Breakdown last night - fuel or cam timing?

[jon_st205]

You need to look at the basics like spark & fuel - spark plug against the block while someone cranks it for you; link out FP & B in the diagnostics to force the fuel pump to run - can pull the fuel return line off and empty into a jug if you want to see if fuel flow is a problem.

If I was a better man I'd say spark - either ignition component degraded or an earth strap disintegrated.

Jon

[1000 PR]

Thanks. I'll try both and report but if still stuck I'll be seeing Tiamat next week!

[1000 PR]

Well finally changed the fuel filter at the weekend but still no better although there was some dirty looking fuel which came out at the end.
Disconnected fuel line at inlet manifold and petrol coming through ok.
Checked for spark and all 4 plugs firing nicely.
On first attempt the car starts and seems to run ok for 5-10 seconds but then revs die off and car stops. On 2nd attempt the engine re-starts but only keeps going for a bit if I pump the throttle unitl it dies. On 3rd attempt the engine struggles to start and starts popping and mis-firing.

Any ideas what next?

Do ECU's ever break down?

[LimeyMk1]

ECU's don't often break on the Mk1 but I've seen one knackered TPS. If you can get the part number off the back of it someone may well have a spare you can try.

Otherwise I'd be looking to the vacuum hoses next.

[1000 PR]

I've checked the TPS and all readings were within the correct range.

Will a ECU off a 'D' reg Mk1 work on an 1985 'B' reg Mk1 ?

[LimeyMk1]

I've checked the TPS and all readings were within the correct range.

Will a ECU off a 'D' reg Mk1 work on an 1985 'B' reg Mk1 ?

Fairy do's, I'd still be tempted to try a different one seeing as the fault codes are pointing that way.

D reg is in the 'transition' area for ECU's so it may not be a perfect match. Again the part number should be on a sticker on the unit itself for comparing. Seeing as we were working on a car with a small port head & inlet controlled by a Mk1a ECU on Sunday that worked perfectly well I'd imagine you wouldn't have a problem swapping them.

[Jaspa]

I think tiamat has a mk1a ecu. Maybe drop him a pm

Stuart

[1000 PR]

The spare ECU was coincidentally exactly the same part code as that in my '85 probably because (long story sorry) I bought it a couple of years back off ebay to replace the one I had taken off to try and fix another Mk1 but left it in the car when it went to the garage and didn't notice at the time that it came back without it!

Anyway swapping the ECU and the circuit opening relay made no difference, nor did turning the mixture screw fully either way, and all the vacuum lines are in good condition, so.

I think the next step must be off with the cambelt covers!

[Boddney]

Is there not a fuel pre filter down the bottom of the engine bay at the back below the battery ish or is that somthing else???

I mean this little baby...

[tottacrolla]

From your description above it sounds like it might just be running off of the cold start injector. The cold start injector only works when cranking the engine over, sounds like there is just enough fuel to start it up and run it for a few seconds.
It could be the fuel pressure regulator in the fuel rail or the injectors.
You can test the regulator by either squeezing the return line with a brake pipe clamp or fitting a blanked off pipe that goes on the return line outlet.

[1000 PR]

Boddney - Isn't that part something to do with the fuel tank? ie. the part that's responsible for the fuel smell when it stops working, unless and until you re-route the return pipe.

Tottacrolla - Thanks. This was one of my thoughts. Something to check for tonight if it's not too cold, wet and dark!

[tottacrolla]

The fuel pressure regulator ensures enough pressure is held in the fuel rail to fire the injectors. If the regulator goes bad it lets too much fuel return to the tank and the injectors have little or no pressure to work.
The regulator lives on the end of the fuel rail by cylinder 4
You could also try disconnecting the cold start injector wire at the plenum to see if the engine will actually run at all.

[1000 PR]

Thanks - so basically by blocking off the return line, the engine will still run? and it's there simply to prevent overfuelling?

[tottacrolla]

Thanks - so basically by blocking off the return line, the engine will still run? and it's there simply to prevent overfuelling?

yes, ok as a test.

[1000 PR]

Well it's not starting at all now with or without the return line clamped off so it's back to square one when I get a chance and it's not so wet and damp. Unfortunately the car is still on the gravel driveway where the recovery truck driver and I pushed it to.

The odd thing is after trying to start it there is a deep humming noise coming from the engine for a few seconds but where from I haven't identified yet.

[Tiamat]

Have you checked ALL the vaccum hoses as Chris (LimeyMK1) suggested?

There are a couple under the car too, which people usually forget.

[1000 PR]

I thought I had but not under the car. Where eactlyish?

[Tiamat]

I will look for a picture, they are normally covered in alot of crud and it can be hard to see them.

[1000 PR]

Had a good look under the car last night and there are 3 vacuum hoses around the airflow sensor / actuator? but all these were in good order. The airflow sensor/actuator? itself though is very rusty looking so could this be the problem?

Checked again for a good spark when holding no. 1 spark plug against the head so no problem there.

Could the fuel injectors have failed and is there a way to test them?

[1000 PR]

Found these on ebay: a good buy?

http://cgi.ebay.co.uk/TOYOTA-MR2-MK1-RE ... 58812e4351
or the whole shooting match from Paul ... 56407ffcb1