Do you really need the cold start injector?

[un1eash]

Ive been having bad mpg so i disconnected the cold start injector to see if it made any difference. Havnt had chance to see if my mpg has gone up but in the mornings my car starts and runs just the same. So is the cold start injector even needed and when is it used?

cheers

[jimi]

It's used every time you start the engine, it's controlled by what Mr T calls a time switch, but is actually a temperature controlled switch ( mounted on the thermosat housing with a grey plug ) it's only normally on for a short time, as it measures the water temp on the engine side of the thermostat. I've tried starting the engine with it disconnected and it's OK in the summer but hard to start in the winter.
hth
Jimi

[dr_wilkinson]

No matter how cold your coolant the cold start injector will not fire for longer than IIRC 8 seconds, so should make no difference to your fuel economy.

Probably something else at fault, such as thermostat, lambda sensor, TPS or one of many other sensors!

[jimi]

No Lambda sensor on a UK spec MK1

[dr_wilkinson]

No Lambda sensor on a UK spec MK1

D'oh! Guess I'm used to the 20v and the superchargers having them

It's bizarre thinking about it, but I've actually never driven a standard mk1 na... Really must give one a go some day...!

[jimi]

Just out of curiosity and because I wasn't 100% sure how the cold start injector was controlled, I had a look at the drawings and the BGB, turns out that it is controlled by 2 things, the ignition switch and the cold start time switch. The injector is only activated when the ignition switch is in the "crank" position and the water temp is low enough to allow the switch to operate. So basically the injector is only in use while you are holding the key over, cranking the engine. As soon as you release it the injector shuts off.
Jimi

It's bizarre thinking about it, but I've actually never driven a standard mk1 na... Really must give one a go some day...!

You really should........it will surprise you

[MartG]

Jimi - just looked at the circuit diagrams too - I reckon you're right, it only operates with the ignition key in the start position

Need to check mine, as it's started to take 4 or 5 attempts to get it started in the morning

[dr_wilkinson]

Just wait and see what Toyota want for a new cold start injector time switch though - ISTR they charge around £130!

I considered adding the time switch to the starter circuit - I can't see any downside to having the fifth injector firing every time at startup - whether or not the coolant is too cold. It's certainly easier and cheaper than forking out for a new one...

[MartG]

£130 And as mine is showing open circuit it needs swapping

As a temporary measure I'll swap the one from my trackday car - it doesn't really matter if that takes a few cranks to get started first thing on a morning

[jimi]

£130 And as mine is showing open circuit it needs swapping

As a temporary measure I'll swap the one from my trackday car - it doesn't really matter if that takes a few cranks to get started first thing on a morning

You could just link it out on your track car, just means it will operate every time you start the engine, the few seconds it will be on shouldn't make any difference if engine is warm.
Jimi

[MartG]

Eventually remembered the AE101 GZE in the track car has the equivalent sensor on the water outlet from the block, so the one on the thermostat housing is spare

Just as well - there is evidence of coolant weeping out of the top of the old sensor, so I'll be swapping it tonight.

Just need to find something to bung the hole on the trackcar now - I was going to use the duff one off the road car but as its leaking I can't do that, unless I can seal it up somehow.

[MartG]

Well I swapped the switch last night, and this morning it didn't take the usual half a dozen goes to get started - one turn of the key and it was away

So in my case, yes you do need the cold start injector

As an aside, it seems the reason for it failing was a split rubber boot on the connector allowing rainwater in ( the switch itself may be OK after the contacts are cleaned up ). On the SC the intercooler vent is directly above the switch, which allows rainwater to drip onto it ( probably won't happen on an NA ) - if the rubber boot on the connector is split the connector fills up with water. Mine is now wrapped in gaffer tape

[dr_wilkinson]

Cheers Mart - maybe I'll go back and take a second look at mine!

[un1eash]

I've had my cold start injector disconnected for a week now and it starts first time every time in the morning. Only done 10 miles this week so will have to let you know after the weekend if my fuel economy is any better.

[HT]

^^ amazed it starts first time: I disconnected mine and even in late september it took loads of atttempts. I would doubt whether any fuelsaving is measurable - as its only on very briefly(seconds), and surely it willbe running a fuel enriched map on start up anyway until running temp is reached?? (anyone)

[GaryR]

And as mine is showing open circuit it needs swapping

How can you test if the switch has failed ?

[MartG]

[NDR008]

No Lambda sensor on a UK spec MK1

Sure on that? I have not looked at it, but would seem odd to me.

[MartG]

Yep, UK Mk1s didn't have a lambda sensor, and didn't have a cat either.

[NDR008]

How xxxx, I am well disappointed now. My mate's AE86 has a JDM AW11 engine in it, and it had a lambda sensor and I never questioned if ours has. So the AW11 must run in open loop all the time....