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Gtir Motorsport club » Tech room » Help and Advice » Fuel pressure mystery

Fuel pressure mystery

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1 Fuel pressure mystery on 14th April 2016, 8:31 pm

Cosmic73

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I thought id test the fuel pressure coming out the fpr,
When i unlclipped the outlet pipe there was the expected spurt of fuel. Very Happy

Connected it to a pressure gage, turned the ignition on, heard the fuel pump pressurise but noticed there was zero pressure reading.
Unclipped the pressure gage and just held the pipe, not a single drop came out. Shocked

So i unclipped the fuel inlet pipe (the one from the fuel filter) and again nothing comes out, even when i crank the engine, not a drop comes out.  Shocked

I expected gallons of fuel to be pumping out.

Is this normal?

2 Re: Fuel pressure mystery on 14th April 2016, 8:45 pm

pulsarmoley

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moderator
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I know it only primes so you shouldn't get much out the pipe, i.e you cant use the pump to drain the tank etc but I thought it would dribble a bit?


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3 Re: Fuel pressure mystery on 14th April 2016, 8:49 pm

gtir_woody

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moderator
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What condition is the fuel filter in? Have you elminated that?

4 Re: Fuel pressure mystery on 14th April 2016, 8:56 pm

johnny gtir

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moderator
moderator
What make fuel pump is it and it's making a noise but is it working

5 Re: Fuel pressure mystery on 14th April 2016, 9:05 pm

Cosmic73

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Its a new oem filter and the tank is full,
Surely fuel should piss out the inlet when i crank the engine right?
study

6 Re: Fuel pressure mystery on 14th April 2016, 9:09 pm

gtir_woody

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moderator
moderator
Correct. Mine would flood the garage just by priming them Laughing

7 Re: Fuel pressure mystery on 14th April 2016, 9:12 pm

Mr B

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gtir technician
gtir technician
When you pull off the return from the fpr you not always going get much out as it only returning overflow to maintain pressure.
With the line off the filter that should be going to fuel rail then if pump got power it should be feeding fuel. I would direct power pump with temporary cable & visually check output of fuel, if got fuel delivery then want do a run test with temp power to pump still connected & also keep fuel pressure gauge plumbed in to monitor readings .
also check fuel lines hooked up right, filter line to rail & fpr to return hose .
I still thinking your issue is feed circuit to pump (dodgy wiring/connectors/relays) or ecu/input signal to control pump.

8 Re: Fuel pressure mystery on 14th April 2016, 9:31 pm

Cosmic73

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I reckon im finally getting to the root of my non start issue,

Im sure I've connected the fuel pipes the right way round, filter pipe goes into the rail pipe, outlet from the FPR goes into the charcoal canister, right,

So to directly power the pump, is the pump located under back seat or the boot,
Also which pump connection do i connect the feed wire too?
Cheers
Very Happy Very Happy


9 Re: Fuel pressure mystery on 14th April 2016, 9:59 pm

Mr B

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gtir technician
gtir technician
Boot , under cover plate, 2 pin plug is pump power earth, one with red trace being live.
other plug is for fuel level float .
If got multimeter check earth resistance & check voltage supply at ign on prime (only few seconds, then power only when engine running), if earth bad run a temp earth to chassis, if earth good try temp line to pump or even a spare battery dumped in boot with -+ feeding pump if not got long cables ;-). be sensible with wiring & have boy wonder on ign duty so you can monitor things/be safe .
Could remove pump & bench test flow to, never bad idea pull pumps & wiring as they get bodged to fuck on R's
Also don't get to excited if got walbro pump as they not great pumps to be honest & known be bit unreliable, bosch or better oem jap pumps (3kZX) are all I use .

10 Re: Fuel pressure mystery on 15th April 2016, 8:14 am

shroom

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My walbro has been in the car 9 yeas now and is still fine :-) cant be that bad?

11 Re: Fuel pressure mystery on 15th April 2016, 10:42 am

Mr B

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gtir technician
gtir technician
^ how long it been parked in those 9 years lol :-)
they not complete junk but pushed hard & here in hot climate have habit of jamming/motor failure.

12 Re: Fuel pressure mystery on 15th April 2016, 12:27 pm

johnny gtir

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moderator
moderator
Lots of fakes about as well. Like anything the older ones tend to be better quality

13 Re: Fuel pressure mystery on 15th April 2016, 12:40 pm

shroom

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Lots of time in the lockup tbh had it mapped with a 3071r which lasted all of an hour then went and since have gone to a 2876 then just back to a stock t28 turbo dynamics job. Made a slow 260bhp on stock boost at RR day needs sorting out.

14 Re: Fuel pressure mystery on 15th April 2016, 4:16 pm

Cosmic73

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Just tested my fuel pump relay,
It clicks when 12v is applied however the resistence across the other 2 pins is 0.6ohms (on the 200 scale)
Sounds a bit high to me, can anyone tell me if its cattled?
Smile Smile

15 Re: Fuel pressure mystery on 15th April 2016, 5:34 pm

Cosmic73

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Mr B wrote:Boot , under cover plate, 2 pin plug is pump power earth, one with red trace being live.
other plug is for fuel level float .
If got multimeter check earth resistance & check voltage supply at ign on prime (only few seconds, then power only when engine running), if earth bad run a temp earth to chassis, if earth good try temp line to pump or even a spare battery dumped in boot with -+ feeding pump if not got long cables ;-). be sensible with wiring & have boy wonder on ign duty so you can monitor things/be safe .
Could remove pump & bench test flow to, never bad idea pull pumps & wiring as they get bodged to fuck on R's
Also don't get to excited if got walbro pump as they not great pumps to be honest & known be bit unreliable, bosch or better oem jap pumps (3kZX) are all I use .

Cheers Mr B,
Another rep point earned
So i checked the resitence on black wire of the 2 slotted female connector and got 1.2ohms, which is ok i suupose.

Checked the voltage across the 2 slots and when the wife switched the ignition on it went to about 0.6v,

Connected the -ve and +ve just like you said and fuel pisses out the pipe!!!

So, i i think its conclusive, the sparky left a bit of the immobiliser still attched to fuel system wiring, fucking knob head,



Last edited by Cosmic73 on 15th April 2016, 5:52 pm; edited 1 time in total

16 Re: Fuel pressure mystery on 15th April 2016, 5:51 pm

johnny gtir

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moderator
moderator
I think your trying complicated things before basics mate. Get a 12 v supply to pump put a bottle on pipe touch it on and off couple times see if fuel is coming out then go from there before you worry about resistance readings etc

17 Re: Fuel pressure mystery on 15th April 2016, 5:53 pm

Cosmic73

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johnny gtir wrote:I think your trying complicated things before basics mate. Get a 12 v supply to pump put a bottle on pipe touch it on and off couple times see if fuel is coming out then go from there before you worry about resistance readings etc

Just done that and fuel pisses out, found the fault at last.
Cheers
cheers

18 Re: Fuel pressure mystery on 15th April 2016, 6:00 pm

johnny gtir

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moderator
moderator
So your fault is wiring and or relay feeding it ? What wires like into bottom of relay or fuse box mate ?

19 Re: Fuel pressure mystery on 15th April 2016, 6:01 pm

Gostek

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Events Organiser
Events Organiser
Does it run fine now??


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20 Re: Fuel pressure mystery on 15th April 2016, 6:16 pm

Cosmic73

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I did it, i did it Very Happy Very Happy Very Happy Very Happy Very Happy Very Happy
Fired up instantly and idles like a dream, no issues whatsoever, just purring away, revs up and down lovely too,
Sounds totally f$¥€ing awesome!
So after all that, its was the twat of a sparky who didnt remove the immobiliser properly!

Anyway, im in too much of a good mood now,
drunken drunken drunken

21 Re: Fuel pressure mystery on 15th April 2016, 6:52 pm

Mr B

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gtir technician
gtir technician
^ exactly what I hinted at in other thread, cat1 alarms generally always have fuel circuit cut .
If not due to alarm wiring it either relay or ecu control of relay low voltage switching.
Least it sorted, hope stays running & all goes smoothly :-)

22 Re: Fuel pressure mystery on 15th April 2016, 7:46 pm

Cosmic73

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Sparkys coming first thing tomorrow morning which means i can take it for an mot on monday,
All going well, i might make Japfest after all,
Very Happy

23 Re: Fuel pressure mystery on 15th April 2016, 7:54 pm

Gostek

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Events Organiser
Events Organiser
Cosmic73 wrote:Sparkys coming first thing tomorrow morning which means i can take it for an mot on monday,
All going well, i might make Japfest after all,
Very Happy

I think I was explaining that already but my English vocabulary is quite poor and for some reason I don't recognised word "might" I do however know word "must" yoursofunny Anyway good news bud!!!


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24 Re: Fuel pressure mystery on 15th April 2016, 8:16 pm

Cosmic73

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Getting it through an mot will be a piece of piss after this Mike,
The thing that confused me was thst i could always hear the pump prime, i assumed (wrongly) that it must be working,
Live and learn...
Smile

25 Re: Fuel pressure mystery on 15th April 2016, 8:44 pm

shroom

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Just listen to Mr B you cant go far wrong then...

You can take a horse to water but you cant make it drink hey Mr B!? Lol they get there in the end

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