Hand pump leaks, ALDA? - PeachParts Mercedes-Benz Forum

SirMatt · #1 11-20-2002, 12:36 AM

Took my "new" '84 300D home today. Still can't push it over 75mph and I can't get the rpms over about 3300 in fourth.

The hand pumps leaks like crazy if you try to pump it. One pump will spew several ounces of diesel out from around the pump handle and onto the ground. Screws down tight and doesn't leak. Is this a problem?

Still no smoke. Ever. At all. Cold, warm, under load, at idle. Nothing. Zilch. Nada. Could it be sucking air or is it the ALDA doohickey. I've seen several ALDA posts that seems to mimick my symptoms. I'm probably 30 secs 0-60. Runs fine at up to about 75 but won't push any faster. Is the ALDA adjustment REALLY a good thing to experiment with. Looks like the Germans engineered specifically so you couldn't mess with it, but from the frequency of the posts it looks like it's done often enough.

Thanks for the help in advance.

lrg · #2 11-20-2002, 12:52 AM

Start with the simple stuff first before you mess with the ALDA.

The leaking pump is typical and it can be easily replaced with an updated design that doesn't leak. The part is listed on Fastlane.

As to the lack of power, before you do anything replace both the fuel filters. Next item to try is to make sure tha plastic hose that runs from the intake manifold (attaches at the rear of the manifold with a banjo fitting) to the ALDA is clear. These frequently get clogged and then the IP doesn't know to add fuel under boost. Try both of these first before you even think about fooling with the ALDA.

engatwork · #3 11-20-2002, 07:31 AM

I'm with Irg - This past weekend I had a car doing the same thing. Changing both filters resolved the "no power" issue.

Palangi · #4 11-20-2002, 08:21 AM

Replace the primer pump first, before you change the fuel filters, otherwise you may have a hard time getting it to restart. Once you get the leak stopped and fresh filters, there will probably be no need to twiddle with the alda.

gsxr · #5 11-20-2002, 10:29 AM

As the others said, do both fuel filters first. Then check the ALDA tube. A very common blockage point is the "switchover" valve on the firewall, part of the the overboost protection circuit. If this gets plugged, you get no power (actually, no fuel enrichment with boost.) You can bypass it temporarily for a test drive to see if that cures it.

If you still need to diagnose further, attach a pressure gauge with a "T" in the ALDA line, either connected in place of the s/o valve OR actually at the ALDA. Go for a drive, watch the gauge, at full throttle in 3rd gear, 4000rpm, you should see at least SOME boost (factory spec is 12-14psi). If you see something over zero (say, 5-7 psi) your turbo is working and you either have low fuel delivery preventing further boost (tweak the ALDA), OR a faulty wastegate. If you get zero pressure and the line is clean, and the banjo fitting at the manifold is clear, the turbo is faulty (impeller blades shot, shaft not spinning freely, or wastegate jammed open.) I actually had this problem on my 1984 300D with zero boost, impeller spun fine, the wastegate was broken internally. I repalced the turbo with a Pick-n-Pull unit for $50 and it's been fine - plus my 0-60 times have dropped from ~25 seconds down to 13-15!

http://www.meimann.com/docs/mercedes/84_300D_performance.txt

Regards,

gsxr · #6 11-20-2002, 10:32 AM

Oh yeah - hand pump - it's not a problem if it doesn't leak while closed. Unless of course you need to USE the pump to prime the system after replacing the main filter!

A new pump is ~$20 from online sources. Wouldn't hurt to replace it.

Wallknight · #7 11-20-2002, 11:38 AM

What is your IP timing set at?

SirMatt · #8 11-21-2002, 12:18 AM

Had a little bit of time this evening to check a few things out on the '84 300D.

Took the banjo fitting off of the manifold. Really crapped up with gunk. Removed the line from the switch on the firewall as well and shot carb cleaner and air through it from both ends. Reinstalled. No change.

Hand pump still leaks but I went ahead and changed the filters anyway. The prefilter was disgustingly fouled. Filled the new filters with fuel and manged to crank the system to life in two or three cranks. Bubble remains in prefilter, but that was there before. (I've got a new handpump ordered). Still no change in power or smoke.

I NEVER get smoke. It'll run up to 75mph or so at about 3250rpm, but won't go any faster and NEVER smokes under load. I can't make it smoke.

It looks like I get full throttle range in idle and I can get the rpms to over 4000 in idle, but never over 3250 or 3300 in fourth gear.

The line from the ALDA to the switch on the firewall is clear. In fact it looks little used. It's...I don't know, dry looking and feeling. Looks completely different than the other lines which are tinted dark from the manifold. It's actually kind of white and crusty looking on the inside. Anyway I'll probably try to bypass the switch tomorrow and go straight to the ALDA and see what happens.

Any thoughts? I've owned this car two days so my learning curve is pretty steep.

Thanks in advance.

gsxr · #9 11-21-2002, 08:36 AM

1- The prefilter "bubble" is normal - don't worry about it

2- Bypass the switchover valve on the firewall and see what happens. If still no change, you REALLY need to connect a boost gauge (any gauge that reads to at least 10psi) with a "tee" at the ALDA and go for a drive, as I described in a previous post.

Regards,

Diesel 924 · #10 11-21-2002, 10:50 AM

Alright fellas, just out of curiosity, I hooked a gauge into the line past the valve closest to the injection pump. My lines have been cleaned out and the car runs awesome. My max boost was 9 lbs. and steady through all gears while running it out. I used a Snap-On vacuum gauge that also has 0-15 lbs of pressure scale. So there!

gsxr · #11 11-21-2002, 01:24 PM

Good job! That is low boost though. Pinch off the rubber hose to the wastegate temporarily and repeat. If the boost is now higher, you need to adjust the wastegate setting closer to 14psi (factory spec). If the boost remains at 9psi and you're sure you pinched it completely, then you'll need to adjust the ALDA to provide more fuel which will produce more boost.

BTW, what's your 0-60 time in seconds, measured with a stopwatch?

Diesel 924 · #12 11-21-2002, 01:50 PM

My 0-60 is measured with a calendar not a stopwatch.

I'll try that wastegate trick later.

SirMatt · #13 11-21-2002, 02:45 PM

Bypassed the switchover valve and I have a definite increase in performance. Pushed it up to 85-90 with no problem. I think that the switchover was the problem.

How long can leave the switch bypassed without the threat of harm?

Haven't had time to really clean on the valve. BTW, how do I clean it?

gsxr · #14 11-21-2002, 04:49 PM

The s/o valve is the overboost protection circuit. A sensor on the intake manifold triggers at 1.1 bar (+/- 0.15) to kill fuel enrichment. You could test your boost output, and as long as it's under max spec (0.95 bar, or ~14psi) there's not a whole lot of risk. The circuit will only activate if the turbo wastegate fails closed, which is a pretty rare failure. I know of a lot of cars that have this bypassed (mine included, but it also won't go over 12psi even with the wastegate deactivated!) Just depends how nervous you are.

You may be able to clean the valve, but they can NOT always be cleaned successfully. If it doesn't clear out, you'll need to replace it. Look at Pick-n-Pull salvage yards for a good one, or they're about $20 new I think.

BTW, factory spec for 0-62mph (0-100kmh) is roughly 13 seconds, so you should be getting at least 15 seconds or faster if the engine is putting out normal power.

Good luck,