V8S coolant & fuel temp sensors
Discussion
Calling V8 guru's.
I have a heat related problem where engine runs fine when cold but feels like a "limiter" kicks in when hot, with no power and coughs/splutters starting from about 3k revs gradually getting worse and kicks in at to 2k revs and eventually stops running altogether.
Reading on SD1, MG RV8 & Range Rover forums, could be either fuel/coolant temp sensor issue - erroneous cross connection as they're close(ish) and same connectors or failed sensors.
Don't think they're cross connected (in error) so possible faulty sensors.
My questions are
a) do the above symptoms sound right to diagnosis;
b) are these the sensors in the following pics:
Fuel sensor?
Coolant sensor?
Got to get this sorted for EuroTour or I will be at the back in the Alpina generally having the pi$$ ripped out of me.
Any help/suggestions/confirmation welcome - would like to go to the motor factors for new ones to fix/eliminate from the issue.
Are they identical sensors so just buy 2 x the same sensor?
Thanks in advance.
Max
I have a heat related problem where engine runs fine when cold but feels like a "limiter" kicks in when hot, with no power and coughs/splutters starting from about 3k revs gradually getting worse and kicks in at to 2k revs and eventually stops running altogether.
Reading on SD1, MG RV8 & Range Rover forums, could be either fuel/coolant temp sensor issue - erroneous cross connection as they're close(ish) and same connectors or failed sensors.
Don't think they're cross connected (in error) so possible faulty sensors.
My questions are
a) do the above symptoms sound right to diagnosis;
b) are these the sensors in the following pics:
Fuel sensor?
Coolant sensor?
Got to get this sorted for EuroTour or I will be at the back in the Alpina generally having the pi$$ ripped out of me.
Any help/suggestions/confirmation welcome - would like to go to the motor factors for new ones to fix/eliminate from the issue.
Are they identical sensors so just buy 2 x the same sensor?
Thanks in advance.
Max
I think the sensors are different, but are standard LandRover 3.9+ ones, so should be readily available.
if you got no other symptoms then its most likely your problem. maybe worth disconnecting when you have the problem to see if it changes, if you its the sensor if not maybe the wiring. (test when hot and cold)
should go into a default mode when disconnected, so should work just not be perfect should be a lot better than it is currently.
if you got no other symptoms then its most likely your problem. maybe worth disconnecting when you have the problem to see if it changes, if you its the sensor if not maybe the wiring. (test when hot and cold)
should go into a default mode when disconnected, so should work just not be perfect should be a lot better than it is currently.
I have spares of each which will be in my boot on Wednesday if you need to borrow one. Check the stepper motor as well.
I'll also bring my Rovergauge cable. So if you download the software to your laptop and bring that with you we can do a diagnostic check to see if there are any error codes. If you want to do this it would be best to locate the diagnostic plug before we go, It's part of the mess of wires which come out of the ECU.
I'll also bring my Rovergauge cable. So if you download the software to your laptop and bring that with you we can do a diagnostic check to see if there are any error codes. If you want to do this it would be best to locate the diagnostic plug before we go, It's part of the mess of wires which come out of the ECU.
Edited by v8s4me on Sunday 22 May 22:53
Have you tested the resistance values on the sensors?
Worth checking they're giving sensible readings, thermistors usually go open circuit when they quit.
Eta.
Looks like they have the same output values, just checked,
mine's reading 800ohm @ 40°c coolant and 1270 ohm @ 20°C fuel rail. (Parked for an hour)
These values look about right to me although I'd need to check to be certain
Worth checking they're giving sensible readings, thermistors usually go open circuit when they quit.
Eta.
Looks like they have the same output values, just checked,
mine's reading 800ohm @ 40°c coolant and 1270 ohm @ 20°C fuel rail. (Parked for an hour)
These values look about right to me although I'd need to check to be certain
Edited by Alan461 on Sunday 22 May 23:06
v8s4me said:
I have spares of each which will be in my boot on Wednesday if you need to borrow one.
Thanks Joe - if I can't get it fixed by Tuesday night, it won't be coming and we'll be in the Alpina - can't risk setting off in this state.But see you weds afternoon/evening in Folkestone/Calais :-)
Yep, they're the fuel & water temp sensors.
From what I understand, failure of these is more likely to lead to poor running (too lean / rich) rather than cutting out all together. Some useful info here:
http://www.actproducts.co.uk/2011/lucas-14cux-fuel...
Another possibility is the ignition amplifier on the side of the dizzy... worth checking to see if you still have a strong spark when hot.
If you do make it in the S I'll have RoverGauge with me so can hook it up & give it a good going over.
From what I understand, failure of these is more likely to lead to poor running (too lean / rich) rather than cutting out all together. Some useful info here:
http://www.actproducts.co.uk/2011/lucas-14cux-fuel...
Another possibility is the ignition amplifier on the side of the dizzy... worth checking to see if you still have a strong spark when hot.
If you do make it in the S I'll have RoverGauge with me so can hook it up & give it a good going over.
PompeyTim said:
Yep, they're the fuel & water temp sensors.
From what I understand, failure of these is more likely to lead to poor running (too lean / rich) rather than cutting out all together. Some useful info here:
http://www.actproducts.co.uk/2011/lucas-14cux-fuel...
Another possibility is the ignition amplifier on the side of the dizzy... worth checking to see if you still have a strong spark when hot.
If you do make it in the S I'll have RoverGauge with me so can hook it up & give it a good going over.
Cheers Tim - swapped that today along with new coil, dizzy cap & rotor arm but symptoms persist. Probably heading to a V8 specialist first thing in the morning. Luckily I'm off now so have 2 days to fix otherwise I won't be in it foe EuroTour - fiesta or Alpina will be used (oh the ridicule I'll get on tour)From what I understand, failure of these is more likely to lead to poor running (too lean / rich) rather than cutting out all together. Some useful info here:
http://www.actproducts.co.uk/2011/lucas-14cux-fuel...
Another possibility is the ignition amplifier on the side of the dizzy... worth checking to see if you still have a strong spark when hot.
If you do make it in the S I'll have RoverGauge with me so can hook it up & give it a good going over.
tel595 said:
Any chance of a faulty ecu plug/socket connection.?
Very possibly but all looked (visually) ok but beyond me. V8 specialist in the morning me thinks now - found one close by (couple of miles) 2 days off work helpsAnd re the first half of your post - may well be the chase vehicle
Don't replace things like that speculatively because you risk introducing more problems and confusion based on what you guess/assume might be the problem. There are umpteen different potential causes for symptoms like this and just because somebody fixed their symptoms by replacing X doesn't mean that's your problem.
Since most of the components involved are inexpensive you will often find it works out cheaper to pay an expert to fix the problem than fix yourself by trial and error.
If you're keen on DIY and want to diagnose the problem yourself then you just need to understand how the fuel and ignition systems work and be willing to spend time tracking the problem down methodically. You can test the fuel and coolant temp sensors at the ECU plug using a resistance meter. A passive strobe light in series with an HT lead is an invaluable aid to test for ignition related problems. A 12V LED / NOID test lamp across an injector is a great help to diagnose ECU and sensor related problems. A fuel pressure gauge is also very useful to discover whether you have any electrical / mechanical problems on the fuel supply side. Once you know what sort of problem you are chasing it is usually a simple matter of elimination. Diagnosis by substitution is almost never the best way.
Since most of the components involved are inexpensive you will often find it works out cheaper to pay an expert to fix the problem than fix yourself by trial and error.
If you're keen on DIY and want to diagnose the problem yourself then you just need to understand how the fuel and ignition systems work and be willing to spend time tracking the problem down methodically. You can test the fuel and coolant temp sensors at the ECU plug using a resistance meter. A passive strobe light in series with an HT lead is an invaluable aid to test for ignition related problems. A 12V LED / NOID test lamp across an injector is a great help to diagnose ECU and sensor related problems. A fuel pressure gauge is also very useful to discover whether you have any electrical / mechanical problems on the fuel supply side. Once you know what sort of problem you are chasing it is usually a simple matter of elimination. Diagnosis by substitution is almost never the best way.
I had a similar problem on my Tasmin 350i (Rover V8). I replaced all sorts of things at considerable expense to no avail only to eventually find that it was the actual ECU playing up.
To cut a long story short, there was a dry joint or crack somewhere in the solder and it required a 're-flow' - carfully running around the two back-to-back PCB's inside the ECU tin with a pointy-tipped soldering iron and a steady but sparse supply of new solder. Naturally, I was sceptical and very nervous about doing it, so Adam Quantrill (Wedge Guru) showed me how to do one side at the annual BBWF at Stratford as a demo piece in the show. I did the other side later the same day at home.
BINGO!
To cut a long story short, there was a dry joint or crack somewhere in the solder and it required a 're-flow' - carfully running around the two back-to-back PCB's inside the ECU tin with a pointy-tipped soldering iron and a steady but sparse supply of new solder. Naturally, I was sceptical and very nervous about doing it, so Adam Quantrill (Wedge Guru) showed me how to do one side at the annual BBWF at Stratford as a demo piece in the show. I did the other side later the same day at home.
BINGO!
zombeh said:
It could well be an ignition problem rather than fuel. A faulty coil could easily do that sort of thing.
I see you changed the coil Max, but was it before you had the problems or after?I bought a new coil from a respected supplier and fitted it so I could put the old one in the boot as a spare. Guess what failed in the heat of the Ardennes? Popped the old Bosch coil back on and never been a problem since.
Is this flapper injection or 14CUX hotwire? RoverGauge will only work on hotwire for diagnosis. Dead simple test on the thermistors- they should read the same value on a cold engine. 
If this is hot wire system a failing AFM will make the car run very rich, so its worth doing a plug check and see if the plugs are heavily sooted.
If this is hot wire system a failing AFM will make the car run very rich, so its worth doing a plug check and see if the plugs are heavily sooted.All resolved now thanks to RT Racing - turned out to be a failing fuel pump (despite being new). Seemed to be full of crap already so replaced, along with new fuel pipe that included a pre-filter.
Appears the consistent heat aspect was a red herring - to be fair it was running horribly this morning from cold so probably fuel pump was deteriorating rapidly.
Thanks for the help and suggests.
Max
Appears the consistent heat aspect was a red herring - to be fair it was running horribly this morning from cold so probably fuel pump was deteriorating rapidly.
Thanks for the help and suggests.
Max
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