A handy fuel pump relay tweak

[S2central.net]

I had a few moments to experiment with this idea tonight and it works well... I'd post a pic but all you would see is a red light glowing in my fusebox as its well dark outside.

The idea is to get a simple visual indication that the fuel pump relay is activated. This verifies the ECU is happy that its getting rpm pulses from the G28 sensor at a suitable rate to activate the relay AND also that the relay contacts have energised for the pump and injectors. Its useless 99% of the time, when car runs well, but priceless when you have a no-start condition.

The tweak is the simple addition of an LED inside the relay and a small hole in the relay case to see the light when you have the lid off the fusebox. Its a simple enough mod for anyone with the knowhow and license to drive a soldering iron (and a drill), but if there is interest for me doing those for a small charge I could be persuaded.

The LED only lights when the ECU has activated the fuel pump... with the ignition on alone, the LED stays off. Pretty simple logic.

Paul

[Bart76]

Good job!

[BrianSmith_S2]

I had a few moments to experiment with this idea tonight and it works well... I'd post a pic but all you would see is a red light glowing in my fusebox as its well dark outside.

The idea is to get a simple visual indication that the fuel pump relay is activated. This verifies the ECU is happy that its getting rpm pulses from the G28 sensor at a suitable rate to activate the relay AND also that the relay contacts have energised for the pump and injectors. Its useless 99% of the time, when car runs well, but priceless when you have a no-start condition.

The tweak is the simple addition of an LED inside the relay and a small hole in the relay case to see the light when you have the lid off the fusebox. Its a simple enough mod for anyone with the knowhow and license to drive a soldering iron (and a drill), but if there is interest for me doing those for a small charge I could be persuaded.

The LED only lights when the ECU has activated the fuel pump... with the ignition on alone, the LED stays off. Pretty simple logic.

Paul

So this relay has seperate contacts for the fuel pump, and a seperate pair of contacts for the injectors? I havent checked this out yet for my current no start/dead injectors problem. If so which relay contacts do what?

[S2central.net]

Funny - I was just thinking about this... I chose the injector contacts - simply as its the last one to get energised by the solenoid. It would be no sweat to use a bicolor LED in here so it glowed red or green if only one half of relay energised - and glowed yellow if both are active.

[BrianSmith_S2]

Funny - I was just thinking about this... I chose the injector contacts - simply as its the last one to get energised by the solenoid. It would be no sweat to use a bicolor LED in here so it glowed red or green if only one half of relay energised - and glowed yellow if both are active.

Ive just been checking my fpr contacts over and using my finger to gently operate the coil there wasnt a good contact between contact 87a (output?) and 30 (12V)

Is this the connection for the injectors? or are the injectors signalled from one of the two going to contact 87?

[S2central.net]

87a goes thru fuses 24 and 28 for ISV, EVAP, WGFV and injectors respectively. Check you get 12V on the black/blue wires on the injectors while cranking. That 12V LED can also be used to see if ECU is triggering them of course.

87 goes thru fuse 13 to the fuel pump and fuse 25 to lambda heating (grey/green wire).

You could use some tape and close the relay contacts TEMPORARILY to see if this induces life into the patient the next time you crank it !

[BrianSmith_S2]

87a goes thru fuses 24 and 28 for ISV, EVAP, WGFV and injectors respectively. Check you get 12V on the black/blue wires on the injectors while cranking. That 12V LED can also be used to see if ECU is triggering them of course.

87 goes thru fuse 13 to the fuel pump and fuse 25 to lambda heating (grey/green wire).

You could use some tape and close the relay contacts TEMPORARILY to see if this induces life into the patient the next time you crank it !

I just put a red (12V) +ve led on the black/blue wire on the front injector connection and earthed -ve against chassis. it turned bright red with ignition on, and then stayed bright red when turning over.... I find that strange... or is it turned on and off via the other wire? the negative?

[Sonic]

I had a few moments to experiment with this idea tonight and it works well... I'd post a pic but all you would see is a red light glowing in my fusebox as its well dark outside.

The idea is to get a simple visual indication that the fuel pump relay is activated. This verifies the ECU is happy that its getting rpm pulses from the G28 sensor at a suitable rate to activate the relay AND also that the relay contacts have energised for the pump and injectors. Its useless 99% of the time, when car runs well, but priceless when you have a no-start condition.

The tweak is the simple addition of an LED inside the relay and a small hole in the relay case to see the light when you have the lid off the fusebox. Its a simple enough mod for anyone with the knowhow and license to drive a soldering iron (and a drill), but if there is interest for me doing those for a small charge I could be persuaded.

The LED only lights when the ECU has activated the fuel pump... with the ignition on alone, the LED stays off. Pretty simple logic.

Paul

Sounds like a neat little idea, one which would save a nice bit of faffing about particularly if you've had an after-market immobiliser installed. It would have saved me a lot of messing about by the side of the road when my car cut out a month or so ago!

Anything that's simple and easy to apply in aiding diagnosis is worth it's weight in gold - just look at how simple a boost gauge is to install and how invaluable it becomes when you have any manner of problems.

[BrianSmith_S2]

Sounds like a neat little idea, one which would save a nice bit of faffing about particularly if you've had an after-market immobiliser installed. It would have saved me a lot of messing about by the side of the road when my car cut out a month or so ago!

Anything that's simple and easy to apply in aiding diagnosis is worth it's weight in gold - just look at how simple a boost gauge is to install and how invaluable it becomes when you have any manner of problems.

So how did you sort your problem out then? Im thinking my no starter is immo related?

[Sonic]

It was difficult because i'd just had the ECU out, quite a few bits and pieces replaced, and lots of relays re-installed, along with the addition of an 044 fuel pump a few days before it cut out.

When it died it was still turning over. I checked all hose connections under the bonnet, all vacuum pipes, took out and re-installed the ECU and then after some help over the phone established that the fuel pump was not starting when turning the key and it sounded like it was trying to crank without fuel.

I got to the fuel pump in the boot to check all the connections were ok, and that it hadn't fallen over or something silly, starving it of fuel.

Anyway.. after a lot of faffing it turns out there was a 5 meter twin-core cable spliced into the loom, more importantly into the power line for the fuel pump.

The cable was just cut and the ends twisted. Upon inspection the ends were burnt. When i cut and twisted them together again the beast started immediatley.

I figure the hacked-in cable is remnant of the old immobiliser, and when it was removed they just cut and twisted the cable together, which burnt out at the connection with the increased current of the 044 pump.

I've since removed the cable and re-connected the loom together as it should be.

One of my many problems having been caused by after market immobilisers.

[S2central.net]

I just put a red (12V) +ve led on the black/blue wire on the front injector connection and earthed -ve against chassis. it turned bright red with ignition on, and then stayed bright red when turning over.... I find that strange... or is it turned on and off via the other wire? the negative?

The black/blue wire stays at 12V via the pump relay, but the ECU opens and closes a path to 0V for each injector - that will be the other wire at each injector, so placing the LED across each injector should see it pulse - never actually verified that the pulses are long enough to be visible by naked eye, but your scope will see them being triggered.

[BrianSmith_S2]

Thanks for that, that is one of my jobs to do tomorrow after work.... inspect the aftermarket clifford immo wiring for any nasties

[S2central.net]

Please make a note of all factory wire colours that are involved - you can send me that privately with photos if you like.

Have you checked the coilpacks are getting 12V via Fuse 32 when ignition is on - usually black wires into the 3-pin white plugs ?

[BrianSmith_S2]

The black/blue wire stays at 12V via the pump relay, but the ECU opens and closes a path to 0V for each injector - that will be the other wire at each injector, so placing the LED across each injector should see it pulse - never actually verified that the pulses are long enough to be visible by naked eye, but your scope will see them being triggered.

Ok, i will scope that tomorrow.... its getting a bit late now for the neigbours to keep turning her over

I cant wait till she fires up again (fingers crossed)

By the way, is it normal when the multimeter is probed across both injector pins that the buzzer is set off during continuity test?

[BrianSmith_S2]

Have you checked the coilpacks are getting 12V via Fuse 32 when ignition is on - usually black wires into the 3-pin white plugs ?

Whats the best way of testing this? just remove fuse 32 and use multimeter/scope to probe against one of the contacts?

Or is it the one of the white plugs at bulkhead along from the G28 and G4 plugs?

Cheers

Brian