Hesitation - Anyone in Bris with a spare fuel pump?

Mine is a 2+0...... I think thats whats vibrating. I didn't block any pipes when I removed the carbon canister.

I will just have to get the gauge in the fuel pressure system and then see if the pump is knackered. Then check the relief valve and move on from there.

I am also wondering if I need to buy the $300 pump with all the bits or could I just get a 040 bosch unit and put the rubber sleve around it?

Beavis

 

There is a short set of hardlines that are connected to the fuel tank by some short hoses, the other end of those hardlines somewhere.

Tucked up in front of the tank somewhere.

Genuine Bosch 040 looks like about $250, I like OEM stuff it just fits and works for a long time.

 

Right I done a fuel pressure test. (Thanks Rollin for the pressure gague )

Ok here are the results

Engine Idle - 36psi
Engine Idle with regulator vac disconnected - 42psi
Engine Idle with regulator vac disconnected and FPCU bypassed - 45psi

During first 10mins of driving

While driving 1st, 2nd 3rd foot down. 36psi rising to top of 43psi on boost
While driving FPCU Bypasse. 36psi - 43psi on boost

After ten mins of driving

1st gear, 36psi rising to 43psi on boost.
2nd gear 36psi rising to 40psi and then dips to 10psi Car hesitates about 4000rpm. Revs drop to 1500rpm fuel returns to 36psi
3rd gear - Couldn't rev it out due to road restrictions

Another run with FPCU bypassed yeilded similar results.

General driving after that had random hesitation issues at anything above 3000rpm. Fuel pressure would drop to 10psi the revs would drop to 1500rpm and the fuel pressure would come back. If I kept my foot on the accelerator the fuel pressure would remain at 10psi until I took my foot off and the revs dropped below 1500rpm.

Idle is alway fine

Things that have been changed

Fuel tank - Replaced with a clean one
Fuel Filter - Replaced yesterday
3/4 Tank of BP premium fuel.

Any idea's?

I am thinking either the second fuel pump is having issues....
The fuel sock in the tank is blocked or not sitting properly in the tank and thus restrictin flow......

Anything else

Can a faulty fuel pump relay cause issues?
Can a weak battery cause any issues with fuelling? (battery is worn out but starts the car)

Beavis

 

Pretty clear its not getting the fuel supply it needs, could be the regulator or a squashed or blocked fuel line

 

Just annoying that it seems quite random grr.

I am going to take the fuel pump out and re-seat it just incase the fuel sock pipe is bent or is not at the right angle in the tank.

I will take a look under the car to see if there is any damage in the fuel lines.

Beavis

 

If you need a stock second hand TT fuel pump let me know - I can Express post it to you.

 

Right!!!!

Well I have done some more investigation and still haven't found the problem.

I put my other second hand fuel pump in and the same thing is happening.

What I have done

Fuel pressure test - Dropping fuel pressure leading to hesitation.

Totally random.

Decided to go for a drive with the FPCU bypassed and the fuel pump was happily pumping away at full pelt.

Now here is somthing different

FPCU still bypassed at this point

When the car hesitates I cannot hear the fuel pump pumping away during the hesitation!!

It seemed like the fuel pump turned off.

So i connected up the multimeter to the + and - of the fuel pump and took it for a drive.

I got a constant 13.8v at the fuel pump even during the hesitation.

Un-bypassed FPCU

Decided to check the FPCU terminal on the connector and it read 7v at idle and dropped as the revs increased (hence increasing fuel flow)

However........

When it hesitated the multimeter went haywire, reading from 0 - 23 It was all over the place. It was an auto calibrating one and i couldn;t tell if the higher number was volts or mV. It might just be gounding and there is a small amount of mV floating around.

Anymore idea's.

I think I also need to try a new pump so I can rule that out, but I wont have one here for at least a week and would like to try to work out the problem

It does seem strange that 2 secondhand fuel pumps act the same way,

Finally I wonder if its the fuel sock collapsing under the presssure of the fuel pump running flat out that is blocking the fuel pump inlet. I have tried 2 different fuel socks and they both seem in good condition and the little support inside is intact.

What else might it be........ FPR? (tested with fuel pressure gauge, 36psi at idle, 43 when vacume hose disconected)
Fuel pump relay?
TPS?

Help!!!

Beavis

 

Woo Hoooooo!!!!

Just wanted to update this thread to give people the results.

Well I began doing some pretty intensive problem solving with my fuel issue.

I had the mutli-meter rigged up to the FPCU to check it was providing the correct voltages to the fuel pump. i bypassed the Fuel pump relay, I bypassed the FPCU, cleaned connectors and nothing worked so I went back to the pump.

I managed to source another pump from a forum member and just before I swapped it my battery died.

So I replaced the battery and pump at the same time and the car runs like a dream.

So happy to have it running right again.

I am just wondering..... can a failing battery affect the running of the fuel pump. If the current draw on the battery is low could that affect the pump?

I want to say a huge thankyou to Roillin for going through some problem solving ideas and diognostics, and a big thankyou to Magic Mike for lending me a fuel pump to try.

My car has had the pleasure of 4 fuel pumps in 6 months

What I have learned.....

Don't have rust in your fuel tank, this will kill fuel pumps.
Don't replace fuel pump with rust still in the tank, this killed the second.
Don't trust a secondhand fuel pump to be perfect.
Have a fuel pressure gague handy, saves alot of time and effort.
Buy a new fuel pump if yours is failing

Thanks again to this forum

Chris