14.9mpg in my SDL, no, the math is right...and the odometer works too... - Page 3 - PeachParts Mercedes-Benz Forum

Brian Carlton · #31 01-10-2005, 09:14 AM

Quote:

Originally Posted by WANT '71 280SEL

I guess I need to go to Autozone tomorrow and buy a boost gauge and we'll go from there.

That's the ticket.

WANT '71 280SEL · #32 01-10-2005, 11:26 AM

So 21 is still bad. Would the gas cap have affected it that much?
Thanks
David

Hatterasguy · #33 01-10-2005, 01:21 PM

21 is still bad but not that off for around town. I pretty much do 75% around town and 25% highway and I get an almost never changing 23.5. These are big cars low 20's around town is good. I would expect over 25 though on the highway. You should be getting another 2-3mpg, however do you know anyone with a handheld gps? That would be a good way to check your odo.

WANT '71 280SEL · #34 01-11-2005, 09:43 AM

Their is definitely something wrong with the engine's power. A member confirmed that. I think it needs fuel filters bad since it sat for a year rarely being driven. When I get home from school I bet my 2 cans of diesel purge are there. Sometimes when accelerating, there seems to be a "dead spot" in the pedal. It seems as if it isn't getting enough fuel. I'll do the filters/DP, then check boost. Then, I'll adjust the ALDA. If the car is still low on power, I'll look into that IP shaft seal I heard that can leak. To check that seal, don't I make sure the ALDA will hold vacuum? how much should it hold and for how long?
Thanks
David

Brian Carlton · #35 01-11-2005, 09:57 AM

1) scroll up

2) read post #33.

3) follow post #33.

4) connect up boost gauge.

5) report back with results.

WANT '71 280SEL · #36 01-11-2005, 10:01 AM

You guys know where I can find a boost gauge? I went to Autozone last night and they only had one, for $60! I told them I'd go somewhere else. Today I'm going to NAPA and Advance. Then, the other day my dad's heater motor went out. I just replaced the blower controller with a used one so I don't know if it needs the motor or controller now.
Thanks
David

KCampbell · #37 01-11-2005, 10:04 AM

I picked up a nice boost gauge with a huge dial for around $30 at NAPA.

Let's be very clear: blocked fuel filters will not cause bad mileage! Quite the opposite if anything!

Kevin

Brian Carlton · #38 01-11-2005, 10:39 AM

Quote:

Originally Posted by WANT '71 280SEL

You guys know where I can find a boost gauge? I went to Autozone last night and they only had one, for $60! I told them I'd go somewhere else.

Purchase one of these. They will give you both boost and vacuum:

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7947030247&category=38660&sspagename=WDVW

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=7946976246&category=38660&sspagename=WDVW

braverichard · #39 01-11-2005, 11:47 AM

Quote:

Originally Posted by WANT '71 280SEL

Their is definitely something wrong with the engine's power. A member confirmed that. I think it needs fuel filters bad since it sat for a year rarely being driven. When I get home from school I bet my 2 cans of diesel purge are there. Sometimes when accelerating, there seems to be a "dead spot" in the pedal. It seems as if it isn't getting enough fuel. I'll do the filters/DP, then check boost. Then, I'll adjust the ALDA. If the car is still low on power, I'll look into that IP shaft seal I heard that can leak. To check that seal, don't I make sure the ALDA will hold vacuum? how much should it hold and for how long?
Thanks
David

I thought you would have replaced your fuel filters by now to see if that will give you more power. For my 617.951 engine both filters cost $10 and I'm sure the price will be about the same for your 603. Also, make sure you DEFINITELY replace those filters after performing the diesel purge cleaning process.

For the 617, 21mpg is about normal for around town driving, but I guess it isn't quite good enough for the 603 (though not bad).

WANT '71 280SEL · #40 01-11-2005, 11:50 AM

richard, I was waiting until my DP came (tonight?) I read it was probably better to replace the spin-on filter BEFORE doing the diesel purge.
Thanks
David

WANT '71 280SEL · #41 01-11-2005, 08:24 PM

I am not disagreeing with you, but someone said something to the tune that not all the DP burns initially, so it returns to the fuel filter. When you replace the filter afterwards you are actually throwing away some of the DP. However, I doubt it really makes much of a difference. I'll do mine before, you do yours afterwards. It's not a big deal.
Thanks
David

Hatterasguy · #42 01-11-2005, 09:23 PM

The spin on filters for these engines are pretty large, I wouldn't worry about it. You would be surprised by how much crap they can trap.

sixto · #43 01-12-2005, 12:00 AM

Quote:

Originally Posted by Brian Carlton

BTW, normal boost on the 603 is 11-12 psi.

Is it? The manual says wastegate spec is 1 bar which is 14.5 psi per http://www.worldwidemetric.com/metcal.htm.

The converted gasser vacuum gauge I finally have working in the SDL indicates that the Garrett is blowing over 12.5 psi just about anytime the engine's turning more than 3000 rpm. I've yet to tee in a proper boost gauge while driving to get a second opinion.

My basis for saying it's over 12.5 psi is that I set the converted vacuum gauge to register 5.5 - 12.5 psi between the pegs. I used a MityVac as a pressure source (why is the outlet smack in front of the gauge?) and had the pressure blowing to the converted vacuum gauge and a VDO 0 - 30 psi boost gauge.

Can an ALDA stick in the boost position?

Sixto
95 S420
87 300SDL

Brian Carlton · #44 01-12-2005, 02:04 AM

Quote:

Originally Posted by sixto

Is it? The manual says wastegate spec is 1 bar which is 14.5 psi per http://www.worldwidemetric.com/metcal.htm.

If the manual states 1 bar (14.5 psi) I'm certainly not going to disagree. However, I don't think that any 603 that is 16 years old is going to make those numbers. Advising that 14.5 is normal would cause quite a bit of alarm to new members who may read 10.5-11.5 psi. 11 psi is perfectly adequate and makes quite a bit of power.

gsxr · #45 01-12-2005, 02:32 PM

I really think you're barking up the wrong tree with Diesel Purge, injector pop testing, filters, etc (assuming the air filter is clean). Black smoke means excess fuel - period. IP timing and cam timing must be checked. If both are OK, there's either excess fuel, or low boost *plus* an IP problem - cracked ALDA perhaps. You cannot test the ALDA with vacuum. And pressure testing it only checks for leaks, not function. A cracked ALDA aneroid capsule will give excess fuel (and smoke) at low boost/RPM but it should clear up at high boost/RPM. Clock the car 0-60mph, should be 13 seconds or so if power is normal. You should not feel the turbo "kick in", it should have seamless power off idle through redline.

About boost pressure. From the various factory service manuals, I believe the offical specs are:

OM617 = 0.75-0.85 bar
OM60x = 0.85-0.95 bar through 1987
OM60x = 0.75-0.85 bar from 1990-93

Every good-running OM603 that I have tested provides 12.5psi of boost. Power should be normal or close to normal above about 10psi.

I suspect cam timing, IP timing, broken ALDA capsule, or serious internal injection pump problems. Wouldn't hurt to make sure the EGR valve is not physically stuck open.