Novice 528i Owner: Intermittent Start

G. Fischer · Post by **G. Fischer** » Wed Mar 28, 2012 1:34 am

Recently purchased a 1980 528i in great shape - has an intermittent start issue. Browsed through the google search, etc. but looking for some direct advice.

When it starts, it runs great. Probably starts 6 out of 10 times. However, it will sporadically refuse to fire. Cranks and cranks but will not fire. Not even a sputter. At times it has been days between starts, other times just hours. Temps here have ranged from mid 60s to high 70s, though this hasn't seemed to be a factor.

From the forums and google search, I think I've narrowed it down to the corroded combo relay, and subsequent CSV failure (though I performed the "test" mentioned on the boards and still heard a click in the relay while the ignition is set to "on" and AFM open).

Would appreciate some expert advice to see if I'm on the right track (new Bosch relay on the way).

Also wondering if there are any hints as to how to get the car going during one of its non-start spells.

Any thoughts would be a great help. Despite the hiccups I'm really falling in love with this car.

Thanks!

Jeff Dennis · Post by **Jeff Dennis** » Wed Mar 28, 2012 9:23 am

I think it sounds like an intermittent ground fault. The experts here will chime in.

Lenny D. · Post by **Lenny D.** » Thu Mar 29, 2012 10:16 pm

After confirming reliable fuel and spark operation (coil, HT wires) two items surface: impulse transmitter (distributor internals) and ICU (on the right front fender under the hood).

peter claassen · Post by **peter claassen** » Thu Mar 29, 2012 10:30 pm

On Thu, Mar 29, 2012 at 8:16 PM, Lenny D <bassplayer51@cox.net (bassplayer51@cox.net)> wrote:

After confirming reliable fuel and spark operation (coil, HT wires) two items surface: impulse transmitter (distributor internals) and ICU (on the right front fender under the hood).

My 81 528i had been wrecked right front by previous owner - the impulse transmitter was mounted with the black rubber wire nipple facing up

after 2 tows from tahoe due to dead spark - my used parts guy told me that the transmitter needs to face down so water can drain from the black rubber nipples

never had any trouble after that - maybe that helps

HTH

'80 528i

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Lenny D. · Post by **Lenny D.** » Fri Mar 30, 2012 1:22 pm

Just to be clear, that is the ICU with the rubber plug (and drain tubes) mounted to the inside right fender, not the impulse sender. I suggest removing the connector and cleaning (motor tool wire brush) the male pins on the ICU for solid contact. I bet it's corrosion city in there...

rew2000 · Post by **rew2000** » Mon Apr 02, 2012 12:06 am

I'm having some similar problems. See my recent post.

G. Fischer · Post by **G. Fischer** » Mon Apr 02, 2012 12:06 pm

Thanks all - will update as soon I do some tinkering.

tschultz · Post by **tschultz** » Mon Apr 02, 2012 10:36 pm

It could be your combination relay... mine went out, and could not get fuel pressure.
Once I replaced, all worked great!

G. Fischer · Post by **G. Fischer** » Wed Apr 04, 2012 5:58 am

Combo relay was my first thought - replaced it yesterday. So far, so good.

Knock on wood.

G. Fischer · Post by **G. Fischer** » Tue Apr 24, 2012 8:40 am

Alright.. some time has passed since I installed the new combo relay. Nonstarts became less frequent, but I still get bitten about 1/10 starts. Most of the time after a moderate cool down period after short run (e.g. trip to the store).

Same symptoms: cranks, won't fire. Seems to be getting fuel, but no spark. Will fire eventually, usually after 15-30 minutes and plenty of patience.

Installed new ignition coil yesterday.. had another no start episode last night. Control unit is nipples down and seems to be in decent shape.

Next up is the distributor cap/rotor, plugs, ignition wires. No noticeable corrosion, etc. but they are due.

Could it be the ECU? Am I missing something?

fidosd9 · Post by **fidosd9** » Tue Apr 24, 2012 12:09 pm

sound like your ignition control module could be faulty or check the connector that connects to the distributor i has a similar problem i have 530i but P.o installed the 528i system so the p.o sold the car because it would start sometimes it would not start similar to what you are talking I check the wiring the connector to the distributor little L shape connector with two wires one green and found out the wire insulation was torn right under the connector and it was grounding out the spark by touching the distributor housing I fix that wire never had that problem again.

http://www.realoem.com/bmw/showparts.do ... g=12&fg=05

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