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E21 (1975 - 1983)

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  #1  
Old 06-14-2010, 07:00 AM
marks82 marks82 is offline
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Location: Toronto, Canada
 
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Mein Auto: '82 320i
Help. Anyone ever check engine vacuum?

I was wondering if anyone has ever checked engine vacuum using a gauge. Anyone have specs on this? Rule of thumb is 16-22" at idle but does this still hold with the E21 M10's? I had a gauge on mine last night and it's only showing 10" at idle. I suspect a huge vacuum leak but pulling out the dipstick or oil cap causes the engine to stall. My acceleration is terrible BTW. Just trying to isolate the problem on this project car I'm trying to get running. Any help would be appreciated. Thanks
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  #2  
Old 06-14-2010, 02:39 PM
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drivinfaster drivinfaster is offline
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have you heard any leaks?? and yes, vacuum should be vacuum should be vaccum when it comes to diagnosis.

have you tried pinching off vacuum lines one at a time to see if that makes a difference?? i would start with the power boooster and go from there.

if it is steady i would rule out an intake manifold, unless it's close to the throttle plate. a bouncy needle is usually an indicator of a runner leaking.

have you tried to richen the mixture to see if it's just lean?? hove you tried opening the exhaust port plugs to see if that makes a difference?? you may have a restriced cat.

there are lots of things that could make a vehicle run poorly, so i would start looking for ripped and worn boots and vacuum lines. mushy lines, too, as these collapse and eventualy tear.

best of luck.


df
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  #3  
Old 06-15-2010, 08:38 AM
marks82 marks82 is offline
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Thanks, Drivinfaster. I have some experience with cars but these K-Jet systems are foreign to me (no pun intended) and extremely sensitive to vacuum leaks as I've found. I thought low vacuum might be normal due to the nature of these non PCV crankcases. I can't hear any vacuum leaks, no but if i put my hand over the air filter intake with the engine running, i can hear a whistling noise but can't locate it. (I figure the engine would stall, but it still runs) which leads me to believe it's got a massive vacuum leak.
I did pinch off one of the lines and found that my vacuum climbed up to a steady 19", which to me, is fine. it was the line from the "Tee" of the valve cover-to intake manifold (smallest of the vacuum lines). This is where i'm stumped, though, because pinching it off didn't improve driveablility at all. At the moment, i suspect it may be the (other) "tee" connector on the intake boot. the one that connects the Valve cover hose (big one) to the Auxiliary Air valve hose. Is it possible that this connector may be reversed, allowing this to suck too much air from the crankcase? I'd think this would allow air to bypass the sensor plate. Hoses all look like they're new, btw. I sprayed intake cleaner and don't notice any change in idle or vacuum.
The car seems to idle fine, and if i rev in neutral, it also sounds fine. Pulling the dipstick stalls the motor, as does removing the oil cap. Driving it is terrible, though. like a bad breakdown. It just bogs with any load on it.
I'd like to hold off on adjusting my mix settings for now, though until i rule out vacuum leaks.
I'm putting this car back together after some serious neglect from it's previous owner and I'm not gonna give up until it's done.
Any idea where I can find a good routing diagram for the vacuum hoses and other lines to/from the intake boot?

Thanks
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  #4  
Old 06-15-2010, 01:51 PM
davidgoerndt davidgoerndt is offline
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I'm not an expert with these cars, but from your description it sounds like a vacuum leak isn't your problem. The K-Jetronic fuel injection can be the source of many problems, like fuel filters clogged as well as injectors. A vacuum leak should show up as a fluctuating idle, with a massive vacuum leak you wouldn't be able to start the car. Pulling the dipstick or taking the oil cap off shows you what would happen with a massive leak, the car dies immediately! Try Bimmerforums if you haven't already. That forum has more traffic and some really knowledgeable members.
http://forums.bimmerforums.com/forum...play.php?f=143

Last edited by davidgoerndt; 06-15-2010 at 01:52 PM.
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  #5  
Old 06-16-2010, 01:56 PM
marks82 marks82 is offline
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Location: Toronto, Canada
 
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Thanks. That makes pretty good sense. I'll check my fuel pressure tonight. Hopefully this is just a clogged fuel filter....
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  #6  
Old 06-17-2010, 09:28 PM
galaxyflier galaxyflier is offline
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Location: Saratoga Springs, NY
 
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Mein Auto: 1981 320i (E21)
Another way to find vacuum leaks is to spray all the hoses with starting fluid while the engine is idling. If you spray somewhere and the engine speeds up a little, you've found your vacuum leak.
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  #7  
Old 06-18-2010, 08:16 AM
marks82 marks82 is offline
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Yeah, i tried with air intake clean and couldn't find a leak. After tightening all of the hoses and moving my vacuum gauge to another port, i was pulling a solid 19" of vacuum. Also, a fuel pressure test was showing 72 psi.
I think this is a fuel related issue within the airflow unit. Given that the car sat for over a year, i think i may have some varnish buildup somewhere in the system. Probably the control plunger in the fuel distributor. Anyone know of a good way to clean these fuel distributors? I'm a bit unsure about taking it apart, given that there are a lot of precision machined surfaces. I doubt RTV is a good way of sealing it back together.
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  #8  
Old 06-18-2010, 10:41 AM
galaxyflier galaxyflier is offline
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Mein Auto: 1981 320i (E21)
A blunt word of advice: Do NOT f**k with the fuel distributor unless 1) you are absolutely sure that that's the problem and 2) you know exactly what you are doing. Every instance I have ever heard of of someone tearing into either the fuel distributor or the warm-up regulator ended in disaster. These are very costly parts and take special skills and tools to repair. The tolerances are extremely tight and therefore the stock gaskets and seals must be used when reassembling them. My 320i is 29 years old, has 297K on the odometer and the fuel distributor has never been touched, ever. When I pulled the cylinder head last year to repair a burnt valve, I unbolted and disconnected only what I needed to move the fuel distributor out of the way. The warm-up regulator went bad years ago and was diagnosed and replaced by a certified Bosch mechanic. Since a fuel distributor goes for about $1500 new (or about $350 on E-Bay for a rebuilt unit) and a warm-up regulator is around $400, I would strongly recommend you take the car to a Bosch mechanic and have it accurately troubleshot first. It might cost you a $100 bill to have it completely checked out, but you'll end up saving alot more if turns out the only problem is a set of clogged injectors, which can be replaced for less than $200. I do all my own work on my car, but I draw the line at major F.I. problems. I'll have someone with the proper test equipment check it out and then decide if I can fix it myself or just let them do it.

Now, clogged injectors you can check yourself fairly easily. Here's how: You'll need four glass baby-food jars or similar containers. (My son was 3 months old when I did this so I used baby-food jars). Anyway, pull out all four injectors and place one in each jar. Leave the fuel delivery tubes connected. Remove the air cleaner and the bellows from the airflow meter. Unplug the fuel pump relay and jump the forward-most slot in the socket to the slot next to and perpendicular to it. This will enable the fuel pumps to operate without the engine running. Then, turn the key to ON and, using a screwdriver, push the air plunger in the airflow meter up for 5 to 10 seconds. Fuel will flow from the injectors into the jars. Watch the spray patterns of the fuel coming out of the injectors. If any are erratic or uneven, then that injector is partially clogged. If something is wrong, it'll be blatantly visible. When the jars are about half full, shut everything off and place the jars next to each other on a flat surface. If all the jars have the same amount of fuel, your injectors are probably okay. But, if the fuel levels in the jars are all different, then one, some, or all of the injectors are bad. Replace all of them as a set.

Hope this helps you out. Let me know.
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