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Thread: dual fuel pump set up for tracked E36 M3

  1. #51
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    Could your relay socket be bad? Give the terminals on one of the relays a little tiwst so they make a better contact/connection in the socket.

  2. #52
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    Quote Originally Posted by MCMM3 View Post
    Well I'm pretty stumped.

    First to answer the question I had first tried a Beck/Arnley replacment , then just tonight thinking both the original and the Beck/Arnley were shot I picked up a IDI brand relay at a local parts store. I installed the relay, turned on the switch, and tested the power at the fuse and saw nothing, so I assumed that I had no clue and the relay wasn't an issue. So I boxed up the IDI I just bought. Popped in the Beck/Arnley relay and tested and still got nothing at the fuse, confirmed the pins like you said and all was correct. Totally stumped I just reaching in and instead of just in the on position I cranked it and it started.

    Now I'm confused, I thought I would see power at the fuse when the key was in the on position but is that my mistake it should be in start (cranking) to test?????

    Still doesn't make sense why it just decides to not start some times?

    I'm too lazy to check the Bentlry but isn't the e36 like the e46. When you turn the key the pumps will come on to prime the system then shut off. Once the car starts they come on again.

    Either way take the power wire to the passenger pump and hook that to slot 86 on a relay, slot 85 to ground, 87 to the battery and 30 to the pumps (put a fuse in line) You can also run a relay for each pump if you wish.

    This will remove the load from the switched power.

  3. #53
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    Quote Originally Posted by capp07 View Post
    I'm too lazy to check the Bentlry but isn't the e36 like the e46. When you turn the key the pumps will come on to prime the system then shut off. Once the car starts they come on again.

    Either way take the power wire to the passenger pump and hook that to slot 86 on a relay, slot 85 to ground, 87 to the battery and 30 to the pumps (put a fuse in line) You can also run a relay for each pump if you wish.

    This will remove the load from the switched power.
    Yeah, I think you are right about the pump only run for a second or two in the on position, I think since I was working alone by the time I would turn on the key, then go to check the voltage at the fuse it had turned off. I think I'm going to confirm that this morning.

    Your comments about running a separate relay for the extra pump have been done by others and I might need to consider changing to that approach.

    One other note, reading more this moring I don't think the EWS is in play here as the can is cranking, and I think if it is cranking that is a sign that the EWS is not at fault, hope my understanding is correct.
    Last edited by MCMM3; 04-07-2013 at 10:22 AM.

  4. #54
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    The factory wiring was designed to support one pump not two the relay is the best option

  5. #55
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    We do it all the time without trouble. But we use a bigger fuse. Two pumps draw double the current.

    Beware used components. Pumps wear out. We've had pumps that work but suffer starvation replaced by new pumps that do not. Also, make sure it's a known good relay capable of switching enough current. We have no problem with a 30A fuse and a BMW fuel pump relay.

    In general, we like to rip all the oem wiring out and rewire what we need. Then we know what we have. Could just be a bad connection somewhere.

    BTW: DIN standard for relays is:

    30: to fused power
    87: to load
    86: + side of the coil
    85: - side of the coil

    Not a big deal if they are backwards unless the relay includes a diode. Then you might hear it POP!.

    See: http://en.wikipedia.org/wiki/DIN_72552
    Last edited by PCarroll; 04-07-2013 at 10:37 AM.
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  6. #56
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    Quote Originally Posted by PCarroll View Post
    We do it all the time without trouble. But we use a bigger fuse. Two pumps draw double the current.


    In general, we like to rip all the oem wiring out and rewire what we need. Then we know what we have. Could just be a bad connection somewhere.
    You don't just stick a 30A fuse on the stock wiring though, right?

    Does anyone know what gauge wiring is used between the relay and the stock fuel pump?
    http://www.offroaders.com/tech/12-vo...gauge-amps.htm
    Last edited by mrf; 04-07-2013 at 11:38 AM.

  7. #57
    NeilM is offline Member BMW E36 M3 Expert
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    Quote Originally Posted by PCarroll View Post
    Two pumps draw double the current.
    Ah, but fortunately they don't.

    Electric motors vary their current draw depending on applied load, and the added transfer pump, which operates at a much lower head pressure, is very lightly loaded compared to the main pump. Max current draw for the stock E36 pump is 5.0A, and I'd be quite surprised if the secondary pump draws even half that. Since the fuel pump circuit is on 15A fuse there should be no problem with two pumps under any load scenario, and years of E36 experience shows that to be the case.

    Disclaimer: I have no numbers for it, but since Peter's S54 operates at both a higher fuel rail pressure and at a greater max flow rate, presumably the main fuel pump is also drawing a higher current. Similarly, all bets are off with non-stock/high capacity pumps.

    @OP: Bentley 160-6 through 8 gives the procedures for testing the E36 fuel pump circuit and operation.

    Neil

  8. #58
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    OK, I really certain now that this is not a case of overloading the 15A fuel pump circuit. I did take the time today to add an additional relay so each pump has its own circuit, and when I was finished the car started right up, went for a 10 minute drive no issues, then brought it home and turned if off/on several times and no problem.

    But I let it sit for about 90 minutes and purposely went out to try it again and it will not start!!!! I'm using a power probe so I can check everything fairly easily. My new relay I can access the bottom connections, the main power is 12v and all others are 0v, when I turn the key I still don't get anything on the pins 86 or 30 no current! I can then apply 12v to pin #30 and I can hear the pump going! I can go up to the main fuse box and test the 15A fuse there and it has 0v, but if I apply 12v I can hear the pump go!

    I'm about out of ideas, now I'm just thinking about things that I know are "different" since the last good sessions at the track.


    1. Had it in for tune, the tech did cut a wire in the port near the fuse box, as I remember he had to go and reconnect this before we were done. I don't know what is in there that he would be clipping? I'm going to get pics of this now.
    2. I added a whole set of gauges, oil temp, oil pres, water temp. The power is from the radio circuit as it was close and I tapped in there before for my transponder, don't think this could be an issue????
    3. I removed the original master light switch and panel, and just tapped into the wires needed for lights (Head, tail, interior lights)
    4. Not new but the ignition switch is not good, it will spin sometimes but has been working OK.


    I'm pretty much out of ideas , if I understnad the EWS system at all, if I had a problem there it would not crank at all, but it cranks but I can prove with the power probe that I'm not geting 12V to my fuel circuit!

    Any ideas?


    Update, this is the area the tech was when he needed to repair a wire???? This connector to the main fuse box area.
    photo.JPG
    Last edited by MCMM3; 04-07-2013 at 07:14 PM.

  9. #59
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    Quote Originally Posted by MCMM3 View Post

    1. Had it in for tune, the tech did cut a wire in the port near the fuse box, as I remember he had to go and reconnect this before we were done. I don't know what is in there that he would be clipping? I'm going to get pics of this now.
    This is very intriguing. Can you call them up and ask why they do that? Also, I'm pretty sure when I installed a different ECU, the engine still cranked. It just wouldn't start.

    when I turn the key I still don't get anything on the pins 86 or 30 no current! I can then apply 12v to pin #30 and I can hear the pump going
    This seems to be contradictory. The relay should not send power to pin 87 (pump on) unless it sees 12v on pin 86.
    Last edited by mrf; 04-07-2013 at 07:26 PM.

  10. #60
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    Quote Originally Posted by mrf View Post
    This is very intriguing. Can you call them up and ask why they do that? Also, I'm pretty sure when I installed a different ECU, the engine still cranked. It just wouldn't start.


    This seems to be contradictory. The relay should not send power to pin 87 (pump on) unless it sees 12v on pin 86.
    I hope to ask them tomorrow what was up with that wire they clipped.

    As for the pins on the relay I'm so burnt on this I may have not expressed myself correctly there.

    I did more testing just as the Bentley manual states and when you test the back side of the main DME relay one pin is supposed to go to ground, and I did see that. But the other pin is supposed to go to 12v, which will then trigger the fuel pump relay, that one was not geting 12v. So I'm starting to suspect the main DME relay now.

    That being said about 45 minutes later I just tossed both relays back in and it started?????????????

  11. #61
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    We generally replace all the wiring too... Much easier than trying to sort out miles of stuff you don't need. And then you know all the connections are in good shape.

    Yes they will not draw double since the transfer pump is not working very hard. That was an oversimplification. But yes, they will draw more than one, so upping the fuse may be necessary. I would at least up it to a 20A with the OEM wiring. They should draw less that 15 but you can't guarantee that under all conditions. And it only takes a moment to pop it.

    I like to provide for double of what is needed. If the load is likely to be 15A, I'll wire for 30A (14AWG and 30A fuse). With recycling all the OEM stuff, you really don't know what the load is going to be on the track. So it's better to be over than under. Using wire that is too small will not necessarily cause a problem. But it could contribute to small voltage drops due to the resistance in the wire. So oversizing the wire means the pump gets full voltage.

    On smaller loads I will oversize the wire more out of durability than anythng else. A race car is a hostile environment.

    Your frustration is why we rewire. It's often easier.
    Last edited by PCarroll; 04-07-2013 at 11:03 PM.
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  12. #62
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    Quote Originally Posted by PCarroll View Post
    We generally replace all the wiring too... Much easier than trying to sort out miles of stuff you don't need. And then you know all the connections are in good shape.

    Yes they will not draw double since the transfer pump is not working very hard. That was an oversimplification. But yes, they will draw more than one, so upping the fuse may be necessary. I would at least up it to a 20A with the OEM wiring. They should draw less that 15 but you can't guarantee that under all conditions. And it only takes a moment to pop it.

    I like to provide for double of what is needed. If the load is likely to be 15A, I'll wire for 30A (14AWG and 30A fuse). With recycling all the OEM stuff, you really don't know what the load is going to be on the track. So it's better to be over than under. Using wire that is too small will not necessarily cause a problem. But it could contribute to small voltage drops due to the resistance in the wire. So oversizing the wire means the pump gets full voltage.

    On smaller loads I will oversize the wire more out of durability than anythng else. A race car is a hostile environment.

    Your frustration is why we rewire. It's often easier.
    Well to your point I have now provided probably for double by having two 15-20A circuits, but I still have some other issue. If I had a lot of time that would be one thing but the car need to roll onto the trailer in a matter of 4 days for an event so I'm looking for a quick win.

    To your point about rewiring, I might not be able to completely rewire but I'm starting to consider to just us a extra switch I have to "force" 12v to my pump circuit and if it has any issues I should be able to get things running.

  13. #63
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    Quote Originally Posted by PCarroll View Post
    ... Beware used components. Pumps wear out. We've had pumps that work but suffer starvation replaced by new pumps that do not.
    Did you suffer starvation from used transfer pump or the main pump? After doing my dual pump set up (new main pump - 1 year old and older, but working transfer pump) I still had starvation problem at about 1/4 of the tank in long right hander turns.

    I'm now scratching my head as to why...
    - 96 328is 6.0L. (LS1 to LS2 build thread: http://forums.bimmerforums.com/forum...ad.php?2098938)
    - 96 328is 5.7L. (LS1 build thread: http://forums.bimmerforums.com/forum....php?t=1289987)
    - 95 ///M3 6.0L. (LS2 build thread: http://forums.bimmerforums.com/forum....php?t=1619249)

    - 97 ///M3. (e46 Fender Flares/track car build thread: http://forums.bimmerforums.com/forum....php?t=1727098)
    - 96 328is (Dual Fuel Pump to Surge Tank thread: http://www.bimmerforums.com/forum/sh...ad.php?1964025)

  14. #64
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    Transfer pump doesn't do much so it's less likely to be a problem. Not impossible though.

    We had starvation on the E46 M3 and were about to add the second pump. Then at the last minute, we had starvation in a straight line! We replaced the main pump with a new one (BMW not eBay). Works perfectly in all directions.

    I think the suction pump mechanism (transfer jet pump) on the E46 M3 is better than what came on the E36. But it needs a fair bit of residual return pressure to work. When the pump gets weak, that's the first thing to go. With the new pump, we have had no trouble at all. And the car gets lots of opportunities to have the problem.

    I have a spare transfer pump ready to go in. Just don't need it now. To save money, I got an E46 non-M pump for the tansfer pump. It was 1/3 the cost. Since it doesn't have to build pressure, I figured it would work fine. No need to test it now.

    I also think that if the suction pump is working, it should do a better job than a transfer pump since it is jammed right against the corner of the tank. I should be able to get every last drop.

    Maybe I should put my slicks on the car and test my theory... They do fit.
    Peter Carroll - http://www.driversmeeting.com/pcarroll
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  15. #65
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    Wire the pump relay to a switch (eliminate ecu ect) and see if the car runs after sitting ect. If it does work back from there.

    Not recommended but if this does work it will at least let you drive the car for the event.

    Why was the tech splicing in the x20 connector?

    Also the pumps work on a ground trigger from the ecu right? Perhaps there is an intermittent there. You can test continuity on said wire.

    May want to consider punting and having a shop that knows these cars fix it and treat the whole thing as a learning experience.

    Good luck

  16. #66
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    Bringing this thread back from the dead, I'm helping a friend with his car. He has the BW dual pump setup, but they are plumbed in parallel instead of having the DS pump transfer to the PS pump. He has had two DS pumps fail after only a few hours of track time each. Anyone else had this issue? I'm going to rework the plumbing to match my setup which has been working well.
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  17. #67
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    Quote Originally Posted by m3bs View Post
    Bringing this thread back from the dead, I'm helping a friend with his car. He has the BW dual pump setup, but they are plumbed in parallel instead of having the DS pump transfer to the PS pump. He has had two DS pumps fail after only a few hours of track time each. Anyone else had this issue? I'm going to rework the plumbing to match my setup which has been working well.
    I think that the problem is that 2 pumps = 2x the pressure in the fuel line. The regulator only allows so much. The DS pump is probably pumping against a wall and burning out. In the normal setup, the DS pump is just shooting fuel over to PS.


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  18. #68
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    That was my theory. Just looking for confirmation.
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  19. #69
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    To be totally clear for all future readers...

    The 2nd pump does nothing more than lift fuel to the accumulator on the main pump. It does not have to build pressure and as such will not put much load on the electrical either. So it doesn't need to be an M3 pump. A used 325 pump will do. Since it's not building pressure, it will flow plenty...

    Running two pumps in parallel is NOT the right way to do it. Regardless what that old Pumpkin Racing tech note says.

    Oops... I already said all that in the distant past.
    Last edited by PCarroll; 10-30-2016 at 03:13 PM.
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  20. #70
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    The PS pump has the small reservoir below it to draw from. When you install a pump in the stock hanger on the DS there is no reservoir at all so when running with low fuel that pump will often be run dry regardless of how you have run the lines.

    I run mine in parallel but I have positioned the DS pump in the rear outboard corner so that when I'm in a long left hand corner I don't get fuel starvation. I've been tracking and daily driving it that way for years now.

    The pumps have internal pressure regulators and the fuel pressure regulator should be able to handle the two pumps in parallel.
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  21. #71
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    I could not run mine in parallel - ran out of fuel quickly and easily - even sitting still on the dyno. Basically, which ever pump side sucks air first, shuts off the car - even if the other side is completely full.

    Make the driver's side pump run fuel over to the passenger side. Use the Passenger side pump to pressurize fuel to the rail then the regulator. Dump the return line into the passenger side.

    I'm not sure why someone would say either of these are internally regulated (they are most certainly not, look up Bosch 044 pump) and I can't imagine two pumps "overpowering" the stock regulator.

    Regulators don't really work like that.
    Last edited by CoMZ302; 11-01-2016 at 03:42 PM.

  22. #72
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    Quote Originally Posted by CoMZ302 View Post
    Regulators don't really work like that.
    They do, sort of. What happens is the bypass hole(s) in the regulator ends up being too small to bypass enough fuel when the volume coming into it is too high. This leads to increased pressure that can't be bled off.

  23. #73
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    Looking on doing this conversion myself as i also suffer form fuel starvation. Since i am running E85 i am using a 320LPH fuel pump, i'd have to run the same pump on the other side at its compatible with E85. My only concern is wouldn't 2x 320LPH pressurize or stress the system too much? I am literally a hair out of either going dual fuel pumps or single fuel pump to Fuel Surge Setup.

    @RJDRIFTS - @BIGDUCKCLUB

  24. #74
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    If you're looking to solve the starvation problem once and for all you need to go to the surge tank setup. Dual pump is bandaid at best that did not work for me or other 3 people I personally know.

    I have a link in my sig of my home brew system that works down to fumes.
    - 96 328is 6.0L. (LS1 to LS2 build thread: http://forums.bimmerforums.com/forum...ad.php?2098938)
    - 96 328is 5.7L. (LS1 build thread: http://forums.bimmerforums.com/forum....php?t=1289987)
    - 95 ///M3 6.0L. (LS2 build thread: http://forums.bimmerforums.com/forum....php?t=1619249)

    - 97 ///M3. (e46 Fender Flares/track car build thread: http://forums.bimmerforums.com/forum....php?t=1727098)
    - 96 328is (Dual Fuel Pump to Surge Tank thread: http://www.bimmerforums.com/forum/sh...ad.php?1964025)

  25. #75
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    Quote Originally Posted by bimerok View Post
    If you're looking to solve the starvation problem once and for all you need to go to the surge tank setup. Dual pump is bandaid at best that did not work for me or other 3 people I personally know.

    I have a link in my sig of my home brew system that works down to fumes.
    Thanks for you input man. I will definitely check it out.

    For future readers, here is BIMEROK's link: http://www.bimmerforums.com/forum/sh...ad.php?1964025)

    @RJDRIFTS - @BIGDUCKCLUB

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