ECU to fuel pump relay earth fault - diagnosis at last! - Page 2

SD1too · 20th December 2022, 10:13

Quote:

Originally Posted by mkilpatr

"But it won't be the sensor, as no new errors appeared on the ECU" said my local garage ...

That's actually fair comment as there is a fault code relating to crankshaft position sensor circuit fault.

Quote:

Originally Posted by mkilpatr

I should have listened when someone suggested the camshaft/crankshaft sensors as a possibility two weeks ago and just renewed the damned things myself to see what happened. What would that have wasted? £100?

You can certainly do that if you wish to risk wasting £100 Michael. Bear in mind that a faulty camshaft position sensor will also produce a fault code (which you don't have) and will not cause a running engine to stop which you have reported happens with your car.

You've said that the auto electrician identified an intermittent connection between the fuel pump relay and the ECM using an oscilloscope. Why is this not being pursued?

Simon

Ducati750cc · 20th December 2022, 10:27

Quote:

Originally Posted by mkilpatr

"But it won't be the sensor, as no new errors appeared on the ECU" said my local garage and "if it's internittent, it won't be a sensor dying from heatsoak so I'm going on a wild goose chase" says the auto electrician.

I think I'm surrounded by buffoons who just refuse to eliminate a simple problem and easily replace a sensor or two and instead make up all sorts of nonsense. And people on the online forums repeatedly going on about the orange clip despite me having said I inspected the fuel filter and it's rock solid.

Its quite ridiculous. I should have listened when someone suggested the camshaft/crankshaft sensors as a possibility two weeks ago and just renewed the damned things myself to see what happened. What would that have wasted? £100?

Michael

The above in red:

What was used as a diagnostic tool ? T4, Toaf, or a generic code reader ?

Also the comments by the garage and electrician wouldn't fill me with confidence, especially the sensor quote.

Perhaps you would have been better going to someone who deals with and is knowledgeable in 75's, or to a good fuel injection specialist !

It doesn't matter how much equipment folk have when doing diagnostics, three things are paramount 1) Full knowledge of how to use a the equipment correctly 2) How to interprate the read outs, 3) The knowledge of how components work and interact with other components and importantly that a code doesn't always mean that component is faulty.

The above in blue:

Folk on forums in general aren't buffoons, quite the reverse, they are not hands on with the car, so all they can do is deal from a distance with what the OP tells them and suggest what solution worked for them with a similar fault.

It may not cure the OP's fault, but it will be a item to be ticked off and on to the next possible item and suggestion along the diagnostic path, if only you had followed this path and took notice of the club member 2+ weeks ago ?

However you say....... " I'm surrounded by buffoons who just refuse to eliminate a simple problem and easily replace a sensor or two ".....

Then you go on to say......."Its quite ridiculous. I should have listened when someone suggested the camshaft/crankshaft sensors as a possibility two weeks ago and just renewed the damned things myself to see what happened "...............

Exactly, I rest my case!

A couple of things in closing:

A) On many threads there will be repeats of suggestions for a few reasons, maybe someone hasn't noticed that it's been mentioned before, or maybe the OP hasn't come back to say that the suggestion has or hasn't worked, either way, no need to get upset about the repeats from good meaning folk, read the first one then skip the repeats.

B) All the folk who do contribute with suggestions do it with good intentions, sometimes, for many reasons, the suggestion may be good, bad, or irrelevant, the bad or irrelevant are not malicious, but in the main are caused by the OP giving an incorrect description of the problem or going about suggestions in the wrong way.

By the way, have you fitted the crank sensor and does it now work OK

mkilpatr · 20th December 2022, 11:04

The buffoon was referring to my local garage in particular. I've since heard that when he left his previous place (now another garage and also very local) he left a whole load of oil barrels and other contamination just lying round the back. Not impressed by that report.

It was someone on one of these forums (possibly not this one, I can't recall) who first suggested the crankshaft sensor. That's who I should have listened to. The time wasted on this mess so far is much greater a cost than a speculative change of the sensor, with or without also changing a second sensor pointlessly.

Michael

mkilpatr · 20th December 2022, 11:45

Quote:

Originally Posted by Ducati750cc

The above in red:

What was used as a diagnostic tool ? T4, Toaf, or a generic code reader ?

Also the comments by the garage and electrician wouldn't fill me with confidence, especially the sensor quote.

I'm glad someone agrees with that. Someone on a forum (possibly here, possibly Facebook a while back) suggested that you don't always get error codes. Yes, that sounds odd - after all, what is all that complicated stuff for if they don't always appear when something is wrong? But I explained earlier in this saga that I had used TOAF and seen some error codes but they had not reappeared after I cleared them. If someone says "component [x] could have failed even if there are no errors" then it's likely that people over the years have encountered this and it's probably true. It also appears to be the case that you can get phantom error codes which are related to components the car doesn't have but which the ECU, having a generic core common to lots of cars. I think the error P1520 may be one of these - and I couldn't clear it using TOAF.

Quote:

Originally Posted by Ducati750cc

By the way, have you fitted the crank sensor and does it now work OK

No, the car is still at the auto electrician. I Whatsapped him to say that various people have referred to the crankshaft sensor and that the ECU cuts the earth, not the positive, to the fuel pump relay so I was a little confused by what he was trying to tell me on Friday about a break in the earth connection between the relay and ECU. *If* there is a fault such as the crankshaft sensor providing no signal at all suddenly, then of course the ECU jolly well will cut the earth to the relay, won't it?

Michael

Ducati750cc · 20th December 2022, 13:09

*If* there is a fault such as the crankshaft sensor providing no signal at all suddenly, then of course the ECU jolly well will cut the earth to the relay, won't it?

Yes, the ECU runs the pump at key on for X seconds to prime the system, then it waits for a signal from the crank sensor to tell it that the engine is turning, no signal for whatever reason = engine not turning = no need to run the pump = no start.

Ref PID's ( error codes) there are many components that don't generate error codes, and there are error codes for say X component, where the component itself isn't faulty but another component affects it.

This is where a good grasp of knowing how systems work and more importantly, how various components interact, without understand this we get the " It wont run but there are no error codes so it should run. " ! or " Well it shows code Y, we've replaced the component and it still won't run " !

Sadly there are many cases of the above where rather than working through it and thinking what else could cause the problem, the parts cannon comes out and several components get changed at great cost and if lucky it runs, but the garage can't say what the exact fault was, ( it could have been a poor connection that got cleaned by replacing a component with a new one, the old one being OK ) or it still won't start and it gets trundled off to someone who actually knows their job !

Ref..........if it's internittent, it won't be a sensor dying from heatsoak..........the sparky is wrong, there are many components that fail when hot, but are OK when cold, coils, injectors, crank/cam sensors and so on, likewise, but rarely, a connector.

If the fault can easily repeated consistently, say if it ticks over whilst hot for 10 mins, stops and will re-start 40 mins later when cool, then depending on the type of sensor the resistance can be checked when cod and again when it fails hot, another way if the component is easy to remove, is to run till it stops hot, whip it out and stick it in a freezer for 10 mins or so, freezer spray is also handy.

Let us know how you go on.

mkilpatr · 20th December 2022, 14:20

Aha! The auto electrician has found water damage to the ECU connector! Now checking the ECU...

It was probably the only sensible answer apart from a crankshaft sensor. As for whether sensors fail intermittently, this also depends on their wiring too, not just the sensor itself. I'm very familiar with intermittent failure of the speedometer transducers on the SD1 - the wiring insulation goes stiff with the gearbox heat and fractures where it exits the transducer, leaving the cable liable to water ingress as well as fraying cables. I would expect better cable design of a late 1990s car, though, especially at the other end of the cable at the ECU.

I wonder if this was a result of autumn storms after I got the car?

I suspect this tells me that my local garage, who insisted the pump was dead and fitted a new one, which I've claimed on fuel the warranty, was completely wrong. He probably saw power to the pump but didn't check the earth, which is what the ECU switches. Then it worked for him, but stalled when I tried to drive it away. What a farce. Good job I don't need this car over Christmas.

Mike Noc · 20th December 2022, 19:00

Quote:

Originally Posted by mkilpatr

No, the car is still at the auto electrician. I Whatsapped him to say that various people have referred to the crankshaft sensor and that the ECU cuts the earth, not the positive, to the fuel pump relay so I was a little confused by what he was trying to tell me on Friday about a break in the earth connection between the relay and ECU. *If* there is a fault such as the crankshaft sensor providing no signal at all suddenly, then of course the ECU jolly well will cut the earth to the relay, won't it?

Michael

Your electrician could well be correct - a break in the earth connection between the relay and ECM. The ECM switches the relay to earth, and if you have a break/bad connection between the two then that could be the problem. Not an unknown fault on the diesels - had something similar myself.

Arctic · 21st December 2022, 00:57

Quote:

Originally Posted by mkilpatr

Aha! The auto electrician has found water damage to the ECU connector! Now checking the ECU..

.

It was probably the only sensible answer apart from a crankshaft sensor. As for whether sensors fail intermittently, this also depends on their wiring too, not just the sensor itself. I'm very familiar with intermittent failure of the speedometer transducers on the SD1 - the wiring insulation goes stiff with the gearbox heat and fractures where it exits the transducer, leaving the cable liable to water ingress as well as fraying cables. I would expect better cable design of a late 1990s car, though, especially at the other end of the cable at the ECU.

I wonder if this was a result of autumn storms after I got the car?

I suspect this tells me that my local garage, who insisted the pump was dead and fitted a new one, which I've claimed on fuel the warranty, was completely wrong. He probably saw power to the pump but didn't check the earth, which is what the ECU switches. Then it worked for him, but stalled when I tried to drive it away. What a farce. Good job I don't need this car over Christmas.

Unusual for a 1.8 to have water damage to the ECU and or it's wiring plugs, but i suppose there is always a first time.

Mike Noc · 21st December 2022, 08:06

Quote:

Originally Posted by mkilpatr

I suspect this tells me that my local garage, who insisted the pump was dead and fitted a new one, which I've claimed on fuel the warranty, was completely wrong. He probably saw power to the pump but didn't check the earth, which is what the ECU switches. Then it worked for him, but stalled when I tried to drive it away. What a farce. Good job I don't need this car over Christmas.

He wouldn't have seen power to the pump if there was an earth fault between the relay and the ECM. It is the relay that sends power to the pump when it is energised.

Niccage · 9th May 2024, 09:39

Hi guys, I know this post is more than 12 months old but it’d be cool if you could kindly advise what the outcome was. Was it finally fixed and if so, did you send the ECU away for testing and repair? Or did you end up adding an additional earth to any wire between ECU & main relay? Greetings from Australia, long story short, I have the same 1.8L engine in my 2000 Land Rover Freelander with the same Mems 1.9 ECU and am having the same crank only but nil start issues.

20th December 2022, 13:09	#15
Ducati750cc Loves to post Rover75 tourer Join Date: Jun 2018 Location: Ashton Posts: 431 Thanks: 121 Thanked 206 Times in 145 Posts	If there is a fault such as the crankshaft sensor providing no signal at all suddenly, then of course the ECU jolly well will cut the earth to the relay, won't it? Yes, the ECU runs the pump at key on for X seconds to prime the system, then it waits for a signal from the crank sensor to tell it that the engine is turning, no signal for whatever reason = engine not turning = no need to run the pump = no start. Ref PID's ( error codes) there are many components that don't generate error codes, and there are error codes for say X component, where the component itself isn't faulty but another component affects it. This is where a good grasp of knowing how systems work and more importantly, how various components interact, without understand this we get the " It wont run but there are no error codes so it should run. " ! or " Well it shows code Y, we've replaced the component and it still won't run " ! Sadly there are many cases of the above where rather than working through it and thinking what else could cause the problem, the parts cannon comes out and several components get changed at great cost and if lucky it runs, but the garage can't say what the exact fault was, ( it could have been a poor connection that got cleaned by replacing a component with a new one, the old one being OK ) or it still won't start and it gets trundled off to someone who actually knows their job ! Ref..........if it's internittent, it won't be a sensor dying from heatsoak..........the sparky is wrong, there are many components that fail when hot, but are OK when cold, coils, injectors, crank/cam sensors and so on, likewise, but rarely, a connector. If the fault can easily repeated consistently, say if it ticks over whilst hot for 10 mins, stops and will re-start 40 mins later when cool, then depending on the type of sensor the resistance can be checked when cod and again when it fails hot, another way if the component is easy to remove, is to run till it stops hot, whip it out and stick it in a freezer for 10 mins or so, freezer spray is also handy. Let us know how you go on. __________________ Common sense isn't a gift, it's a punishment because you have to deal with everyone who doesn't have it.

9th May 2024, 09:39	#20
Niccage Newbie 1.8 Land Rover Freelander & 3.2 FL2 Join Date: May 2024 Location: Sydney Posts: 1 Thanks: 0 Thanked 0 Times in 0 Posts	Cranks but nil start. Hi guys, I know this post is more than 12 months old but it’d be cool if you could kindly advise what the outcome was. Was it finally fixed and if so, did you send the ECU away for testing and repair? Or did you end up adding an additional earth to any wire between ECU & main relay? Greetings from Australia, long story short, I have the same 1.8L engine in my 2000 Land Rover Freelander with the same Mems 1.9 ECU and am having the same crank only but nil start issues.

20th December 2022, 11:04	#13
mkilpatr Regular poster Rover 75 Saloon Join Date: Sep 2022 Location: Cambridge Posts: 42 Thanks: 1 Thanked 0 Times in 0 Posts	The buffoon was referring to my local garage in particular. I've since heard that when he left his previous place (now another garage and also very local) he left a whole load of oil barrels and other contamination just lying round the back. Not impressed by that report. It was someone on one of these forums (possibly not this one, I can't recall) who first suggested the crankshaft sensor. That's who I should have listened to. The time wasted on this mess so far is much greater a cost than a speculative change of the sensor, with or without also changing a second sensor pointlessly. Michael

20th December 2022, 14:20	#16
mkilpatr Regular poster Rover 75 Saloon Join Date: Sep 2022 Location: Cambridge Posts: 42 Thanks: 1 Thanked 0 Times in 0 Posts	Aha! The auto electrician has found water damage to the ECU connector! Now checking the ECU... It was probably the only sensible answer apart from a crankshaft sensor. As for whether sensors fail intermittently, this also depends on their wiring too, not just the sensor itself. I'm very familiar with intermittent failure of the speedometer transducers on the SD1 - the wiring insulation goes stiff with the gearbox heat and fractures where it exits the transducer, leaving the cable liable to water ingress as well as fraying cables. I would expect better cable design of a late 1990s car, though, especially at the other end of the cable at the ECU. I wonder if this was a result of autumn storms after I got the car? I suspect this tells me that my local garage, who insisted the pump was dead and fitted a new one, which I've claimed on fuel the warranty, was completely wrong. He probably saw power to the pump but didn't check the earth, which is what the ECU switches. Then it worked for him, but stalled when I tried to drive it away. What a farce. Good job I don't need this car over Christmas.