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paulh · Joined: 14 Sep 2006 Posts: 38

I know there are hundreds of post similar, but I just can 't find exactly my problem.

I've just replace the fuel pump, I couldn't get the exact same. See the pic.

I have made piece that will join new to old. Bit of a drama, but it's installed and seems to be working. ie I have pressure in the system, and it switches on when I crank. The car even gave a couple of kicks but didn't start.

I'm getting around 8~10 volts at the pump.

When the car was running I've long blamed the cold start injector as being the reason for bad or slow starts. So I removed that and cranked for testing, and it just dribbled, (so that could be the whole problem but still not sure.) I have cleaned with solvent and re-installed. But still no start. Should I remove and test the cold start? in clean another way.

Forgot to mention that when I last tried to start the car with the old fuel pump, it back fired really loudly and blew off the rubber air connector at on the top front of the engine.

Any suggestion, it's a 1980 924NA Auto

Lizard · Posted: Sat Feb 03, 2007 3:05 pm Post subject:

the new pump looks more like the factory, the other pump doesnt look like it has a check valve,
what is the new pump for?

and you should see more than 10V at the pump
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3 928s,

paulh · Joined: 14 Sep 2006 Posts: 38

The new pump was supposed to be for a 924.

I'm concerned about the check valve, I have made a simple threded pipe to connect to the fuel line as per the old pump.

are there 2 pumps on this model?

paulh · Joined: 14 Sep 2006 Posts: 38

Actually it looks more like 6 volts at the pump.

just tried to start again, and it gave just one little kick.

paulh · Joined: 14 Sep 2006 Posts: 38

Re-installed the old pump car started, but ran very badly.

Still only around 6 volts at the pump.

Ozzie · Posted: Sat Feb 03, 2007 6:40 pm Post subject:

You have to make sure your volts (12 or more) are correct and the corrosion could even be on the fuel pump relay terminals.
Do you have the in tank pump?
Is this running also?
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Peter_in_AU · Joined: 29 Jul 2001 Posts: 2745 Location: Sydney, Australia

One thing you could try (very carefully) is to "hard wire" the external pump to the battery and then try and start the car.

Disconnect the pump. Connect some jumper cables to the battery and connect the other end of the cables to some chunky insulated wires that you have connected to the pump.

Check your connections at least 5 times before you make the final connection

Get the connections wrong and you'll arc weld something to something.

When the pump starts to buzz try and start the car.

If the engine starts then you are looking at a bad electrical connection or a damaged wire to the pump.

Just be careful.
_________________
1979 924 (Gone to a better place)
1974 Lotus 7 S4 "Big Valve" Twin-cam (waiting)
1982 924 (As featured on Wikipedia)

Learn to love your multimeter and may the search be with you

paulh · Joined: 14 Sep 2006 Posts: 38

Thanks Peter,

you know that was my next move, I too hesistate as their some safety issues here.

I'II give it a go.

But I wonder where the voltage is going?

Foolishly lent my Haynes, which is fuse/relay that I might jiggle.

Also did you see the fuel pump I bought, is it missing the fuel regulator?

Paul

Lizard · Posted: Sun Feb 04, 2007 2:40 am Post subject:

the new pump you have is the proper one, the fuel regulator is attached to the engine not the pump,

I have hard wired a pump on a 944 so we would be able to get it from one location to another, now that was funny,

I would tend to believe you just dont have enough voltage to the pump, and I would check the ground first, so put the volt meter + on the + at the pump then put the ground to a section of the body or rear suspension, this will tell you how many volts your ground it loosing.
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3 928s,

!tom · Posted: Tue Feb 06, 2007 2:33 am Post subject:

Bad relay perhaps? The contacts on the fuel pump relay may be good enough to conduct, but poor enough to cause a large drop so insufficient power is available to the pump.

Obviously check the wiring too, but I'd look at the relay and connections to it next.
_________________
78 924 NA
5-lug

paulh · Joined: 14 Sep 2006 Posts: 38

Hi !Tom

sounds good, which one is the fuel pump relay?

Think I'II buy another Haynes

Ozzie · Posted: Tue Feb 06, 2007 7:40 am Post subject:

Top row second from left.
You could bypass the relay, jumper 15 and 87 to switch via the ign switch.
Use this as a temp fix only.
_________________
Porsche 924 1984 (UK import) NA
Its AUTO and its BLACK
Montego Black on black/red
Engineer of Electro/Mechanical Systems Maintenance

Benino · Posted: Tue Feb 06, 2007 7:59 am Post subject:

no disrespect to ozzie but I'd recommend jumpering pins 30 and 87 instead of 15 and 87. 15 is power from the ignition switch, so if you jumper 87 and 15 the current for your fuel pump will be going through the ignition switch. A lot of current for the switch. The whole point of the relay is to not have this happen. 30 is direct power from the battery. There is no harm in jumpering these two pins. And if this works you could run the car indefinitely this way without damaging anything, until you have ordered a new fuel pump relay. It's just a pain to have to connect and disconnect this wire each time you want to start the car. As soon as you connect them the fuel pump will come on independent of the ignition switch. You just need a wire with a male spade connector on each end to jumper the two connections on the relay board, once you remove the fuel pump relay.
_________________
1980 Porsche 924 N/A USA
1980 Porsche 924 turbo USA
1987 Porsche 944S USA

Paul · Posted: Tue Feb 06, 2007 9:08 am Post subject:

Or install a fuel pump switch across 30 and 87. Mount it where you can reach it if you ever crash.....
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Owned and repaired 924s since 1977
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Ozzie · Posted: Tue Feb 06, 2007 2:19 pm Post subject: