Overfuelling and not charging, I will not be beaten!

[Ginjaninja92]

Hi guys,

First things first, I realise I only ever seem to post here when I'm in need of free help and advice so please except my apologies. I plan to change that

My MR2 is in the process of becoming my daily driver, from being an occasional use track car/garage dweller. I've actually owned the car for 6 years and just done fun project type things/track days. My daily driver was written off so I decided it was time to take the plunge.

I had thought the car was in good condition, so when I took it down for the MOT 2 weeks ago I wasn't massively worried. It was also running a bit rich so I pointed my mechanic towards the idle control valve, thinking it would be straight forward. The MOT came back as needing a brake line, rear top mounts rattling, and emissions. Not too bad I thought.

But he also reported back that he was unable to find the source of the over fueling problem, and the car isn't charging off the alternater

He has now had the car for 2 weeks and not made any real progress.

The car is Rev1 N/A with Rev3 N/A engine, it was last out n about in July at a track day where the clutch went, so since then I have changed the clutch and had the alternater refurbished, this was only just completed before it went for the MOT.

I tried to check the fault codes but got nothing :/

Can anyone help me to point my mechanic in the right direction?
Beer tokens will be handed out in return for problem solving advice

Thank you all.

[fingers99]

Get your mechanic a copy of the Big Green Book.

The alternator may be faulty (return under g'tee?) or you may have an electrical fault somewhere else in the charging circuit. All the tests are in there.

Overfuelling might be engine temperature sensor or stuck open thermostat, but that by no means covers all the possibilities.

[MRturboTom]

Replace the green ecu temp sensor first for fuelling issues.

Have the wiring from the alternator checked for continuity. The wiring is known to corrode and break from the alternator to the engine bay fuse box. Or at least check there's battery voltage at the 3 wires of the alternator plug.
If it's all ok, could be a faulty regulator on the alternator

[Ginjaninja92]

Fingers, thanks for the reply. I have given him links to the two relevant wiring diagrams. So hopefully that helps.

Yeah we'll find out if the alternator is ok, if not I will be taking it back to the shop that refurbed it.
I had changed the coolant temp sensor myself before it went down. I didn't realise the thermostat could cause overfuelling. Is that to do with the cold start system?

Tom, like I said I have replaced the temp senor already. Ok I'll pass this onto him.

Thanks for the help so far. I'll get an update tomorrow.

Dan

[fingers99]

If the stat is stuck open, the engine will take an age to warm up -- until it does, the engine temperature sensor will respond to the temperature (which is all it knows) and the ECU will run the engine rich.

[Chris_D]

Could also be lambda sensor causing overfueling. This can be tested by checking the output is between 0.2 and 0.8V once warm (I think there are tests in the BGB)

What are the actual readings from the emissions fail ? CO, HC etc. I presume it was a non-cat test for a rev 1 car ?

Also, noting it's an engine conversion:

Which ECU are you running, the rev 1 or the rev 3 ?
Does it have an AFM or is it MAP sensor, was this also swapped from the rev 3 ?

[Ginjaninja92]

Ok so I popped down on Sat morning for a wee update. It appears the over fueling is being caused by the cold start valve staying open, due to it getting a constant live, even when the ignition is off!!! So he should hopefully be able to trace that back to a wiring defect.

There is also a drain from a wiring circuit under the intake manifold, although he's still to nail down exactly which circuit, this also a constant live even when the ignition is off.

Now that he has the wiring diagrams he should be able to get to the bottom of it.

Fingers - Ah ok, I've never checked the thermostat. For future reference, it's housed on the front right hand side of the engine is that right?

Chris - The lambda was recently replaced so I would be surprised if it was that. I'm not sure on the readings for the emissions test, they would have been horrendous though. Yeah non-cat.

I'm using the rev3 ECU and loom, and it's got a MAP sensor, think it's the original rev1 MAP sensor though. Are they different between rev1 and rev3?

Thanks again for your replies. It's a real help

[fingers99]

Fingers - Ah ok, I've never checked the thermostat. For future reference, it's housed on the front right hand side of the engine is that right?

This is good.

I'm using the rev3 ECU and loom, and it's got a MAP sensor, think it's the original rev1 MAP sensor though. Are they different between rev1 and rev3?

I'm not sure. You'd think that a MAP sensor is a MAP sensor is a MAP sensor, so as long as the range is right, no probs. But there may be subtle differences to the wiring.

[Ginjaninja92]

Cheers Fingers that is a good link.

Yeah that was my thinking, had a wee look online and it appears there's no difference between rev1 and 3.

Hopefully get an update tomorrow.

Thanks again.

[Chris_D]

I'm using the rev3 ECU and loom, and it's got a MAP sensor, think it's the original rev1 MAP sensor though. Are they different between rev1 and rev3?

Thanks again for your replies. It's a real help

Yes. Rev 3 goes to a higher pressure for the same voltage range. A Rev 1. sensor will fool the ECU into thinking there is more pressure so it will add more fuel.

They are a straight swap electrically & mechanically except the brackets are diferent.

[Ginjaninja92]

I had a look and there's nothing online about them being different

Anyhoo, spoke to my mechanic yesterday and he said it's that the whole fuel injection system getting full power even when the ignition is off

Anyone ever seen a problem like this before? Is there a chance it's to do with some of the wiring changes between rev1 and rev3 ECU have came loose etc?

Any and all suggestions welcomed.

Thanks again.

[fingers99]

I had a look and there's nothing online about them being different

Easy way would be to pop into Toyota, ask them to check the part numbers.

Anyhoo, spoke to my mechanic yesterday and he said it's that the whole fuel injection system getting full power even when the ignition is off

That's pretty odd.

There's a comparison of the harnesses here.

[jimi]

It should be easy enough to find out why it has power with the ignition off. Sounds very much like a wiring fault or possibly a faulty relay, has it ever run correctly since the conversion?
Even pulling a couple of fuses/relays should narrow it down pretty quickly, all you need is a multi-meter and a set of correct electrical drawings (and someone who knows how to use them)
If you/your mechanic aren't comfortable with those tools then get an auto electrician on the job, it will be quicker and easier in the long run.
No offence meant but trying to diagnose an electrical fault via the internet with inexperienced people isn't very quick or easy and can be very frustrating for all concerned (been there many times and have a fine t-shirt collection)

[jimi]

I had a look and there's nothing online about them being different

Easy way would be to pop into Toyota, ask them to check the part numbers.

According to the EPC there's only one part number for a UK N/A MAP sensor covers all years

89420 - 17040 Sensor Assy, Vacuum (for EFI) 1989/12 -