Fuel pressure problem with hotwired walbro

[Klasman]

Hi

Hot wired my pump today and now fpr wont go below 4 bar (58psi).
Which in my mind is bad bad.

Ive got an aeromotive fpr so it should be able to hold down the walbros pressure shouldn't it?

If i return to standard not using my hot wire loom it settles down to 3 bar and i can even go lower.

Any thoughts about this?

I'm guessing its the fpr which is the problem but what can i do about it?
Sticky membrane? I have checked it and it seemed to work.

/Fredrik

[Turbo_Steve]

Is that 4Bar with vacuum or at atmospheric?

Yes, you should be able to reduce the fuel pressure a bit more than that regardless.

[Klasman]

Thats with vacuum and then gets higher when vacuum hose is removed

[Nutter_John]

iirc it should be adjusted to be 3 bar with the vacumn disconnected . On the fpr there will be a screw on there to adjust it

[Klasman]

Ye i know but i have already adjusted it to its lowest setting and it wont go lower then 4 bar.

Seems it wont cope with the flow/pressure from hot wired walbro.
Because i can adjust it to 3 bar with original original loom.

[Wodjno]

Ye i know but i have already adjusted it to its lowest setting and it wont go lower then 4 bar.

Seems it wont cope with the flow/pressure from hot wired walbro.
Because i can adjust it to 3 bar with original original loom.

Whats your Vacuum reading at idle ? Has that changed ?


Cheers

Wodj

[Gly]

with the original loom the fuel pump runs at 7v at idle,
(they do this for temp and ware tare reasons)
the voltage increases with revs/load


when you setup an aftermarket FPR on it, (factory loom)
there is a relay that needs to be triggered to make it run at full voltage

then you set the the base pressure, 3bar at idle with no vacc hose,
this will drop when you attach the vacc hose, and then again when you dissconnect the trigger on the relay,

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on you hotwire (constant full voltage) setup you should just set it to 3 bar at idle with no vacc hose,
refit vacc and it should drop a little,


---------------------------------------------------------------------------


now your issue, either points to a faulty gauge or FPR,
you will need to borrow another gauge? to confirm which is at fault.

[Klasman]

Im idling at -0,6 bar


Whats your Vacuum reading at idle ? Has that changed ?


Cheers

Wodj

[Klasman]

I have now removed my hotwire loom for now and i have set it to 3 bar with vac hose removed and it seems to work as intended.

I'm guessing it just wont cope with the walbro being hotwired.
But ofc a aeromotive should probably be able to do it but mine is faulty or something im talking to my supplier atm about it.

[The Vee]

Does indeed sound like the fpr being overwhemed or even the return pipe flow being restricted somewhere

[Wodjno]

Does indeed sound like the fpr being overwhemed or even the return pipe flow being restricted somewhere

Sounds good..

Your Vac is in the right area so no probs there..

Have u changed and pipework on the return route to the tank ? (more restrictive, maybe a joiner)

Wodj

[Klasman]

Hmm ye actually i used a joiner when i had to make the return hose longer. Could it be that restrictive? And what should i do about it? Original hose is to short.

[Wodjno]

Hmm ye actually i used a joiner when i had to make the return hose longer. Could it be that restrictive? And what should i do about it? Original hose is to short.
Well my thoughts were along the lines of? If the return pipe is restricted after the FPR, Then maybe that would back up against the FPR and increase the pressure! Only way of stopping this is replace the 2 piece pipe with the joiner/restriction with a new 1 piece pipe..

Wodj

[Wodjno]

Maybe the following test would prove the theory ?

I know the pump is Now wired back to original so flow at idle will be less.. But try squeezing the rubber return pipe with a pair of pliers and see if the fuel rail pressure rises ?
If it does them my theory may hold some water ...

[Klasman]

Will try that tomorrow great tips much appreciated :)

[Klasman]

Sorry for the late update.

Tried your theory and yes the pressure rises if i squeeze the return pipe but wouldn't it do that even if there isn't a problem?
I mean im guessing that more people are running fpr with hotwire and havent heard anything about replacing the return hose.

[Wodjno]

Sorry for the late update.

Tried your theory and yes the pressure rises if i squeeze the return pipe but wouldn't it do that even if there isn't a problem?
I mean im guessing that more people are running fpr with hotwire and havent heard anything about replacing the return hose.

But the problem is possibly the restriction in flow back to the tank.. Is there anyway u can try the set-up with full pressure on pump without extending the return pipe ?

Wodj

[Gly]

get a bit of hose instead of returning to the tank, return to a bucket perhaps?


did you set the FPR the way i said when not hotwired?
if not its set wrong.

[Klasman]

But the problem is possibly the restriction in flow back to the tank.. Is there anyway u can try the set-up with full pressure on pump without extending the return pipe ?

Wodj
Hmm i dont think its long enough but ill check that tomorrow.


get a bit of hose instead of returning to the tank, return to a bucket perhaps?


did you set the FPR the way i said when not hotwired?
if not its set wrong.
Hmm ye could try the bucket idea

And yes i used your method when i removed the hotwire.

/Fredrik

[Klasman]

Was going to try the bucket idea today since the hose wasn't long enough when i discovered something, it appears that i have been a massive o-cock.

Since i haven't realised that my gauge reads in psi and not in bar as i was expecting so 4 bar was rather 40 psi and therefore 2,75 bar, i have now set it to 3 bar atmospheric pressure with hotwire mod.

So it seems to be working just not the spanner operating it :uhoh2:

Anyway thanks for the help, it might help someone else.

/Fredrik

[Wodjno]

Was going to try the bucket idea today since the hose wasn't long enough when i discovered something, it appears that i have been a massive o-cock.

Since i haven't realised that my gauge reads in psi and not in bar as i was expecting so 4 bar was rather 40 psi and therefore 2,75 bar, i have now set it to 3 bar atmospheric pressure with hotwire mod.

So it seems to be working just not the spanner operating it :uhoh2:

Anyway thanks for the help, it might help someone else.

/Fredrik

Klasman /duh /duh /duh

Klasman /bat

Klasman /whip

Klasman /boxing

Klasman /Hyper /pan /bananaroc :laugh: /Elmo /Devil5 :quasi: :P :d :p :unbeleeva :unbeleeva :unbeleeva /Nuuu :bigcry: /bestpostever /bestpostever /bestpostever /bestpostever /bestpostever /bestpostever

[Klasman]

Bah there should be a bigger psi sticker imo :rolleyes4

[Turbo_Steve]

Awesome :) Glad it was something cheap.

[Mark 4]

Sounds just like me. :5shots:

[Wodjno]

Sounds just like me. :5shots:

Nooooooooooooooooooo :skull:

Not 2 of you /wall

[VR4Kaos]

erm 3 of us hehehehe

[Wodjno]

:unbeleeva :givemebee
erm 3 of us hehehehe

[The Vee]

Glad it's sorted. If I do something like that I just put it down to my age!