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Thread: Working on the fuel system...

  1. #1
    Join Date
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    Working on the fuel system...

    Car has sat for a while (understatement - right Ron?)
    -Fresh fuel
    -Pumps won't run, even with power applied directly
    -Only way to get power to rear pump electrical connector is to pull the relays and jump the pins
    -New relays - still no power to connector when car is switched on

    sigh

    working my way through the threads now

  2. #2
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    So do the pumps run when you apply 12v to the pump carrier socket?

  3. #3
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    nope - unhappy pumps is one issue that will be resolved - looks like a combination of failures

  4. #4
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    Never seen them both fail from sitting, I lost one after 3.5 years of sitting but not both.

  5. #5
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    I have seen several cars with both pumps dead...
    Here is what you will need to do:
    https://www.bimmerforums.com/forum/s...-Pump-Assembly

  6. #6
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    Yeah - have your thread bookmarked

    Marv - slightly more complicated than just sitting. Would start the car and move it around from time to time. Began running worse and worse and finally wouldn't start at all about 6 months ago.

    My SWAG is that the pumps were failing, and all that cranking burned out something else along the way. New relays + filters in now, and will be tackling the pump upgrade soon. Still gotta figure out why I'm not getting power back there when I switch the car on though. Checked the inline fuses on the battery with a meter and they get a thumbs up. Gotta read through the threads and see what else might be making her unhappy now.

  7. #7
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    replace the pumps first if they don't run with 12v to the fuses. Then try it with new pumps installed...
    the pumps don't run all the time when the key is on, only a pulse and then constant once the engine cranks/runs... makes it hard to tell if there is actually a relay problem or not if you know the pumps are no good.

    And no, contrary to a certain someone's "purist" opinion - you can't ruin the pumps if you apply voltage to the fuses - as long as the pumps are in gas!
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  8. #8
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    Thanks for the tips -

    I figure that the pumps should be running in my case when the key is on as I had drained the lines when I installed new filters. Also - no power to the electrical connector back at the pumps.

    I'm hoping it turns out to be something stupid - but not too difficult to track down!

  9. #9
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    Quote Originally Posted by 8eights View Post
    Never seen them both fail from sitting, I lost one after 3.5 years of sitting but not both.
    Have seen many, many, once upon the time we had about 30 E32 750 in storage in our wrenching group, changing respect. re-awakening fuel pumps was one of the main taks always when we came there 200 miles from home.
    Shogun tricks and tips for the E32 series are HERE!

  10. #10
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    Quote Originally Posted by rockytt View Post
    Thanks for the tips -

    I figure that the pumps should be running in my case when the key is on as I had drained the lines when I installed new filters. Also - no power to the electrical connector back at the pumps.

    I'm hoping it turns out to be something stupid - but not too difficult to track down!
    Like I mentioned, the car will not power the pumps for any more than a quick blip with just the key on - the engine has to be turning, either by the starter or on its own. This makes it tough to "test" the pump voltage. Pressure/no pressure - pumps don't know this... So you won't get any "extra" action over what I described above. If they don't run with 12v applied directly to the two fuses, pumps are bad. Once you replace them, youll likely find the car actually does power them and it will run. If it doesnt, then we deal with that end...but my bet is you won't have to.
    Last edited by cartoonz; 09-15-2017 at 03:29 AM.
    '91 Dinan 860 Stage III (new 6L engine)
    '91 Dinan 850 TT stage III (brand new engine) 21st Century Tech meets 18th Century Dinan...
    '91 850i 6sp (mint) (sold)
    '90 Dinan 750iL TT stage III (Guido - The Beast)
    '94 850 CSi The Detroit Auto Show car (restored to factory perfect) (sold)
    '96 850Ci, The George Carlin car
    ''73 3.0 csi, '08 535i, '03 X5 4.6is
    ...and a few other non BMW cars

  11. #11
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    Awesome - hope that fixes things up - will report back in a couple of days after Mr. UPS brings me some new bits

  12. #12
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    Too bad I'm leaving town for a week tonight or I'd volunteer an extra set of hands. Maybe when all your "bits" arrive the collective wisdom/knowledge of SoCalEights can have an impromptu Wrenchfest at your castle?
    1993 850Ci.....18 years & 165,000 miles and counting!

  13. #13
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    Maybe next weekend I supply beer, pizza and cigars for those who want to hang out and offer support/guidance/unnecessary opinions - pumps aren't here yet anyway.
    Maybe the 24th?

  14. #14
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    If with the new pumps you still don't get them to work you should check the relays in the right side relay box and the fuses in the fuse box. If they check out then unfortunately you will probably have to dig out the harness that connects the relays to the fuses and check it for shorts. It's a thick bundle of wires wrapped in cloth tape. It's mounted to the firewall underneath the cabin air inlet. Older cars exhibit individual wire insulation cracking and flaking which allows the conductors to short. It's tedious, but you should wrap or heat shrink electrical insulation on each wire to prevent shorting.

    Ask me how I know...

  15. #15
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    question: Given the fact that the pumps don't work unless the engine is pumping - is there a preferred method to pressurizing an empty system after replacing all the bits? Just crank away on the starter? Jump one of the relays until the lines are full? Apply power directly to the pumps?

  16. #16
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    Quote Originally Posted by rockytt View Post
    question: Given the fact that the pumps don't work unless the engine is pumping - is there a preferred method to pressurizing an empty system after replacing all the bits? Just crank away on the starter? Jump one of the relays until the lines are full? Apply power directly to the pumps?
    There is a blip in power before the crank so the system gets primed.

  17. #17
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    Zeke, how long since fresh gas was added? The non-running '91 I rescued had sat for 3+ years with old gas, and the chemical properties of gas can change dramatically over time. Golden color and smelled like kerosene. The fumes in the tank disintegrated all wire insulation and rubber mounts. I don't recall a blip with key-on, but did get 12v to the connector during cranking. Jeez, I regret trying to jump the pumps directly once I removed and saw what they looked like. Yikes. The fuel siphon/sending unit on the other side was equally destroyed.
    Fuel Pumps - Yikes.jpg

  18. #18
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    Hi Gary - just popped 5 gallons in a couple of weeks back when I started the fun - tank was essentially empty for the last year or so

    There is a blip in power before the crank so the system gets primed.
    Well - a 'blip' would cover it if there were already fuel in the lines - since mine are completely empty, including the filters, I'm guessing I'll need more than that - yes?

  19. #19
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    Blip meaning 12v for a very short period measured at the electrical connector at the pump. You should get continuous 12v while cranking. With new pump unit installed, I flushed the lines by disconnecting the two fuel lines near the firewall on driver's side, ran extension hoses into a bottle, and cranked until clear. Pull the pump unit and inspect. I'm available on 9/24 or to offer "support/guidance/unnecessary opinions". Beer and pizza is good, but no cigar for me. Just give me a call anytime. Still not clear to me if you have an electrical and/or mechanical issue.

  20. #20
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    Still not clear to me if you have an electrical and/or mechanical issue
    Hopefully it's one or the other (and not both!)

  21. #21
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    Wow. Good luck with this guys. I'll be following this thread. Impressed with the support from others!

    Cheers.

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