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Fuel Pump Preventive Maintenance?

4K views 25 replies 7 participants last post by  RobertDenali 
#1 ·
So recently I was left stranded with what appears to be a bad fuel pump relay (after Terrabass's useful video on testing it seems to point to the relay and not the pump):

https://www.youtube.com/watch?v=apOHpW_K_Lk&t=57s

Fortunately it was at a friend's house, so I plan to make the repair on site. Ordered the relay and will install when received. The problem with a fuel pump relay or fuel pump failure is that you are screwed. There is no "limp mode" to get you home when the engine is not getting fuel. I had a fuel pump failure at 126,000 miles. Now at 255,000 I am thinking to just go ahead and replace the pump (and fuel filter) as well.

Anyone on the board subscribe to fuel pump replacement even if it has not failed?
 
#3 ·
To answer your question directly first, there is no PM you can do for the pump. People will say don't run the tank down to low but I've never subscribed to that theory and I got more than 130k out of a replacement pump before it went.

For your situation, you should probably start thinking about replacing the pump. 100-130k miles is pretty typical lifespan. The relay may have gone bad because the pump is making it work harder all the time... gets hot and eventually died.

You could be weird like me and just keep a pump and a few tools in the trunk to change the pump where ever it dies... including on the side of I-90! If you've "been in there" before then you really don't need much... flatblade screwdriver, a hammer or in my case a small block of wood I keep to use with the scissor jack, and a razor blade from your temporary flat repair kit if you keep one. In order for this to work you need to just replace the pump itself. I've been running a Walbro. You have to change the connectors but once done, it's plug and play for another Walbro or the factory Pierburg.
 
#4 · (Edited)
Yes, once I get it home, I am now thinking of replacing the pump anyway. I might keep the old one in the trunk per your suggestion. Still shopping for that since their seems to be significant cost differences and am curious if it is justified by performance or longevity.

A curiosity: When I go to realoem.com it shows the relay behind the glovebox as a normal 5 prong 86/87/30 relay. These are relatively cheap--generally a few dollars. But when I went to order, of course, the BMW one is special with 8 prongs and a $110 - $140 price tag. Example at FCP:

https://www.fcpeuro.com/products/bmw-fuel-pump-relay-z3-m5-m3-61357892976


But realoem.com is showing the 5 prong version here:

https://www.realoem.com/bmw/enUS/showparts?id=DE93-USA---E39-BMW-M5&diagId=61_4007

When I get back to my car with the part, am I going to be surprised when I drop the glovebox with the wrong relay?
 
#5 · (Edited)
.... A curiosity: When I go to realoem.com it shows the relay behind the glovebox as a normal 5 prong 86/87/30 relay. These are relatively cheap--generally a few dollars. But when I went to order, of course, the BMW one is special with 8 prongs and a $110 - $140 price tag. Example at FCP:
https://www.fcpeuro.com/products/bmw-fuel-pump-relay-z3-m5-m3-61357892976

But realoem.com is showing the 5 prong version here:
https://www.realoem.com/bmw/enUS/showparts?id=DE93-USA---E39-BMW-M5&diagId=61_4007

When I get back to my car with the part, am I going to be surprised when I drop the glovebox with the wrong relay?

If you drop the glovebox, you will find the relay that was pointed to in your realoem link, but you will be disappointed if you buy a new one of this type of relay and install it: It is not the real EKP-relay (K96)! The EKP-relay (K96) is in the trunk, the big black one behind the right cover with 8 pins. The fcpeuro link shows the correct relay, only their price isn't right and that of several other providers ...

The EKP-relay is a PWM (pulse width modulation) controlled relay. I have to look up which of the smaller pins receives the PWM-signal. The flow of your fuel pump is controlled with it. Another small pin receives a signal from the DME (engine management unit) if the EWS (drive away protection) allows it. A missing signal there or a missing pin, if you would insert a standard 5-pin relay, will prevent your car from starting ...

On realoem the right (8-pins) EKP-relay (K96) can be found here:
www.realoem.com/bmw/enUS/showparts?id=DE93-USA---E39-BMW-M5&diagId=61_4492#61357892976

My remark above about the 'wrong' price, is based on the realoem price for a K96 relay, BMW no. 61357892976, of $40.25 and the experience that realoem-prices are always above actual prices. Things have changed now obviously, if I look at prices of other suppliers on the web ...
 
#6 ·
All,

Thanks for the help!

OK, so from the research it seems that for 2001 and later (mine is a 2002) the relay is behind the glovebox--not in the trunk. Not sure that was an improvement.

Once the glovebox is dropped, will the 8 pin relay plug in there?

Thanks
 
#7 ·
Nah, pretty sure the fuel pump relay you're looking for is in the trunk. I remember there being confusion regarding WDS and its location.
 
#11 · (Edited)
The bimmerfest link shows an E39 indeed, but not an E39 M5: Our M5 battery is sitting in the middle of the trunk. If you scroll a few plots downwards on the bimmerfest link, you can see the battery sitting on the right side of the trunk, under the relay carrier. The relay setting between various E39 models differs considerably.

The realoem plot-location of your wrong (5-pins) relay, shows the right location for the black, 8-pins*, EKP-modele = K96 relay: The relay carrier, behind the right side cover, in the trunk.

Before dumping your present K96 relay, you could have a look inside (open it up with 4 cocktail-sticks between bottom plate and the casing walls). Re-solder the connections of especially the small pins 1 and 7 to the PCB. You'll need a regulated soldering iron for this, because the solder connections require a bit increased temperature setting before they melt.

*) Only the relay female-connector X10156 has 9 pins. Connector 3 is not occupied. Connectors 4, 5 and 9 carry no wire. You would almost start thinking 5-pins is enough ...
 
#10 ·
#12 ·
Seems we have to do this again. I get this is a hard topic because it is confusing, the company puts out poor and incorrect information. I just thought that a topic that has caused so much anger and frustration in the past, might have lessons that stuck.

You have to identify you relay physically. If it is the standard relay then that is in the glove box(after a certain year), but if it is electronic (big black) it will be in the trunk.
The difference between the two devices is for OBDII compliance. There has been discussions and some evidence that standard relays might have gone in some US cars, but to the best of my knowledge no one here has ever found one.
Euro cars and others not using OBDII are different. There have been more than a few later model UK cars that did have a standard relay, then to make matters worse it was in the freaking trunk!

YOU MUST FIND YOURS IN CAR! Although on a NA car it seems super likely it will be electronic and in the trunk, it is said some were made the other way. These parts do not interchange because the DME has different programing for both.
 
#13 ·
Sailor,
I seen where you had some passion around this topic in previous posts to where you were engaging your engineer friends to come up with something better.

My trunk does not have the big black relay in the trunk that I recall (US 2002 E39 M5), but the part I ordered is the big black relay based on my VIN and the part supplier. That is why I was assuming (perhaps wrong) it would be behind the glovebox.

I will certainly find out soon when it arrives and I ride my bicycle to my car with relay in hand and hopefully start it with said bicycle on roof when coming home to then also change out the pump and filter. Otherwise it will be an angry round bike trip to get the right relay!
 
#21 · (Edited)
First, thanks to all for the helpful posts and threads. My frustration with the situation can sometimes leak into posts.

Second, I got back to my car and installed the expensive big black relay in the trunk. Relay works--voltage is now present at the pump--but the pump did not come on. Old relay did not click. New relay does. No surprise. I already ordered a pump and filter and they just arrived. I plan to go back to the car for install tomorrow. Odd that both the relay and pump would fail unless the failed pump somehow also created failure of the relay. In all this the 25A fuel pump fuse is still intact. Makes one wonder if the current rating is best or if a lower current fuse should be used.

A couple of questions:

1. Unfortunately, I have a nearly full tank of fuel (I know a rarity in an E39 M5). How best to siphon it off? How much until it is at the level of the fuel pump cover under the seat--or can I just siphon from there? I seen videos that show siphoning from the fuel pump cover, but am not clear how high the cover for the fuel pump is relative to the tank overall. Looks to be easier to siphon from the fuel pump cover.

2. I want to get the beast home then install the fuel filter--about 23.5 miles from home (I know since I did the 47 mile round trip on my bike expecting to drive the car home after relay install). I think that install could wait until I get home unless there was some really bad gas I got. More than likely the fuel pump failed a normal old age death though (about 135,000 miles)


Thanks
 
#22 · (Edited)
The relay should not click! It is solid state, no moving parts. Do yourself a favor and use that thread I linked you to.
Yes good idea to wait to put the filter in, unless it is totally plug but I doubt that. You should always run a pump for a bit into the old filter so any debris moves to the filter, then change it out, no sense making your new filter dirty seconds after install.
 
#24 ·
Considering his was in fact dead how would he know? It was discussed later in the thread.... Wading through misinformation is a feat unto itself. Reading any thread through to completion is important in any forum. Never heard one click, never felt one click, although you can feel something, but it is not a click. There are several threads here where we pulled them apart and showed how they work, no click. There are other relays beside it that might click and confuse you, but there is nothing in the big black on to go click.
Although a normal relay is an electro magnetic switch, this device is not that at all.
 
#25 ·
Thought I would close this out with the results. Not surprisingly, the issue was the fuel pump and the relay. The order of failure is not known. I also want to share a general comment about parts. As we know BMW sources parts from various suppliers that meet their specifications and standards (OE and OEM). As most know, the OEM fuel pump can be significantly more than a fuel pump that claims to meet the specifications of the OEM item. There are some places where that risk may be worth considering. This is not one of them, and I made a rookie mistake (that I full well know be now) to go with a cheaper alternative that included an adapter for the electrical connections. I am sharing this embarrassment to prevent someone else from making this error.

Red Flag #1: When the pump arrived, I noticed it was about 2/3 the size of the one I removed.
Red Flag #2: The adapter seemed like it would work, but this made the wiring longer, so to make it fit right, it needed to be wrapped around the hose.

Given my situation of being stranded, I decided to go ahead and install anyway. After install, the problem was not resolved. After frustrating review of other potential areas, I decided to pull the new pump out given that the connection showed it was getting power. The adapter terminal disconnected, I suspect during the yoga required to get the part in.

I immediately ordered an OE part and when it arrived, installed it. Car started after about 3-4 cranks.

Incidentally, I returned the small pump without issue.

Thanks again to the members on this board for the help.
 

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#26 ·
People want to save money on parts so they buy the cheap manufacturers instead of genuine or the original manufacturer. Then they come back to the forum saying the new part doesn’t work. I gave up stating why to the never ending amount of bmw owners doing this...

There should be a sticky on these forums saying “buy cheap parts equals wasting money and a car not operating correctly.
 
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