928 Fuel Pump

[danhay]

Hi folks.

I suspect the fuel pump (or it's relay) on my 1981 928S is not working. The car won't start, not even fire. I've checked and the plugs are sparking. I've put fresh petrol and a water scavenger in the fuel tank. Even after a minute or so of trying to start in a confined space there was no smell of petrol. All of which leads me to suspect the pump or relay. Does anybody know where the fuel pump is or have any other advice?

thanks
Dan

[danhay]

Thanks Alex,

I found the pics, they are just what I needed.
I think I will check the relay first as it's a lot easier to get at!

Dan

[danhay]

Thanks Dogsharks.

The car has done 135k miles. It's got the moulded plastic relays, but I happen to have some patch cables for hotwiring relays, after having had a problem with a pop up light relay. If the relay has got the normal schematic on it somewhere, I should be able to work out how to "run a bypass".

I'm really hoping it's just the relay!

[danhay]

Well the relay is definately broke.

I took it off, and discovered that although it's got a plastic case rather than a metal one, it's not moulded, and I was able to remove the plastic casing. I observed that the relay didn't switch when the ignition key was turned.

I inserted a plastic tab to lock the relay in the on condition, this elicited a small spark from the contacts and a single click from the fuel pump. Whenever I switch the relay either on or off, I get a single click from the fuel pump.

I tried to start it for about 60 seconds in total...first with about 20 secs of cranking, then with shorter bursts of 10 secs or so with a gap in between.

But alas still no sign of firing at all from the engine and no smell of unburnt petrol from the exhaust either.

I think a call to Mr Anderson may well be in order.

[danhay]

dogsharks said:

You know, it's not uncommon to have more than one thing going wrong with the older cars at the same time. Dogsharks

Too true.

If I had £500 for every time it went wrong I'd still be out of pocket

[danhay]

It Lives!!!

I was beginning to doubt I'd ever see the day, but I got the 928 started for the first time in 2 years.

I have replaced the fuel pump and it caught on the first turn. It ran beautifully for a couple of seconds then died. After several minutes of restarting it was running ok, and even managed to move under it's own power. Once up to temperature it promplty started emptying the contents of it's cooling system through a hole in the radiator...

Next step I think will be a new Thermo Time Switch and possibly a Temp II sensor in a bid to sort out the misfire when cold.

[danhay]

Update:

While waiting for the new Fuel Injection bits to arrive, I've repaired the hole in the Radiator. Today the new bits have arrived and I've fitted the relay and Thermo Time switch, but I can't seem to find where the Temp II sensor goes?


Any ideas?

[danhay]

Thanks Dogsharks.

I've found the Thermo Time Switch, which was quite well hidden, though easy enough to get at once you know where it is! It's mounted horizontally, in line with the engine and goes into the cooling system. Am I right in thinking that the Temp II sensor goes into the cylinder head? Is it vertically mounted?

Will have another look.

>> Edited by danhay on Saturday 15th May 14:37

[danhay]

Thanks once more DS.

I've received a new Thermo Time Switch and Temp II Sensor today. I managed to find the Thermo Time Switch at the front of the engine in the location you mentioned before, and it matched the old one exactly. It's the Temp II Sensor I'm having a problem finding. I've found another water temp sensor pretty much underneath the Oil Filler pot thingy, near the TTS. I've had it off, and it doesn't match the replacement Temp II sensor I've got at all. In fact it's got VDO written on it which leads me to believe it's the sender for the water temp gauge. I think I might check at the back of the engine as there's nothing matching the new bit I've got at the front!