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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Fuel Pump Wires Getting Hot



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      02-06-2016, 07:40 PM   #1
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Fuel Pump Wires Getting Hot

I've searched the web high and low, no one seems to have had this issue before.

So I've been running a single Walbro 450 for a few years now, I forget what "option" it was, and was before Fuel-It was around. I've ran mostly E85 and occasionally as low as E60 with a backend flash, never had issues up until a few thousand miles ago.

Picked up my car from getting the front diff replaced and the car died while driving, fuel pump warning came up, no blown fuse and I figured it had been about 30,000 miles since a hose came off in the tank so it must be that. I spun off the retaining ring and pulled the bucket to find the fuel pump wires melted together...inside of the tank. They were soldered and heat shrunk when I did the install. Called up my brother and he brought me a spare 450 I had in my tool box, threw it in with butt connectors and was on my way.

When I got home I put some power straight to the pump that I had pulled with the melted wires and it still worked.

About a month later my new pump also stopped working, the connector had began to melt at the top of the bucket assembly. I was able to unplug and plug it back in and the car started up again. I replaced the top of the assembly from a spare pump and was on the road once again. This time I switched back to 91, to see if maybe E85 was too much for the pump.

Now it happened again, this time nothing had melted, but I unplugged the connector and plugged it back in, the car started right up. While driving the car, I reached back to the pump wires and they were hot to the touch, I was afraid they would melt again.

Can anyone shed some light on what is going on?

I know a pump drawing too much current will cause heat, everyone else is on a factory harness why are mine melting?

Did I just have two bad pumps? Fuel It uses a 450 in their stage 2 with a stock harness and no one I know of has had this issue.

Fuel filter? I've got 108k on the clock and have only changed the sock on the walbro twice since 50k miles. Never the one on the driver's side of the tank. (The pressure regulator assembly or whatever that we have seen on ECS and Turner.)

Bad fuse? Idk.

Fuel pump control unit? The black and purple box.

I would like to figure this out and save someone in the future a lot of trouble and a headache if they have a 450.


Thanks in advance!
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      02-06-2016, 08:17 PM   #2
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Being you have had this occur with two pumps and have changed out the top hat. I would investigate other components such as the fuel pump driver.

May also consider checking the fuel filter to see if its clogged causing higher then normal amperage draw with reduce cooling flow across the pump rotor. Also would t hurt to out a meter on the wires and measure amperage draw while driving and of course make sure the wires are separated. Hopefully no need to paint a picture of what arcing wires in a fuel tank might cause.. Yikes..
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      02-06-2016, 08:44 PM   #3
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Lcvette, yeah no need to paint that picture lol.

I'll be putting a meter to it tomorrow, how many amps am I looking for though? What's too high and what's right?

Is the fuel filter the one on the driver side in the tank, the silver part? (Sorry if I sound like an idiot, I am pretty mechanically inclined but I'm not aware of any other fuel filter on our cars)

Thanks for the help so far.
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      02-06-2016, 08:54 PM   #4
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Correct filter is on the drivers side of the tank.

Here's walbros flow charts with amperage draw.

http://walbrofuelpumps.com/media/wys...-chart-650.jpg

I would say if they are over those values at the pressure achieved and the correct voltage to the pump to look at a glow restriction.

Could also disconnect the fuel line and see if amperage draw changes to within spec at zero head pressure for a comparison, just make sure there is a hose on the pump outlet aiming I to the tank and secured, they spray some fuel!
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      02-09-2016, 04:25 PM   #5
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Put a meter to it, amperage is sitting at 13.1-13.5 wires are still getting hot with the meter in line. If the pump was bad internally would it still be able to pump out at 75psi? And would it draw excessive amperage or no?
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      02-09-2016, 04:38 PM   #6
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You put in a fuel pump that draws way more current than stock and you're keeping the stock gauge wires... yes they will probably get warm. In the LS world, it is rare to upgrade the fuel pump without upgrading the wiring, i.e. running dedicated wires usually from the battery or fuse box. Not sure what the stock wire gauge is on LS, but it's typically upgraded to 12 or 10 gauge.

Here's a good chart: http://forum.flitetest.com/attachmen...7&d=1424126035
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      02-09-2016, 04:51 PM   #7
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Yes, i understand but am I the only one having these issues with a 450? I'm getting good pressure, my voltage is right, current is in acceptable range, so my pump must be good.


And I'm thinking about just running a custom top hat with a relay and some 10 ga from the battery... Would that be a good idea at this point? And would the factory harness signal be a good trigger for the relay even though it's a voltage varying system?
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      02-09-2016, 05:02 PM   #8
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Are you sure you measured 13.1-13.5 amps? Sounds like you were measuring voltage. Most generic multimeters cannot measure more than ~100 mA. According to Walbro the 450 should be pulling more like 18 amps.

It's common to run a dedicated power wire to the pump and use the stock pump power wire to trigger the relay. However, with our cars' easy-to-piss-off electrical system, I'm not sure if there would be any troubles with this.

But you're right, doesn't seem like anyone else is having this issue. Did you do the pump yourself or is it from Fuel-it? If the latter, I'd ask Steve.
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      02-09-2016, 05:17 PM   #9
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Put the meter in DC Amps, Moved the red lead over to the fused Amp side, and ran the pump through the meter on the power wire and jumped the ground. Range was set to auto.

I Might just have to pick up one of those current testers that can plug into the fuse slot.

I did this myself years ago before Fuel it was around. Same setup as Steve's stage 2 I believe. The pain is going to be running a larger wire though the factory hat.

Thanks for all of your help so far, I really appreciate it.
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      02-12-2016, 02:12 PM   #10
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I'm wondering if more people are having this problem and are unaware of it. I also have the Fuel-it stage 2 pump, I don't have any issues other than the fuel pump warning in idrive.

What's weird to me is the wire going to the walbro on the BMW is WAY too small compared to what every other platform out there does. I've meant to ask Steve about it but never really got around to it
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      02-12-2016, 02:29 PM   #11
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Subscribed! Interesting topic for sure.
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      02-12-2016, 03:18 PM   #12
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Quote:
Originally Posted by Milan View Post
I'm wondering if more people are having this problem and are unaware of it. I also have the Fuel-it stage 2 pump, I don't have any issues other than the fuel pump warning in idrive.

What's weird to me is the wire going to the walbro on the BMW is WAY too small compared to what every other platform out there does. I've meant to ask Steve about it but never really got around to it
Bumping this cause it has me very curious if others have checked.
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      02-15-2016, 12:18 AM   #13
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      02-15-2016, 10:03 AM   #14
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providing the factory size fuse is still in place It is rated for the wire size used and will fail if the amperage draw on the factory harness is too high. So unless you changed it for some reason you should be fine.
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      02-19-2016, 03:58 PM   #15
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Quote:
Originally Posted by lcvette View Post
providing the factory size fuse is still in place It is rated for the wire size used and will fail if the amperage draw on the factory harness is too high. So unless you changed it for some reason you should be fine.
That's exactly the problem. The factory fuse is 20 amps, and the Walbro 450 can draw more than that.

I actually changed mine out to 25 amps because I didn't want to get stuck on the way home someday because my pump pulled too much current.

There is actually a thread of this happening to someone on the other forum. I've always wondered why Fuel-It hasn't addressed the wiring issue, especially since they have all sorts of other weird fuel mods.

If you have ever done a Racetronix harness on your Corvette you know it makes a huge difference in fuel delivery. Extra 1.5 volts to the pump!

Milan
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      02-19-2016, 08:09 PM   #16
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Yup,

But that isn't good practice especially with a fuel system with smaller wires. I've been running the factory fuse with my Walbro for 8 months now and no issues. I would keep a spare just in case, but I don't think I would add a higher rated fuse on factory wires. Just not good safe practice. If you want to increase the fuse, increase wire gauge and mke sure the plugs are rated for the new fuse amp rating.

I've wired more fuel pumps then I would ever care to share for turbo cars..lol and many Corvette fuel pump harnesses.

According to Walbro pump shouldn't pull more then 18 amps for our pressure setting. So if you are popping a 20 amp fuse. I would look at reasons it is blowing and why the pump is drawing more then it should. Just my 2 cents .
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      02-22-2016, 10:35 AM   #17
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If you already swapped out a new pump and it still is happening I don't think it's the pump drawing to many amps. I think you have a grounding issue honestly.
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      02-22-2016, 11:19 AM   #18
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Quote:
Originally Posted by lcvette View Post
Yup,

But that isn't good practice especially with a fuel system with smaller wires. I've been running the factory fuse with my Walbro for 8 months now and no issues. I would keep a spare just in case, but I don't think I would add a higher rated fuse on factory wires. Just not good safe practice. If you want to increase the fuse, increase wire gauge and mke sure the plugs are rated for the new fuse amp rating.

I've wired more fuel pumps then I would ever care to share for turbo cars..lol and many Corvette fuel pump harnesses.

According to Walbro pump shouldn't pull more then 18 amps for our pressure setting. So if you are popping a 20 amp fuse. I would look at reasons it is blowing and why the pump is drawing more then it should. Just my 2 cents .
But putting in a fuel pump that has the ability to draw more current than the factory wires/fuse support IS good practice?

I'm willing to bet more people are having fuel pump issues than what is apparent on the forums.
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      03-04-2016, 11:25 AM   #19
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So I swapped the fuel pressure regulator/filter on the driver's side with a new one, thinking a clogged filter would cause the pump to pull excessive current. Drove fine on E85 for about 100 miles, then the fuel pump warning came on and it stalled at a stop light.

Luckily it was about a block away from my destination so I pushed the car into a parking lot. When I came back it fired right up and drove home no problem.

I really didn't want to put a relay and power to the pump directly but it seems like I'm going to have to hack up the top hat and the harness a bit to get it reliable again.

At least that way I'll know I have a good ground and power.

I wish more people shared their experiences and issues especially on a platform like the N54, would help a lot of people out and improve the platform.
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      03-04-2016, 06:24 PM   #20
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Being I build upgraded fuel pumps for this platform now, I have seen many buckets come through from older cars and wonder if maybe the issue is the factory harness plug connections are loosening over time or maybe corroded. I know I have cleaned a few bad ones on older buckets. May be worthwhie checking it out.
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      03-04-2016, 10:15 PM   #21
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Right on man, I have come to notice that the connector when unplugged and plugged back in it fixes it for the time being, is the connector pigtail available from anywhere?
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      03-04-2016, 10:46 PM   #22
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Fuel it stage 2. New VDO build option - no issues at about 10 months now. I've ran E85 through it but 92 over winter. Stock fuse, etc. Just plugged in and was good to go.
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