anakilat

1980 Euro (non-S) early VIN.
I had what felt like a fuel starvation problem so I dropped the tank and cleaned it. While the tank was out I replaced:
In-tank fuel filter and outside regular fuel filter
Hose from the tank to the pump
Banjo fitting and hard line from the pump to the filter (w/new crush washers)
Hard fuel line in the rear wheel well to the accumulator
Accumulator (used)
Soldered new ends on the fuel pump wires and installed new boots
Painted the tank and the tank carrier and added new "rubber" tape to it
Pressure washed the wheel well area and underside of the car
Thoroughly cleaned, inspected and painted anything else fuel related in the rear of the car.

Put it all back together and it won't start. It turns over just fine but I hear a loud hissing from the back, but that's it.

I started checking for fuel flow and as I worked my way backward to the tank I found everything dry. I pulled the hose from input to the fuel pump and had plenty of fuel coming out of the tank. I reversed the wires on the pump for a couple of spin ups and put them back and tried again. Still no fuel out of the pump. I get a lot of loud hissing but no fuel.

I'm starting to think I have a vapor lock or something like that. Can anyone take a look at the photo's and tell me if you see something obvious that I've connected wrong? I'm not sure of the accumulator connections. Right now fuel from the pump goes in the center fitting and fuel output is connected to the outside fitting. Is this correct? Any help is appreciated.

tailpipe

Try another fuel pump I have had a couple here that make a humming sound but do not pump fuel it seems sometimes the impeller comes off the motor inside.

jpitman2

Looks ok physically. Hav you tried cracking open the filter outlet (NO POWER APPLIED!) to see if fuel dribbles out ? You have added enough fuel to cover the inlet filter ? Things woul need to be up around 100F to get a vapour lock.
jp 83 Euro S AT 54k

WallyP

Are you absolutely positive that you don't have the pump wired backwards?

jpitman2

After you have checked that you have the wires to the pump around the right way - the original fiitings are for different dia bolts to ensure ypou cant reverse them, but if they have been removed and you have refitted them, anything is possible. If you remove the access cover in the trunk, and run the pump, and its wired backwards, you may hear bubbles being blown into the tank?
Try this :- get a good length of 2 core flex that can reach from the fuse board to the pump area; fit male spade tags to each wire at one end; fit a momentary switch at the other end (ie default open). remove the pump relay, and fit the spade tags into the relevant sockets (30 and 87 IIRC) - check that be pressing the switch, you hear the pump.
disconnect the RETURN line at the cam cover in the engine bay, fit a length of fuel hose onto the pipe coming off the engine (NOT the one going back to the tank!), and run it into the largest glass or clear plastic container you have, ensuring that it cant tip over. Hit the switch - its possible you have something in the line that needs blowing out.
jp 83 Euro S AT 54k

anakilat

Tailpipe: I've got a second used pump that came with the car but I don't know it's history. That may be a viable next step.

Jpitman2: I did crack open the outlet end of the filter and it was dry as a bone. I put 5 gallons of gas in which should be enough to cover the inlet tube. It is 98 degrees outside with very high humidity (it's Georgia). When I captured some fuel from the tank in a low plastic tray it formed water bubbles within a minute. The fuel felt very cold. The air was not.

WallyP: The pump has a + and - cast into it. The red/green wires are on the + and the brown wires on the -. I did reverse the wires to see if the impeller was stuck and still had no fuel in the pump or filter afterwards. I'll take a multimeter out today and check that my red/green is actually the hot wire.

Thanks for the many ideas. I'll keep you posted.

anakilat

UPDATE: Old/other fuel pump installed. It's dead.

jorgens

This is just from memory, but; I seem to remember that the fuelpump and filter was "flush" mounted on mine? Seems like your filter os very offset (see clamp)? Is everthing connected right there? but, it`s just from my memory, I`m not sure.


Jørgen

anakilat

You're right about the big offset. The hard line that connects the pump to the filter is about 1.25 inches longer on the older models. The problem is that Porsche superseded the P/N for that line to be the same for all years. Now you can't get a new hard line that's long enough for the older cars. I've been searching for the correct line for about 3 months now with no luck.

Newest Update: Both fuel pumps are now bad. The old one doesn't spin up and the newer one spins up but doesn't pump fuel. I put a hose directly on the output of the pump (took off the check valve) and turned it over - no fuel output. It's funny because I drove the car around for an hour to burn off some fuel just before I started this whole maintenance job. That newer pump was removed and has been sitting on a shelf in my workshop for a few months. I have no clue why it doesn't pump fuel now. This could very well have been the root cause of my fuel starvation problems.

WallyP

At this point, I would test the pump on the bench, using a non-flammable liquid, such as water. Jumpers to + & - from a 12-volt source (car battery, lawn mower battery, charger, etc.) and stick the inlet side down into the water. If it doesn't pump fluid, the problem is obvious. If it pumps liquid, get the water out. Make sure that the filter is clear.

Another thing to check - look at the fitting where the fuel exits the tank - do you have electrical wires attached? If so, you have an in-tank fuel pump. Does it run?

outbackgeorgia

Something is getting into the pumps. The filter is after the pump, so any pieces of rubber from an in-tank pump, or broken screen/no screen junk will go directly into the pump and seize it.
Visually check from the fuel level sensor port if possible.

WallyP

If there is an internal pump, it is common for the hose to it to fail and shed pieces.

Pagnobito

OP said he replaced the in tank filter

tailpipe

Take the old pump thats dead and have it ultra sound cleaned it may come back to life if you can't find someone who can do that I have had good luck boiling them in a pot of water for about an hour.
Its the new gas with manganesse in it, it seems as soon as the pumps go dry the impeller locks right up.

anakilat

I ordered a new fuel pump today.

Wally: I kind of did a bench test with it on the car. I disconnected everything from the pump output, including the check valve and put a big heater hose on the snout going to a coffee can. Using the fuel tank as a supply, I applied power to the pump. It hissed loudly but nothing came out of it. I took the pump out completely and verified there's no problem with fuel flowing from the tank - what a mess, lol. I don't have an in-tank pump and I had already replaced both the in-tank filter and the post pump filter when I cleaned the tank. Oh yeah, there was a small cone shaped strainer in the pump intake that was perfectly clean as well.

Outbackgeorgia: I probably didn't explain very well, but the oldest pump was in a box that the previous owner included with the car. I didn't know it's condition until today (bad, doesn't spin). The existing pump that had been working fine apparently doesn't pump any more. I'm guessing the impeller is detached. The existing pump had a cone shaped strainer that was/is clean. The in-tank filter wasn't in bad shape either. Someone had done this job before. By the number rounded off connectors on everything in the fuel system, I suspect they didn't own metric tools.

tailpipe: I have an ultrasonic cleaner that's just big enough to submerge this fuel pump. I wonder if mineral spirits would work better than water? I don't suppose it would hurt to try now. If it fixes it I'll have a spare.