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Tref

My e28, 525e's engine keeps cutting out.

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The e28 525e is having problems. I'd be the first to admit it's been neglected recently, only covering short distances a few times a week for the last couple of years, However with it's upcoming MOT I'd begun to get on the things that need doing and then this started...

   After starting without issues it will run for 4-6 minutes before instantly cutting out, sooner if I'm driving, longer if it's left idling outside at home. Going to start whilst still 'rolling' so to speak the engine will just turn over without catching. The temporary solution I've found is to pull over, and go through the ignition on for 10 secs, ignition off, repeat a few times and then it starts as normal. The engine either runs for less than a minute before instantly cutting again. Or it's fine as I turn around and head the few minutes back home, with everything crossed, whilst I'm stroking the dash and murmuring positive platitudes (as if that will help!). I'd like to see if it would then run indefinitely as I continue on my way, I suspect not and being proved right would involve being recovered which is not really something I'm keen to have happen.

 

The instant cutting out rather than 'choking' to me says electrical/ignition system rather than fuel, it's almost as if it's running up to temp and then something is failing and cutting off the electrics, as when it's running it seems fine.

 

But the fact that the ignition/priming trick seems to work (it could be incidental) would lead me towards the fuel system being at fault. As it's easy to do I've checked the pump relay, fuse and changed the fuel filter, without solving the problem.  

 

I thought I'd ask if this seems familiar to anyone?

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To eliminate the main relay, make up a jumper as below and plug in place of the relay. That is pin 30 to 87 and 87. Dont leave it in place with the engine off as it will run down the battery.

 

You can eliminate the ignition switch and intervening wiring by running a wire from battery positive to terminal 15 on the coil.

 

post-28888-0-39787500-1394781946_thumb.jpg

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Thanks JohnH...

 

I went for the ignition bypass first, figuring I could spend the testing time making up a relay jumper... a good plan as the bypass seems to have solved the problem, engine running for 20mins without cutting out. I'll take it for a drive later when it's quieter and try some idling without the bypass just to confirm.

 

But it looks like the ignition switch or related electrics is at fault, narrowing it down to at least a sub-system is a relief.

 

Thanks for the information, Trevor.

 

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Trevor,

Take a look at the C101 connector on the side of the fusebox. pin 12 is the ignition supply from the ignition switch which you just overrode. Its not uncommon for the pins in it to backout, especially if its been disconnected before.

Regards

John.

 

PS take a look at Duncan's troubleshooting guide at the top of this page. Its got some good tips. 

 

Is yours fitted with an OBC (On Board Computer)? its not uncommon for the Code function to fail cause intomitant* ** ignition failure. 

 

* how do you spell that? 

 

** Thanks Mick. I was going to Strike through it, but there is no Strike Through!!!

Edited by JohnH
Attempt to fix spelling

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This morning tested idle from a 'cold start' with no bypass to try and confirm the fault.... the engine ran for 15 mins without cutting. So it appears to have fixed itself (I know this is absurdly optimistic). I'll do some more driving later without the bypass to see what happens.

 

The only thing I noticed this morning was around the time it would normally cut 6/7 minute mark there would be a single stutter, like it was going to cut out and then caught itself. It then ran fine for a while then another stutter. This happened a couple of times till 8/9 minutes then stopped and the engine ran steadily.

 

I've removed, checked the C101 connector and that's fine, the Eta is missing the OBC thankfully, I know some people like them. But the fewer old computers the fewer problems to my mind.

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Afternoon testing... Bad news is the ignition bypass doesn't work, Good news is I can reliably force the fault.

 

I went for a test drive, and the engine cuts less than a mile from home, at roughly the same area/road it always has when heading that way. I connected the ignition bypass and set off and it cut out again before the end of that road. Removed the 'ignition bypass' and set off to the gym (just under a mile) with no further problems. Out of the gym I head off for a varied drive and the engine starts and runs fine for the next twenty odd miles (about an hour) of town,country and A roads.

 

From a cold start (no issue starting hot or cold) as the engine is warming something is failing, if idling it's causing stutters, driving/under load it's causing the engine to cut. But once the engine is warm there are no further problems. So does anyone know what could cause that? 

Edited by Tref

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Okay!

 

So did you make up a main relay jumper?

 

It maybe an DME fault (the main computer) but I think they are pretty reliable.

 

I dont think its a fuel pump / fuel pump relay problem (just yet).

 

One step at a time.

 

 

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I tried the main relay jumper this morning and drove it past the 10 min mark without cutting or other issues. I'll test the relay later when I've a spare moment,   

 

So I'll keep at it every morning from cold with the bypass, while I hunt down a new relay. I'll refrain from calling it fixed, but it's pretty well narrowed down where the fault might be. 

 

I'll post in a few days to update the thread. Thanks for you help with this JohnH.

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On 20/08/2017 at 8:41 AM, duncan-uk said:

I have a couple of dme relays at home.

 

Hi Duncan I've sent you a PM.

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Small update, the relay jumper hasn't solved the issue (it might have reduced the rate at which it occurs) a weeks worth of test drives has lead to only two roadside 'rests' so to speak.

 

On 21/08/2017 at 8:16 PM, Sir Anthony Regents-Park said:

Could be a failing crank position sensor - the one for TDC. They can go open circuit at a certain temp.

 

Crank Position Sensor/Pulse Generator are we talking about the same part? If so according to 'Bentley' "...from March 1987 and later are equipped with Motronic 1.1 which uses a single front-mounted pulse sensor to sense engine speed and crankshaft position..." My Eta is a 7/1987, so just the one to sort out.

 

There is a brief testing method but considering the faults random nature I think I'll just go for a replacement. 

 

 

 

 

Edited by Tref

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1 hour ago, Tref said:

Small update, the relay jumper hasn't solved the issue (it might have reduced the rate at which it occurs) a weeks worth of test drives has lead to only two roadside 'rests' so to speak.

 

 

Crank Position Sensor/Pulse Generator are we talking about the same part? If so according to 'Bentley' "...from March 1987 and later are equipped with Motronic 1.1 which uses a single front-mounted pulse sensor to sense engine speed and crankshaft position..." My Eta is a 7/1987, so just the one to sort out.

 

There is a brief testing method but considering the faults random nature I think I'll just go for a replacement. 

 

 

 

 

I would be very surprised to see a front mounted sensor on a Euro 525e - that was the last of the USA 528e cars with the E30 325e 'SuperEta' engine. Nothing's impossible of course - put up a photo of yours.

Edited by Sir Anthony Regents-Park

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I think the American market had Moronic 1.1 in their run out 528e's and these are known as "super etas", hence the Bentley reference to the front crank sensor.

 

I have an April 87 525e and a November 87 525e and they both have two sensors bolted to the bell housing on the passenger side.

 

Regards,

 

Mick

 

Edited by Ordnator

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Final Update (fingers crossed.) The engine issue started to occur more frequently and sooner, even when idling. Which started me thinking that I might have been fixated on electrical rather than fuel as the source. I changed the sensors over and for good measure the fuel pump, the e28 has been behaving for a week now so it appears to have solved the problem. It would have been more methodical to try one then the other in order to narrow down the culprit. But with the weather down here lately I just wanted to be able to go places and arrive dry! 

 

Thanks again for the inputs and ideas Gents.

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Nice one Tref. Make sure you change the fuel filter at the same time. My E30 was suffering from similar problems which essentially turned out to be a blocked filter which in turn knackered the pump. Fingers crossed the issue is now resolved as it's so satisfying knowing that the engine is back up and running how it should be! ^_^

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