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Thread: E32 750iL questions to electronic gurus (long)

  1. #11
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    Default Thanks whit, told him your suggestions

    Just could call him and he sent me emails:

    Well I think I finally found the problem. One more 5:00 am morning checking things before work!!

    After checking and swapping MAF's, DME's, DME relays, I made a breakthrough discovery, My car was in a sort of Limp Mode. I crawlled under the car to check the CATS and noticed that the one side was cold to touch. Thinking spark or fuel issues I checked the fuel pump relays, coil, induction test on the plugs, vacuum lines, fuses - all checked ok. After recieving an idea from Shogun and Harywithit I was heading to Johan's site for the fuel pressure regulator change. Part way through it details jumping the fuel pump relays to check for fuel quantities. Sure enough, the side that wasn't working wasn't receiving any gas!

    All I can think of is in the morning I'll check the connector at the tank to ensure everything is good to that point, before coughing up $200 or so for a new fuel pump.

    Having said all this and seeing the light at the end of the tunnel, does anyone have any other ideas in case this doesn't pan out?

    Real
    ---------------------------------------------------
    That is the status as of now.
    If any ideas/proposals, just me me know.
    I am checking now for a used pump in Japan. Or does anybody know what other maker than Bosch can be used. BMW p/n for the pump only is 16141179710.
    Bosch p/n (not sure) is E300-150664
    Regular price is $ 306,-, so it will cost here in Japan abt. double that price.
    Checked various online vendors in USA like expressautoparts.com, autopartswarehouse.com, prices 237,22 and 215,47.
    But there is a pump at bavauto.com with their p/n GFP316 which costs $ 199,95.
    That seems to be not a Bosch pump. Does anybody know the maker of another brand for this pump and/or the specification/size etc. for the pump? Maybe they are also available in other japanese cars, so then we could get a pump much quicker and probably cheaper herre in Japan.
    Thanks

  2. #12
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    Default

    Sounds like he is on the right track. Hey, not a cherry-red cat or manifold, but an ice-cold one, eh? Interesting.
    I would try this test (only if the car is NOT a daily driver): take the known working fuel pump and swap it with the one that is not working. Swap them both to the opposite sides and hook them up.

    1. If there is no change and everything works the same way then both fuel pumps are good, but something else is preventing the pump from working on the "cold side." Repaired connections will fix.
    2. If the hot and cold sides are reversed, the pump that started out on the "cold side" is probably bad. New pump will fix.
    3. If everything stops working then you may have 2 things wrong: both bad pump and a bad connections from that "cold side." Need both repaired connections and new pump to fix.
    4. If everything suddenly works, you got lucky and shocked the monkey or scared the ghost in the machine. Knock on wood, ask no questions and be happy for a while. I once had a starter solenoid that would not work in a classic Mustang, but worked great in an old Jeep. It still works. Why ask why?

    The "swap" test could tell you whether or not you need to shell out $200-300 for a new fuel pump. You might not need it. The problem could just be the way the pump is connected, blocked or bent fuel lines, fuel filter, electrical signal, etc. I would try this test before I bought a new pump (I am cheap), but only if the car was not a daily driver. Wish him luck.
    Last edited by Whit; 03-09-2005 at 04:30 AM.
    Whit
    1988 750il (whoops, tricky title--probably not a 1994!)

  3. #13
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    Default

    I edited this when I realized there were some more possibilities.

    Quote Originally Posted by Whit
    Sounds like he is on the right track. Hey, not a cherry-red cat or manifold, but an ice-cold one, eh? Interesting.
    I would try this test (only if the car is NOT a daily driver): take the known working fuel pump and swap it with the one that is not working. Swap them both to the opposite sides and hook them up.

    1. If there is no change and everything works the same way then both fuel pumps are good, but something else is preventing the pump from working on the "cold side." Repaired connections will fix.
    2. If the hot and cold sides are reversed, the pump that started out on the "cold side" is probably bad. New pump will fix.
    3. If everything stops working then you may have 2 things wrong: both bad pump and a bad connections from that "cold side." Need both repaired connections and new pump to fix.
    4. If everything suddenly works, you got lucky and shocked the monkey or scared the ghost in the machine. Knock on wood, ask no questions and be happy for a while. I once had a starter solenoid that would not work in a classic Mustang, but worked great in an old Jeep. It still works. Why ask why?

    The "swap" test could tell you whether or not you need to shell out $200-300 for a new fuel pump. You might not need it. The problem could just be the way the pump is connected, blocked or bent fuel lines, fuel filter, electrical signal, etc. I would try this test before I bought a new pump (I am cheap), but only if the car was not a daily driver. Wish him luck.
    Whit
    1988 750il (whoops, tricky title--probably not a 1994!)

  4. #14
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    Default

    Just got the following ifo from someone on another board:

    careful . . . .

    . if your car is in limp mode (you previously indicated it was not), a shutdown of the cpu will shut off the fuel pump to the disabled side, as the control signal for the fuel pump relay is routed through the dme (safety reason--not good to flow raw gas through one side of the motor and into the exhaust).

    In other words, you might be seeing a symptom and not the cure.
    ----------------------------
    Hmmh,
    could not talk to him today. Let's see what he found out. Will keep you updated.

  5. #15
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    Wow, it looks like he needs to find out if he is really in limp mode. These cars are just too darn sophisticated--I need to do a lot more reading. I still think a bad fuel pump or a poorly connected one could show the same symptoms and that a fuel pump swap (from side to side) would be worth the trouble. It might even help diagnose a limp mode (if the car runs the same way after the swap) and would also let him know that both fuel pumps work. Keep me posted.
    Last edited by Whit; 03-09-2005 at 04:21 PM.
    Whit
    1988 750il (whoops, tricky title--probably not a 1994!)

  6. #16
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    Default

    We found a used fuel pump in Japan and it will probably arrive today or tommorow.
    Time is important.
    Just to be sure that we are on the right track with the pump: how to check the installed pumps with a multimeter best without running them dry when removed from the tank? Resistance?
    There is something on Johan's page where Sean checked it, but he is also asking for a better way
    http://bmwe32.masscom.net/sean750/fu...t/Fuelpump.htm
    Will keep you updated.
    Last edited by shogun; 11-21-2013 at 11:03 PM.

  7. #17
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    Default New update since last post (from Real)

    Well I thought it was the fuel pump and it still maybe. I was pressed for time so I went ahead and installed it without checking if there was fuel between the pump and the fuel filters. I checked at the engine and I still do not have any fuel to the left bank (7-12 cyls?).

    Jim and others mentioned "Limp Mode" is there a way that the engine can go into limp mode and not display an EML or other warning? As I stated in a previous post I have swapped MAF, DME, DME Relays, Fuel pump relays, inductve spark check on both sides. The problem remains on the left side.

    The only other thing I can think about is that I will rout a piece of hose from the sending unit to a bucket to see if I have fuel there, if so, I'll check the fuel filters. I doubt that if it is a fuel filter issue that it would have clogged so abruptly (working in the morning and not in the afternoon). Any ideas on this. If there is fuel at the sending unit the only thing between there and the engine bay is the fuel filters right?

    Shogun has asked about the EML. Prior to start up it lights for a couple seconds and then shuts off.

    Does anyone know of any other reason why fuel is not making its way to the engine?

    Still plugging away at this, hopefully it will be solved soon.
    ---------------------------------


    I tested the fuel pmup in the engine bay as described in the previous post. At that time I checked the fuses again and noticed that since I installed the new pump my fuse #24 (fuel pump) was blown. I changed it out with a new one had then had my wife check the car after starting it. That same fuse is burnt out again. Is it possible knowing what I know now that the fuel filter may be pugged solid not allowing any gas to go through, in turn causing the pump to over work and blow the fuse?
    Last edited by shogun; 03-10-2005 at 09:07 PM.

  8. #18
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    Is it blowing the fuse right away or did you say it works for a while? If it works for a while, can you test the wiring connections with a multimeter for continuity with a ground and with surrounding wires? A loose connection or a frayed/melted/hanging wire could be grounding and blowing the fuse.
    Could be a blocked fuel filter, or kinked/crushed/blocked line, but you need to see if fuel is getting to the engine WITHOUT the fuse blowing. If you can keep the fuse from blowing, I would do the bucket test, you might get some flow. It it will be hard to tell what the proper flow is--if you test it at the rear it might actually flow back there. I would do it at the front of the car, so you can tell if fuel is actually getting up there--there could be a blockage along the way. If you get some flow, then check the good pump too. See if you can compare the flow rate visually and then the volume in the bucket of each. I don't know if you could really do that, but it might be worth a shot if you get both to flow for a while and not blow the fuse.
    I don't know, but my gut tells me that the pumps are good and that this is a wiring short (the blown fuse) or just a clogged line or filter that could be overworking the pump (the blown fuse). On the other hand, your old "problem side" pump and the new/used one could both be bad and blowing the fuse. Hmmm...I would put the known working pump on the problem side--swap it with the new/used one just to eliminate possibility of bad parts. I once had two sets of new points and I tried to use each for a tuneup. BOTH were bad and it took me forever to figure out the problem. Bad parts are not impossible.
    Shogun, sorry, I just am used to old Jeeps and classic muscle cars--they are much easier to diagnose and fix. My other cars in the US are under the manufacturer's warranty, so I let them do the wrenching. I am slowly learning that the computer controls and electronics on these 7-series cars need to be respected and I have to keep learning. Wish I could be more help. Good luck to your buddy.
    Last edited by Whit; 03-11-2005 at 02:20 PM.
    Whit
    1988 750il (whoops, tricky title--probably not a 1994!)

  9. #19
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    Thanks, Whit.
    Passed the message on and now this reply: (I distributed it to get some more feedback)
    quote:

    Help! Can't find short

    I checked and it appears the Cats are on correctly.

    Here is what I know at the moment I attached this to the original thread before seeing this reference post:

    After extensive checking I am having trouble locating the short or electrical problem that I am having.

    At the present I am still blowing fuse #23 (fuel pump) but only when I start the car. If I have the key in position 2 the fuse doesn't blow. I believe is the problem may be with an overvoltage protection relay, more on this later. Here is part of what I know let me know if this gives any clues:

    1. Key in off and I attempt to jumper 30 and 87 at the fuel pump
    relay nothing at either relay;
    2. Check with a multimeter 30 and 87 and there is nothing;
    3. Turn the key to position two and I get just above 12 volts on
    both relays at 30 and 87;
    4. With the key still in position 2, 30 and 87 jumpered, I checked
    voltage at the connector and I get about 3.4 V at 4,5 and 4,6 on
    the connector;

    The only time the fuse blows is when I start the car. I am not exactly sure of the direction of electricity flow but it appears to be ign coil - fuel pump relay - fuel pump - fuse, with the main (DME?)relay, DME, and some overvoltage protection relay(any one know where and what this is?) connected also.

    I have just about given up here and may have to breakdown and go to the dealer to check this out....HELP PLEASE!!!

  10. #20
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    So, the pumps are each fused individually, right? The "bad side" keeps blowing. It still sounds like a defective pump to me. OK, I am going with my original advice: replace the fuel pump on the "bad side" with the one you know is good. You need to swap the good side and bad side pumps. That used one that you bought could be just as bad as the one it replaced.
    After the swap, if it blows on the SAME side, the connections are the problem. If it blows on the opposite side, it is the pump. Swap them or you won't know for sure if it is the pump or the connections. You need to eliminate one possible cause before you can move on.


    Quote Originally Posted by shogun
    Thanks, Whit.
    Passed the message on and now this reply: (I distributed it to get some more feedback)
    quote:

    Help! Can't find short

    I checked and it appears the Cats are on correctly.

    Here is what I know at the moment I attached this to the original thread before seeing this reference post:

    After extensive checking I am having trouble locating the short or electrical problem that I am having.

    At the present I am still blowing fuse #23 (fuel pump) but only when I start the car. If I have the key in position 2 the fuse doesn't blow. I believe is the problem may be with an overvoltage protection relay, more on this later. Here is part of what I know let me know if this gives any clues:

    1. Key in off and I attempt to jumper 30 and 87 at the fuel pump
    relay nothing at either relay;
    2. Check with a multimeter 30 and 87 and there is nothing;
    3. Turn the key to position two and I get just above 12 volts on
    both relays at 30 and 87;
    4. With the key still in position 2, 30 and 87 jumpered, I checked
    voltage at the connector and I get about 3.4 V at 4,5 and 4,6 on
    the connector;

    The only time the fuse blows is when I start the car. I am not exactly sure of the direction of electricity flow but it appears to be ign coil - fuel pump relay - fuel pump - fuse, with the main (DME?)relay, DME, and some overvoltage protection relay(any one know where and what this is?) connected also.

    I have just about given up here and may have to breakdown and go to the dealer to check this out....HELP PLEASE!!!
    Whit
    1988 750il (whoops, tricky title--probably not a 1994!)

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