924Board.org

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

Does anyone know exactly what voltage and what curent drain must the pumps have?

the CIS test indicates 4.5 BAR where it should be 5.5 BAR so before throwing 200 EUR on a pump i want to be sure that the old one is dead beat

_________________
Supercharger and EFI kits
https://www.the924.com

Ozzie · Posted: Thu Feb 01, 2007 9:54 pm Post subject:

Which pressure is 4.5bar?
CIS tests are for checking the operation of the WUR/control pressure and system pressures.
Adjustment of the pressure valve in the fuel dist with shims can increase the system pressure.

The fuel pump runs at 12v and draws about 8amps IIRC.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

well with the pump running there should be 5.5 bar. its only 4.5 and thats why with new injectors the system cannot feed all 4 injectors and when i step on it only 3 injectors run.

_________________
Supercharger and EFI kits
https://www.the924.com

Smoothie · Posted: Fri Feb 02, 2007 4:00 am Post subject:

Some other possibilities would be clogged fuel filter/s and blocked in-tank screen.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

Smoothie · Posted: Fri Feb 02, 2007 4:11 am Post subject:

How did you hook-up for the test? With WUR line removed from that port and the gauge attached alone with one line there, then yes you should see system pressure. -But with a proper CIS FP tester hooked-up and its' valve opened (or some other rigged setup that leaves the WUR line connected and open), you would have been reading the control pressure.

-And pardon me for forgetting, but what year is your car?
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

83 ROW NA<--for now

Everything on this car is new...fuel filter is new too. whats a in-tank screen?

Yes i disconected that line and mounted the gauge. sys pressure should be 5.5 bar there...and its only 4.5 bar.

However i tested the fuel pump in the same way, gave it some gas to suck in...and mounted a gauge on its output...left it like that for a couple of seconds...gauge was reading above 6 bar.

i'm going to check the voltage and curent draw tomorow.
_________________
Supercharger and EFI kits
https://www.the924.com

Ozzie · Posted: Fri Feb 02, 2007 7:10 am Post subject:

Inside the port facing us in the pic is a plunger, 'o' ring, spring and maybe a shim or two.
Adding shims increases the pressure at the top.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

i checked today and with the engine off and ignition ON i have these voltages:

SMALL IN-TANK PUMP: 8V
BIG EXTERNAL PUMP: 10V

i did not check the voltage with the engine on but i guess they are under 12V anyway.

Does the smaller pump have a smaller voltage? is this normal ?
I'm going to fix the alternator the next week because it does not recharge the battery. i only get 12.5V at the battery with the engine on

_________________
Supercharger and EFI kits
https://www.the924.com

Lizard · Posted: Sat Feb 03, 2007 9:59 am Post subject:

you should have 13.6 volts or there abouts at the battery when running check the grounding of the alt to chassis and to engine block.

you should also see the same voltage to the pumps as well, if you arent seeing this voltage at the pumps then you are seeing corrosion which is acting as a voltage block
_________________
3 928s,

Ozzie · Posted: Sat Feb 03, 2007 10:00 am Post subject:

You wont get the correct pressure with voltages like that.
I found the pressure will drop with voltage as the pumps cant run up to speed under load.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

John Brown · Joined: 07 Nov 2002 Posts: 903 Location: Leesburg VA

Ozzie · Posted: Sat Feb 03, 2007 1:56 pm Post subject:

Your battery needs to be fully charged and the connections at the pumps should be clean and there should be 12v or more with the car running.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

Thanks for that tip Ozzie.

no no the injectors are NEW, the old ones wich are very used spray equaly.
When i put the new injectors on only 3 of them spray but its not always the same injector that does not spray.plumming is ok, filter new.
And i've checked..its 4.5bar where it should be 5.5 bar.

I think the problem is bad/coroded wiring. I cannot check today as its raining like diareea here

but if it does not rain.. first thing monday...i get under the pork.
_________________
Supercharger and EFI kits
https://www.the924.com

Ozzie · Posted: Sat Feb 03, 2007 8:23 pm Post subject:

Well the injectors open at 2.5 to 3.6 bar so I would say the voltage is the cause and you are not getting enought fuel flow or pressure.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

ok so aparently the problem is solved.

The main electrical problems of old cars is that all the consumers like starter, headlights,fuel pumps go trough the ignition and the ignition(where you stick the key in) is not taking the abuse anymore.

I was not getting the 12V at the pumps because of this problem so had added a 74 AMPS relay that fuels the pumps with the 12V and the amps that they need and now the pumps go much faster(the sound).

I replaced the injectors today(with new ones) and the pumps push trough them even at full load so i guess that the pressure is within range now.

The car starts like crap when cold...it does not idle...i need to keep the foot on the gas to keep it alive. but as soon as it heats up it idles smoothly and above 1000 RPM. so i guess my next step is to fix the WUR.

So for all of you who got problems with performance....check the voltages and the electrical stuff too.
_________________
Supercharger and EFI kits
https://www.the924.com