seconds, waited a minute and cranked again for another 30 seconds. Again, it seemed to wanna start - just not quite.

I didn't suspect the fuel filter as it was running fine before I shut the car off. Regardless, I changed the primary filter again to be sure it wan't that - to no avail.

I assume that if I keep cranking (re-prime) it will fix the problem, but my primary concern is that the seafoam may have not been completely burned off in my short drive/run time and it has now settled into the low-point of the vacuum system. Do I risk hydro-locking if I try to keep cranking?

If not, anyone have any suggestions as to how best get her up and running again?

 

[ccrobin]

UPDATE:

I got it running. I had to crank it again for quite a while, but it finally started. Seems to still be starved for fuel though. Had to pump the accelerator to get it to start and stay started at first. Also still seems to lack power (though it is idling much better). I guess I need to pull the tank screen (grrr...I just topped the tank off with fuel). I'll have to drive it now till I'm on the reserve and then get the "diesel shower" experience I've been reading about.

In the meantime, does anyone know an easy way I can test the fuel lift (primer) pump to make sure that isn't the culprit? I've heard that they can go bad and cause similar symptoms. If that pump is weak I'd like to get one ordered as it will take a few days to get in.

 

[harlz]

I don't know much about diesels unfortunately, but if it was full of sediment from the last owner, perhaps it was adjusted for the restrictions by increasing the injection amount etc. Maybe since the seafoam has cleared the system out, could there be more fuel going in than needed now?

I think they use a cam driven piston pump but I guess there's a way to adjust them, but again, I don't know much about the diesel systems! So may not be the issue.

 

[Rmac58]

I understand the primer pump on those engines are internal, sorta. They're automatic anyway.

 

[ccrobin]

Yes, the priming is "supposed" to be automatic with these engines - though it means you need to have a good battery because it often takes 1-2 minutes of cranking to get it primed. There is no hand primer like on the 617 engine.

My joy at getting the car started was short-lived, as it left me stranded the next day on the side of the road. As it turns out my lift (primer) pump was shot. I ended up having to bypass the OE pump and I'm using an electric pump for the time being (I can't find a replacement OE pump locally). Runs like a champ now - and the electric pump makes the priming sooooo easy. I might just leave it in place and forego the OE mechanical pump indefinitely.

 

[86-300SDL]

Drawing Seafoam into the Vacuum System?

The "Blue Saucer" is a vacuum amplifier used to assist the transmission shift.

Why were you drawing seafoam into it? I believe you would be pulling seafoam into the vacuum pump and not fuel system nor the combustion system.

Check your oil level, you may have dumped the seafoam into the crank case via the vacuum pump. or maybe just filled the vacuum pump with seafoam.

Clean vacuum lines is good but your method does not make sense to me.

I generally either replace the lines or pull the line off and run a solevent through i.e. carb cleaner etc.

P.S. Re Fuel Priming...the delivery process should not need several cranks to get the fuel to pressure. Unless there is a leak or has been sitting for a while (like days or weeks) My 335,xxx mile motor fires on the first hint of the starter motor rev. It may crank for a moment if I don't let the glow plugs heat up, but otherwise these SDLs (603.xxx) usually fire immediately.

 

[ccrobin]

As it turns out my lift pump was shot. That is why I was having so much difficulty getting the engine primed. I have since bypassed the mechanical pump with an electric and it fires up instantly now.

The reason for dumping seafoam into the vacuum system was not to clean the vacuum lines (though it is a nice benefit), but rather to get the seafoam into the intake while the engine is running. This provides a stronger concentration compared to just dumping it into the fuel tank. Using the smaller vacuum line also reduces the chance of hydro locking the engine compared to other methods of dumping it into the intake. It really does work quite well (at least it always has for me).

 

[86-300SDL]

Mr. Crobin Re: Seafoam & Vac Lines

On a SDL the "Blue Saucer" (Vacuum Amplifier) vacuum lines do not communicate with the intake manifold. Or should not. Those lines operate on vacuum created by the vacuum pump. I think what you intended to do was connect the line from the manifold to the switch over valve which provides overboost protection...and with the engine running I'm not sure it would draw fluid due to no manifold vacuum rather possible positive pressure should it exceed 14psi or so.

Maybe your lines are crossed?

I've attached a vacuum diagram you may want to take a look at!!! Easy to get the lines mixed up...Hey your trans may even operate better after the lines get sorted out. Not sure though that Seafoam is good for the rubber diaphrams / seals in the alda, vacuum amplifier, & vacuum pump?

By the procedure you described I think your Seafoam was sucked into: your crankcase via the vacuum pump, alda, lines, trans vacuum modulator, or vacuum control valve rather than the intake / combustion chamber. Might want to check 'em out! Remember diesels don't create manifold vacuum like a gasser (no throttle plate to restrict air flow). That is why they have vacuum pumps....

 

[ccrobin]

Wow, thank you. This will help a ton! I was looking over the vacuum system yesterday (replacing worn/bad fittings, etc) and was beginning to wonder if everything was where it is supposed to be. A quick glance at the diagram makes me think it is, but I will check everything good to be sure.

I was concerned because I wanted to clean out my banjo bolt to see if I could correct my seeming lack of power (I am now suspecting the turbo is not kicking in, or my wastegate is malfunctioning). I found a good article how-to on the banjo bolt, but upon inspection it doesn't appear my intake is equipped with one (or am I just missing it???). I traced the vacuum line going from the alda unit to the switch-over valve (it was OK), but the other line coming from the switch-over valve I was expecting to see hooked to a banjo bolt. Instead it is simply hooked to a nipple coming out of the intake. Is this normal, or am I missing some hardware? Here is a photo of it:

The lines and valve seemed to be OK (no soot buildup), so I am now thinking I need to inspect the wastegate to see if it is working properly. I've found quite a few posts referring to it - but no good article actually explaining the process of checking it. If anyone can point me in the correct direction it would be appreciated.

 

[86-300SDL]

Mr. CCorbin - Laggy Turbo - Try This !!!

Re: Turbo & Boost....First by pass the Over Boost Protection Valve
I think you will be smiling shortly:thumbsup:

Re route some of the lines as shown in the marked up photo. Ultimately the lines will run as shown in Red.

Configure overboost valve (switch) lines to run to itself (loop) and take it out of service.

Run the line from the manifold nipple (once running to the overboost switch) to the "Y" connect comming off the Alda that is now available 'cause you already pulled the other hose and looped it back into the overboost protection switch.

Next pull the vacuum line connect attached to the EGR Valve and stuff a golf tee into it.

Now go enjoy performance better than "Delivery Day"

 

[ccrobin]

Thanks. I'll give it a try. Do I run any risk of an engine melt-down by bypassing the overboost protection valve?

 

[86-300SDL]

Melt Down?

Thanks. I'll give it a try. Do I run any risk of an engine melt-down by bypassing the overboost protection valve?

Naw.... just don't try to pull a trailer through the Alps at WOT (Wide Open Throttle)...Your Waste Gate system has got ya covered any way. The Overboost Valve was actually removed from service in newer cars i.e. 1990 & on.

Good luck! Let us know how she runs...Then we got a couple more ideas for ya:sawzall:

 

[ccrobin]

Ha! OK, no mountain climbing with the Benz in bypass mode.

I'll try the new configuration in the morning and post my results. I plugged another fuel filter today, so I am suspecting my tank screen is likely plugged too.

My tank is almost low enough that I should be able to drain it and clean the screen this weekend. I am told that can also affect performance.

 

[ccrobin]

OK, I did the bypass trick you showed me and it did seem to help, though I am still suspecting my turbo system is not working properly. I'll have to try and figure that out to verify.

I also replaced the motor mounts today and that made a big difference. No more rattle-rattle-rattle when I am sitting at idle (I mean, the engine still sounds like a bucket of bolts...but no more unintended rattles).