MR2 SC dies but will run with Intercooler off??

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Pro5
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MR2 SC dies but will run with Intercooler off??

Post by Pro5 »

This is a strange one...

History: Had my MR2 (actually 3) for over 20 years, my current NA > SC conversion was done back in 2009, and it started fine everytime for 10 years even though I didn't drive it all that time - it just sat in my garage :laughing cos I had other jobs to done on it but it wasn't my daily driver.

When I moved house I went to start it (though it wasn't drivable as it's not MOT'd etc and in fact the brakes are off it and the clutch slave cylinder needs swapping) and it does this (and still does this 3 years - through covid - and now in my new house with a nice sized garage to finally get to rejuvenate the entire car)

1. Fresh from being left a day or so... cranks great and starts then immediately dies.
2. I will then not start again (for hours... usually I just try the next day)
3. It always restarts after being left but the cycle repeats

Now to save everyone time I've done nearly everything you could imagine, some I wanted to do anyway... i.e new fuel filter, new sparks, new dizzy, spare ECU swap/test, spark test, injector sound test (not noid light), coolant looks good, HG should be fine as it wasn't even used or revved up much back when it used to start. Checked all ground wires and re fastened them ,brand new high quality battery, tried 3 coil packs/igniters (to tons of spares here to try), could only do a COLD compression check (obviously car won't run with IC on and I'm not running it like that for more than a couple of seconds to test!) but was as fine as it was 10 years ago etc

All that changed between it starting and not.. was that my old garage was an outside one from the 50s that wasn't very useful in regards to damp... a good bit of the metal bits in the engine bay got a bit oxidised (whiteish) and my valve cover got bubbly from moisture in the air...

I noticed the ground wire over on the left under the intercooler (joining suspension post frame) look a little loose, tightening it caused the bolt head to sheer off (and trust me I didn't turn it much) this was obviously from the moisture above... it had kinda rusted in the hole and weakened the metal. Anyway, I eventually drilled the hole out and refastened that, and cleaned all other ends of (most) earth points.

So for a long time I was assuming some electrical fault, then.. based on how it WOULD start after being left.. a fuel fault. My reasoning was fuel wasn't getting through enough but after being left, whatever fuel had been pumped into the fuel rail, built up enough to start after being left then.. no more fuel so dies.

This was why I changed the fuel filter. Oh and yes all old petrol was siphoned out and fresh super unleaded put in.

Soooo.. now let me get to the point, this was an almost accidental discovery on how to make it start AND RUN everytime.

I had the intercooler off and forgot to put it back on, started the car and it fired up and ran just fine... uhmm well other than the popping/banging and black soot dumping out of the exhaust from the (I assume) ultra-rich running due to tons of air being swallowed into the now open cylinder (no SC or Throttle body.. afm or anything in the way).

So I then set about process of of elimination to see how far back in the air chain I could go, but if I disconnected the AFM and the pipe leading to the TB it was exactly as before, no start unless left then dies. So it seems it's nothing before the TB). After the SC (to intercooler) I could leave either side of IC connected and it would start and run (so not the IC).

This means the issue is somewhere between the TB in and the SC out... (I should mention I have a modified pulley so have done the ABV mod - I did that 20 years ago and used it for many years on the road just fine so the mod should be fine).

Now... to those more expert than me, hopefully with enough info to go on:

Does this sound like an air problem OR could a fuel problem like weak pump still be the cause and the fact I let the engine swallow in tons of air is just working better with however much fuel is coming in?

or

Could it be a vacuum leak (turns out the plastic pipe down from the Intercooler towards rear of car that goes into the metal SC output pipe - the mikalor clamp there was LOOSE but... had prob been loose since I fit the engine in back in my garage 10 years ago and had started fine for years) - if it is a vac leak, why would removing the IC - causing a major vac leak actually make it start? And wouldn't a vac leak prob start and run but just idle rough or die each time rather than just once then never start?

The weird thing is the time between starting (again made me think fuel i.e flooding?) but it will start everytime if I leave the IC off and never flood. With IC on *IF* it's starting once THEN flooding, is it an air restriction?

I could imagine either fuel building up slowwly through clogged stuff ready for that one start after many hours... I could imagine flooding needing to sort out before it starts again (most likely but WOT while cranking doesn't have any effect on this!) but I can't see how/why 'air' would build up after many hours to enable it to start?

So of course.. that leads us to the TPS, ABV etc... and what would 'most likely go wrong' for no reason, just sitting in a garage and starting/running fine a few weeks previously.

Sorry this is an essay but I've put in a ton of detail so anyone who's had similar or could give advice has a lot to go on rather than too little.

I don't know what disconnecting the Intercooler is doing to the fuelling but I can guess it's basically giving the car tons of air to work with, so with it on - whatever is meant to regulate air is either stuck closed or electronically at fault? There are no blockages in the pipes (no forgotten rags etc) btw.

Thoughts of the cold start injector (during 'normal' tests)... but why does it then start everytime with IC off? and stay running (badly due to massive vac leak and no air control + giant fuel dump)

Lastly.. with the ABV mod I wondered if it's trying to get air past the SC but maybe the SC is seized (I think there's enough 'room' for air to get around though even with the mod... hmm like when the SC clutch isn't engaged.. that said, I think the mod is only for purging built up air and intake air (with SC off) should still go through the usual channels yes?

I also tried disconnecting the AFM and the TPS connectors to 'bypass' them, and the usual Fuel Pump diagnostic (always on).. no change. I guess it could still be the AFM when it's all buttoned up, not sending the correct signals but bypassing it should at least start it no? same with TPS?

Any help would be massively appreciated. Thanks


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Re: MR2 SC dies but will run with Intercooler off??

Post by jimi »

You haven't mentioned fault codes, is it showing any fault codes when you link T & E1 on the check connector ?
There's very little knowledge on here about SC's since they are relatively rare in the UK as they were never available new in the UK, so they are all imports.
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Pro5
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Re: MR2 SC dies but will run with Intercooler off??

Post by Pro5 »

jimi wrote: 13/05/22 11:01 You haven't mentioned fault codes, is it showing any fault codes when you link T & E1 on the check connector ?
There's very little knowledge on here about SC's since they are relatively rare in the UK as they were never available new in the UK, so they are all imports.
No fault codes (would have mentioned) ... yeah I know about SCs in the Uk cos been around the forums and sites for years , my first SC was a fresh import back in 2000 which is where my two swaps came from since then (same engine with 45k on at the time and still only around 70k)

I think this is quite a genral, non specific to sc, fault though as air fuel and spark plus all the sensors, other than abv I think, are kinda common to the na too. I think Paul Woods for example should know about these as he’s dealt with many swaps? But even just anyone who’s seen this issue or “starts with ic or part of air piping off” with any non NA engine would probably have an idea. That’s what I’m hoping anyway before I have to strip down the TB and SC etc... and yes I have the BGB (physical copy) from way back but doesn’t mention anything about this in troubleshooting...nor does it detail the flow and circuits too well betwix throttlebody and post SC12 unit.

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jimi
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Re: MR2 SC dies but will run with Intercooler off??

Post by jimi »

What happens if you join the IC hoses together, i.e. take it out of the circuit but leave the airpath complete?
On another note are you sharpfish on IMOC ?
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