Cret

Most subarus use cam & crank sensors that are a plug type connection and have no integral cable, except for some of the very early cars which use a cable type one (of which mine is one).

I've currently got an intermittent starting problem that I think is down to one of these sensors (already checked the temp sensor and its ok), but the early type sensors are very few & far between on ebay etc.

I don't want to (can't afford to) spend £200 or so on the offchance that I still have the problem after replacing both sensors, so what I want to know is whether it's purely the cable type that's different (ie the sensor unit itself has the same properties between new/old ones), or if that's not the case?

I have 2 spare cam sensors - one of each type. I swapped out the cable one and the problem has been less frequent since, but still happens. It's always possible it's just coincidence of course.

Anyway, I want to try wiring in the later plug type sensor that I have since that's much newer and stands a better chance of solving the problem, but not sure if it's compatible.

It does have 2 pins whereas the wire has 3 conductors, but that's ok since the third is only a shiled connection.

Does polarity matter on these sensors? I've read that they're basically just magnets but I'm not sure if that's correct or not.

Thanks!

ZEN Performance

If you buy a replacement sensor these days they come as a new style sensor with a loom that has a plug at teh sensor end, so what does that tell you?!

Cret

Do they? Sorry - I didn't know that was the case.

But for some reason anyway I was convinced that they were bought as just the sensor itself, and that the cable leading to it was an integral part of the engine wiring loom that wasn't detachable. I take it that's not the case after all.

In that case then I will try to see if I can mock up some sort of connector to go on the newer sensor plug for now for testing it.
If it seems to solve the problem then I'll have to make that permanent.

I just wanted to make sure there was not an electrical difference between the early & subsequent ones.


Is there any relatively easy way of distinguishing between a faulty cam sensor and faulty crank sensor?
Can't check standard error codes due to using an aftermarket ECU, and I don't have the access to known good sensors to try borrowing/swapping them out.

Cheers

ZEN Performance

What is the problem? What is the ECU?

Many aftermarket ECUs will allow you to work out which sensor is working fine. If it's a motec M48 pro though, try spacing off the cam sensor a little with a thin m6 washer.

Also check the cam timing as an issue there will sometimes show up as a sensor error because the ECU is seeing teeth when it's not expecting to.

Cret

The problem is intermittent starting. Oddly, the car will start first time every time when it's been left, but it can run for 10 seconds or half an hour and potentially if turned off and cranked immediately it may or may not fire. If left for 20 seconds or so it then normally starts ok. So it's re-starts rather than starts, and not necessarily hot ones.

It's a simtek (really like it). I've taken some log files and numbers accumulate in the c/c err columns, when the car cranks but does fire.

One suspect thing already was that the long plugleads I had (due to remote coilpacks) were causing interference with the IAT sensor in the FMIC piping to the throttle body, but having relocated the coils and even temporarily shielded/moved the iat wire I don't think that was the problem. Will be changing back to coilpacks soon though instead of the bosch coils I currently have.

All the digging I'd done pointed at cam/crank/temp sensor for this intermittent start issue, and after swapping the cam sensor it 'seems' to have improved, although the amount I've used the car is limited since then.

I wouldn't have thought these sensors would suffer from varying grades of degradation as such (ie to have one slightly better behaving than another but still faulty), but it seems to be the case and I suppose that's why the issue is intermittent & not permanent. It might just be coincidence of course, and the problem may lie elsewhere.

Also, I don't really think it's the crank sensor at fault since if that had an intermittent fault I'd expect it to cause the engine to cut out when the problem occurs, as well as difficult starting. Hope that makes some sense!

Hopefully in the next couple of nights I'll be able to try wiring up that newer cam sensor to see if that helps.

With regard to the cam timing, do you mean if a cam was a tooth out on the belt? Presume it must be as the standard cam wheels can't have their timing changed I don't think.

Cheers
Jim

Cret

Well, last night I tried to make a hybrid cam sensor using the cable from an old era one, and the plug type newer sensor. Simple enough since they only have two pin connections.

Got it nicely soldered up and heatshrunk etc and swapped it over. Tonight I started the car with the new sensor and it fired up really easily - definitely faster than normal and idled nicely, BUT when I tried to rev the engine it point blank refused and just spluttered.
Odd if the cam sensor is not used other than starting up? As the engine got warmer it seemed slightly as if it was accepting a little more throttle but I might have been imagining it.

Took a log file then swapped back to the old sensor again and sure enough the engine revved up no problem.

Real shame that as I thought I'd hit the nail on the head when she fired up with the hybrid one, but there's obviously more to the different sensors than meets the eye, ie the newer sensors are more than just a different form of connection.

I did test the resistance across the pins between the two types, and the old cable sensors give 1600ohms, whereas the newer plug ones are nearer 2000ohms. That difference in resistance must be the culprit for the running problem above idle rpm, but don't think I can do anything about that. A failed idea it seems.

So back on the earlier cam sensor, and no idea still what is causing the starting issue.

Log file of horrible running linked here:
http://www.uklegacy.com/forums/index...e=post&id=6563

Appreciate any further input on this.