second thread this week:

having done all the deferred maintenance, valves, filters, fuel line hoses,disassembling and cleaning of the injectors, oil change, valve cover gasket, biocide,
anti gel additive, belts, shocks are on the way here. lift pump rebuild kit is on the way.

I was reading this treasure trove of information and found a topic about alda adjustment thought that a little won't hurt
and truly the difference was remarkable, just 1/2 turn out and i'm merging faster into traffic rather than waiting for a larger gap so that i can sedately merge....

so the question is: even with the easier starting, steady idle and overall improvement in the car
on occasion the starts will be difficult, slow to respond to throttle input and to attempt to solve this
a stop and restart which usually solves the slows what causes this?
will be happy to try out your suggestions..

best regards

my first thought is the throttle bushing on the firewall. they are notorious for failing, resulting in lazy throttle response randomly.
next would be junk in the fuel tank/plugged or partially plugged tank screen. shutting down lets the fuel flow back from lack of suction, and unclogs the screen... also a plugged tank vent bell can give these symptoms.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Searching around this sight and reading various threads, this appears to be not so rare of a problem. I had the same car, an 83 SD, and it drove me nuts. The car started and ran fine as long as you didnt get on the highway, but had zero boost. Turbo was fine, but I put a kit in it anyway. Tank was clean but replaced all filters including sock. Tested the lines to the tank, blew through them, etc.. I tested the fuel flow on the lift pump, rebuilt the hand pump, still nothing.

What it would do is roll up to 70, 80, even 90, maybe even stay there a while, then slow down. Sometimes, if you kept your foot on the floor, it would drop down to 45 mph and just stay there. Once you eased up it would pick up a again, but most often 55 to 60 was maximum speed you could maintain.

My thoughts are that I should have put a lift pump in it, and looked at the ALDA. Had those not solved the two problems, the next place to look was at the injection pump itself.

One thing I read recently is that vacuum problems could cause the fuel shutoff to close, or partly so, which could cause similar problems, but I recall pulling the line off the pump and experiencing the same issues, so in my case that was not the problem.

Might seem crazy trying to solve a problem I experienced with a car I havnt owned in almost 15 years, but I would like to get another and any and all knowledge can only help. If not me, someone else.

so search out the sneaky vacuum leaks.
I'll get after that and report back
one thing perhaps related when i turn the key off and remove it
the engine occasionally runs on until i step on the brake pedal
presume that reinforces the leak theory.

stop me if you think I'm chasing ghost's

Had similar problem on two cars. What worked for me was cleaning out the fuel tank vent lines. They were clogged and would slowly allow a vacuum to be pulled on the fuel system. Making it harder for the fuel pump to supply adequate fuel for higher speeds.

Had some time this afternoon to play with my three week old (to me) toy
1983 300sd (617)

was occasionally frustrated by the seemingly random hard starts or the slows (like there's no fuel getting to the motor) thought that the only avenue I've not traveled is the way into vacuum land. So armed with a mityvac i started looking for leaks, found a bunch in the cabin, enough for a weekend of searching. but i confined my search to the engine bay there's a spring loaded fuel shut off that hides on the back of the ip in the engine bay the leak that i found was in the elbow attaching the vacuum line to this spring loaded fuel shut off I'm sure there will be more fun little challenges (console lights, door locks....) but for today a small success. easy starts
good throttle response, easy shifts and very little black smoke[played with the alda again just to see how it all works{3/4 turn ccw from stock setting}]

High crankcase pressure can cause the shutoff valve to move toward the shutoff position, limiting fuel delivery.

See post #237 (p 16) and subsequent.

http://www.peachparts.com/shopforum/diesel-discussion/105386-loss-power-briefly.html

I think you're chasing a ghost on that one Guy.

Yes the vacuum shut off valve is located on the back of the injection pump. It is spring loaded in the off position. It receives vacuum from the brow line attached to it when the keyed ignition is not in the start or run position.

If you did indeed find a leak in the elbow attaching the vacuum line to this spring loaded fuel shut off then that is not the source of your loosing power and or hard starts problems.

A leak there could cause the engine to keep running after you turn the key off.

I assume you used the midyvac to stop the engine by vacuuming the shut off valve?? it should shut down the engine pretty quick

there could be a leak at the ignition switch that could cause vacuum to leak when the key switch is in the run position.

IIRC i do think that is pretty rare with those but not impossible.

Check for the presents of vacuum coming from the brown line while the car is running. Jiggle the key while you do it to try and make it happen. If you see vacuum from the brown line when the engine is running that means that you have a problem in that vac circuit somewhere. Its one of the simplest circuits of all and if there is vac there with the engine running then it is definitely the ignition switch.

If you haven't done your lift pump rebuild yet then i would get that tackled first. I'd betcha that you'll feel some improvement immediately after that job.

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

If it's spring-loaded to the OFF position, why is vacuum applied when the key is not in the start or run position?

If vacuum is lost, will the engine not run? Or will it not shut off?

Please excuse my unclear wording. When the valve sees vacuum it does work to pull a little leaver that shuts off the fuel supply to the pump.

If vacuum is lost the engine will not shut off. If it were not there the engine would still run.

__________________
Current fleet
2006 E320 CDI
1992 300D - 5speed manual swapped

former members
1984 300D "Blues Mobile"

1978 300CD "El Toro"

A leak there could cause the engine to keep running after you turn the key off.
this was happening with varying lengths of time between key off and shutdown. The only way i could force the shutdown was to step on the brake. still not clear on why that is.
but aside from that i just picked up the lift pump rebuild kit so that will be installed next.

thanks for the direction

Mine didnt have any blowby, so that wasnt it, but it did have some ongoing vacuum issues. The vac pump seemed to work okay (produced enough at idle/within spec) but never checked it out on the highway.

The lift pump put out enough volume at idle as well, but there too, I wonder what it produced at higher speed.

I sure liked driving that old bugger, like to have another someday.

The brake booster is operated with vacuum. Stepping on the brake opens the valve inside the booster, creating a system wide loss of vacuum (pressure increase).

Until a perfect piston ring is invented, every engine will have blowby.

For an old engine (238K) there is very little blowby at idle, which by the way is very steady
at 750 rpm,
Will test drive today to see if anything acts up.