Anatomy of a fuel pump

[mcandmar]

A few pics for anybody who is curious to see whats inside. This pump had the characteristic whine so in hindsight i should have changed it sooner. However the time from it showing signs of struggling to total failure was less than 80 miles.

Problems started after dispatching a Celica with TURD stickers coming onto the motorway, by the end of third gear the car started to hesitate so i knew something was up. Backed off and cruised at motorway speed for the next 40 miles. Coming off the motorway i quickly discovered anything over .5bar caused it to stutter and sounded like it was pinking. Penny dropped at this stage it was fuel starvation.

For the return journey i drove like a granny, about 30miles in i had to keep it off boost and below 3000rpms to keep it running smooth. I was limping along like a hyper miler swearing and anybody who got in my way. Then about five miles from home turning onto the uphill slip road it spluttered to a stop. Kaput.

Lesson learnt, if its noisy and starts to stutter on high load / boost, turn around and go home

[mcandmar]

Onto the pump, the issue is clearly worn out brushes and commutator. Wore out just like any other electric motor. The mechanical pump looks in perfect condition, probably good for another 100k miles.

The lower section is actually two pumps, first a plastic centrifugal pump to feed the high pressure pump. From there fuel is forced up though the motor and out the top of the pump body. On the top cap there is a small one way valve on the output, and a spring loaded ball bearing for a pressure release valve.

Even after two days sitting in my garage the internals were still lightly pressurised and full of fuel. There surprisingly well sealed.

[quattro84]

It's good to see that there are other people around that have the urge to open up (broken) stuff
Didn't knew it looked like this.. nice share!

[Flat on my back]

.

A quick skim will see you right...what you worried about...

Groovey...

[A80Avant]

the trouble is, what do you do when you have an intermittent noisy pump, esp after long trips not even ON boost all the time, OR when the pump goes noisy on hotter days.
My pump is noisier than the OEM (044) and not always,but sometimes it gets noisy before i turn the engine off after those mentioned conditions. Never had a problem with it so far and has already done about 50K kms.

[mcandmar]

the trouble is, what do you do when you have an intermittent noisy pump, esp after long trips not even ON boost all the time, OR when the pump goes noisy on hotter days.
My pump is noisier than the OEM (044) and not always,but sometimes it gets noisy before i turn the engine off after those mentioned conditions. Never had a problem with it so far and has already done about 50K kms.

Thats pretty much what it was like, and like you say i always noticed it in the driveway before shutting down. Noise alone may not be sign of impending doom, but if the sound fluctuates rapidly and sounds like its struggling i'd bet its almost done.

For example i'm temporarily running on a fuel pump i got from a scrapyard and its even louder. If i turn the indicators on it makes a RRRRRrrrrrRRRRRrrrrrRRRRRrrrrr noise. Think its safe to say i'm on borrowed time

Fuel level also makes a big difference to how noisy they are. I've heard people say that they need to be submerged for proper cooling. Not sure if there is any truth in that.

[A80Avant]

yes but 044 pumps are made to work outdoors rather than submerged and maybe that shouldnt be a problem. However mine still works and performs adequatelly even after so many kms. it makes you wonder... i do have a replacement though...

[macspring]

For example i'm temporarily running on a fuel pump i got from a scrapyard and its even louder. If i turn the indicators on it makes a RRRRRrrrrrRRRRRrrrrrRRRRRrrrrr noise. Think its safe to say i'm on borrowed time



Mark,

Could this indicate that the power supply to the pump is not great ?

Maybe consider running a temporary + & - from the battery to the two respective power wires going to the pump to see if it still does it?

Just a thought.

Kind regards.

[mcandmar]

My pump is noisier than the OEM (044) and not always,but sometimes it gets noisy before i turn the engine off after those mentioned conditions. Never had a problem with it so far and has already done about 50K kms.

I've been running on the 044 pump for a few weeks now, i found it much quieter than the OE pump inside the car. But outside the car its much louder. Make a high pitched zzzzzzzzt noise, where as the original made a whiiirrrr noise that resonated throughout the car. Goes much better too

[Sleeper_Avant]

the pump should get 14v, dont hard wire it from battery as it will fry in a matter of minutes!
Must be relayed

[urS6Tom]

I've been running on the 044 pump for a few weeks now, i found it much quieter than the OE pump inside the car. But outside the car its much louder. Make a high pitched zzzzzzzzt noise, where as the original made a whiiirrrr noise that resonated throughout the car. Goes much better too

I've recently had an 044 pump fitted and agree with the above. However, sometimes, mine makes the high pitched noise INSIDE the car and it's really irritating. It's intermittent though. Most of the time it's quiet but occasionally the noise fills the cabin. I've noticed that it gets noisy when the tank is around half full and it gets much quieter when going around corners (when it gets recovered with fuel?). Anyone got any ideas on what's happening?

Tom

[mcandmar]

Anatomy of a fuel pump part II

For Part II of this thread i have a Bosch fuel pump taken from our 1993 S4. This particular pump just suddenly died without warning unlike the VDO pump from the S2's that seem to fail gradually.

The pump has two part numbers stamped onto it, BOSCH 0 580 453 070, and Audi 8A0 906 091 A. Interestingly the Audi part number was dropped on Feb 1994 and replaced with 8A0 906 091 G which would imply this is the original fuel pump fitted to the car. I find this utterly amazing as the car had 252k miles on it when the pump failed

On initial testing i found the pump had gone open circuit so it did nothing with power applied. After opening up the unit it was clear the commutator had broken apart and part of it had wedged itself into the top cap preventing the brush from making contact. The brushes them selves were in surprisingly good condition.

In terms of design and how the pump operates it is virtually identical to the VDO unit. In fact they are and both designed to fit into the same carrier so they are interchangeable with each other. The Bosch unit does have an addition of a small gauze filter on the input side, and two pressure relief valves on the output side, but apart from that they are the same.

Having dissected both the VDO and Bosch pumps i can say without doubt the Bosch pump is superior in terms of quality. And considering the average life expectancy for the VDO pumps seems to be ~120-140k miles this particular Bosch pump had clocked up twice that mileage. Compare the photos of them both for yourself and decide which looks the better made unit. For me its with out doubt the Bosch unit.

[UrS4boy]

Great post(s). I have taken the liberty of consolidating the text and your photos into one post on my home UrS4/S6 forum (credit given to you fully). I always wondered what exactly was inside those 091A/G pumps. Thanks to you, now I know.

http://forums.quattroworld.com/s4s6/msgs/179948.phtml

[mcandmar]

Anatomy of a fuel pump part III

Erst Klassig. A what you ask? When the above Bosch pump died in our S4 we needed something in a hurry so i sourced this Erst pump from GSF. I would never have put this into my own car, but it was fine for my father to pootle about in.

The car has sat unused for 3-4 years and in that time the pump had seized solid. Had it not sat idle for so long it would probably work fine.

Its pretty similar feature wise with a check valve and pressure relief valve in the top cap. It also has a small capacitor across the terminals to filter out EMI noise. Its overall construction seems alright, until you get to the two pump sections. The low pressure pickup is a plastic vane pump which is fair enough, but so is the high pressure section

Contrast that to the machined metal gear sets of the above pumps its a mystery how this thing ever made enough fuel pressure and flow rate to meet the demand of a homefried motor. My guess is it didn't, best to avoid this one!