WANTED: Vitara throttle position sensor

[StuartL]

I believe my TPS is faulty as it's returning 0.01 ohms to infinite resistance (measured on a 200-20M scale digital ohm meter) in about 0.5 degrees of movement.

Does anyone have a TPS kicking around?  It's from an injection Vitara and seems to be part of the same loom as the injector itself so I may need both.

TIA,
Stuart

[Evilgoat]

Will keep my eyes open. I seem to recall seeing it on the front seet of the vitara I was grubbing in for a sun visor on sun. If I go back I'll grab it for ya.

I still havent got my list of bits yet. Really need to see a CFi manifold :(

[StuartL]

If the CFi manifold you want to see is the same as the SPi/TBi manifold I have (which I think we previously determined it was) then you're very welcome to either have photos as required or, perhaps more usefully, just come round with whatever you need to look at and photograph mine.

[StuartL]

Hmm, I've just reread the Haynes.  It's a bit unclear whether the TPS should give a proportional reading or a "digital" one...

[Evilgoat]

Hmm, I've just reread the Haynes.  It's a bit unclear whether the TPS should give a proportional reading or a "digital" one...

Let me drag the bentley manual out and look.  digital would seem a bit posh for the vit :) As for the maifold, its a cas of working out if carb/injection are the same.

I actually found a pic of a cfi I rebuilt so I should be ok, problen is that its nice and clean in the pic without years of baked on crud :)

[Evilgoat]

Ok you SHOULD have 6 pins with the following colour wires attached (like these ever match)
Grey + yellow stripe is one end of the track
Grey + red is the tother

Should be a constant resistance beween these two

Grey is the wiper and should vary between the two wires above
Blue is defined here as not used/ISV valve (Idle Stabiliser)
Green + black  is defined here as Not/Used /WOT Switch (Wide open throttle)
Remaining wire (blue+red) is the idle switch

[StuartL]

The TPS reads very low (0.1 ohms) at idle (sprung return) and infinite at fully open, which is all the Haynes suggests you check.  However it's not varying the resistance proportionally within that movement and seems to become infinite resistance at about 30 degrees.  Different DVM ohm meter ranges don't seem to make a difference.

I can't see that this behaviour is correct and the injector isn't firing so the TPS seems a prime candidate to replace.  Can you think of any other reasons for the injector not to fire?  There's some voltage at times on the injector wires but it's too brief for my DVM to get a fix on.  I need an oscilloscope!

Edit: I have a carb 8v and an injected 8v literally side by side by my house.  If you want to compare the two you'd be very welcome :)

[Evilgoat]

I can't see that this behaviour is correct and the injector isn't firing so the TPS seems a prime candidate to replace.  Can you think of any other reasons for the injector not to fire?  There's some voltage at times on the injector wires but it's too brief for my DVM to get a fix on.  I need an oscilloscope!

Edit: I have a carb 8v and an injected 8v literally side by side by my house.  If you want to compare the two you'd be very welcome :)

Sounds like you have the idle switch :) Haynes manual isnt great on this tbh I would use the pins above to meter it out. If all else fails I di have a scope sat in the cupbard yet waiting for me to do a refurb which you are welcome to borrow, not sure how well it works though. Add me on your msn

[StuartL]

My TPS has four wires (pink, beige, turquoise and black) that go to four pins on a six pin connector block.  The other two pins go off to the injector and the other side of the block disappears into the loom.

The colours on the other side of the block aren't the same as your book either with most of them being multicoloured...

Will signal hunt and see if I can find a proportional signal somewhere...

[StuartL]

[!Expletive Deleted!].

Found a proportional signal varying between 500 ohms and 1.5k ohms (for my limited test range).  It's not the TPS.  Scratch that idea.

Maybe the injector itself is [!Expletive Deleted!]?

I'd give my left arm for an oscilloscope.

[Evilgoat]

!Expletive Deleted!.

Found a proportional signal varying between 500 ohms and 1.5k ohms (for my limited test range).  It's not the TPS.  Scratch that idea.

Maybe the injector itself is !Expletive Deleted!?

I'd give my left arm for an oscilloscope.

Mine came from a bootsale for £5, just needs the pots cleaning. Works as is, just not much use fo rthe tiny signals I'm using in its current state. More than adequate for car stuff though.

Meter out the injector then make sure you are getting a pulse to it. If you are, check for fuel pressure/flow. Pressure and no reaing over it = injector o/c and dead. other way round and time to look at the fuel pump.

Given what suzukis are like for electrical niggles, you might just need to clean things up.

*drags wiring diagram out*

Injector is driven direct by the ecu so check fuses and control relay. Not sure that a dead sensor would cause no injection.

[StuartL]

There's definitely fuel pressure (see all that petrol all over the engine!) so the oscilloscope I borrowed last night from my Dad (120 mile round trip for a darn oscilloscope!) should give a simple binary diagnosys.  Electrical signals mean broken injector, no signals mean broken or confused ECU.

[Evilgoat]

There's definitely fuel pressure (see all that petrol all over the engine!) so the oscilloscope I borrowed last night from my Dad (120 mile round trip for a darn oscilloscope!) should give a simple binary diagnosys.  Electrical signals mean broken injector, no signals mean broken or confused ECU.

or Nadgered wiring, pick the inector signal up at the ECU if its not at the connector on the throttle body. If you have a stable trace iirc the width of the injector pulse should vary with throttle position and engine speed.

As a thought, have you got a correctly timed spark and tacho?

[StuartL]

Oscilloscope is refusing to work (completely dead, no traces), so that's an awkward conversation with the father yet to happen.

A second attempt at the DVM across the injector terminals shows zero voltage.

That can't be right.

Guy on difflock reckons that the ECU output drive for the injector can go, which would correspond perfectly with the symptoms.  I'm toying with the idea of putting 12v across the injector (if I can figure out the polarity) to see if it works.

If the injector works (which I guess it might) and the oscilloscope remains dead I have to assume that the ECU is dead.  This means either locating another ECU (argh), checking the wiring (bit of a PITA) or just ditching the TBI system and resorting to traditional carb.  That'll mean basically rewiring the whole Vit not to use an ECU...

MMmmm.   Projects...