inertia switch

[uglymug]

Hi all,
Please can you tell me what an inertia switch is like ( photo needed ) and where will it be situated on my 350i........................thanks Mark

[Gerry Attrick]

Never heard of it - unless you mean a brake balance device. If you find out, let me know!

[shpub]

There isn't one. Later TVRs do have them though. It is normally used to disconnect the fuel pump if an accident occurs. The ECU switches off the fuel pump when the engine is stopped.

Steve
www.tvrbooks.co.uk

[chunder]

I am no expert but the only inertia switch I have heard of is to cut off a fuel pump in the event of a crash - not aware that TVR fitted them to any wedges though.

Do you have a problem with the fuel pump ?

[uglymug]

The car refuses to start, no matter what I try. Engine turns over good spark, but the petrol pump does not cut in, and injectors don't operate to get the engine running.

[mikeb]

Have you had a good check of the fuses and relays. The contacts on my fuses were all oxidised and most things did not work until I replaced all of the fuses and cleaned the contacts.

Also have a good poke around for any immobilisers or alarm systems, when i first had my 350i i pulled out three dud ones still partially wired into the loom. in the 450 I have come across two which don't seem to do anything. i have also found a good many wires which have just been cut and have been left dangling in the engine bay probably powering up 'phantom' alarms?!?.

You may also wanna go around and make sure all the earths are making good contact and have a general check around the relay/fusebox area for loose wires.

Good luck

MikeB

[rev-erend]

I'm not a great expert and there is nothing in your profile to say what car you have ... but I'll assume a 390 / 400 - with a flapper airflow meter.

The flapper airflow meter controls the fuel pump - when you turn the key - the piston causes air to flow
and the signal is sent to start the pump.

You might like to check the fuses and wiring to the pump .. particularly the earth..

Or you could disconnect all pump wires and wire it seperately and see if it runs.

If this works .. then it's probably the airflow meter ..

But my money is on a fuse (can't remember if there is an inline fuse near the pump..) or on a bad earth..

[gsx600]

Whilst you are there take the air filter of and manually push the flap with the ignition on. You should then hear the fuel pump cut in.

The only fuses I remember I think is a main fuse for the ecu, but you could also have faulty relays feeding the pump- again from memory mine was a red colored relay.

There was on this forum a link to efi fault finding that was fairly simple to follow if you have a multimeter, was useful in helping me set up a new system on mine
May be on here somewhere
www.roversd1.nl/sd1web/index.html


>> Edited by gsx600 on Tuesday 9th November 16:27

[uglymug]

thanks guys....have done all of the tests that you have suggested and more. Earths are all shiny! No breaks in any of the wires ( continuity tested everything !! )still no luck. Have suspected the steering module tho. Well the one in the car seems to be just an ordinary relay type. Have a new one coming from Rimmers tomorrow £30. Will try that. Will let you know.

[chunder]

uglymug said:

thanks guys....have done all of the tests that you have suggested and more. Earths are all shiny! No breaks in any of the wires ( continuity tested everything !! )still no luck. Have suspected the steering module tho. Well the one in the car seems to be just an ordinary relay type. Have a new one coming from Rimmers tomorrow £30. Will try that. Will let you know.

What's the steering module ?

[rev-erend]

Surely if you have wired the pump direct - no relays etc .. and it does not work - well it's a defective pump !

[wedg1e]

chunder said:

What's the steering module ?

Commonly known as the 'red relay'. It's a diode matrix that controls how the injection system relays operate.
No need for it to cost 30 quid though...


Ian

[jvaughan]

chunder said:

I am no expert but the only inertia switch I have heard of is to cut off a fuel pump in the event of a crash - not aware that TVR fitted them to any wedges though. Do you have a problem with the fuel pump ?

I have one on my 400SE. it is located on the bulkhead, next to the brake servo.

[rev-erend]

Also see :

www.pistonheads.co.uk/gassing/topic.asp?t=135220&f=9&h=0

[chunder]

jvaughan said:

chunder said: I am no expert but the only inertia switch I have heard of is to cut off a fuel pump in the event of a crash - not aware that TVR fitted them to any wedges though. Do you have a problem with the fuel pump ? I have one on my 400SE. it is located on the bulkhead, next to the brake servo.

They must have known you'd be driving it

[redcar]

chunder said:

jvaughan said: chunder said: I am no expert but the only inertia switch I have heard of is to cut off a fuel pump in the event of a crash - not aware that TVR fitted them to any wedges though. Do you have a problem with the fuel pump ? I have one on my 400SE. it is located on the bulkhead, next to the brake servo. They must have known you'd be driving it

So do I.

[iainjones]

jvaughan said:

chunder said: I am no expert but the only inertia switch I have heard of is to cut off a fuel pump in the event of a crash - not aware that TVR fitted them to any wedges though. Do you have a problem with the fuel pump ? I have one on my 400SE. it is located on the bulkhead, next to the brake servo.

Jason, what does it look like? Rectangular about 1.5" by 1" x 3/8" with a red button about 2/3rds of the way down with two spade terminals?

If so its an SD1 unit.

Regards
Iain

[jvaughan]

yes, mine has a black button on it. The plunger does work too.

It appears to be sealed with a resin or some thing.. not sure how many wires goign to it.

[redcar]

iainjones said:

jvaughan said: chunder said: I am no expert but the only inertia switch I have heard of is to cut off a fuel pump in the event of a crash - not aware that TVR fitted them to any wedges though. Do you have a problem with the fuel pump ? I have one on my 400SE. it is located on the bulkhead, next to the brake servo. Jason, what does it look like? Rectangular about 1.5" by 1" x 3/8" with a red button about 2/3rds of the way down with two spade terminals? If so its an SD1 unit. Regards Iain

Iain, thats the same as mine, wait for it, what does it do?

[shpub]

When the car is exposed to high G as in a crash, it trips and disconnects the power to the fuel pump so that the engine stops and in the case of a broken fuel pipe, fuel is not sprayed everywhere...

Tried one on the 520 (fixed but not connected but it kept tripping on the track...