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-   -   Fuelpump running but no fuel supply ??? (https://rennlist.com/forums/928-forum/602509-fuelpump-running-but-no-fuel-supply.html)

GerritD 11-19-2010 12:38 PM

Fuelpump running but no fuel supply ???
 
Hi guys,

I recently restored the tank support brackets and replacing all fuel lines in the process.
So when tring to restart the car (after a long time with an empty tank and fuel lines) it did not work.
Fuel tank is filled with about 4 gallons fuel.

I jump started the fuel pump (via pin 30 & 87 at fuel relay) . fuel pump is working but no fuel is coming out ????
As if it is running dry...since pump becomes also warm and you can hear it pumping air ??

Could it be a problem with little curved hose from tank to pump , since I had to replace this one with an extra adaptor. Adaptor was needed since diameter of pipe fueltank is smaller than diameter pipe fuelpump ??
(When disconnecting this curved hose, fuel is coming out of the tank)

Gordak 11-19-2010 01:50 PM

make sure your not running the pump backwards :) I did that once.

GerritD 11-19-2010 02:01 PM

Yep, that is a possibility , although I marked - and +.
- (brown wire) and + (red/green wire)

I'm completely lost now...and then I'm beginning to doubt everything

blown 87 11-19-2010 02:26 PM

Got gas in it?

Leon Speed 11-19-2010 04:39 PM

No fuel coming put where? Can you post a picture of your installation?

PRC928 11-19-2010 04:51 PM

Hi, I replaced my fuel lines on my '79 once and the fuel hose was slightly too long and with the pump and cover in place the same thing happened. Fuel pump ran but no fuel to the engine. I just unbolted the cover and this took the kink out of the hose. Fired right up. Just had to shorted the hose.

GerritD 11-19-2010 07:57 PM

Aryan,

here is a picture :
http://www.cleo-instituut.be/fuelpump.jpg

Indeed, the hose is a little bit longer than the original, due to the fact that I also had to add the adaptor piece (black plastic piece needed to enlarge from small diameter to larger diameter in order to fit on my fuelpump)

How is it possible that I could not reuse my original hose. It was too narrow on diameter at the end that fits on my fuelpump.
Although it had fit ????

GerritD 11-19-2010 07:58 PM


Originally Posted by PRC928 (Post 8070253)
Hi, I replaced my fuel lines on my '79 once and the fuel hose was slightly too long and with the pump and cover in place the same thing happened. Fuel pump ran but no fuel to the engine. I just unbolted the cover and this took the kink out of the hose. Fired right up. Just had to shorted the hose.

Paul , could this be my problem ?
Is it that sensitive when changing the length ?
What kind of hose did you use to solve the problem ?

Tails 11-19-2010 09:29 PM

Gerrit,

Your hose appears to be flattened on the curved section and may be restricting or cutting off the flow.

In addition did you renew your filter, as it may be blocked from debris?

Do you have a set of electrical drawing for your car to check that the electrical connections are correct. For some to check for you, if you don't have electrical drawings, we require to know what model car you have?

Tails 1990 928S4 Auto.

GerritD 11-19-2010 09:40 PM

I did notice this when installing but thought it should not be a problem...
I did renew my filter. Is there also a filter in the tank that I should check ?
Wiring is correct according to the electr scheme.

So the only issue can be the hose...

karl ruiter 11-19-2010 10:44 PM

If you pull the input line off the pump (power off), do you get fuel there? There is an in-tank pump and fuel strainer that can plug. Also, the strainer to the input pump has to be completely covered in fuel and that requires more than you would guess. You might consider geting the correct line that goes between the two pumps and put that in to avoid kinking at some point in the future. I seem the recall that that hose is pretty inexpensive.
Next step would be to pull the output line off the pump (power on) and see if you get fuel there.

Mrmerlin 11-19-2010 10:47 PM

First thing is to get the correct hose this has a car fire written all over it,
dont add any connectors to the hose fit the correct part.
The wires will only fit on the pump one way as the power wire end is smaller ID than the ground connector fitting and the studs on the pump are also different sizes. Also the hose you used may be disintagrating from the fuel .

PRC928 11-20-2010 12:21 AM

Gerrit,
I agree with Tails, that hose looks flat in the bend. It has been about 10 years since it happened on my car but I remember being surprised how sensitive the hose was to lenght to keep it from kinking.

jwillman 11-20-2010 09:37 AM

Gerrit,

From the photo you have an intake pump and not a strainer (wires running to the pump). The in tank pumps have a rubber tube that connects the pump to the outlet and these are a weak point. When they deteriorate the intank pump simple recirculates fuel into the tank. With the fuel relay jumped and the main pump electrically disconnected you should hear the internal pump spinning but if the rubber connector is ruptured you are still just recirculating gas. Need to pull it to visually inspect. I have read that you can pull the intank pump by just loosening the tank strap to give enough access.

The intank pump or strainer is threaded into a metal insert which is pressed into the plastic tank. I believe it requires a 36MM (memory) socket to get the intank pump out. Be very careful as the inserts are known to start spinning in the plastic tank (pump / strainer frozen to metal insert) and if that happens you will need to replace the tank or use JB Weld to repair the insert (ask me how I know). If the intank pump is bad you can replace it with a less costly strainer and the car should run fine (intank pump is suppose to be for hot /high environments so I am told). Once the insert spun I ended up dropping the tank.

I used sharksin's tank drop write up (link below) and had the tank out by myself in less than 2 hours.

http://members.rennlist.com/sharkski...0-FuelTank.htm

BTW the OEM hose used to connect an in tank pump to the external pump is different from the one used to attach a in tank strainer to the external pump so get the right hose depending on what you end up with in the tank.

Good luck!!

Leon Speed 11-20-2010 10:14 AM

Another possibility: a reversed check valve.

Anyway, the only way to find the cause is to work you way back from the fuel pump. Take off one component at a time and check if fuel flows.


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