When I first start my '83 300D Turbo it has barely enough power to not stall when I shift into drive. I'm not exaggerating how little power it has. If I try to drive off the car won't go more than 5 mph. Then, usually within 10 seconds, something clicks in and the engine has good power. What's going on here?

Some background that my be useful. The car has a slow vacuum leak. If I don't run it for three days the doors and trunk won't automatically unlock until it's started. I've avoided trying to find the leak because I fear that finding a slow vacuum leak may be a real challenge. This vacuum leak may be why the first second into first downshift after starting makes a noticeable clunk. The car runs strong. I drag raced my friend with an identical car and after an even start pulled out two car lengths before hitting 60 mph. I checked the glow plugs and all are functioning.

The engine experts at work (engineers have a theory on everything) think that the vacuum fuel shutoff is waiting for full vacuum before opening up. BTW if the car has been recently run (2-3 hours) it starts with full power.

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JSR

1983 300D Turbo
1995 E320 Wagon
2001 MR2 Spyder
2001 Subura WRX Sedan

Fuel shut off is actuated (shut off) by vacuum being applied to it. Therefore no vacuum would leave the fuel shut off valve open (fuel flowing). IE engineers theory is wrong.

P E H

Weak vaccuum could be a bad diaphram in the pump, dumping oil in the engine. When hot this isn't a problem, but when cold makes for hard starts and low power because it starts burning before injection takes place. Once it burns off, normal operation. Ditto for bad valve guides or seals -- there will be quite a bit of oil in the combustion chamber after sitting.

Check the line from the vaccuum pump to the intake -- if there is oil in there, replace the pump diaphram. Not hard. Save a bunch of oil, too!

Otherwise, check for a fuel leakdown -- if you have a bad fuel line that allows air into the suction line from the tank, the fuel will leak back into the tank, not onto the ground. You will get a big slug of air when you start up, resulting in low pwoer. Goes away when you get more fuel. Will eventually prevent starting when it gets really bad.

Vaccuum leaks are easy to find with a MitiVac hand pump (about $30) -- just unplug the yellow line in the engine compartment and pull a vaccuum with the pump -- if it leaks down, lock system, if not, try the green one (AC). And so forth.

The most common cause of vaccuum leaks (pump aside!) is deteriorated rubber connectors in the engine compartment. Check and replace any that are hard or squishy. Very likely you will find the problem. Also, much harder to locate, are the bushings on the vaccuum tanks -- one under the left front fender and usually one in the bumper in the rear, or in the trunk.

The only real pain in the butt with the vaccuum system (locks and AC servos) is that they can be hard to get to -- you will need to take the door panels off if you have a bad actuator, for instance.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks

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JSR

1983 300D Turbo
1995 E320 Wagon
2001 MR2 Spyder
2001 Subura WRX Sedan

Jon:

You may also have bad glowplugs. Check them, and if marginal, replace all of them. They aren't expensive.


Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Glow plugs will have no effect on your problem. They are shut off as soon as the engine starts. If enging starts easily, GP are not your problem.

P E H

I too have the slow running upon first start of the day. Accelerator response is weak. Lately, I have gently been depressing the pedal untill the rpms rise while in park. It feels as if it is not running on all cylinders for a while, then they gradually catch. Once I get it up to say 3K rpms, pedal response is fine, and the car has normal get up and go. I do get smoke on startup.

I'll check my vacuum hoses for oil. Am I looking at valve seals if the vacuum pump is okay?

Could something other be the cause of this symptom? I don't know the condition of my injectors, glow plugs are new, some blow-by, but not extreme.

Thanks for the help.

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

Peter,

You have to give more information for someone to diagnose your problem. What car, what engine, how many miles, gas or diesel ETC.

P E H

That would be a 1985 300TD, turbo 5 cylinder diesel, 217K miles.

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

Peter:

Very likely vavle guides seals (or valve guides, for that matter!) if not done recently. You are probably due for a valve job if one hasn't been done yet.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Sorry, I remembered that the engine is a reman, supposedly from Benz, according to the PO. I am guessing the mileage on it is closer to 60K at this point. I have my doubts, but there is some reference in the service records.

What fouls valve seals or guides? I have it on Mobil 1 now, with about 7-8K of highway driving 70+mph (four hour trips generally) over the past four months.

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Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K

Nothing fouls valve seals or guides. Valve guides wear form the valve sliding in them. Seals usually die from old age and the heat in the engine. The seals are made of a rubber like polyomer that hardens with age.

The result is oil consumption, but other than that, seals and guides have little affect on a Diesel engine. On a gasoline engine too much oil consumption can foul the spark plugs and cause miss fires.

If your engine has only 60k miles, your guides and seals should be OK. Keep going with the Mobil I. No need to change more often than every 10k miles with your kind of driving.

P E H