1987 300D Turbo/Fuel Efficiency Question - Page 3 - PeachParts Mercedes-Benz Forum

Skid Row Joe · #31 05-25-2014, 07:05 PM

Quote:

Originally Posted by vstech

... 18SECONDS to 60!!!

Change your fuel filters. Check or change your air filter... Repeat test and report back...

That car should do 60 in 10 seconds...

I agree - something's bad wrong with that car......however his running it @ 80 mph, it's getting what I would expect for the parameters of mpg logging he's reporting.

treetops · #32 06-22-2014, 07:09 PM

Quote:

Originally Posted by jay_bob

On the intake manifold there is a hose fitting. The hose goes to a solenoid valve on the firewall.

From the valve it goes back to the ALDA on the injection pump. The ALDA gives you extra fuel to burn, matched to the extra air provided by the turbo.

There are a couple failure modes here:
- hose plugged with goo (thanks to the evil EGR valve) - self explanatory
- solenoid valve stopped up - boost signal can't get to the ALDA or else it's stuck in the "dump" position.
- solenoid valve stuck in the "dump" position - boost signal dumped to atmosphere and never reaches the ALDA
- electric over pressure switch in the intake manifold stuck on, energizing solenoid all the time, puts it in dump position. Switch is right next to the hose fitting. Power applied to solenoid coil, switch provides the ground to actuate the coil on overpressure.

Not to hijack ospreys thread, but I've followed this one as I had a somewhat similar problem. I could hear the turbo at lower speeds not at higher speeds also low mpg to me(approx 20-21) and low or little power at 55+. Did what Jay_bob suggests and followed osprey's steps....viola much improved results.

In my case the the overpressure switch, solenoid valve and pressure line nipple were practically 100% clogged. The line from the solenoid to the ALDA was ok. Cleaned with brake cleaner, cleared them out and I like the results: significantly better pickup like other's have said a 'caged stallion'. If I understand the ALDA right, the clogged lines/parts gave it very little/zero pressure to adjust enrichment so that WOT pedal would dump fuel and lower mpg?

I had previously replaced the air and fuel filters in the engine bay and diesel purged with so-so results. Next up is to change the tank filter and at some point pull the intake manifold and clean that out which is probably better than 50% clogged too.

Many thanks to the forum.

Treetops

iamtheosprey · #33 07-10-2014, 01:04 AM

I recently have got as low as 22 mpg but I have been traveling in excess of 90 mph at times(wide open West Texas highway where the speed limits are either 75 or 80 anyway).

When I floor it I will get a tiny puff of black smoke but that's it.

When trying to pass on the highway at 75-80mph I have a hard time sometimes getting by people.

Is that normal?

My 0-60 times are still crap but like I said I will get a little puff of black smoke suggesting that maybe the ALDA isn't bad?

I still need to get my head wrapped around which bolts need to be loosened to remove the ALDA.

Are they underneath the body of the ALDA just above the IP?

Skid Row Joe · #34 07-10-2014, 01:19 AM

Quote:

Originally Posted by iamtheosprey

I've had several MB turbo diesels and I could hear the turbo whine a bit with all of them except my current 1987.

I've also noticed that my mpg is never better than 25 driving between 75 and 80 mph.

Could I have a turbo issue?

The power seems adequate most of the time but I don't ever hear any turbo whine and my mpg makes me wonder if something is up.

Without a check-up on your car, it's anybody's guess. However, 25 mpg sounds about right for that car - given your description.

Quote:

Originally Posted by iamtheosprey

I recently have got as low as 22 mpg but I have been traveling in excess of 90 mph at times(wide open West Texas highway where the speed limits are either 75 or 80 anyway).

When I floor it I will get a tiny puff of black smoke but that's it.

When trying to pass on the highway at 75-80mph I have a hard time sometimes getting by people.

Is that normal?

My 0-60 times are still crap but like I said I will get a little puff of black smoke suggesting that maybe the ALDA isn't bad?

I still need to get my head wrapped around which bolts need to be loosened to remove the ALDA.

Are they underneath the body of the ALDA just above the IP?

Yes.

If you have any doubts - take it in for service with a good indy mechanic.

Good luck!

vstech · #35 07-10-2014, 07:56 AM

Quote:

Originally Posted by iamtheosprey

I recently have got as low as 22 mpg but I have been traveling in excess of 90 mph at times(wide open West Texas highway where the speed limits are either 75 or 80 anyway).

When I floor it I will get a tiny puff of black smoke but that's it.

When trying to pass on the highway at 75-80mph I have a hard time sometimes getting by people.

Is that normal?

My 0-60 times are still crap but like I said I will get a little puff of black smoke suggesting that maybe the ALDA isn't bad?

I still need to get my head wrapped around which bolts need to be loosened to remove the ALDA.

Are they underneath the body of the ALDA just above the IP?

Yup, if you look under the body of the alda there will be two hex sizes on top of each other. Hold top still, turn lower nut cw looking from above, and it will release the Alda.

Silber Adler · #36 07-10-2014, 08:31 AM

Step one is to have your car tuned up. Assuming that it had been done because you see leaks is bad juju.

5000 miles a week. I can't imagine that. Oil change and filter once a week. Tires every 5 monhs. $7-800 a month for fuel. 70 hours on the road a week?