dont think my temper is the only thing having a short! fuel pump woes inside...HELP!

[MIKe30]

edit: added some cliffs

done some research but still have questions. to start off my car is a 91 m50 swapped 318is. no i didnt do the swap myself. yes, i bought it post swap. (in school and wouldnt ever have the time/money to swap it myself until i'm done with school)

anyway, i've had the car two months or so. got home from work last week, parked it outside for bout an hour. got in to go to the gym and she started, as i was rolling my windows down i got a rough idle. i shut the music off to listen and boom, stalled. started again, idled less time, still rough, then stalled. started again, less cranks, stalled. and again, less cranks, then stall.

great.

first instinct said fuel. jordan said jump pins 30 and 86 on relay k3, so i did, and voila, heard the pump and car started. car wouldnt shut off tho, so i stalled it in gear. started fine, stalled it in gear to shut it off and remove the wire to see if it'd work without the wire. it did, but within minutes it stalled and was back to its old ways.

fast foward to yesterday. finally found my haynes manual (yea big help! haha) and jumped pins 30 and 87 like it says in there, still no luck. my old man was touching stuff here and there, nothing in particular, and it finally started working again. 10 min later i drove it down to parts store to take it for a spin and pick up a hose clamp (found some air/vacuum leaks too ) got in the car to go home and no start again.

fuses are all good. fuel filter was replaced first day i had this problem last week. still dont hear fuel pump, not even with pins jumped.


sorry for the long post.

cliffs: car cranks but doesnt start. jumping relay worked once, doesnt work anymore. dont hear any fuel pump buzzing or whirring noise. what should i check with a voltmeter (now that i have one to use) and whats the difference between the MAIN relay and the FUEL PUMP relay and where are they located?


thanks so much. this is my daily!!! arggg

-mike

[Ruffian]

With the correct pins jumped, try lightly tapping on top of the fuel pump. Naturally, you can get to the pump by pulling out the rear seat bottom, and then removing the cover on the passenger side of the floor pan under where the seat was.

I was having an intermittent problem with my fuel pump, and the pump would run sometime, and not sometime. When I would tap on the top of the pump unit, it would start, then stop again. If that's your case, you need to replace the pump.

[kellie]

I was having an intermittent problem with my fuel pump, and the pump would run sometime, and not sometime. When I would tap on the top of the pump unit, it would start, then stop again. If that's your case, you need to replace the pump.

That's exactly what I was going to suggest. Start there. If the car runs okay after tapping on the top of the fuel fump, then you've found the source of the problem. Give that a shot, then post up the results. If it doesn't work, check the connector, make sure there is no corrosion and the connection is solid, make sure there is no obvious damage to the wiring, etc. The most likely problem is a dying pump though.

[MIKe30]

With the correct pins jumped, try lightly tapping on top of the fuel pump. Naturally, you can get to the pump by pulling out the rear seat bottom, and then removing the cover on the passenger side of the floor pan under where the seat was.

I was having an intermittent problem with my fuel pump, and the pump would run sometime, and not sometime. When I would tap on the top of the pump unit, it would start, then stop again. If that's your case, you need to replace the pump.

arg, thanks i'll try that. my car is over in a lot a few blocks away right now.

what/how exactly should i test with the voltmeter to see if it is even getting current?

That's exactly what I was going to suggest. Start there. If the car runs okay after tapping on the top of the fuel fump, then you've found the source of the problem. Give that a shot, then post up the results. If it doesn't work, check the connector, make sure there is no corrosion and the connection is solid, make sure there is no obvious damage to the wiring, etc. The most likely problem is a dying pump though.

k thanks. will do. none of the connections look corroded tho. i dont think the cover under the seat has ever been taken off before last night... it was almost like it was sealed on and the screws felt like they've never been touched since they left the factory. all the more reason to believe its just a dying pump

[kellie]

I don't have a wiring diagram handy, and I've never taken a close look at the connector to an E30 fuel pump, so I don't know which pins are which. Usually ground is brown, so set your multimeter to DC voltage, and if it isn't automatic, choose 20V max. Unplug the connector from the pump, and touch the black lead to the pin going to the brown wire, and the red lead to the other pin. Have someone crank the engine over, and watch the voltage. It should be around 12v.

[MIKe30]

I don't have a wiring diagram handy, and I've never taken a close look at the connector to an E30 fuel pump, so I don't know which pins are which. Usually ground is brown, so set your multimeter to DC voltage, and if it isn't automatic, choose 20V max. Unplug the connector from the pump, and touch the black lead to the pin going to the brown wire, and the red lead to the other pin. Have someone crank the engine over, and watch the voltage. It should be around 12v.

k, thanks again.

if the fuel pump is supposed to be making a buzzing/whirring noise when the key is turned to "on", shouldnt the key just need to be turned to "on" to get the 12V or does it still need to be cranked? only ask because i think i'll be there by myself. dont know if i can quite reach and turn the key with my feet while holding the voltmeter in the back

[kellie]

Try sticking a paperclip in each pin of the connector and attach the voltmeter leads with alligator clips, then set the voltmeter on the center console where you can watch it. I'm pretty confident in the good old tapping on the fuel pump while cranking method. It works almost every time.

[MIKe30]

Try sticking a paperclip in each pin of the connector and attach the voltmeter leads with alligator clips, then set the voltmeter on the center console where you can watch it. I'm pretty confident in the good old tapping on the fuel pump while cranking method. It works almost every time.

k thanks... AGAIN! haha.

part of me wants you to be right (to get this whole deal over with) the other part doesnt (because i dont want to buy a new pump and i dont really love the idea of getting a used one)

i found a schematic of the relays... but i cant tell which is the "fuel pump" relay and which is the "main" relay.

http://tech.bentleypublishers.com/se...18i%201984.pdf

if anyone can chime in (maybe kellie? lol) that'd be great and i'd be on my way

[Ruffian]

k, thanks again.

if the fuel pump is supposed to be making a buzzing/whirring noise when the key is turned to "on", shouldnt the key just need to be turned to "on" to get the 12V or does it still need to be cranked? only ask because i think i'll be there by myself. dont know if i can quite reach and turn the key with my feet while holding the voltmeter in the back

The pump will not just whirr when the key is in the "on" position. it won't receive the signal to turn on until the dme says it's okay. The dme reads signals from the crank sensor, temp sensors and some others before it sends the signal to the fuel pump. THAT is why you need to jump the relay points of contact before you'll know if it's the pump or not. The fuel relay is one of the three relays under the black box just forward of the main fuse block that you pictured.

The relays do get switched around from time to time, so just saying it's the front, middle, or back one doesn't work. when you look at a wiring diagram, you'll realize that the fuel pump relay is the one with four wires leading to it, red/red-white/brown-green/violet-green I believe are the color combos. I'm just going off memory on that though.

[Ruffian]

Also, you should be able to test for 12v strength by connecting leads of your voltimeter to the two wire lead that goes to the pump. Then have someone crank the engine to start. It should read 12v once you start cranking.

[MIKe30]

The pump will not just whirr when the key is in the "on" position. it won't receive the signal to turn on until the dme says it's okay. The dme reads signals from the crank sensor, temp sensors and some others before it sends the signal to the fuel pump. THAT is why you need to jump the relay points of contact before you'll know if it's the pump or not. The fuel relay is one of the three relays under the black box just forward of the main fuse block that you pictured.

The relays do get switched around from time to time, so just saying it's the front, middle, or back one doesn't work. when you look at a wiring diagram, you'll realize that the fuel pump relay is the one with four wires leading to it, red/red-white/brown-green/violet-green I believe are the color combos. I'm just going off memory on that though.

Also, you should be able to test for 12v strength by connecting leads of your voltimeter to the two wire lead that goes to the pump. Then have someone crank the engine to start. It should read 12v once you start cranking.

ok thanks. i think i have enough info now. thanks again, will report back hopefully soon!

[MIKe30]

...The fuel relay is one of the three relays under the black box just forward of the main fuse block that you pictured.
...

is it literally under the main fuse block? because i dont see it anywhere around it...

also, the tapping (read hitting ) the top of the pump did not work, and since i forgot to grab the voltmeter when i went out the door, i am headed back soon.

[Ablice]

Black side box in front of the main fuse box...

Just give the car to me, I'll fix all the problems

[MIKe30]

Black side box in front of the main fuse box...

Just give the car to me, I'll fix all the problems

ha, part of the joy of picking up someone else's m50 swap is having to shovel all their shit. little black side box you speak of is nowhere to be found

fix that


edit: the lead to the pump is getting 10.5 volts when cranking. think that should be enough power to get it moving?

[Ablice]

ha, part of the joy of picking up someone else's m50 swap is having to shovel all their shit. little black side box you speak of is nowhere to be found

fix that


edit: the lead to the pump is getting 10.5 volts when cranking. think that should be enough power to get it moving?

I can fix that, just send it over here.

Sounds like you'd better find those relays, because if your main relay bites the dust and you have no idea where it is you're in trouble. 10.5v should be fine. What do the connectors look like?

[MIKe30]

I can fix that, just send it over here.

Sounds like you'd better find those relays, because if your main relay bites the dust and you have no idea where it is you're in trouble. 10.5v should be fine. What do the connectors look like?

connectors look really clean once you detatch them. now that i think of it, i think i may know where the relays are. didnt know what they were when i first saw them, but now i think i know where they are... (not in engine bay)

[FredK]

Yeah it's easy to find the relays on an M50 swap. Just inspect the cable bundles on the firewall. There should be a set of three relays coming off a single cable on the driver's side of the car. The PO might have gotten cute and mounted the relays underneath the 318is wiring cover.

The main relay is the only one with five pins, and has only red and red/wht wires leading to it. The fuel pump and O2 sensor relays are four pin relays.

[kellie]

If you're getting voltage to the pump, and you still don't hear the pump, it's probably toast. If you do hear the pump, then you may have other issues.

[greese]

I got a used pump about a year ago and still works (I think, I'm having hard start problems). You can get a used pump from the junkyard, if it doesn't work, take it back.

[Ruffian]

I got a used pump about a year ago and still works (I think, I'm having hard start problems). You can get a used pump from the junkyard, if it doesn't work, take it back.

I also got a pump from the wrecker. I took a couple leads, pulled the pump from the car, and jumped it to an old battery in one of the cars to test it first. Problem is, at least in my area, is that it's hard enough finding post '89(or whenever they switched to a single in-tank pump) e30's, let alone one's that haven't had the fuel tank pulled from the car. (in my area, the wrecker's are "supposed" to pull the tank before sitting it on their lot)

[MIKe30]

Yeah it's easy to find the relays on an M50 swap. Just inspect the cable bundles on the firewall. There should be a set of three relays coming off a single cable on the driver's side of the car. The PO might have gotten cute and mounted the relays underneath the 318is wiring cover.

The main relay is the only one with five pins, and has only red and red/wht wires leading to it. The fuel pump and O2 sensor relays are four pin relays.

i think its actually under my dash just over my glove compartment. there was a bunch of relays and what not i had no idea what they were for when i replaced my dash, so i just tucked them there cuz thats where they were when i started. if they're not there i'll check the firewall. thanks for the heads up on the 5 pin/4 pin info

If you're getting voltage to the pump, and you still don't hear the pump, it's probably toast. If you do hear the pump, then you may have other issues.

nope, dont hear jack. i just wanted to jump the relay to really MAKE SURE it was the pump, i'll do it if/when i find it.

I got a used pump about a year ago and still works (I think, I'm having hard start problems). You can get a used pump from the junkyard, if it doesn't work, take it back.

i may take a ride tomorrow after work (nearest u pull it place is near where i work) but usually they dont have late model e30's. maybe i should just call.

[MIKe30]

relay wound up being where i thought it was. found it and jumped the pins. got almost 12v to the connector lead but still no start or buzzing/whirring noise.

so my only question(s) left is, what are the chances my sender is bad too? pain in the ass to just change the pump and not sender? smarter to just do both?

parts store has a new pump for 71.xx (instead of 250+ at dealer) and their comp says sender is a dealer item (+-$80 from my dealer, iirc)... what say you bf.c?

[Ruffian]

Sender is going to be fine. IF you buy the pump, be prepared that it may just be the pump, and not the whole unit. You can pull the unit out of the car now to have a good look at it. You'll see that the pump is just one part of the unit.

Just before I got the pump I needed at the junker, I had purchased an upgraded pump on ebay. I ended up not needing it and the seller was nice enough to let me get out of the purchase with no negative feed back. Go to ebay and do a search for 255lph pumps. Walbro and truperformance. I would say to go with one of these as you have the m50 swap and more fuel is better than less. Our fuel systems allow for the return fuel to be let back into the tank so there really isn't anything to worry about moving too much fuel. I did a LOT of searching before buying, and felt good about my purchase, right up till I got a replacement whole unit from the wrecker for $40.

[MIKe30]

Sender is going to be fine. IF you buy the pump, be prepared that it may just be the pump, and not the whole unit. You can pull the unit out of the car now to have a good look at it. You'll see that the pump is just one part of the unit.

Just before I got the pump I needed at the junker, I had purchased an upgraded pump on ebay. I ended up not needing it and the seller was nice enough to let me get out of the purchase with no negative feed back. Go to ebay and do a search for 255lph pumps. Walbro and truperformance. I would say to go with one of these as you have the m50 swap and more fuel is better than less. Our fuel systems allow for the return fuel to be let back into the tank so there really isn't anything to worry about moving too much fuel. I did a LOT of searching before buying, and felt good about my purchase, right up till I got a replacement whole unit from the wrecker for $40.

thanks for all the info. yea i saw the picture of the pump on the guy's computer screen at the checkout, it was just the pump so thats when i noticed and asked bout the sender.

what were those upgraded pumps going for? not a bad idea to upgrade, but in your research did you find that these stock pumps lacked the capacity to properly fuel a swapped car?

[Ablice]

You won't need upgraded fuel pumps unless you have bigger injectors and cooresponding intake and ECU upgrades.