Ilike928

I took out fuel pump in the tank and it looks normal as far as I can tell. I thought maybe a pick up tube dropped off or something. Maybe when it's full of gas there is enough "head" to make the fuel pump work properly but when it goes down a bit there is not enough static pressure (head) anymore? Also I did clean out the fuel system system not too long ago so I don't think it's gunk causing the problem (because it had the same issue both before and after the cleaning). Any ideas are much appreciated!

Thanks!

Mike

soontobered84

I didn't think '82 cars had in tank fuel pumps. Conversely, what model number is the external fuel pump?

If there is no external fuel pump, what you have supposed is probably correct: with a full tank on top of the internal fuel pump, you might have enough head pressure to get the engine to start.

Mrmerlin

need more info about the running condition what is exactly happening

GregBBRD

^^^^^^100%

......because gravity and the fuel level have very little to do with these cars running.

dr bob

What does "looks normal" actually mean? It amuses me sometimes when we verify pump function based on appearance. Sorry.

The in-tank pump actually needs to run and pump fuel for the engine to run. If the in-tank pump stops running for whatever reason, it becomes a serious restriction in a low-pressure part of the fuel system. Further, the main pump is trying to pump liquid by sucking it through the frozen/seized/failed in-tank pump, and is boiling the fuel to vapor as it does so. A nearly-full tank might offer just enough pressure downstream of the in-tank pump to allow the main pump to pump some.

Recommendation:

-- Listen to the main pump for surging noises, telltales of boiling the fuel to vapor.

-- Test fuel pressure and delivery per the WSM procedure if you have any doubts.

-- Pumps sometimes get crud inside, and can benefit from reversed power-supply polarity to un-jamb the little rollers inside when that happens. But... the in-tank pump has a strainer on the inlet, and if that's in place then the crud will still be inside the sock, and will be drawn into the pump again when normal flow is restored. You will want to remove the in-tank pump and strainer and clear it.

-- Pull the in-tank pump and test in a small container of mineral spirits. Mineral spirits will still cool the pump as you test it, will help dissolve varnish and the like as it passes through. It also won't go BOOM in your face from the spark connecting/disconnecting the pump to a 12V power supply.

-- After all this, you'll still want to install a new in-tank pump and strainer. Or risk getting stranded on the side of that hot lonely highway, with she-who-is-not-happy, remembering how much you saved by half-fasting the fix. In my limited experience.
--

James Bailey

Mike where was the "in tank fuel pump" ?? on top of the tank ?

Ilike928

Awesome ideas Dr. bob and exactly what I was looking for. I'll chase those down and see if I can find the source of the problem. Yes I should have added a "fwiw" to the "looks normal" comment. I meant to say I don't see any obvious physical issues with fuel pump "fwiw".

Ilike928

yes on top of tank accessible via hatch.

James Bailey

That is the fuel level sending unit and the hose there is the return fuel line.

Ilike928

running condition is perfect when fuel tank is full. Starving for gas when tank is down some (fairly minor drop in tank level relative to tank capacity) and won't start until filled back up. I.e. It acts like its out of gas.

Ilike928

ah I see, that is a whopping big fuel sending unit! Thanks a lot! Cheers!

James Bailey

Your fuel pump is under the tank outside. There is a metal cover on rear of the cradle which supports the tank. Two small studs and nuts up under the rear bumper cover allow it to hinge down. There you will find the fuel pump and fuel filter.

Ilike928

ha ha that is wisdom right there! The real risk comes later when she says, "you want to buy another 928?" "No way!" : )

dr bob

Might read "There you will find the Main fuel pump and fuel filter."

There's a fitting in the tank with a hose attached, hose running to the main pump. That fitting -may- include a couple electrical connections, and if it does it means you have a pump inside the tank. The in-tank pump lives on the backside of that fitting, with a short hose connecting the pump outlet to the fitting. There's a filter/strainer on the inlet of the pump.

Both the in-tank pump (if you have one) and the strainer should be visible when you have the level sender pulled out. Unfortunately, you can't easily inspect the condition of the connecting hose between the pump and the tank fitting through the sender hole.

-----

Curious if the problem appears only when the level is less than full, vs a short while after putting fuel in the car. The tank has a pressure-balancing hose between the main section and the top of the filler neck section. It also has a liquid separator and connecting hoses that allow air to back-fill the tank with air as liquid is withdrawn from the bottom. If you close that off anywhere between the tank and the engine bay, you risk creating a vacuum in the tank as fuel is withdrawn. Stupid-simple test is to remove the filler cap when the car is suffering from the fuel starvation. You might hear a littl whoosh as air goes into the tank. Will the car start and run OK then for a bit?

James Bailey

Most 928s do not have an intake pump....especially not a 1982..