Inside a failed Fuel Pump

[RWebb]

This is from a 1986 VW Vanagon, but I thought it might be of interest as Bosch makes a few types of fuel pumps that are used on a wide variety of vehicles. The EFI on this vehicle is most similar to the EFI on a 1984-89 911, and has a basic ECU for electronic control (not a "hydraulic" control signal like CIS). VW calls this their DigiFunky system.

After replacing the fuel pump, I got curious (yellow) about why it failed, so I cut it open - the shell can also be uncrimped for a neater disembowelment, but that is too long a process and insufficiently caveman for me.

Here is the removed pump; note that some bozo was told to undercoat the vehicle and did not cover any components underneath to protect them from the spray. I had previously "Warrenized" the electrical terminals with vinegar to make sure the problem was not just bad contact.

[RWebb]

Here is the bottom, showing the slot used for a fuel intake - there are a bunch of small rollers (stainless steel?) in there but they don't show in the photo.





The rotor:

[RWebb]

I am wondering if the area on the rotor where the brushes make contact caused the failure. Here is a cropped closeup of that area:

[WolfeMacleod]

I don't know much about fuel pumps, but I do know a bit about coils...

[RWebb]

Here are the brushes:




They also do not look real healthy to me. Anybody think that the brushes and/or contact area for them on the rotor assembly caused the pump to fail?


BTW - I do not know the mileage on the pump for certain as I do not have a receipt in the information I got from PO's. But if it is original, then it lasted for ~~197,000 miles.

[jwgn777]

Was the pump sitting around for a long time before you cut it open? Because where the brushes would meet the commutator plane looks corroded. That would stop the pump other than a frozen bearing or as you said bad contacts. It doesn't look like water got in there. The wires on the armature were not that way when you pull it apart! LOL

[RWebb]

The vehicle sat for 7 months before I was able to diagnose the cause and then pull the pump.

"where the brushes would meet the commutator plane looks corroded" - is that the black area? or can you draw an arrow on the pic?

[jwgn777]

Whether it be a starter or alternator or fuel pump that failed and you take it apart the commutator plane would most likely be shiny where the brushes make contact unless it was corroded with some substance.Or sometimes the brushes freeze causing a jumping spark that causes discoloration. Judging from the photo it looks like it was sitting a long time with all that black stuff in the photo. Yes that would be considered the commutator plane where the black stuff is.

[manbridge 74]

Originally Posted by RWebb

I am wondering if the area on the rotor where the brushes make contact caused the failure. Here is a cropped closeup of that area:

Yes. OD of rotor where brushes contact should not be stepped. Likely due to buku miles or dirtier than normal fuel tank.

[RWebb]

since I've owned it, it has sat during winter and then gotten driven some during summer - not sure why all the black is in just those two spots (one is shown in the photo & the other is about 180 deg across from it)

possible that it sat for a long time, but it was running when I bought it

[RWebb]

the fuel filter is downstream of the pump; OTOH when I first pulled the old fiter out, I cut it open and it seemed clean - if it was just lots of miles then wouldn't the black area be distributed around the entire circumference and not concentrated in two spots? (the two spots make me think that they are where the brushes sat for a long time)

I may break out the macro lens & big camera to take a better look at that area of the commutator

[manbridge 74]

Black spots can be burning when arcing happens due to insufficient brush length/tension.

[M.D. Holloway]

Dude DON'T CLEAN IT! Send it to me and I will analyze it for you at no change and send it back!!!! Seriously.

[RWebb]

Mike - do you really want it? Email me your address and I'll send it to you. I don't want it back - just toss into your metals recycle bin.

[rusnak]

I would be too scared to cut one of those open. At least you know you got a lot of use out of it.

[RWebb]

from fire? I drained it for a few days, then cut with a hand hacksaw and kept an extinguisher handy...


Here is a related thread:

http://www.jag-lovers.org/xj-s/book/83FuelPump.html

[RWebb]

here are the rollers; one can barely be seen in the top pic in post #2 - look above the boss

I dropped a couple on the floor, hence the missing gaps





it is interesting to think that all the rest of the assembly (and all the wt.) is only there to spin this little gizmo - it is the pump, per se

[RWebb]

I am shipping this to der LubeMeister, more investigation pending.

It weighs 618 g, BTW