gcthree

While changing the fuel filter on my '89 S4, I needed to remove the entire pump console due to way overtightened fittings precluding undoing on the car. So, the 'S' pipe, check valve and seals were replaced. I also pulled the in-tank siphon pump while I was at it and checked the filter screen only to find that the rubber coupler on the pump was ruptured.

I've heard that the pump isn't necessary on these cars other than in extreme heat locations (I'm in Virginia), and it should be deleted and replace with the simple strainer.

Any opinions and reasoning?

Thanks,
Bob

jeff spahn

I deleted mine 5 years ago and never have had an issue.

MainePorsche

That would be my answer too.
I read a post regarding this, and someone had said he only noted a difference when trying to accelerate while going up a steep incline.

MainePorsche

And for everyone's viewing pleasure, here is a pic of a strainer that the poster said was removed after someone in a shop sabotaged him with dried auto paint dust residue. As you can imagine he had running issues. Nasty !

gcthree

OMG! Nothing against independent shops, but there's only one kind of caring attention applied to cars serviced in the home garage.

I had previously owned my car 16 years ago and have bought it back, and the intervening owners kept and shared service receipts. I personally did the TB/WP around 30k miles during my first go-around. The local indy-Porsche shop here did it again at 40k miles (despite my records attesting to the service), and foisted it and a huge bill on the previous, no-so-knowlegable owner.

Back to the pump, I appreciate the input!

Bob

Arnoud

As I wrote earlier this year: IIRC the in-tank-fuel-pump purpose is to make sure that in very hot climates, as in: much over +40 Celsius = much over +104 Fahrenheit, fuel get's still delivered fine.

However as documented here many times: sooner or later the in-tank-fuel-pump internal hose will split and debris of that internal split hose will get into your main exterior pump, which will then get jammed and seizes...
Hence I followed the advise as was given to me, and pulled my in-tank-fuel-pump out before such could happen, and yes: it's hose had started to split. One less moving part that will go wrong to worry about

See for example this thread for more info: https://rennlist.com/forums/928-foru...pump-hose.html

Hai gebissen

I just pulled my strainer today:

gcthree

Yikes!! Not much filtering going-on there! Also noticed that the red paint guy was on your car, too. What is with all the red paint??

kurt_1

Bob,

same here: broken hose plus a ripped wire to the pump.

I replaced the hose with a piece of re-inforced "Space Shuttle-grade" hose from Greg Brown and resoldered the wire. Took all of half an hour and works fine again!

FWIW: The primer pump seems to work with a different main pump (different part number) than the strainer. Whatever that means in practice.

Kurt
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90 S4 satin black metallic

Dave928S

Here's what I did to repair mine, and it's been fine since ... https://rennlist.com/forums/928-foru...with-pics.html

I figure that Porsche put it there for a reason (probably to prevent cavitation of the main pump), and thought that 18 years wasn't an unreasonably short period of time for a repair or replacement to be required. Bear in mind that even if you don't think you live in a hot climate, the bitumen road surface in summer can get to incredibly high temperatures, which is directly below where the pumps are located. Heavy slow traffic, and a low fuel level combined, can result in near boiling fuel .. and that's when you might need that (multi-stage) pump combination.

Arnoud

More additional background information in this thread: https://rennlist.com/forums/928-foru...-in-japan.html

Kurt, Bob: I actually looked into the Bosch main fuel pump specs a while ago, as per above thread and my post #13 in it. The later main fuel pumps have a slightly marginal higher flow rate, but as that is only +4% more I would call them equal from that point of view.

I have been driving without my in-tank-fuel pump and with the strainer since November 2011, and happy ever since (as I wrote: one less moving part that will go wrong to worry about ), while having driving outside temperatures ranging from between -20 Celsius (Finland, where I live) to +35 Celsius (driving trips through Germany + the Netherlands).

FredR

I have fuel delivery problems with an tank pump [with everything in good working order] if i pull away from the lights sharpish with lowish fuel level in the tank [i.e. when the time to refuel indicator comes on]. If on an incline it just will not pick up at all.

I cannot see how deleting this pump will improve things but of course I do live in a hot climate.

I remain puzzled as to how/why some S4's have the in tank and some do not - I get the impression it must have been "flavour of the month" at Porsche.

For the OP, I would have that debris analysed if you can. It is one thing what is may look like, perhaps another altogether as to what it actually is. Could easily be debris from a failing underground storage tank protective coating- I would not immediately assume someone spiked your fuel- albeit a distinct possibility from some spiteful fatherless creature.

Regards

Fred

kurt_1

Arnoud: thanks for the information. I guess that in most cases there will be no problem. I don't know much about pumps but there may be other factors than thflow rate e.g. the "suction" the pump generates.

However, I am quite sure that my in-tank pump was not doing anything for quite a while as the current noise of two pumps running is quite different than I was used to hear. There was no difference in fuel delivery I would notice or see in ST logs.

I was lucky that the old hose just split and no pieces fell off to jam the main pump.

Anyway, I fixed my in-tank pump because it was the cheapest and easiest option and with the new braided hose I am sure it will be working well for quite a while.

Dave: it was exactly your write up that I was following when I rebuilt mine. Time for a little late "Thank you!"

Kurt
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90 S4 satin black metallic
OC charter member