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Car starts, but dies when in gear

12K views 11 replies 6 participants last post by  mercmad6.3 
#1 ·
Hi guys! My 1979 450SL had trouble starting this morning. Check all fluids, oil was down, added some, tried again, and voila, it started. The minute I put it in reverse it died. Idles great in park and neutral, but put it in gear and it dies. It seems to be flooding the minute I put it in gear. Quick check of hoses, don't see anything out of place. It ran just fine yesterday, didn't do anything weird or out of the ordinary. Parked in driveway, and now it's doing this. Any thoughts or ideas of what it could be?
 
#2 ·
Question

This also sounds like it could be the fuel/air mixture. This may sound dumb but what controls that in this vehicle? I know that there is a part right next to the air filter which has a big screw on it, which you can turn. The mechanic I took it to, awhile back, had it screwed all the way down because it was idling really rough when hot, and would die. Never did find out from the guy what the part was, and he said he could get for 140 bucks, but would charge me 350 to replace it. So, I said no. But I'm think this is the part that is bad. I've attached a picture of what I'm talking about. Can anyone tell me the part number or even name of this part?
 

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#3 ·
Some good news...

So, the guy who looked at my car got it running, sort of. He told me there is a major vacuum leak at the intake manifold. He said the bolts were loose, so he tightened them up and since the car had been running so rich, the plugs were all fouled up, and he cleaned those, and adjusted the idle mixture. I can drive for a bit (just to get me to the store and stuff) but it starts to act up after a couple of miles, and I have to put it in park at stop lights to keep it from dying. He said he could get it all fixed for around 1100.00, mainly labor, which I don't have, so I will be doing the work myself. Is it hard to redo the seals on the intake manifold? Or just time consuming? I am also going to replace all the vacuum hoses to the intake. Anything I need to be aware of as I do this? Thanks in advance for your input.

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#4 ·
At this point there are SO many things to consider,
How many miles on the car?
First and number one how is the compression?
If you get into the motor and you need a valve job?
You have to start at the basic stuff,
can't just throw band-aid fixes at the motor.
IT need an assessment of condition.

Then there are so many other details to fix while the intake manifold is off,
 
#6 ·
Well, I'm pretty sure that this all revolves around the air/fuel and the K Jetronic system. The engine runs great as long as the car is in park or neutral. The engine has about 200K on it. The last mechanic I took this car to said that the air control valve was broken and he screwed it all the way down to fix the problem. So it has been running rich for a while, but I did replaced the cap, rotor and plugs about six months ago. I knew I need to get in there and work on it, but the car was running great, and time passed. My friend who looked at this last week said that he put in a good air control valve (I don't think that's the name of it, but nobody seems to know the actual name of that part I posted a picture of) and it was still doing the same thing. Vacuum leaks are a big part of my problem with this car, and I need to get in there and change all the old hoses out. I'm going to study that guide you pointed me to, and get into this weekend. My husband also suggested I replace the fuel filter, as about a week and a half ago, I let the tank get down to the point that the reserve tank kicked in, and he said that since I never do that, there could have been gunk in the tank that clogged the filter. I'm a decent mechanic for a girl, but this will be my first time really getting into a car. Mostly, its been changing alternators, radiators, starters, and such. So, I may be back here again, asking questions. Thanks for the help.
 
#9 ·
Another Question

Okay, I'm pretty sure this is probably self-evident to most of you, but it's not to me. I am going to start removing the intake manifold tonight, but have been examining the manuals and such. One of the directions has me confused. It says "Deactivate fuel lines." Exactly what does that mean?
 
#11 · (Edited)
Okay, I'm pretty sure this is probably self-evident to most of you, but it's not to me. I am going to start removing the intake manifold tonight, but have been examining the manuals and such. One of the directions has me confused. It says "Deactivate fuel lines." Exactly what does that mean?
Not really familiar with your car but that usually means relieve the pressure in the fuel lines, in carbs there usually isn't much, in fuel injection there is. might be a nozzle with a valve like a bike tire on it, or just undo a fuel line (which you'll have to do anyway I think), either way do it with the engine cold (it would probably hurt to remove the manifold with the engine hot anyway) or you'll have fire damage to repair too...

Also disconnect the fuel pump or pull the fuel pump fuse to avoid that whole issue
 
#10 ·
If you've been replacing alternators and starters then you can also deal with the intake manifold. Basically all rubber parts in the V should be replaced as they have been cooked with heat and time. Not too expensive, but time consuming. This includes the seal rings between the plenum and the runners (between higher and lower part of the manifold).
 
#12 ·
STOP!
Start with the basics.
REplace the cap,rotor,leads and plugs. Set the timing correctly.
Check the engines compression.
Do the valves (if it has the adjustable tappets)
Check the throttle linkage to make sure you are getting full throttle and no play exists in the linkage .All parts are available and after 200,000 the linkage Will be sloppy.
Replace the manifold O rings.
With the manifold apart you will need to get the injectors cleaned ( there are plenty of places that do it for a cost per injector).
i would also consider replacing the fuel distributor at that milage too. Again there are places that do an exchange service on these.
Once you have that organized,consider changing the cold start injector.
This is probably what is causing the excess fuel as it may be stuck open.
This is all very basic stuff .
The complex stuff begins now.
At that milage the timing chain and tensioner need replacing.
If the car has been running rich there is every chance that the bores are getting worn so the compression may be down a bit.
Check the thermostat and see if it is closing properly. A cold running engine will run rich continually.
Although the Kjet cars aren't as powerful as the djet injected 450's it should still be a spirited performer on the road.
 
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