Advice needed - high emissions , central locking , fuel pump

[200OOM]

Hi, looking for a bit of guidance

Had the MOT today, and it failed on emmissions. I thought it would as it set of the carbon monoxide sensor in the garage this morning.

Before the MOT I have had a few electrical problems.

Fuel pump relay clattering and not engaging fuel pump. - I installed a new relay as described in previous posts . So the fuel pump is always running, as opossed to priming when the key is turned .

Then i noticed the central locking light lit. With the engine running and the doors closed if I pressed the button the engine stopped , and can be restarted usually. If the dors are open pushing the button has no effect .

Are the 2 related? Could the fuel pump running all the time cause over fuelling and high emmissions?

The car is a 1994 4lt, with key opening behind the doors. By inserting the key half way or so and turning it would lock and arm the alarm and immobiliser I presumed. Now it won't do this .

I have the dash top off , to see if any wires are shorting etc, but I don't appear to have a fox-guard alarm box , only a big black central locking box. Should I have the alarm box where I think it should be?

If I were to unplug the central locking would it do any harm? I only ask as if it's all central locking related I will just get rid of it.

Please help, the weathers getting good again.

[Belle427]

Is it possible someone has botched in an alarm/immobiliser somewhere causing your issues?
Weird it cuts out when operating the central locking.
It may be better to find a mobile auto electrician or a local member good with electrics that could assist you.

[200OOM]

Thanks for the reply, I am the second owner and have had it for 15 years, never a problem before , so thinking something has just deteriorated ? If I remove the central locking module the car won't start. But there is a separate twin wire plug on the same module , if this is disconnected the car will run, and although the central locking light is lit , pressing It doesn't stop the car as previously said!!??

What does my immobiliser look like? Can it be by passed , if so could someone PM me with how to.

[Belle427]

The immobiliser brain lives under the dash top on mine, ive also read it could be in the lower radio area somewhere.
Do you have any remote style fobs for the car or just the keys?

[200OOM]

hello, Its all worked from the keys. No fob or stick thing. I have deactivated the door solenoids. And I have never really locked it. I have also removed the black box under the back of the arm rest. I am basically looking to try and remove anything to do with the central locking, immobiliser or alarm. Once sorted I will get something retro fitted. Just need advise on what to remove and how to bypass .

[Belle427]

The black box under the armrest/tunnel area is the microwave detection, it is on mine anyway. Did you follow the wires back from this as it will lead you to the alarm brain.

[Belle427]

It may help to read the thread here about the poor central locking wiring as the symptoms experienced there were somewhat strange too.

[Yex 450]

I see your profile shows you as in Cambridge so if you can get the car over to Matt Smith he should sort out the issues for you. Might not be cheap but he gets a lot of very good press on here and you should get a car you can use reliably over the summer.

http://www.matsmithsportscars.com/

[BoostedChim]

What relay did you replace the fuel pump one with? They're not normal relays and need to be replaced with the same dual output ones.

[200OOM]

Hi, The fuel pump relay, the one with the 5 prongs, was continuously clattering. so after a bit or searching on the forum I have removed this relay and wired in the fuel pump directly via a standard 4 pin relay. The only difference being that the pump is running continuously from when the ignition is switched on, previously it would just prime, then run once the engine is running. With the new set up is there a possibility of over fuelling? When in its standard set up is the speed of the pump regulated at all , or is it just running flat out all the time? I would like to get back to the standard set up, but without the alarm, immobiliser and central locking.

[Belle427]

In the event of an accident the fuel pump won't cut out, also as said previously by others the relay also has some other functions such as power to the lambda sensors, which may explain the over fuelling.

[200OOM]

Ah, did not think about the Lambda sensors. that would confuse the system. So how do I effectively power the lambda sensors?? is it a permanent live when ignition on? what part of the original fuel pump relay housing do I need to get power to?? I think we may be getting somewhere.

[Belle427]

http://www.g33.co.uk/fuel_injection.htm
Some good info here regarding operation and wiring diagrams.

[200OOM]

That's a great help, it has told me that the heating of the probe / sensor is controlled from the fuel pump relay. Since I have removed the relay its not getting any voltage, so not giving any readout , thus giving high emission readings, Will splice in a 12v supply triggered by ignition on. Thanks for your pointers on this. much appreciated. will update once done.

Thanks

[Steve_D]

The fuel pump relay has 5 pins.
85 & 86 are the activation coil.
Pin 30 is the power in and is a permanent +12V supply.
The final 2 pins are both marked 87 and both become live when the ECU trips the relay.
One of those pins does fuel pump and purge control. The second does left and right Lambda.

You can't just bridge the relay with link wires as everything would be on all the time so your only option is to fit the correct relay.

The main power relay is the same type.
Its outputs are...MAF on one pin and ECU, fault display connector and injectors on the second.

Steve

[200OOM]

Hi, My fuel relay was clattering, so I replaced it with the same results. so I by passed it and via a new relay powered the fuel pump. but I believe by doing this I have removed the 12v to the Lambda's. Would everything not work if I put a switched 12v to the lambdas down the same wire from the old relay socket?

[Steve_D]

200OOM said:

Hi, My fuel relay was clattering, so I replaced it with the same results. so I by passed it and via a new relay powered the fuel pump. but I believe by doing this I have removed the 12v to the Lambda's. Would everything not work if I put a switched 12v to the lambdas down the same wire from the old relay socket?

But did you replace it with the correct type?

You could (for test purpose only) wire a switched supply to both the 87 pins however this will not answer why the relay was chattering.
The relay was either defective or the circuit activating the relay is at fault. The only layman way to confirm which is to fit a new relay of the correct type.

Steve

[Belle427]

I'd agree, you seem to have an issue with the original set up at either pin 85 or pin 86. (12 volt switched supply and negative)
Both should be fairly easy to check with the aid of a test lamp and multimeter.

[200OOM]

Ok, I have a multi meter . What do I need to do? Switch to volts. Red probe on the terminals black to earth. What should I see from the 5 terminals . Really would like it back to standard. Will post the results once done. I feel progress is being made. Thanks for all your help .

[Steve_D]

First check the battery voltage. All manner of problems result from low battery.

Put the old relay back in and see if the fault is still there.
If it is then remove the relay and connect your multimeter across sockets 85 and 86 in the relay base to read volts.
Turn on the ignition and watch the meter. For a few seconds (fuel pump prime) there should be about 12 volts and the reading should remain steady until it goes off.
If the reading is not steady try moving the test lead from 85 and connecting it to earth. With the ignition on etc you should have a steady reading. if not there is a fault somewhere in the supply which comes via the immobiliser.

That should do for now.

Steve