How to wire up fuel pump directly to the battery?

[ninetyseven1]

hey guys, experiencing an intermittent stalling , hiccup issue while cruising on highway. Car feels like its running out of gas. Finally dies on me last night on the side of the interstate, a friend came with my tools and a new fuel pump, however it was a universal 255lph LS1 fuel pump , looked like our factory one. Swapped it out and car started up and ran fine. Then this morning im on the way to work and same issue. Car started acting like it was running out of gas , so i got more gas and no change. I thought of running the pump directly to the battery and see how it runs and then go from there. I just dont want to be stranded again on the highway . So how would i wire directly to the battery? Can anyone chime in please? Jim Lev?

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E39fuelpump.JPG

[ross1]

Are those your notes in red? They are incorrect, pin 85 receives a ground signal from the DME.
Jumping 30 & 87 ought to activate the pump, provided wiring is good. Have you checked ground?

[BimmerBreaker]

Yeah but what about the fuel filter?

[ninetyseven1]

i thought about the fuel filter too, its possibly clogged but i do want to try to wire up the pump directly. It would be much easier for now. I take it i would connect another wire to the wht/bl wire going to the fuel pump harness under the back seat and go directly to the battery? and the brown wire in that harness is ground?

[JimLev]

O, are we friends again?
Repeating what has already been said you can jump the pins to keep the pump running.
The fuel filter as BB said could also be your problem.

When the DME provides ground at pin 85 it will read maybe 0.4volts, not 2-3 volts.

Trunk_Relays3.JPG

[BimmerBreaker]

i thought about the fuel filter too, its possibly clogged but i do want to try to wire up the pump directly. It would be much easier for now. I take it i would connect another wire to the wht/bl wire going to the fuel pump harness under the back seat and go directly to the battery? and the brown wire in that harness is ground?

Its not gonna be easier if it doesnt work
It doesnt seem to be an issue of power to the pump seeing as youve had two pumps functioning

Easier to bypass a filter in an emergency then to hardwire the pump. Also easier to reverse. Just sayin

[ninetyseven1]

Its not gonna be easier if it doesnt work
It doesnt seem to be an issue of power to the pump seeing as youve had two pumps functioning

Easier to bypass a filter in an emergency then to hardwire the pump. Also easier to reverse. Just sayin

well just drove to a restaraunt on my lunch break and car stalled in the middle of the highway!, then i restarted it and drove normal for like 2 miles and it started sputtering again and coughing, if i press the gas pedal it does nothing. then it kicked back in and started running normal again. IM stumped here.

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just ordered a fuel filter from my local auto parts store as no parts stores have one in stock! i doubt this is the issue tho

[edjack]

Re-read Jim's and ross' posts again.

[ninetyseven1]

Re-read Jim's and ross' posts again.

Turns out on my lunch break earlier i was actually running out of gas again for the third time!! This doesnt really look like its a fuel pump issue at this point, the car did the same thing with the stock pump, i think its going through fuel like crazy. Fuel trims are -7. Which isnt too bad but i still shouldnt be getting such horrible mileage. I put in 3.5 gallons after work and made it home barely. My commute is only 30 miles. So im getting like 8 mpg. Someone else told me to check for a broken fuel pressure regulator or a stuck injector. I couldnt find any visible fuel leaking from the vehicle anywhere. BTW, the pump i installed is a 255lph pump which i was told is not much bigger than our stock pumps.

[ninetyseven1]

Re-read Jim's and ross' posts again.

excuse me? are you gonna chime in and offer advice or not?

[edjack]

You are trying to run the fuel pump manually. Both referenced posts suggest how to do it. Just sayin'.

[ninetyseven1]

You are trying to run the fuel pump manually. Both referenced posts suggest how to do it. Just sayin'.

edjack, at this point i dont think the pump is the issue really. I mean its a 255lph pump which i know flows more than stock but I still shouldnt be geting 8mpg just because i swapped to this pump. Im running out of gas super fast now and when i thought my stock pump went out last night it could of been the car just running out of gas although my gauge which has been accurate for years said I still had a 1/4 tank! So i mean what else would not throw a code but still cause a car to run out of gas so quickly? Bad FPR or a stuck/ leaking injector? How can i test for these things? The car runs awesome otherwise. Fuel trims are on the rich side slighlty -7 LTFT on both banks.

[TheAngryBear]

Sounds to me like two problems: Fuel is cutting out and bad mileage.

If you are running out of fuel while the gauge reads qty you should do Test 6 through the IKE. If you arePhase 2 or 3 then repair the senders. If you are Phase 1 then see what the qty of fuel is on each side. You may have a clogged/broken Venturi so fuel isn’t transferring from left to right. You could also have gunk preventing fuel pickup by the pump.

A trim of -7 tells me either potential leaky injectors or the O2s are going bad. Have you checked the wave forms and ranges of the O2s?

And are there any codes?


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[ninetyseven1]

Sounds to me like two problems: Fuel is cutting out and bad mileage.

If you are running out of fuel while the gauge reads qty you should do Test 6 through the IKE. If you arePhase 2 or 3 then repair the senders. If you are Phase 1 then see what the qty of fuel is on each side. You may have a clogged/broken Venturi so fuel isn’t transferring from left to right. You could also have gunk preventing fuel pickup by the pump.

A trim of -7 tells me either potential leaky injectors or the O2s are going bad. Have you checked the wave forms and ranges of the O2s?

And are there any codes?


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

ok, i checked test 6 and the readings look ok, i have owned the car for years and always use tests 6 and 7 everyday. there was some black sandy dirt in the tank, the o2's readings havent changed much since the car was running normal a few weeks ago, the waveforms look like the usual. no codes! However , i wonder if the -7 LTFT readings are coming from me changing to the higher output 255lph fuel pump? idk. or is that indicating the injectors are leaking internally or stuck? I wish there was a way to check the fuel pressure but i have no schrader on the 97'. So maybe the stock pump wasnt bad to begin with? i was just out of gas due to this fuel issue. I mean i have been all of a sudden getting 8 mpg or less. Getting closer to figuring this out though. Thank you very much for your input guys, keep it coming.

[geargrinder]

LOL.

Typical Ol' 97.

Although I realize the thread-title-topic is obsolete now, still I have to say:

There is almost - and even then I hate to say almost but I suppose I can imagine some 'anything is possible' situation - zero scenario where hot-wiring the fuel pump is a great solution or even a useful diagnostic... if you think there's a relay current flow problem, first you just immediately and easily swap another green relay...

Of course this won't stop some dopes from finding this thread in a search in the future and then deciding its a great idea and they have to try it too for their POS car... but just wanted to put that stake in the ground - HEY future person reading this thread - THIS IS A DUMB IDEA DON'T THINK IT IS YOUR SOLUTION.

On to the POS at hand:

1. Now you think you're running out of gas cuz you're getting terrible mileage!? You need to know if you really are out of fuel or not. Is the tank empty when it says 1/4 or not? This seems completely uncertain and unverified. If you have gauge issues and the tank is empty, that simply explains all. If not, and you find that there's plenty of gas when it says 1/4 still, then its very possible that what you think is "out of gas" has really been some other thing happening when you fill up the tank etc. +1 to AngryBear on this. LOOK in the tank using those 2 things that are stuffed in the holes up at the top of your skull, check the two raw sensor readings, see if any of the data thereby collected makes any sense at all. HOWEVER - in the very first OP above you say "so then I got more gas but no change"... so how is it that you're convinced it is running out of gas now!? Seems like adding gas "worked" a couple times but not others, so therefore I'm not sure it ever "worked" at all but was just a coincidence to some other thing resolving or resetting or whatever.

2. Have you monkeyed with your evap system at all (Ol'97 would be just the type to delete evap and plug the lines cuz derpderphazraisins)? If the tank is getting vapor locked, it could starve the pump for fuel, then "putting gas in" would work cuz it be venting the tank and eliminating the vacuum. The short-term solution or even quick diagnosis to that would be driving w/ the gas cap loose.

3. Trims are -7? That's not "a little rich" thats "YerMama's ASSLOAD rich". With a trim like that something significant is wrong. If that's been that way for a while then you've had something really wrong with the car. I dont' give a crap if you say "it runs awesome" (also frankly I don't trust your opinion and report that that is actually true, based on history... with you, it usually turns out to be "runs awesome... OK well I didn't mention about the black exhaust and residue on the back bumper and the occasional backfires and-and-and... cuz derp that's probably something else and besides I don't really mind any of those things...") That is a major fault condition, period. There is a solid chance that it is whatever your crappy super rich running issue is that is also causing the hiccups and stalling.

4. Test the running fuel pressure. Preferably not just at idle/no-load but also while driving (the ol' tape the gauge to the windshield or other tricks usually required...). Other potential causes for super super rich = primary O2 sensors crapped out / contaminated, leaky (or wrong) injectors, etc. etc. etc. but I'd chase this one down first. Too-high FP would easily account for your trims... not sure it would account for your stalling-then-runs-again-when-gas-added-to-tank problem, but as above, I'm not sure the adding-gas-fix is as simple as it appears.

5. For reasons the pressure might be screwy. Re: the new fuel pump, its well established that a big ass fuel pump can overwhelm the OE fuel pressure regulator. So if the high trims only happened after the new pump I'd say look into that, however A. seems they didn't, and B. the pump you have I assume is one of those everywhere 255lph pumps (they come in various brands but Walbro etc.) and, that pump should be fine w/ OE FPR and return system. So probably - especially since symptoms are unchanged since the swap - the new pump is fine. So why else could your pressure be too high causing those trims? A. bad FPR, B. blocked / pinched return line, C. problem with vac line to the FPR (not seeing vacuum when it should therefore running higher than expected pressure). A clogged fuel filter would cause low pressure obviously and therefore normally would be low trims which doesn't seem to be the case. As a rule I'm skeptical at all about the fuel filters clogging on these cars, more money has been wasted on fuel filter replacements on these cars that does nothing than probably any other part but if you're having weird pressure issues you can't rule it out completely. All this to say, both idle and driving fuel pressure readings are called for.

6. You can also try watching your trims and O2 readings as you drive and see if you can catch what is happening when it starts hiccups and stalls. Would be interesting to see if the rich condition exists all the time or not. If the rich condition is a false-read by the ECU (bad O2's for instance) then maybe its running the engine so lean that it chokes out and stumbles.

7. There's also just the pure chance of a wiring fault someplace with an intermittent thing like this. That's an excellent possibility even not fuel related.

8. As AngryBear says: Codes? No codes?

That's all I have energy for at the moment

[geargrinder]

ok, i checked test 6 and the readings look ok, i have owned the car for years and always use tests 6 and 7 everyday. there was some black sandy dirt in the tank, the o2's readings havent changed much since the car was running normal a few weeks ago, the waveforms look like the usual. no codes! However , i wonder if the -7 LTFT readings are coming from me changing to the higher output 255lph fuel pump? idk. or is that indicating the injectors are leaking internally or stuck? I wish there was a way to check the fuel pressure but i have no schrader on the 97'. So maybe the stock pump wasnt bad to begin with? i was just out of gas due to this fuel issue. I mean i have been all of a sudden getting 8 mpg or less. Getting closer to figuring this out though. Thank you very much for your input guys, keep it coming.

OK - posted while I was typing.

Still seems you need to look in the tank while taking the readings to see if they match up to reality.

That black sandy dirt prob is disintegrating rubber or plastic I bet. Not a huge cause for concern given the screens on the fuel pump and on the fuel filter etc. etc. etc. - the gas gets screened many times before it gets to the injectors. Impossible to pass a grain of sand to an injector without a massive string of failures or hacking up of the car.

As above, no, it seems like your pump was fine. Above, you seemed to imply your high trims were there before.... which is it? Were they always that way? Or new?

Still possible to test pressure, easiest way is probably down at the FPR (you should probably have the 3/2 valve fuel pressure regulator). Just tap the output of the whole Rube Goldberg device that goes up to the rail and see what its sending up there. Harder to do a 'while driving' test on that one unfortunately as the 'tape to windshield' trick is out of the question. Maybe drive with window open holding it in your left hand? ;^P

[ninetyseven1]

well im assuming im really running out of gas cause when the bogging and hiccuping starts it eventually get worse and worse until the car wont start anymore and the only that starts it back up and get its running normal for a while is if i put in gas! no i have no black smoke from the exhaust. The exhaust note is slighltly deeper than before though. The fuel trims have been 0 and sometimes +2 at the highest for the past few years so -7 doesnt seem overly rich to me. The car has not lost power due to being overly rich. The car doesnt seem to run any different with fuel press reg vacuum hose disconnected and plugged though so im wondering if the regulator is bad? or stuck open maybe? idk, but i think your right about the o2s , they could use replacing im sure. Their readings seem normal though.

[BimmerBreaker]

Also Im not sure the saddle tank siphon pump thing will work properly with an aftermaket pump. Danny's wagon kept dieing at 1/4 tank when he didnt have his side tank siphony boi hooked up properly. It wont be able to siphon fuel from the other side of the tank so itll show 1/4 but the side of the tank the pump is on is empty...

[ninetyseven1]

idk, there was this black plastic tube in there that came from the other side of the tank yeah , but it was just sitting there dumping into the side the fuel pump was on so i moved it and snapped it onto the plastic case that held the fuel pump , thats where it looked like it belonged. My car also dies at a 1/4 tank or less yet my test 6 says i still have gas.

[BimmerBreaker]

One of the tests will tell you how much gas is in each side of the tank... Maybe look there to make sure both sides have fuel

[geargrinder]

Also Im not sure the saddle tank siphon pump thing will work properly with an aftermaket pump. Danny's wagon kept dieing at 1/4 tank when he didnt have his side tank siphony boi hooked up properly. It wont be able to siphon fuel from the other side of the tank so itll show 1/4 but the side of the tank the pump is on is empty...

Graham I think it should as long as its hooked up to the return line properly. Pump brand shouldn't affect it? But that's the kinda thing I could see guys not hooking up properly when they do the swap.

[TheAngryBear]

There are a few ways to do the Test 6
1) see what is the volume on each side. If left is more than right and phase 1 then Venturi is suspect.
2) if left is more than right and phase 2 or 3 then senders are suspect.
3) if you “run out of fuel” and test 6 says you have fuel on the right senders are suspect and/or you may have a clog (regardless of phase).
4) for 1-3 validate findings with visual examination of fuel level.

Other thoughts:
Validate alternator output with test 9
Ensure ALL grounds are solidly connected
As GG said, validate the breather is open (crack gas cap as simple test)



2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[ninetyseven1]

IMG_0182.jpg

There are a few ways to do the Test 6
1) see what is the volume on each side. If left is more than right and phase 1 then Venturi is suspect.
2) if left is more than right and phase 2 or 3 then senders are suspect.
3) if you “run out of fuel” and test 6 says you have fuel on the right senders are suspect and/or you may have a clog (regardless of phase).
4) for 1-3 validate findings with visual examination of fuel level.

Other thoughts:
Validate alternator output with test 9
Ensure ALL grounds are solidly connected
As GG said, validate the breather is open (crack gas cap as simple test)



2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

ok, so car was approaching a 1/4 tank today so i threw in $20 worth of gas, here are the readings i just got back from test 6

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the second pic was after i took a few sharp turns to the right and left while driving through my area.

[TheAngryBear]

Each side has about 32.5L with a 5L “common” area for the total of 70L.
The left is drawn to the right by the Venturi to the fuel pump. If you look again the left should be drawn to the right. So that appears normal.
If you hit the “select” again you can see the second aspect of test 6. That will show Phase # and an average total reading. The Phase # is 1,2, or 3.
1 = all good; 2 = one sender is off, 3 = both senders (or something else) is wrong.
Assuming you show Phase 1 it appears that your tank and senders are okay.
There may still be something wrong with the breather or regulator.

Edit: you will want to fix your temp sensor that is missing (in front of front right wheel) so your mirrors don’t burn out).


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

[ninetyseven1]

Each side has about 32.5L with a 5L “common” area for the total of 70L.
The left is drawn to the right by the Venturi to the fuel pump. If you look again the left should be drawn to the right. So that appears normal.
If you hit the “select” again you can see the second aspect of test 6. That will show Phase # and an average total reading. The Phase # is 1,2, or 3.
1 = all good; 2 = one sender is off, 3 = both senders (or something else) is wrong.
Assuming you show Phase 1 it appears that your tank and senders are okay.
There may still be something wrong with the breather or regulator.

Edit: you will want to fix your temp sensor that is missing (in front of front right wheel) so your mirrors don’t burn out).


2001 750iL DD74441
Stock

RIP: 2003 540iA Sport GS56111
H&R front springs, Ultimate Cup Holder, Euro Dash & Armrest, Grom, BavSound Stage1

Just ordered a new regulator will keep u posted.