Needs advice re vacuum advance - BMW Forum - BimmerWerkz.com
3-Series (E21, E30) Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.

 
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#1 (permalink) Old 08-26-2004, 05:07 PM
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This is my first post and I hope it's not considered poor form to start prevailing on your collective goodwill so soon. But, I'm really in a bind....so forgive me.

I’m attempting to fix a vacuum problem that’s been plaguing me since I got my ’85 318i back from the motor shop last week. After an unexpected costly head gasket job and cooling system overhaul (incl. new radiator), the mechanic announced triumphantly that it doesn’t overheat anymore…. but it hasn’t any advance and runs poorly. He said he adjusted the idle to get the car running as smoothly as it could (under the circumstances) but he didn’t have time to look into it that day (as, laughably, he said he wanted to keep the cost down!). I guess it’s a separate job that he could charge me for another day. And just like he said, my car runs terribly – no power, shaking etc.

Now that I’m broke, I’ve decided to try to fix it myself even though I have really no great confidence I’ll be able to see it through. From the outset, I have to admit I know (or at least knew) nothing at all about any of this stuff. SO if my questions sound a bit stupid, that's why.

So to catch up, I’ve closely read and re-read page 5.20 of Bentley over several nights and, after getting a grasp of what’s going on, I’ve tried the recommended testing procedure. I have deduced that the problem must be the vacuum advance relay but I’m still unsure.

Using a multimeter, I can get a continuity reading between terminals 5 and 2 on the relay and the respective (+) and (-) wires at the solenoid. So I know they are connected. I have voltage at terminal 5 on the relay. However, when I try to get a voltage reading at the solenoid, there’s nothing. I can’t imagine why not? What gives? Is it because the relay isn't switching voltage to the solenoid? I did manage to blow #9 fuse (15 amp) when, being ignorant of what can happen, put 12v across one side (-)?of the solenoid's connection in an effort to see if it would start (I know, I know........)

Secondly, the mechanic suggested to me that the vacuum diaphragm at the distributor was probably the culprit. He figured I’d be up for a new distributor as the offending part probably wasn’t available separately. Naturally, when I disconnected the hose from the diaphragm, there was no change in idle. However, when I connected a hose to the diaphragm, stuck the end in my gob and sucked, the idle changed. Am I right in thinking that the diaphragm is OK?

As I said, I think it’s the relay (at the risk of sound too confident/stupid). Any suggestions? (apart from telling me to go to a BMW service centre which is, I'll admit, probably advisable).

I've had a great week reading all the posts and FAQs and articles about everything. I've had my BM for 13 years (276,000kms) - platanengrun metallic - looks almost like new - and still believe the E30 design to be the last word in motor vehicle body shape. Damn fine looking cars (no power granted...but they do look good). Next I'll probably be asking about the brakes.
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#2 (permalink) Old 08-28-2004, 09:11 PM
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You need a mityvac to test a vacuum advance.

http://www.mityvac.com/

It may react, but not hold, it may react only at high vacuum.

Attach a mityvac, watch how much vacuum it takes to make the engine change.
Watch the gauge to see if it leaks down.

Check your local auto salvage yard for the parts you need.
If you are lucky, total cost will be under $50.00........
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#3 (permalink) Old 08-29-2004, 01:54 AM
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Thanks heaps for the reply and information. There's not much I can do further with my limited knowledge and equipment. I did finally work out that the solenoid worked (well it made a click...if that qualifies as "working") when I got 12v across it(to the correct connection this time) and bypassed the relay.

I decided to change the relay (acting on my "hunch"). BMW wanted $68 for a factory 4-pin relay - the guy at the local BMW wreckers charged me $10. So I'll also take your advice re salvage yards. Thanks again. I was worried no one would answer.

Oh, and for the record, changing the relay didn't fix anything. Still no voltage to the solenoid. Groan.
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#4 (permalink) Old 08-29-2004, 02:00 AM
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trace the wiring back further... checked the fuse panel, etc?
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