heinrich

I agree. I've always agreed.

Spun

No... once the whine starts it will whine at idle. I removed the in tank pump and put the 044 system in from this thread. Did not have a whine prior to this.

I am thinking about removing the cover and next time I hear it checking the surface temp of the pump to make suer it is not getting hot.

I have not changed any relays (I saw a recommendation for an additional relay to go with the 044 pump), but will conciser/and or do it if someone has a good plan on how to best do that.

any other thoughts?

Bjbpe

With two pumps in series, one possibility is that the first pump is a booster to prevent cavitation of the main pump. Just speculating. If that was the reason, eliminating the booster would ultimately result in the main pump failing from cavitation damage but that might take quite a while.

T_MaX

This is what I did and it worked great, all the way to ~320 hp/tq RWHP NA!

Spun

I am running this kit without a stroker ot booster. Could that be why the whine? Pushing more fuel than needed?

heinrich

Many years' 928's had no in-tank fuel pump, and lo and behold they ran great. My Godzilla put down 299hp and 299ft-lbs at the wheels and still has its original single fuel pump after 200k miles.

heinrich

No.

Sometimes the pumps whine when fuel gets low. I've experienced this on almost every 928 I've owned.

heinrich

Lex remember this is rubber with stainless steel wrapping.

Ducman82

my pump whines when it gets hot out. loud too....

andy-gts

this may be way different, but on my other vehicles a whining fuel pump means it is on its way out I would just replace the pump and be done with it....and as Andrew olsen has shown, his way works well.

andy

Spun

The pump is brand new... I will watch it though.


It has not whined the last couple days, so I will see what happens this winter. It is loud as well.

Hmm... OK. I will watch to see if this is an issue, but since the internal pump is now gone, I would guess that will not be a driver.

Thanks gents.

jcorenman

I would like to add a page to this memorable thread. Many knowledgeable folks have posted that the in-tank does no good, and is not needed. The most compelling evidence offered was that Porsche omitted the in-tank pump for many years before bringing it back in '89, and those cars all ran fine.

To those who share that view, please allow me to share an alternate opinion:



This saga started on a Sunday at the end of June, on Canyon Road between Yakima and Ellensburg in eastern Washington, on a tour with the local PCA group. It was warm, around 105, the aircon was working great and we've driven (the GT) in lots hotter weather that that. This was our S4, stock fuel pump (and no in-tank pump in '88).

The group stops for a quick break at a rest stop (911's tend to stop a lot) and about two minutes later the engine begins stuttering. At first it was just when I pulled out to pass, then within a minute it would hardly run at all. I bailed into a turnout, shut it down and waited a few minutes, and it would restart briefly and die.

My first thought was fuel pump. This one was only a couple of years old (previous saga here: https://rennlist.com/forums/928-foru...p-failure.html) but failures happen.

I had a fuel-pressure gauge in the tool kit but I couldn't get the fuel-rail to stop spitting fuel. Normally when I open the test port I get a couple CC's of fuel from the dampers, but this kept spitting and trying to spray fuel on a hot engine, and wouldn't stop. After sitting for a bit, things were heat-soaked and fuel was boiling in the lines somewhere, creating pressure that would not go away.

So clearly we had fuel pressure (vapor pressure at least...) so I jumpered the fuel pump (replaced the relay with a test-switch) and tried to start the engine. Same thing, sputtered and quit. As I flipped the switch on and off the pump would sometimes run normally, sometimes buzz loudly, sometimes not run at all.

I was also reminded of Don Carter's recent saga, diagnosed as a fuel pump:
https://rennlist.com/forums/928-foru...orn-texas.html

So we called AAA, we baked for another four hours waiting for them (busy day, apparently), still no start (and still hot), and made it home the following day.

So back in the shop (around 70F) I jumpered the pump again and now it sounded fine. I then fit the pressure gauge (no problem, only a couple cc's of fuel under pressure), steady 55psi with pump jumpered. I disconnected the return line and did the flow test, a bit over 1.3L of fuel in 30 sec (spec is 1.25) which is OK. Drove it around, ran fine.

So my diagnosis was vapor lock at the pump inlet. Fuel was clearly boiling somewhere (residual pressure at the rails) and it ran fine once things cooled off. Everything else was normal: temps were warm but not unreasonable, altitude was 1500 feet, fuel was Shell purchased that morning from a proper station just off the highway with a little over half a tank remaining, air-con (and fuel-cooler) was working well, strainer was clean, hose from strainer to pump was fine.

My other data point is that we've driven our GT in lots of hotter temperatures without any heat issues. That car is a '90, with the in-tank pump.

So my conclusion is that Porsche knew exactly what they were doing when they returned the in-tank pump to production in '89 (or whenever it was). Sure, maybe a less-restrictive strainer would have helped, but our fuel was thoroughly cooked and positive pressure trumps less-negative pressure every time. This car is virtually stock, but the fuel today is not the fuel that was being sold in the late 80's.

So we upgraded the fuel system to the later spec, added an inline pump with GB's cosmic hose, a new 89+ fuel pump (the old one would have been fine but it is now the spare). When I wired in the in-tank pump I also added a disconnect for the main pump so that the pump/filter assembly can be easily pulled and swapped as a unit-- much simpler than fiddling with the pump wiring on the side of the road.

One thing that is important is to change the short piece of hose. It's easy to do, we used a short (27mm) length of high-tech fuel hose from GB.



I did a flow test on the in-tank pump after we got it installed and fuel in the tank. flow was 4.6L/min with a 1' head or about double what the main pump needs.

docmirror

Ethanol. See post #4. You would prolly have been just fine with pure 91MON summer pump gas.

If memory serves, Porsche took one of the 928s to Dubai or something in the ME and flogged it at high speed in high temps for hours. They prolly got a load of poor gas somewhere that started to vaporize as well, and so Hans and Franz decided to add a pump submerged to feed the monster under all conditions.

Ethanol separates and settles in the gas station tank also. It might have been 10% Eth going INTO the gas station tank, but coming out, no one knows but your engine. 20%? 25%? 28%? Somewhere the line was crossed, and when you stopped, it was all she wrote for that day. Of course, you could have just let it spray hot gas everywhere, and reduce the pressure in the line, then climb under and spray the pump with cool water from your cooler for a while until it built up pressure. Ask me how I know...

<edit: in 2002, I bought a load of gas in my ancient class C truck motorhome, towing a 21' boat, in the middle of summer coming back from Lake Powell. I took a 'short cut' and this is where I vapor locked, right in the middle of the road, blocking both directions. I wasn't going to try backing up downhill with no power brakes.

Moki Dugway, Muley Point Overlook, Utah 261, Mexican Hat, UT https://www.google.com/maps/@37.2757.../data=!3m1!1e3 It was -- unpleasant. >

AO

Well Jim... that sucks. I'm surprised that even with running the Fuel pump (engine off) that you weren't able to clear the vapors. I'm also surprised that the fuel cooler didn't do it's job.

Well if you feel the need to run the in-tank pump, you did the right thing by replacing that crap piece of hose. Hope it doesn't strand you again.

Don Carter

Jim,

Very interesting writeup. My situation may not have been due to the fuel pump, but the mechanic's opinion that the FP had an issue and was generating too much heat and thereby cooking the fuel seemed to make sense. We drove about 30 min to his shop, first thing in the morning and he said the fuel was much hotter than normal when he disconnected the lines. We had no problems after the new FP was installed, but we also broke up our trip home over several days, so not quite as much non-stop driving.

If this can happen with a good FP and working AC, then it's surprising we don't hear about more issues like this in Texas and other hot states.