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BMW E28 5 Series 1982-1988 (528e, 533i, 535i, M535i, M5) 85 528E Gas Mystery


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Last Post: Oct 21, 2011 6:34 PM Last Post By: mike 84 528e
Jared

Posts: 5
Registered: 12/09/03
85 528E Gas Mystery
Posted: Jul 1, 2003 10:42 PM
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Hi,

Man, I love my BMW. Hands down the best car I have ever owned. A friend sold it to me for $500. Not the prettiest car in town, but it ran great and kids arenít too embarrassed to ride in it.

I was driving my 528E down the road, (running as good as it ever has) and all at once it coughs, sputters and stops in the middle of the road. The gauge said I had gas but it just felt like I had run out so I went and got a couple of gallons. I started the car, it started fine and ran for about 5 seconds and coughed to stop. After letting it rest I would try to start it and it would run for a few seconds and then die. Itís been four months now and I still canít figure out what is wrong. It no longer will start and run perfect for a few seconds. It still tries to start but it is much weaker and still dies quickly.

I have:
Gone through the Bentley manual
Replaced the fuel filter
Tested the fuel pumps, 30+ lbs and it holds the pressure well over 5 minutes
I have tested and or replaced with a known working part, the rotor, distributor cap, the coil, computer, the two flywheel sensors, the fuel pump relay, the main relay, all the fuses.

I have checked power to the injectors (have it), checked for ignition spark (have it and it tries to start), I have removed and reinstalled the ďon boardĒ computer, but I havenít tried replacing it.

Does anyone have a clue what it might be? Sure would appreciate some ideas. I am totally stumped.

I barely earn enough money to make rent for me and the kids, so I have to fix it myself or let it sit. Meanwhile the only vehicle I have to drive 50 miles to work is my 69 Chevy pickup (8 mpg) and itís really hurting.

Would it make any sense to take it to a BMW shop or are they just going to ďdiagnoseĒ me to death and not figure it out until Iíve spent $500 and then want $1500 to fix it.

Thanks in advance for any advise.

Jared
Charlie

Posts: 4,776
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 9:56 AM   in response to: Jared in response to: Jared
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Sounds like you are down to the control unit? I had a 1988 528e that I drove into the driveway, shut it off and went in to bed. The next morning it started and ran crappy, etc. It was a bad control unit. When these units fail on the 'Eta' engine they tend to fail in the rich direction. Do you think it is running too rich? Have you tested the coolant temp. sensor?
Jared

Posts: 5
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 10:27 AM   in response to: Charlie in response to: Charlie
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Charlie,
Thanks for the reply, I really appreciate it.
I have replaced the control unit with a known good working unit, with no change in the symtoms.
I have not tested the water coolant temp sensor but I will do that tonight after work.
I wouldn't think it was running two rich. Seems like it is not getting enough gas. When it first broke it would run a few seconds perfectly and then sputter and die. It was as if it was being fueled by the "start valve" and then when it was time for the rest of the injectors to kick in they just don't.
Bob at the alt.autos.bmw news group suggested it may be a bad transfer fuel pump. I will check that this evening also.
Thanks
Jared
Charlie

Posts: 4,776
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 10:58 AM   in response to: Jared in response to: Jared
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I would say you can rule out the pump. You have good fuel pressure. Are the spark plugs wet after you have been cranking for a while? How about the air flow sensor? Have you checked this? Sounds like you are not getting fuel and the mass air flow sensor would be a logical culprit.
Jared

Posts: 5
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 11:25 AM   in response to: Charlie in response to: Charlie
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Charlie,
I have not checked the air flow sensor, nor have I looked at the plugs after cranking for a while. I will make both of these tests this afternoon if I can manage.

I don't have a lot of faith in the idea that the fuel pump is the problem but I have not individually tested each pump to absolutely rule them out.

At least now I feel like there is something I can check to further diagnose. I was at the top of my knowledge and quite stuck.

Thanks for the ideas.

Jared

Stuart

Posts: 1
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 3:40 PM   in response to: Jared in response to: Jared
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Just saw your message. I think the others are on the right track.
Both my 83 and 84 528's had a similar problem a couple years ago (the '83 has 680,000 on it!).
They both had a 'dealer installed lean mod' - essentially a second coolant temp sensor wired in series with the 'main' one. The 2nd one was installed in the small (10mm) hose running from the thermostat housing to the intake manifold. I removed the 'wiring harness' for this mod and hooked just the one temp sensor up and all was OK.
A couple other things to check:
Is the In-Tank transfer pump working? If Not a Vapour Lock in the fuel system in warmer temps (80 F and above) is common. If you need to replace it I can provide some suggestions for how to do it for around $50 instead of >$200.
Also - Is the Fuel Pressure regulator OK?
Stuart
'83 528e; '84 528e; '85 535i
Jared

Posts: 5
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 4:10 PM   in response to: Stuart in response to: Stuart
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Stuart,

I appreciate your feedback. I will check the coolant temp sensors this PM as well as the transfer pump. I'm excited to see if any of these suggestions will be "the one" because I really miss driving my car!

680,000 miles, wow! Now that's impressive.

Jared
Jared

Posts: 5
Registered: 12/09/03
Re: 85 528E Gas Mystery
Posted: Jul 2, 2003 11:14 PM   in response to: Stuart in response to: Stuart
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Stuart.
Hi,
I just got though testing the temp switch and sensor, they are in spec.
However when I went to test the cold start valve I discovered I have no fuel or pressure at all. I switched the relays but still no power through the pump fuse at the fuse block. I'm baffled now. I had good pressure and delivery and it still had the problem. Now I have nothing at all. Perhaps the main pump is intermittent and now dead. I'll test this weekend.
Thanks for the tips.
Jared
No nickname sel...

Posts: 9
Registered: 10/07/04
Re: 85 528E Gas Mystery
Posted: Oct 7, 2004 11:58 PM   in response to: Jared in response to: Jared
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Ok. Two things to check and most likely it's one of them:
1. The main relay.It powers your fuel pump relay. if it is dead, your pump will not run.
2. The fuel pressure regulator.

I need to know if you have spark and or fuel! before I can explain further.
mike 84 528e

Posts: 2
Registered: 10/21/11
Re: 85 528E Gas Mystery
Posted: Oct 21, 2011 6:34 PM   in response to: No nickname sel... in response to: No nickname sel...
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i have 84 528e ive owned over 15 yrs now its cranking over but no start ive replace sensors relay now after looking around online i was told checking main relay for power and the red/white wire on main relay is not getting power with ignition on therefore im getting no spark no start please please help

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