front 044 - 2nd failure... diagnosing fault?

[krasuskyp]

Last we left our fearless Stuper Hero here, I'd had a newish front 044 fail and Amazon credited me for a new one upon return.

The replacement suffered the same fate this fall . Don't think it's an issue with the part / source (being a knockoff, etc.) as all the "real deal" tells have all been present on all the 044's I've gotten from this source via Amazon. Besides, the rear 044 from same source has been fine, so...

Prevailing wisdom back when I'd first mentioned this failure was that the fuel tank inlet screen was clogged and some of the clog was making its way thru and chewing up the pump. Symptoms began as the front pump not coming on and causing the rear one to audibly strain. Get under, literally 'touch' the front pump - zing - zipped to life.

This would eventually devolve into needing to literally wail the piss out of the pump to get it to spring back to life. Limped it home this fall via a series of about 97 pull-over Chinese fire drills w/ my passenger turning it over when it cut out while I got under and smacked the fukker. "Fun".

Sooooooooooo...

Finnnnnnnnnnally drained the tank this weekend, and pulled the tank plug which has the inlet screen attached. Was disappointed to find a relatively clean screen. Sure, it had 'some' trace debris @ the lower corners, hair, grit, etc. - but not the "ah ha" magic moment I'd hoped for. Damn.

That said... what now is the likely culprit?

One recent suggestion was wiring. I *DID* extend the +/- OE harness wires to the FP with crimped on 2" extenders after creating about 47 new swear words fighting to get the "exaaaaaaaactly the right fukking length not a c-hair to spare extra!" OE wires affixed to the pump a few installs ago. The crimps I'll add are strong enough that I was able to dangle the FP from the wires upon removal this time (not too smaht, I know - but they're apparently solid connections?).

Might my crimp connectors be causing some voltage issue, and thereby nuking the front pump?

Should I consider running fatter gauge wire with a relay straight from the battery or fuse block?

Any insight appreciated as always - TIA gentz! New 044 arrives from Amazon tomorrow and I'd like to tackle the install stat - try and get some seat time in before the f'n snow flies. Sigh.

[pkabush]

I'd start by checking the connections. Just b/c the connectors can hold the weight of the f/p doesn't insure they're good. Perhaps solder and shrink wrap them. Before the new pump is hooked up you can put a voltage tester on it to verify full voltage, then check it under load. Another idea would be to bench test your old pump by attaching some leads to it and hooking it directly to 12V pwr. Although, if it works after smacking it around (not unlike what Ronnie pays strange men to do to him) I'd suspect the unit. Anyhoo, I'm sure others will chime in with better advice, I hate auto electrical problems. Good luck, I'm sure you'll get it sorted.

[Ronnie's.930]

How dare you, Mr. 70'sbush - I've never had to pay for the smacking!

Paul, maybe the pumps wouldn't fail so quickly if you resisted "bothering" them prior to install?! That said, have you verified that your fuel return line has good flow (unlike you) back to to the tank - not obstructed in any way?

Originally Posted by krasuskyp

Might my crimp connectors be causing some voltage issue, and thereby nuking the front pump?

Highly unlikely - unless the crimp is done totally improperly, that method is just as sound as soldering. Also, the wire is only going to pass as many amps as the pump asks of it (given no shorts to ground, etc.), so voltage/amperage problem is likely caused by the pump itself.

Originally Posted by krasuskyp

Should I consider running fatter gauge wire with a relay straight from the battery or fuse block?

Nope.

[Norm K]

Originally Posted by krasuskyp

wail the piss out of it to get it to spring back to life.

Fluffers, I hear, are fare more gentle. Try it next time you experience this "issue".



_

[Ronnie's.930]

^^^

Or . . . .

[turbo owner]

Originally Posted by Ronnie's.930

^^^

Or . . . .

Quite the stash you have there, Ronnie

[pkabush]

How dare you, Mr. 70'sbush - I've never had to pay for the smacking!
Cant beat a free beating

[Ronnie's.930]

Originally Posted by turbo owner

Quite the stash you have there, Ronnie

Yes indeed - helps with those disturbing, worse-than-double-bagger, situations!

[klefroid]

Same thing happen to me. but mine did not work at all :-) Strange thing was, there are two electric connectors on the fuel pump... (round ones) a small M5 and a bigger M6, so I connected the wires without checking the positive and negative because it was impossible to put them on in the wrong way... turned out to be wrong so I connected negative to positive and positive to negative and fuel pump was death... also a 044 btw

[pkabush]

Originally Posted by klefroid

Same thing happen to me. but mine did not work at all :-) Strange thing was, there are two electric connectors on the fuel pump... (round ones) a small M5 and a bigger M6, so I connected the wires without checking the positive and negative because it was impossible to put them on in the wrong way... turned out to be wrong so I connected negative to positive and positive to negative and fuel pump was death... also a 044 btw

Wow! Good to know, thx

[Bucketlist]

I just drilled out the m5 connector to make it fit the m6 post and skipped the wiring rework.

[reclino]

Maybe the outlet screen in the fuel tank is too small for the flow of the 044 pump and the pump is cavitating. So how could we rig up a longer screen with twice the surface area....
David

[bpu699]

Could there be a blockage down stream? Fuel filter, etc? Is the rear pump ka-puut and the front is try to work past it?

Go buy an inline amp meter ($20 at a lot of online sites for radiocontrol cars, etc. Called a Watt-Meter)... And solder it up inline, and see what your amp draw is. That tells you how hard the pump is working...

[klefroid]

If there was any blockage in the return then your wcp would go up and she would not be running well.
I would never put a 044 up front unless the rear pump has the same or more flow rate... your 044 is pushing the other one forward? Maybe I'm wrong... my 0000.2 cents

[JFairman]

Originally Posted by reclino

Maybe the outlet screen in the fuel tank is too small for the flow of the 044 pump and the pump is cavitating. So how could we rig up a longer screen with twice the surface area....
David

The fuel tank screen that screws out of the bottom of the tank is big and would not restrict flow if it wasn't clogged. I remember it being around 3 to 4 inches long and around an inch wide.
When I removed my gas tank to restore and paint it the internal filter was clean with just a few little specs of dirt on the screen.
Water in the bottom of the gas tank from todays E10 gasoline phase seperation in humid climates is a more of a problem than dirt in the gas these days.

I've been through 3 different 044 pumps trying to find one that would not buzz loudly after a half hour when mounted in front. One was a little quieter than the the other two but after 3 of them I gave up trying.
I think the 044 pump is the wrong pump for a CIS 930 in the front position because maybe they flow too much fuel volume for the tiny little CIS fuel head system pressure regulator and return line system.
If the car sits for a long time gas can leave varnish deposits inside the skinny return line inside the gas tank and clog it too. That's a fun one to diagnose and requires gas tank surgery to fix but some people have been there and done that.

Bosch fuel pumps have an internal pressure release valve that opens and recirculates fuel round and round inside the pump to keep it from laboring too hard and overheating and burning out if the fuel flow it's pumping is restricted.
Fuel flows through the pump motor all around the armature, brushes, and everything else while it's running and the pump is lubricated and cooled by the fuel flowing through it.
The pump rollers are in the exit end of the pump so the fuel flowing around the motor armature, bearings, and brushes so before it reaches the spinning rollers it is not under pressure yet. It's under suction at that point so that increases the chance of cavitation.
I know this because I took a seized Bosch fuel pump apart years ago. Had to cut and peel the aluminum casing apart with a couple pairs of vise grips but I wanted to see the insides. I still have the curved armature motor magnets from inside it.

If the pump overheats after 30 minutes of gasoline recirculating around and around inside the pump the pump and gasoline inside will get very hot and could start to vaporize inside the pump and then you have cavitation bubbles whirling around and around with the gas in between the pump rollers inside the roller chamber in the exit end of the pump and then it makes a nasty loud buzzing noise and the pump eventually burns out.

That's my theory and maybe I'm wrong.
I still say from my experiences the 044 pump may pump too much fuel volume for the stock 930 CIS system pressure regulator in the front pump position and the original stock fuel pumps are better.
For whatever reason the rear 044 pump I put in my car has always been relatively quiet.

A couple pics of different front 044 fuel pump installations I've done on my car trying to find one that doesn't drive me nuts with the loud buzzing noise after 30 minutes of driving.

First one using the original front fuel pump mount.



Second or third 044 pump installation with the two piece rubber cover Porsche used in the 964 and 993. It fits the 044 pump like a glove and does muffle some of the buzzing noise. It definately helps. Chris at Turbokraft turned me on to the part number for it. It was around $25 from Sunset Porsche in Oregon. They had to order it from Germany but they get big shipments of parts from Porsche in Germany every week so they didn't charge me for the shipping from Germany.
I used the larger wire eyelets and rubber covers Bosch supplies with the pump. I crimped and soldered them to the wires.

[krasuskyp]

other than some audible buzzing tho Jim - you are still running the dual 044 setup with no running issues right?

So doubting that is what my issue here is then. A number of others here do as well IIRC.

Car runs great when the front pump runs. First one lasted a few thousand miles. 2nd one maybe a couple thousand. So doubting it's a flow issue, bubbles, etc. Just my gut based upon those datapoints of running great for miles.

My fuel filter is newish (miles-wise). I'll do some current / draw testing tonight when the new pump arrives and SC/Alfa John up the road here arrives w/ his expertise.

thanks for the thoughts - please keep them coming

I'm getting damn good @ FP R&R 8-/... grrrr...

[reclino]

I have googled around a bit more today and roller cell pumps like the Bosch 044 are very sensitive to cavitation due to restriction on the inlet side. One way to put it is these pumps don't like to suck. Looking at my inlet strainer I just don't think it's large enough to support the flow. One other contributing factor is the vapor pressure of ethenol is lower than gas. This means gas/ethenol blends are more prone to cavitation. Cavitation on the inlet side of pumps will kill the pump.
David

[krasuskyp]

thanks David - if this one packs the fudge (like Ronknees), I'll replace with something more conventional

[Ronnie's.930]

^^^

Paul, is that a packing request?!?!

[reclino]

Does anyone have a fuel tank outlet screen that they have replaced. I would like to experiment with fitting a larger strainer to the brass fitting but don't have a spare.
David