Hi everyone,


I have a 996tt and I have a feeling my fuel pump is not working. I checked for the typical cracked rubber hose on the feed line and visually it seems ok from what I can see. I need to pull the pump assembly out completely to confirm this. So can any one confirm this, If I disconnect all three hoses that connect to the top of the tank opnening and leave the electrical connector plugged in, if I turn the ignition to the on position or try and start the car wouldn't the fuel squirt out of one of the 3 hose connections? from my inspection it should be the one marked "V". I'm assuming that the car primes the fuel system when the key is turned to the on position correct? If i'm not getting any fuel squirting out is it safe to say that the pump is either:

• Not working
• Loose wire connection to Pump somewhere
• Or in fact there is a cracked hose

Please let me know anyone can shed some light on this. Thanks guys.


J

 

The best way to check your pump pressure is with a pressure gauge connected to the fuel filter port in the engine compartment. You should get 3.8 bars +- .2 (55 pounds/square inch) (Repair manual page 543)

Here,s a link to a good explanation of the fuel pump: https://www.6speedonline.com/forums/...-pictures.html

 

Use your durametric to turn on the fuel pump. If you can hear it, it's working. If it's whining it's about to go out. If you don't hear it, it's broken or the wires are bad. All of this is done with the engine off.

 

I used the durametric to start/stop the master fuel relay, sounds like the pump is running and I can hear fuel swooshing around. I need to confirm that the fuel is actually being pumped thought the supply line to the engine. What I might do is disconnect the supply hose and connect a hose from that supply connection on the fuel hat and have it terminate in a container to see if in fact its delivering fuel. I'm sure if I do this by turning the key to the on position it should send fuel through that line to prime the system, this way I can confirm if fuel is actually being delivered. Then I will test for the pressure.


@jpflip thanks for the link!


Anyone else have any other suggestions?

 

Probably stupid question but have you changed fuel filter recently, possibly plugged?

 

totally not a stupid question, I was just about to replace it. so this would be one of my "must do's". I haven't changed it. Do these filters typically get clogged a lot? all my other cars i've changed them but they were never dirty.

 

My f350 at 39k was so plugged it wouldn't start= replaced and it started right up. I couldn't blow through it at all and it wasn't due until 50k I believe. Checked my records was done per book at 30k so I must of had some dirt etc?

 

i'll check it tomorrow and report back. I would be so happy if this was the reason.

 

ive had two pumps fail the only symptoms were immediate startup.. and immediate shutoff engine off fuel starvation. nothing else. that'd be great if it was only a clogged filter but a failing pump has some pretty obvious symptoms. gl with it!

 

^ Was that two pumps including the original or three total= that would get costly.

 

two pumps failed on two separate cars. one was replaced under warranty, the other on my dime.

 

Ok in the quest to find out if my pump is actually putting out fuel I did these quick tests.


1st test
Turn key to on position, then off position. My understanding is that this primes the pump and should pressurize the feed line, feed line should stay pressurized or at least have fuel in it. I then continued to disconnect the feed line. No fuel whatsoever, everything bone dry.


2nd Test
Disconnected the feed line, connected clear hose to feed line connection port on the tank top hat and terminated end of line into empty Gerry can. Connected up my Durametric cable, opened up "activations" under the engine menu, located "fuel pump relay final stage" I commanded this to run, I heard the pump running some sloshing of fuel in the tank but no fuel was being sent to the feed line out into the Gerry can.


3rd Test
Disconnected the Durametric cable, kept the same setup with the clear hose attached to the feed line port, again terminating into Gerry can, inserted key into ignition turned key to on position but not starting the car expecting fuel to prime feed line. Observed no fuel being sent through feed line.


4th Test
Again kept the same setup with the clear hose attached to the feed line port, again terminating into Gerry can, inserted key into ignition turned key to on position expecting fuel to prime feed line then continued to start the car. Observed no fuel being sent through feed line.


So can anyone confirm that I've done pretty much what I can do to find out if the pump is feeding fuel to the feed line. I would assume that at least I would see the pump prime itself on ignition position "ON" or "starting the car"


Would the fuel pump relay be my next step to check? I assume that if I used the durametric cable to command "fuel pump relay final stage" to activate and I heard the pump running I would assume the relay is working correctly?


Now my only other last test that I would like to preform is, from my research some times the venturi feed tubes do not suck fuel in if the tank is at half for below. Currently my tank is at a bit below half. So I will add some fuel to the tank and retest all the above to ensure its not a problem scavenging fuel from the tank. Also I will remove the fuel pump system and inspect all hoses as a last resort.













VIDEO OF ACTIVATING FUEL PUMP VIA DURAMETRIC - Click link below or attachment

 

My money is on a hose in the tank!

 

Sure looks like it.

 

^^ those are what commonly "split" anyway.. so it probably is the hose.