Breakdown Blues :-(
- Thread starter PaulHere
- Start date
The fuel pump relay was faulty it seems, would have been a simple fix if the recovery people hadn't left the relay disconnected and confused the issue [
] It all turned out fine in the end though.
This doesn't really help with the 924S, but a fuel pressure check (which a good specialist can do) would be a good starting point I think.
] It all turned out fine in the end though.This doesn't really help with the 924S, but a fuel pressure check (which a good specialist can do) would be a good starting point I think.
924nutter
PCGB Member
Paul, try Porscheshop in Halesowen, they have a wide range of 924 spares. I know Porscheshop do a very good replacement fuel pump too, and yes those doughnuts are right gits when they rust up. Also they are about £7 a pop now, but a much cheaper alternative can be bought from RS Components, for about £1.50 if you know anyone who has an account with them. Beware Audi fuel pump relays, they sometimes have round pins, I know, I have one that I bought for the same reasons of availablitiy, assured that the relay was interchangable- not. Now a word of caution. You have to ask yourself why the fuel pump relay failed. If you can hear anything more than a faint zzuzzing hiss from the pump then it is under too much load, and consequently drawing too much current. Remember it is protected by a 16 amp fuse in the first place, and that is a hell of a lot of heat if it is drawing 15.5 amps continuously. This can lead to melted insulation on the power supply to the fuel pump on the back of the fuse board, so check the condition of the socket for the relay.
Guest
New member
Hi Paul & everyone!
Sorry to re-ignite this old one, but with all this talk of Fuel Pumps and the like, I just wondered if anyone knew the voltage to expect across the Fuel Pump contacts?
Let's say one utilises the jumper-lead switch described in the Haynes Manual (replacing the Fuel Pump Relay for testing purposes), and completes the circuit, what voltage should the pump be supplied with? Full 12volts or less?
I've finally got online, hope to visit very frequently, and must say I'm impressed with the site as a whole and particulalry the 924 forum.
Sorry to re-ignite this old one, but with all this talk of Fuel Pumps and the like, I just wondered if anyone knew the voltage to expect across the Fuel Pump contacts?
Let's say one utilises the jumper-lead switch described in the Haynes Manual (replacing the Fuel Pump Relay for testing purposes), and completes the circuit, what voltage should the pump be supplied with? Full 12volts or less?
I've finally got online, hope to visit very frequently, and must say I'm impressed with the site as a whole and particulalry the 924 forum.
937carrera
New member
"full 12 volts", when the engine is running should be about 13.6 to 14.2 volts, when the engine is running.
Voltage drop to the pump should be about 1 volt, but as 924nutter says, without the engine running this will be lower, say 11.5 to 12 volts. I suggest disconnecting the connections to the tank pump to avoid current drain in that direction.
Voltage drop to the pump should be about 1 volt, but as 924nutter says, without the engine running this will be lower, say 11.5 to 12 volts. I suggest disconnecting the connections to the tank pump to avoid current drain in that direction.
Guest
New member
Thanks ppl! Right, the problem presently is this - I can't get the car running!
In 'the good ol days' when turning the car over on the ignition on the odd occasion it failed to fire, you would always hear the fuel pump give a two-second whirr before going quiet.
Trouble is now the pump doesn't make any noise at all, and I am wondering if it isn't starting because it isn't being fed with sufficient power. There is approx 5v present at the pump with jumper lead switch on regardless of the ignition key position, but no pumping action occuring, and the jumper lead fuse is getting extremely hot!
If I recall correctly, one should be able to operate the jumper lead (and fuel pump) irrespective of the ignition switch. Ie: If one has to resort to using the jumper lead temporarily, flicking the j/lead switch even with the ignition switch in the off position, should cause the pump to operate.
As you have kindly informed me, it would appear insufficient voltage is getting through to the pump, at this moment in time - 5v as opposed to 12v
In 'the good ol days' when turning the car over on the ignition on the odd occasion it failed to fire, you would always hear the fuel pump give a two-second whirr before going quiet.
Trouble is now the pump doesn't make any noise at all, and I am wondering if it isn't starting because it isn't being fed with sufficient power. There is approx 5v present at the pump with jumper lead switch on regardless of the ignition key position, but no pumping action occuring, and the jumper lead fuse is getting extremely hot!
If I recall correctly, one should be able to operate the jumper lead (and fuel pump) irrespective of the ignition switch. Ie: If one has to resort to using the jumper lead temporarily, flicking the j/lead switch even with the ignition switch in the off position, should cause the pump to operate.
As you have kindly informed me, it would appear insufficient voltage is getting through to the pump, at this moment in time - 5v as opposed to 12v
924nutter
PCGB Member
Disconnect the battery. Measure the battery voltage. If you have 11.5 or 12v there then get your head under the passenger side of the dash and remove the fuse board and draw it towards you so that you can have a butchers. Reconnect, then check voltage between supply to the fuseboard and earth. That's enough to be getting on with. Get back to me (us) if you find anything untoward on the supplemenatry socket for the fuel pump relay that clips to the top of the fuseboard.
The pump is trying to genterate 3 bar and at 5 volts its just gonna sit there and hum. Its my guess that the pump is on it's last legs. Can I ask,
a) Was the pump particularly noisy?
b) Did you have a myserious misfire?
The pump is trying to genterate 3 bar and at 5 volts its just gonna sit there and hum. Its my guess that the pump is on it's last legs. Can I ask,
a) Was the pump particularly noisy?
b) Did you have a myserious misfire?
937carrera
New member
If the jumper wire across the relay connections doesn't fire the pump up try the following
1. Disconnect the wires to the lift pump / in tank pump
2. Run two lengths of wire straight from the battery to the lift pump. Make sure you have the correct polarity (little + on one terminal) and don't let the two wires touch [:-]
3. If the lift pump is working you will hear a very faint hum, of put your finger on the tank near the pump & get a slight vibration.
4. Working ? good, now you know the lift pump is ok and so is the wire.
5. Now connect the jumper wires to the loose connectors to the fuel pump ( a nice easy connection, saves having to disconnect / remove the pump)
If the pump fires into life then it's a wiring problem which you would need more to trace. If the pump doesn;t work then it's an easy fix.
1. Disconnect the wires to the lift pump / in tank pump
2. Run two lengths of wire straight from the battery to the lift pump. Make sure you have the correct polarity (little + on one terminal) and don't let the two wires touch [:-]
3. If the lift pump is working you will hear a very faint hum, of put your finger on the tank near the pump & get a slight vibration.
4. Working ? good, now you know the lift pump is ok and so is the wire.
5. Now connect the jumper wires to the loose connectors to the fuel pump ( a nice easy connection, saves having to disconnect / remove the pump)
If the pump fires into life then it's a wiring problem which you would need more to trace. If the pump doesn;t work then it's an easy fix.
Guest
New member
Yep, there is the full 12v one would expect at the battery.
Pump was purchased about 5 years ago, and hasn't been overly worked during its life. It has always been audible, but not particularly noisy. My brother had an Audi 80 a few years ago, and thats pump certainly was loud - the 924 is definitely not in that league.
Misfire-wise, I have refurbished the injection system at the front end (due to sticking cold start injector), and it never really ran as smoothly as it had in the past, but I wouldn't necessarily describe it as being a misfire.
I appreciate the symptoms I have presented might lead one to conclude a faulty or failing pump, and am willing to investigate any possibilities.
The pump is external to the tank (lift-pump presumably) and I am hopefully gonna disconnect it this evening, and provide it with a source of direct 12v, and see what happens "" as 934 Carrera has very kindly suggested. Hopefully I will then be able to ascertain if the pump or wiring is at fault.
I'm in North Devon, by the way. Sincere thanks for all your input "" I'll provide some hopefully positive feedback tomorrow!!
Pump was purchased about 5 years ago, and hasn't been overly worked during its life. It has always been audible, but not particularly noisy. My brother had an Audi 80 a few years ago, and thats pump certainly was loud - the 924 is definitely not in that league.
Misfire-wise, I have refurbished the injection system at the front end (due to sticking cold start injector), and it never really ran as smoothly as it had in the past, but I wouldn't necessarily describe it as being a misfire.
I appreciate the symptoms I have presented might lead one to conclude a faulty or failing pump, and am willing to investigate any possibilities.
The pump is external to the tank (lift-pump presumably) and I am hopefully gonna disconnect it this evening, and provide it with a source of direct 12v, and see what happens "" as 934 Carrera has very kindly suggested. Hopefully I will then be able to ascertain if the pump or wiring is at fault.
I'm in North Devon, by the way. Sincere thanks for all your input "" I'll provide some hopefully positive feedback tomorrow!!
924nutter
PCGB Member
The reason I asked about the misfire is that when the pump is on it's last legs it can barely make the required pressure resuting in a smooth idle but a bl**dy annoying misfire when attempting to accelerate hard. This hapened on my car. Eventually it stopped dead, and on investigation all the wires leading into the fuel injection relay were melted about 1 inch back. I wired in new lengths using a 30 amp terminal block, and had to plug the wires dircectly onto the relay as the socket was ruined by overheating too.
Guest
New member
That would all make sense, and be extremely annoying at the same time!! I fear my pump may have become deceased also!
Disconnected the pump yest and when powered directly from a 12v source, it emitted a single "Thunk"-like sound every time 12v was applied (but no constant whirring or thunking!).
The original feed to the pump appeared to be around 8-9v, and a sucking sound could be heard within the 'reservoir' at the base of the tank, when the voltmeter was applied. (The power feed and return goes initially to the external pump, then on to feed the component within the tank itself).
There are apparently 3 different pumps for the 924 according to dear old Bert Gear (Berlyn Services), mine being produced between '78-'80. Priced at £168 it ain't cheap, but £50+ cheaper than OPC prices who claim they can only import the part direct from Germany.
Anyone any ideas, or shall I just bite-the-expensive-bullet? Due to its high-pressurisation requirements and being a sealed unit, it isn't possible to dismantle and refurbish the internal diaphrams anymore.
Disconnected the pump yest and when powered directly from a 12v source, it emitted a single "Thunk"-like sound every time 12v was applied (but no constant whirring or thunking!).
The original feed to the pump appeared to be around 8-9v, and a sucking sound could be heard within the 'reservoir' at the base of the tank, when the voltmeter was applied. (The power feed and return goes initially to the external pump, then on to feed the component within the tank itself).
There are apparently 3 different pumps for the 924 according to dear old Bert Gear (Berlyn Services), mine being produced between '78-'80. Priced at £168 it ain't cheap, but £50+ cheaper than OPC prices who claim they can only import the part direct from Germany.
Anyone any ideas, or shall I just bite-the-expensive-bullet? Due to its high-pressurisation requirements and being a sealed unit, it isn't possible to dismantle and refurbish the internal diaphrams anymore.
937carrera
New member
I believe the "thunk" is the pump trying to operate but failing because it is siezed.
Time for a new pump........and possibly jubilee clip and rubber mounting bungs. You'll have to find something to stop the fuel coming down the pipe when you remove the pipe to the pump, and be prepared to get wet with fuel, which these days can sting a bit if not washed off immediately.
Try Eurocarparts as a source...........
Time for a new pump........and possibly jubilee clip and rubber mounting bungs. You'll have to find something to stop the fuel coming down the pipe when you remove the pipe to the pump, and be prepared to get wet with fuel, which these days can sting a bit if not washed off immediately.
Try Eurocarparts as a source...........
924nutter
PCGB Member
Porscheshop.co.uk at Halesowen have a replacement pump for £114.80 plus vat. It is supplied with two types of check valve new electrical terminal connectors and new nuts.
Fashion a peice of wooden dowel into a tapered plug. It needs to go from about 6mm to 10 mm, or pre blank an off-cut of fuel pipe and be ready to fit it over the outlet of the internal pump.
Wearing latex gloves disconnect the outfeed pipe from either the internal pump and plug blank the pipe stub, or take the pipe off of the main pump and plug the pipe. You will get a bit of petrol on the gloves, and they will react and go baggy. Take them off! The new check-valve will greatly improve the warm start of the 924. Been there, done that. Have a new jubilee clip the diameter of the new pump plus 2mm. Dont mess about, cut the old jubilee clip off. When I changed my pump the pump was holding on with rust. If you attempt to undo the doughnuts you may just wind the metal end off the rubber.
Fashion a peice of wooden dowel into a tapered plug. It needs to go from about 6mm to 10 mm, or pre blank an off-cut of fuel pipe and be ready to fit it over the outlet of the internal pump.
Wearing latex gloves disconnect the outfeed pipe from either the internal pump and plug blank the pipe stub, or take the pipe off of the main pump and plug the pipe. You will get a bit of petrol on the gloves, and they will react and go baggy. Take them off! The new check-valve will greatly improve the warm start of the 924. Been there, done that. Have a new jubilee clip the diameter of the new pump plus 2mm. Dont mess about, cut the old jubilee clip off. When I changed my pump the pump was holding on with rust. If you attempt to undo the doughnuts you may just wind the metal end off the rubber.
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