Help with 528i start but not run

turbo-rampage · Post by **turbo-rampage** » Tue Jan 12, 2010 7:06 pm

Hi, hopefully you guys can give me a bit of a hand.

My 17 year old bought a 79 528i with L-jetronic which was running before it was parked 2 months ago because the previous owner cracked the oil pan on a curb.

Now it will fire and run for a second or 2 and just die like you turned off the key.

I have looked through the FAQ section here and spent the last 2 days working on it, and have found various problems I have fixed, but it still is acting the same.

Here are the things I've looked at:

1. Verified both fuel pumps run, and has about 30 psi fuel pressure.
2. Verified the "combo relay" is functioning as it should. The relay energizing the ECM with the key on is working, and the fuel pump relay is functioning when the engine is cranking, and when the "airflow switch' (run mode). Resistence across the contacts are nearly 0, so they are clean
3. I took apart the mass airflow meter and cleaned the fuel pump run switch, and the "variable resistence coil". Seems to be working OK.
4. Set the idle microswitch properly, and it seems to be functioning fine.
5.Verified the ballast resistor is OK. Even tried running the car with a full 12V on the positive coil terminal.
6. I disconnected the cold start injector and it won't even try to start.
7. Tried to start it with the ECM unplugged, and it does the same thing for the first start attempt, then it just cranks. Plugged ECM back in and back to the same thing.

Any suggestions? Cam timing? ECM? Hall effect pickup in the distributor? Ignition module?

grumpsjr · Post by **grumpsjr** » Tue Jan 12, 2010 7:54 pm

Welcome!

It sounds like a problem I had with my first E12 (an '80 528i 5-speed) that ended up being solved by replacing the Ignition Control Module located close to the ballast resistors. Given that you've ruled out most of the other common culprits, that would seem like a good next step.

Do you have a known good one that you swap out?

Best of luck,
Brian

On Tue, Jan 12, 2010 at 4:06 PM, turbo-rampage <turbo-rampage@hotmail.com (turbo-rampage@hotmail.com)> wrote:

Hi, hopefully you guys can give me a bit of a hand.

My 17 year old bought a 79 528i with L-jetronic which was running before it was parked 2 months ago because the previous owner cracked the oil pan on a curb.

Now it will fire and run for a second or 2 and just die like you turned off the key.

I have looked through the FAQ section here and spent the last 2 days working on it, and have found various problems I have fixed, but it still is acting the same.

Here are the things I've looked at:

1. Verified both fuel pumps run, and has about 30 psi fuel pressure.
2. Verified the "combo relay" is functioning as it should. The relay energizing the ECM with the key on is working, and the fuel pump relay is functioning when the engine is cranking, and when the "airflow switch' (run mode). Resistence across the contacts are nearly 0, so they are clean
3. I took apart the mass airflow meter and cleaned the fuel pump run switch, and the "variable resistence coil". Seems to be working OK.
4. Set the idle microswitch properly, and it seems to be functioning fine.
5.Verified the ballast resistor is OK. Even tried running the car with a full 12V on the positive coil terminal.
6. I disconnected the cold start injector and it won't even try to start.

Any suggestions? Cam timing? ECM? Hall effect pickup in the distributor? Ignition module?

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turbo-rampage · Post by **turbo-rampage** » Tue Jan 12, 2010 8:53 pm

Thanks for the reply.

No I don't have a spare module. I sent my son to look for one at the local PnP, but they didn't have any BMWs.

I don't really want to throw a bunch of parts at this thing since he is financially challenged. I was kind of hoping it would just be a bad ground or something.

grumpsjr · Post by **grumpsjr** » Tue Jan 12, 2010 11:58 pm

Where are you located? If it's close, I wouldn't mind letting you borrow an ICM for testing.

jayne58 · Post by **jayne58** » Wed Jan 13, 2010 12:18 am

Just what Brian said, it might be the ignition control module. Try opening it and check the back of the board and see if there is/ are cracks on the soldering, this would be very visible if you look close. if there is/are cracks most often it is not properly connected as it should be. I would use a soldering iron and heat up all the soldered point to make sure that they are all soldered properly. it happened to me once and it was a cheap fix. Good luck!

JAYNE

turbo-rampage · Post by **turbo-rampage** » Wed Jan 13, 2010 1:31 am

Ok first off, thanks for the offer Brian, but I'm western Canada, no where near California.

However I did more testing, and I'm not sold its the ICM. I removed one of the spark plugs and taped it to the MAF with the plug lead attached, and it actually has really good spark while cranking. Seems to still have good spark for the 1-2 seconds it was running.

From this I think I can safely rule out the ICM.

Next I removed the cold start injector and again cranked the engine. The cold start injector sprays like it should for about 15-20 seconds (which from what I read is about right). While doing this the engine never even attempted to start.

Which brings me to my latest theory. Its got spark, but I think it is only getting fuel from the cold start injector. Once the engine starts to fire, it quickly comsumes more fuel than the cold start injector can give, and dies.

Which leads me to think the injectors are not pulsing. Is there a way to test them to see if they are in fact pulsing? Would the ECM still activate the cold start injector if it was fried?

Oh and I also tightened all the ground connections on the intake manifold from the ECM.

YouTube · Post by **Peter Florance** » Wed Jan 13, 2010 6:23 am

If the car sat for a while, the injectors might be stuck shut. Do you know how long it sat?

There's a way to unstick them, but first lets see if ecu is firing them. Can you get a injector test light (most auto parts store) and see if the injectors are pulsing after you release the key?

turbo-rampage · Post by **turbo-rampage** » Wed Jan 13, 2010 10:05 am

It probably sat a couple months at least.

I will go get an injector test light and give it a try.

Also on a somewhat related note, I noticed last night that there are rubber jumper hoses between the fuel rail and injector. A couple of these are leaking.

Are these hoses a dealer only item, and if so are they even still available?

Again thanks for all the help.

YouTube · Post by **Peter Florance** » Wed Jan 13, 2010 10:08 am

turbo-rampage wrote:It probably sat a couple months at least.

I will go get an injector test light and give it a try.

Also on a somewhat related note, I noticed last night that there are rubber jumper hoses between the fuel rail and injector. A couple of these are leaking.

Are these hoses a dealer only item, and if so are they even still available?

Again thanks for all the help.

couple of months shouldn't do it.

I buy BMW fuel injection hose and burn the old hoses off with big solder iron.

Cut to fit.

grumpsjr · Post by **grumpsjr** » Wed Jan 13, 2010 10:26 am

Peter may need to chime in here, but I do believe that the ICM is responsible for sending the injection pulse to the injectors after starting. Failing that, I suppose it could be the magnetic pickup in the distributor, but I'd still check that the ECU is sending a signal first.

Keep us posted.
Brian

On Wed, Jan 13, 2010 at 7:08 AM, Peter Florance <peter@firstfives.org (peter@firstfives.org)> wrote:

turbo-rampage wrote: It probably sat a couple months at least.

I will go get an injector test light and give it a try.

Also on a somewhat related note, I noticed last night that there are rubber jumper hoses between the fuel rail and injector. A couple of these are leaking.

Are these hoses a dealer only item, and if so are they even still available?

Again thanks for all the help.

couple of months shouldn't do it.

I buy BMW fuel injection hose and burn the old hoses off with big solder iron.

Cut to fit.

Peter Florance
First Fives.Org - The E12 Registry
1981 E-Street Prepared Euro BMW 528i w/3.5L & Megasquirt Fuel Injection
1981 US BMW 528i "Repo Car"
http://www.firstfives.org
mailto:peter@firstfives.org (peter@firstfives.org)

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turbo-rampage · Post by **turbo-rampage** » Wed Jan 13, 2010 10:50 am

That does make sense, but the tach still works also, and I kind of got the impression that same signal went to the ECU. Guess the real proof in the pudding is if they are pulsing.

If it is the ICM, getting back to the other comment about pulling it apart and checking the solder joints.

I did try last night to take it apart. There are 4 screws on the bottom, but you really can't get at any of the electronics that way. The rest of the box seems sealed, bit it appears the front cover may be removed with some type of mechanical persuation. Is this required, or did I miss something?

I priced out a ICU from Rockauto. $400 for a rebuilt and $900 for new. Yikes.

Anyway it will have to sit for a few days as I'm back to my real job.

grumpsjr · Post by **grumpsjr** » Wed Jan 13, 2010 11:09 am

If it comes down to the ICU, don't buy one - there are enough floating around here from guys on the board. No sense in paying $400 or $900 for one, if you get to the point where you've determined that you need one.

Keep us posted,
Brian

On Wed, Jan 13, 2010 at 7:50 AM, turbo-rampage <turbo-rampage@hotmail.com (turbo-rampage@hotmail.com)> wrote:

That does make sense, but the tach still works also, and I kind of got the impression that same signal went to the ECU. Guess the real proof in the pudding is if they are pulsing.

If it is the ICM, getting back to the other comment about pulling it apart and checking the solder joints.

I did try last night to take it apart. There are 4 screws on the bottom, but you really can't get at any of the electronics that way. The rest of the box seems sealed, bit it appears the front cover may be removed with some type of mechanical persuation. Is this required, or did I miss something?

I priced out a ICU from Rockauto. $400 for a rebuilt and $900 for new. Yikes.

Anyway it will have to sit for a few days as I'm back to my real job.

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YouTube · Post by **Peter Florance** » Wed Jan 13, 2010 11:19 am

Pull one plug, if it has spark all the way to 0 rpm, the ICU is fine

Check the glove box and make sure the dash harness is connected to fuel injection harness (single tab connector)

jayne58 · Post by **jayne58** » Wed Jan 13, 2010 12:55 pm

Hi if you come to decide and open up the ICM, you need to grind flat the 4 head of the sort of rivet on the front cover. and pry it open with a screw driver thru the side. Once opened you would have to solder off the six connectors at the bottom and take off three more screws that hold the circuit board. assembling back, a good epoxy paste will do for the cover, it has a rubber sealant anyways. But I would check the injectors first as Peter suggested.

Good luck
Jayne

Lenny D. · Post by **Lenny D.** » Wed Jan 13, 2010 2:54 pm

My turn..

As I've stated here many times, the connections in out cars are the likely suspects generally, before component failure. I had your complaint that turned out to be the female pins of the AFM connector. There is a post about that in the archives, but check the connector for cleanliness, and check that the female sockets stay in the connector housing as you connect it to the AFM. My car would do exactly that, start and die, even at operating temp.

I do not suspect the impulse sender in the distributor, when they go south you have a complete no-start condition.

While tending to the ICU, make sure the contatcs are all clean - the rubber boot is supposed to seal out moisture and water but it's mounted in the bottom, and that was thirty years ago.

Check all electrical connections!