Just got an 83 300D. Runs ok, but seriously lacks power.


Checked the turbo and its in great shape. Quiet, spins well and almost no play.
I cleaned the banjo bolts on the back of the intake, made sure the line was clear and hooked up a pressure gauge. It just vibrates around 0 PSI.


So being that I am new to these engines. What are the possible spots for an leak?


I was thinking it could be the intake manifold gasket, or maybe the waste gate is stuck open. Where should I start?


If it is the waste gate, where can I get one?

Start by examining all your connections from the pressure side of the turbo to the intake.

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

ok so I checked all that I could find. Still no luck..


I listened for hissing, felt around, sprayed some suds while being careful not to get in the intake. Did it at both idle and not. My tac is not working so I can't tell you what RPM it was at. Just revved it up off of idle a bit and checked around.



Here is what I checked.

• connection from turbo to the intake manifold.
• hose from turbo to wastegate
• banjo fitting on the back of the intake manifold
• Sensor on top back of the intake manifold
• around the waste gate.
• around the top side of the intake manifold gasket.

Hold on here, were you checking at idle?

__________________
2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold

I checked at what I can only guess is 2000- 2500 rpm. And since i had no luck, i also checked at idle. I also revved it way up and held it to see if I had any pressure. Nothing.

How are you checking boost? The engine needs to be under load to make any meaningful boost (this means driving around). Your boost sense line needs to be functional all the way from the intake manifold, through the switchover valve, to the ALDA on the injection pump. If you are opening that line to check boost pressure, you just killed your boost since you'll get no fuel enrichment.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

How are the fuel filters?
Fuel starvation = no power.

Also, boost pressure won't build if the ALDA is kaput, as fuel enrichment will be lacking.
The internal o-rings/aneroids might be shot.

With the car not running, check the ALDA, try to pull a vacuum with a Mity-vac.
If it holds vacuum, it should hold boost pressure.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

ok, i didn't realize it needed to be under load. I will give that a try.


Right now i have a gauge hooked directly up to the line out of the intake.


When I rev it up I can't hear the turbo spooling up.

You have the pressure gauge teed into the circuit, right?

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

You can't measure boost by just plugging the sense line into a gauge. You broke the path from the intake manifold to the ALDA. No boost through the sense line, no fuel enrichment. No fuel enrichment, no boost built. It's a feedback loop. You can add a "T" to that line to measure boost, but you cannot just plug your boost gauge into the end of the line and expect it to work.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Agree with most of what's said, except for the no boost without an ALDA part. My engine turned out to have a hole melted in the ALDA line, and still made over 10psi...remember there's still enough heat in 88hp or whatever worth of fuel to get a turbo working (even these horrendously inefficient stock T3 turbos)

__________________
1978 300D, 373,000km 617.912, 711.113 5 speed, 7.5mm superpump, HX30W turbo...many, many years in the making....
1977 280> 300D - 500,000km+ (to be sold...)
1984 240TD>300TD 121,000 miles, *gone*
1977 250 parts car
1988 Toyota Corona 2.0D *gone*
1975 FJ45>HJ45
1981 200>240D (to be sold...)
1999 Hyundai Lantra 1.6 *gone*
1980s Lansing Bagnall FOER 5.2 Forklift (the Mk2 engine hoist)
2001 Holden Rodeo 4JB1T 2WD

So I just took it for a spin with just reading the pressure from the intake manifold. I got at most 8lb, but obviously the alda is disconnected so still no power.


Before I tested the pressure I had bypassed the overboost valve by connecting the manifold line directly to the alda line with a peice of flexable vac line.



The guy i purchased it from said he had recently done the fuel filter, but i doubt he did the tank screen. It is also leaking a bit of fuel around the filter housing & the return lines on the injectors. Enough to drip from the bottom of the fuel filter.



It had 1/2 tank of 3 year old fuel in it. I mixed in some fresh.


I am sure it also needs a valve adjustment. I have the wrenches and feeler gauge on order.

ok, i ran to the store and got a T to check the boost & vac test the alda.


The boost gets up to 8lb, so that's great. Still crap power though.


I did a vac test on the alda. Holds 20hg but is not perfect. Took 1.5 minutes to drop to 15hg. I think its a small leak in my mightyvac because everything i test with it slowly drops like that.

May not have full activation of IP rack by throttle linkage.
The pivot mount for the accelerator linkage (on the firewall) is prone to disintegrating.

Test to see if you have more IP rack travel:

Engine off, buddy depressing the accelerator pedal.
Manually pull on the thottle lever.

https://www.pelicanparts.com/cgi-bin/ksearch/pel_search_2016.cgi?command=DWsearch&description=1233001340
Shows as NLA on sponsor web store, but available on amazonian web site.

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78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022

Just tested and inspected. The throttle only moves about 1/8 of an inch past full throttle on the peddle.