AO

Jim I had a FP sieze on me on my '91. It took several tries (I did this with the pump out of the car), but reversing the power then putting it back the right way, back and forth like that dis-lodged whatever was jamming it. The culprit was the in-tank pump. The hose that connects the two part was cracked and allowed something to get in past the mesh pre-filter.

I did replace the in-tank pump, but if I were to do it again, I'd just get the strainer option and forget the in-tank pump entirely.

Hope you get it going.

worf928

I missed Jim's post in which he said the in-tank pump was done a couple of years ago.

jcorenman

Update: Thanks for all the suggestions. I realized last night that the low voltage at my test-switch was probably the result of too-skinny wires to the test switch, so I redid that this morning with 14ga wire. (We happened to have stopped at West Marine in San Diego to pick up shrink-tubing and an assortment of wire).

So good volts to the pump but still no pumping, just a quiet "clunk" as it tries to turn. I then tried various combinations of forward and reverse polarity and physical abuse, no luck at all- just that same quiet "clunk" in either direction. I didn't want to start disassembling fuel lines in the espresso-kiosk's parking lot, that seemed like a poor way to repay their kindness.

(Fidalgo Bay Coffee, corner of 12th and Commercial in Anacortes-- highly recommended)

So we called AAA and the guy came right out, and we made the 9:30 ferry for home. They sent Jim's Towing in Anacortes who I would also highly recommend, no drama at all.

The plan is to drain the fuel and pull everything apart and find out what is going on. New pump for sure (on its way from 928int'l).

I am undecided on the second pump. Andrew has a good thought, to replace it with a strainer ala pre-89. But it does serve a purpose in keeping the fuel pressure higher on the inlet side of the main pump, which may help avoid vapor lock in extreme conditions. Any other reasons to keep it?

One thing I never understood is why they didn't put the filter before the main pump, when the second pump was fitted-- i.e. use the in-tank pump to push fuel through the filter, then through the main pump to the fuel rails. Is there any hazard of the main pump shedding debris? (What sort of pump is it? A vane pump might shed debris).

Thanks again for all the suggestions and ideas. I'll post an update when we get this apart.

AO

Bummer. Sorry it ended this way. Let us know the result.

docmirror

Ethanol strikes again. I would just go with one pump. I don't think you'll ever get into a situation where vapor lock will be an issue unless you're running at 1/4 tank, in a high altitude desert at > half throttle for long periods of time.

jcorenman

It's not so bad, the only thing hurt was my pride. AAA has a "plus" plan which covers longer tows and also pays the ferry fares.

The problem was the classic deteriorating hose syndrome. My error was thinking that when the PO went through it, it got done properly. (Just to be clear, we bought this car from Louie last year but it was the PO before that who had last gone through the fuel pumps).

When I pulled the in-tank pump it came out in three pieces: The tank fitting (which was not thankfully not corroded), most of the rotting hose with clamps and finally the pump and remainder of the hose. The hose was not reinforced and appeared to be a molded part, looked like the factory hose. The clamps seemed too thick for the application, and were marked with both "7/8" and 20-23 (millimeters I presume).

I'm blaming the ethanol-infested gas we bought in Springfield OR, that was our last fill-up prior to the pump going TU.

Lessons learned:
1. Don't assume anything about anything that you haven't personally disassembled and fondled.
2. If you have in in-tank pump, take it apart and fondle it. And maybe replace the hose.
2. Add 7mm and 8mm 1/4"-drive sockets to your traveling toolkit, those are needed to disconnect the wires from the fuel pump.
3. Plan your breakdowns so that you can coast into a parking place between an espresso drive-thru and a hardware store, and within walking distance of a decent motel and a good restaurant.

Here's some pics, and thanks again to everyone who offered ideas and suggestions.

Here's what came out first:


Which left this behind:


This was next. (Do those look like factory clamps??)

And finally:

Mrmerlin

those are factory clamps as is the crumbling hose.
The filter needs to be after the pump as when the pump is working small pieces of metal come off of the different areas, any doubts just blow the filter out from the outlet into a clean container you should see small pieces of metal in there.
Before you junk the outside pump try blowing it out with some compressed air, there is a good chance that the pump has a chunk of rubber in it locking it up, then go with the reverse polarity if it does get running make a small loop hose, this will let the pump run backwards so to flush it ,you might toss the new pump in the glovebox as the outside pump may still be good.
Run the pump with marvel mystery oil.

Mrmerlin

Put some anti seize on the thread prior to installing the new inner pump or New inner tank filter

jcorenman

Very Interesting...

I've also got a high-current 24v power supply which might come in handy...

Is it OK if I put the new one on the car and this one in the glovebox?

Aha!! Not-too-flammable, compatible with gas, Perfect!

Won't the fuel just wash it away?

Thanks,

FredR

Jim,

Classic failure- before you give up on the pump altogether try back flushing it with water from a garden hose- preferably pressurised- that has the most likelihood of breaking free any debris as it will also try to rotate the pump backwards thus tending to undo the jammed component. Do remove the check valve first though.

Although not impossible, I doubt that the last fill of gasoline had anything to do with it although doubtless an interesting topic to investigate in its own right.

Agree that what you pulled out looks stock. I used some petrol hose to replace it when mine failed several years ago. We crimped it with a couple of SS jubilee clips I seem to remember. I presume the in tank pump is still serviceable.

Did you notice or feel any drop off in performance?

Regards

Fred

worf928

ORLY?

IHO, ethanol-infested gas may accelerate disintegration of the hose on the in-tank pump, but it is all the other stuff in our gas that gives the hose a far less than 10 year life.

IIRC there is a thread around here somewhere discussing the ins-and-outs of this little hose.

And.... if you decide your existing pump is dead and get curious, take it apart. My next bet is that you'll have little bits of the intank pump's red wires stuck in the pump..

Mrmerlin

the anti seize will let you remove the tank strainer next time it should stay in the threads even if its submersed in a liquid otherwise it hurt anything

Landseer

Needle nose vice grips with hoses on the jaws to pinch the inlet hose to keep gas in the tank
Screw driver to remove the clamp/hose from the inlet side of pump.
Wires with alligator clips. Disconnect the pump wires, use these to feed the pump, reverseable.
WD 40 with a straw to squirt into the normal inlet side of the pump while reversing.
Try forward / backward / forward / backward.
Never more than 10 seconds or so each way.
Have a helper operate the key or the relay jumper.

Sparks are not your friend. Can flamebroil all within a 20 yard radius with a little bad luck.

Cleared one in the driveway and one at a toll booth with this method.

jcorenman

Agreed, that hose obviously deteriorates over time. But it's fun to pick on Oregon, I think it is the only state where pumping your own gas is illegal...

I'll need to reassemble the in-tank pump to test it, Orly and I will dive into that this weekend.

And the car was running great right, right up until it quit-- zero warning.

Yep, I found a bunch of threads, including the recommendation to use Napa fuel hose. Sue grabbed some at the local Napa store, Weatherhead H10108 general-purpose hose, Nitrile inner tube and Neoprene outer tube with fiber braid between, rated for up to 10% ethanol.

What's odd about this application is that the outer jacket is also exposed to fuel, not just the inside. Is Neoprene OK with 10% ethanol? I find conflicting answers on the web but most say it is OK.

What we decided to do was stick with the two-pump configuration and replace both pumps, keeping the old ones (if serviceable) for spares. If the hose on the new in-tank pump looks like the same molded-rubber part we'll replace it with the Napa hose.

I also like Louie's idea to fit a small filter or strainer between the in-tank pump and main pump to catch any debris. But I can't find anything that would fit easily, there's only limited room down there without doing sheet-metal mods.

I'll buy that, assuming you meant "can't hurt". I assume the corrosion is caused by water accumulating in the bottom of the tank (e.g. condensation). Ironically the ethanol probably helps, by absorbing the water.

and thanks all!

jcorenman

Update: I had no luck getting the pump going, so I did the next-best thing and took it apart. I tried beating on it, flushing it with mystery oil and blowing it out with compressed air in both directions, and got out the big power supply and tried both polarities up to 24 volts (it was drawing 30 amps at that point...). Nothing, zip, nada.

So I chucked it up in my little toy lathe and cut the crimped end off, and pulled out the guts and disassembled it.

Caution, graphic pictures follow...

Here's where I made the incision:


That "groove" is a crimp which holds the whole thing together. Note the o-ring I just missed-- cutting it a few mm farther up would have been better.


The end-cap just pulled out, taking the brushes with it:


Here's the brush assembly. They looked almost new, almost no commutator wear:


The rest of the guts just pulled straight out...


Leaving an o-ring and this funny little plastic capsule behind. At first I thought it might be the problem but it's too big to get through any of the hoses, I think it is there in case the fuel somehow expands and builds pressure. (I know, it's not possible, but remember this is a Bosch pump).


Here's the assembly pulled out, with the pump on the end of the motor shaft:


And with the armature pulled out of the magnet assembly. Still would not turn, even with significant force.


Remove clip and shim, and slide motor armature off of the (stationary) shaft. Normally you would expect the shaft to rotate with the motor, but here the shaft is fixed to the pump body, and the armature rotates around it. Note the tab at the far end of the motor, that drives the pump.


Finally, pull two torx screws and remove the top-plate of the pump itself. A vane pump, with steel rollers as "vanes". Note the small notch on the nearside, that's where the tabs on the motor armature fit.


Aha, what's this lying on the clean towel after we pulled the guts of the pump out?


Close-up: Looks like a flake of plastic:


Another view:


We didn't see where it came from, but note the tight clearance between pump rotor and housing. The clearance between rotor and end-plates is also very tight. The in-tank pump (and screen) were disconnected so it could have been anything floating around in the tank, or from a recent fillup.

Is that what ethanol looks like ??

This pump had lots of life left, but unless I want to make a new housing it's not going back together. A housing with a threaded end-cap would allow non-destructive disassembly, but a simpler approach is to make sure that the in-tank pump stays attached. That's tomorrow's project, Fedex should have a new-from-Porsche in-tank pump for us and it will be interesting to see what the hose looks like.