Help !! Bypass immobiliser?
Discussion
similar happened to me - RAC tested current across the terminals of the fuel pump, established there was power and so fuel pump must be knackered. Low loader ride home. If you find the same then what followed was - lots of help from people on here - call to v8 developments for a new fuel pump (cheapr than dealer) and a couple of hours under the car away from the kids - hey presto it goes again. really easy to do and I am a complete numpty with spanners. Good luck.
The electrical circuit that powers the fuel pump is moderately complicated and there are plenty of ways for it to go wrong. To start with, I suggest you put a fused 12v feed direct to the pump and check the car does start and run.
Hopefully it will, in which case you have a bit of troubleshooting to do. Are you comfortable diagnosing simple electrical circuits using a multi-meter/test light?
Hopefully it will, in which case you have a bit of troubleshooting to do. Are you comfortable diagnosing simple electrical circuits using a multi-meter/test light?
OK. Here's a quick summary of the circuit:
There are two metal cased Bosch relays. One powers the ECU, the other powers the fuel pump. On mine, the one for the fuel pump is in a blue socket.
The fuel pump relay has a permanent fused 12v supply to terminal 30. It has an ignition switched feed to terminal 85 (coil feed), which comes via the immobiliser and another fuse. Terminal 86 (coil return) is earthed via the ECU when the ECU want to run the pump. Terminals 87/87A are normally open, and the relay switches these to terminal 30 when the coil is energized. Terminal 87 supplies the fuel pump via the intertia cutout switch. Terminal 87A feeds the lambda sensor heaters if fitted. (87/87A could be wired up the other way, can't remember, doesn't matter.)
You should be able to hear and feel the relays switching so this is the first thing to check. You should find both relays click when you switch the ignition on, the fuel pump relay wll click again after a couple of seconds, the main power relay should click again a few seconds after you switch the ignition off.
If the relays are clicking then you're looking for a fault on the switched circuit (30, 87/87A).
If they aren't clicking then you're looking for a fault on the control circuit (85/86).
Hopefully given an understanding of how the circuit is supposed to work, your pal will be able to track the problem down. My money is on it being a dead relay, by the way.
There are two metal cased Bosch relays. One powers the ECU, the other powers the fuel pump. On mine, the one for the fuel pump is in a blue socket.
The fuel pump relay has a permanent fused 12v supply to terminal 30. It has an ignition switched feed to terminal 85 (coil feed), which comes via the immobiliser and another fuse. Terminal 86 (coil return) is earthed via the ECU when the ECU want to run the pump. Terminals 87/87A are normally open, and the relay switches these to terminal 30 when the coil is energized. Terminal 87 supplies the fuel pump via the intertia cutout switch. Terminal 87A feeds the lambda sensor heaters if fitted. (87/87A could be wired up the other way, can't remember, doesn't matter.)
You should be able to hear and feel the relays switching so this is the first thing to check. You should find both relays click when you switch the ignition on, the fuel pump relay wll click again after a couple of seconds, the main power relay should click again a few seconds after you switch the ignition off.
If the relays are clicking then you're looking for a fault on the switched circuit (30, 87/87A).
If they aren't clicking then you're looking for a fault on the control circuit (85/86).
Hopefully given an understanding of how the circuit is supposed to work, your pal will be able to track the problem down. My money is on it being a dead relay, by the way.
Thankyou very much for that post. Lots of info in there.(will have a look tomorrow if required)
I ordered two relays today, just in case, so im realy hopeing they will do the trick. (Can keep them as spares if not needed.)
Last thing i tried tonight was running a direct 12v feed to the pump and it primed, so pumps looks like it stil works at least.
I ordered two relays today, just in case, so im realy hopeing they will do the trick. (Can keep them as spares if not needed.)
Last thing i tried tonight was running a direct 12v feed to the pump and it primed, so pumps looks like it stil works at least.
just one other thing you could try, under the LH side of the dash is the fiel pump cutout - it's a black box with a plunger coming out of it. Mine was just behind the mappocket passenger side. I had a similar issue after I had a poke around trying to sort out an intermittent alarm issue, when I tried to start the car the fuel pump didnt kick in so wouldn't start. after pushing the plunger back in (or out can't remember) the car fired up straight away. May be worth a look as it won't cost you anything to rule it out at least.
Its working!!!.
I hadn't noticed the two fuses that are on the same loom as the Fuel pump and ecu relays
Much relief when I found out one was blown. Replaced and straight away after putting the ignition on I heard that great sound of the fuel pump priming. Started the car and enjoyed that V8 roar again.
Very Happy to be back on the road
Plus I have two spare relays for my spares kit now £24 for the two bosch ones
I hadn't noticed the two fuses that are on the same loom as the Fuel pump and ecu relays
Much relief when I found out one was blown. Replaced and straight away after putting the ignition on I heard that great sound of the fuel pump priming. Started the car and enjoyed that V8 roar again. Very Happy to be back on the road
Plus I have two spare relays for my spares kit now £24 for the two bosch onesHi guys, new here.
I have a 1993 Chimaera which I totally adore! I have spent hours sorting the interior, sound system, new wheels, carpet, wing mirrors, updated thermostat control for cooling fans, radiator, cooling fans etc etc. I have over the last month or so had problems in starting the car. This has happened a few times.
I use the imoboliser nipple to de activate, all dash lights and electrics work, but no starter motor. The fuel pump primes and all else works, just no starter motor?? I have also noticed that my cooling fans run off a live feed from my alternator. if I turn the thermostat to Zero with key out of ignition, my fans still come on. This morning the fans would not come on? Don't think I have any power to the Alternator? Could this be the 100 amp fuse? Could it be the imoboliser??? HELP!!!
I have a 1993 Chimaera which I totally adore! I have spent hours sorting the interior, sound system, new wheels, carpet, wing mirrors, updated thermostat control for cooling fans, radiator, cooling fans etc etc. I have over the last month or so had problems in starting the car. This has happened a few times.
I use the imoboliser nipple to de activate, all dash lights and electrics work, but no starter motor. The fuel pump primes and all else works, just no starter motor?? I have also noticed that my cooling fans run off a live feed from my alternator. if I turn the thermostat to Zero with key out of ignition, my fans still come on. This morning the fans would not come on? Don't think I have any power to the Alternator? Could this be the 100 amp fuse? Could it be the imoboliser??? HELP!!!
TVRk77eff said:
Hi guys, new here.
I have a 1993 Chimaera which I totally adore! I have spent hours sorting the interior, sound system, new wheels, carpet, wing mirrors, updated thermostat control for cooling fans, radiator, cooling fans etc etc. I have over the last month or so had problems in starting the car. This has happened a few times.
I use the imoboliser nipple to de activate, all dash lights and electrics work, but no starter motor. The fuel pump primes and all else works, just no starter motor?? I have also noticed that my cooling fans run off a live feed from my alternator. if I turn the thermostat to Zero with key out of ignition, my fans still come on. This morning the fans would not come on? Don't think I have any power to the Alternator? Could this be the 100 amp fuse? Could it be the imoboliser??? HELP!!!
Starter motor perhaps needs a service. Check electrical feeds. Earth etc. Stuck pinion?I have a 1993 Chimaera which I totally adore! I have spent hours sorting the interior, sound system, new wheels, carpet, wing mirrors, updated thermostat control for cooling fans, radiator, cooling fans etc etc. I have over the last month or so had problems in starting the car. This has happened a few times.
I use the imoboliser nipple to de activate, all dash lights and electrics work, but no starter motor. The fuel pump primes and all else works, just no starter motor?? I have also noticed that my cooling fans run off a live feed from my alternator. if I turn the thermostat to Zero with key out of ignition, my fans still come on. This morning the fans would not come on? Don't think I have any power to the Alternator? Could this be the 100 amp fuse? Could it be the imoboliser??? HELP!!!
The immobiliser or more accurately the alarm unit in effect just acts as a switch, the circuits you're looking for are simply looped through the unit.
If you think about it like a switch (open circuit & closed circuit) it doesn't take long to work out how to bypass the thing on one or more circuit.
Just buy a multimeter if you haven't got one already and be systematic, you'll suss it.
But just remember a bypass while effective is not really a professional solution to the problem, more of a cheap temporary get you out of trouble bodge.
To do the job properly you need a new alarm system fitted by a respected alarm fitter, ideally one who knows his way around the wonderful world of TVR wiring
If you think about it like a switch (open circuit & closed circuit) it doesn't take long to work out how to bypass the thing on one or more circuit.
Just buy a multimeter if you haven't got one already and be systematic, you'll suss it.
But just remember a bypass while effective is not really a professional solution to the problem, more of a cheap temporary get you out of trouble bodge.
To do the job properly you need a new alarm system fitted by a respected alarm fitter, ideally one who knows his way around the wonderful world of TVR wiring
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