Kangaroo EFI Rover V8 on Acceleration
Discussion
I have an EFI Rover V8 from the 1980s of the flapper type. It's in a Marcos Mantula and runs fine until I accelerate hard. At this point the car kangaroos quite violently. I thought originally that this was me not keeping my foot steady on the accelerator but I now think that it's an engine problem. The engine is 3.9 and was built ages ago by NCK Racing and so has a sports camshaft etc. Any ideas please?
Thanks John
Thanks John
All my experience is with the hotwire (14CUX) but I suspect your flapper setup may be either 13CU or 14CU. Both of these have a throttle position sensor as well as the mass air flow sensor.
All of these sensors use a resistive track to measure the position/flow and the track can eventually wear out, leading to eratic signals. These problems can often be seen through an osciloscope. In extreme cases they can be see by using a volt meter to monitor the resistance across the sensor as it is moved. I've had problems like this with my 14CUX setup and the symptoms were very similar to what you're describing, sometimes only around cruise conditions but also sometimes under full power - basically, anywhere the sensor gives a duff signal.
All of these sensors use a resistive track to measure the position/flow and the track can eventually wear out, leading to eratic signals. These problems can often be seen through an osciloscope. In extreme cases they can be see by using a volt meter to monitor the resistance across the sensor as it is moved. I've had problems like this with my 14CUX setup and the symptoms were very similar to what you're describing, sometimes only around cruise conditions but also sometimes under full power - basically, anywhere the sensor gives a duff signal.
gog said:
I had almost exactly the same problem, turned out to be the coil breaking down!
I have replaced the ignition leads and coil. Initially the car ran great but as it warmed up the old kangaroo was back again on acceleration. Will need to look at potentiometer and flapper air valve now.
GreenV8S said:
All my experience is with the hotwire (14CUX) but I suspect your flapper setup may be either 13CU or 14CU. Both of these have a throttle position sensor as well as the mass air flow sensor.
All of these sensors use a resistive track to measure the position/flow and the track can eventually wear out, leading to eratic signals. These problems can often be seen through an osciloscope. In extreme cases they can be see by using a volt meter to monitor the resistance across the sensor as it is moved. I've had problems like this with my 14CUX setup and the symptoms were very similar to what you're describing, sometimes only around cruise conditions but also sometimes under full power - basically, anywhere the sensor gives a duff signal.
Hi, I have taken the top of the air flow meter and it seems very clean inside. I looked closely at the track and I cannot see any damage to it.All of these sensors use a resistive track to measure the position/flow and the track can eventually wear out, leading to eratic signals. These problems can often be seen through an osciloscope. In extreme cases they can be see by using a volt meter to monitor the resistance across the sensor as it is moved. I've had problems like this with my 14CUX setup and the symptoms were very similar to what you're describing, sometimes only around cruise conditions but also sometimes under full power - basically, anywhere the sensor gives a duff signal.
So, I have turned my focus and was wondering about the fuel pump. When I last drive the car a few days ago, it initially went fine and then after a few miles started the kangaroo again. I was wondering if the fuel was initially cold in the tank, which warmed up and so maybe the fuel pressure started dropping? Have ordered a new fuel pump and see if that help.
John
JohnR27 said:
Have ordered a new fuel pump and see if that help.
Sometimes the only way to fix problems in the ignition system is by trial and error, but be wary of using the parts cannon as a diagnosis tool. Every time you change something you introduce more risk and uncertainty. It would be possible to monitor the voltage across the pump to rule out an electrical problem, and the pressure at the fuel rail to rule out a pump problem. You can monitor the voltage at the ECU temp sender input to rule out problems causing wrong enrichment.Which distributor do you have?
If it's one of the type with the amplifier bolted to the side of it they can fail due to heat & playing up once warmed up is one of the symptoms.
So much so that LR came up with a kit to remove the amp from the dizzy & mount it on the inner wing.
LR part STC1856.
https://rimmerbros.com/Item--i-STC1856P
or
https://simonbbc.com/search.php?search_query=stc18...
If it's one of the type with the amplifier bolted to the side of it they can fail due to heat & playing up once warmed up is one of the symptoms.
So much so that LR came up with a kit to remove the amp from the dizzy & mount it on the inner wing.
LR part STC1856.
https://rimmerbros.com/Item--i-STC1856P
or
https://simonbbc.com/search.php?search_query=stc18...
GreenV8S said:
JohnR27 said:
Have ordered a new fuel pump and see if that help.
Sometimes the only way to fix problems in the ignition system is by trial and error, but be wary of using the parts cannon as a diagnosis tool. Every time you change something you introduce more risk and uncertainty. It would be possible to monitor the voltage across the pump to rule out an electrical problem, and the pressure at the fuel rail to rule out a pump problem. You can monitor the voltage at the ECU temp sender input to rule out problems causing wrong enrichment.JohnR27 said:
I'm still not sure if its an ignition or a fuel/mixture problem.
Then I would start by trying to establish that.A passive strobe in line with the HT leads will give you a rough visible indication of spark strength. If it's fading when the problem happens, that's a clue.
A NOID lamp across an injector will give you a rough visual indication of injector duration. If this is OK you can rule out a whole host of potential problems relating to the engine management sensors and wiring.
A fuel pressure gauge will tell you whether the fuel supply is sufficient. If it is, you can rule out pump and pump supply problems.
A wideband lambda sensor will tell you whether the engine is heading towards a lean misfire.
The point is that by having a theory and getting evidence to support or refute it, you can track the problem down methodically. The alternative approach will take more time and money.
Some of these techniques need equipment which isn't cheap, but some can be done very cheaply. And the money you spending getting set up, and the skills you acquire, will transfer to every engine you work on subsequently.
GreenV8S said:
Then I would start by trying to establish that.
A passive strobe in line with the HT leads will give you a rough visible indication of spark strength. If it's fading when the problem happens, that's a clue.
A NOID lamp across an injector will give you a rough visual indication of injector duration. If this is OK you can rule out a whole host of potential problems relating to the engine management sensors and wiring.
A fuel pressure gauge will tell you whether the fuel supply is sufficient. If it is, you can rule out pump and pump supply problems.
A wideband lambda sensor will tell you whether the engine is heading towards a lean misfire.
The point is that by having a theory and getting evidence to support or refute it, you can track the problem down methodically. The alternative approach will take more time and money.
Some of these techniques need equipment which isn't cheap, but some can be done very cheaply. And the money you spending getting set up, and the skills you acquire, will transfer to every engine you work on subsequently.
Thanks for the suggestions. I have solved this eventually by replacing the aged original Lucas fuel pump and cleaning the petrol filter prior to the pump. After lack of use over the years, I assume there is some surface rust in the tank. I had removed all the old petrol but clearly not the surface corrosion. John A passive strobe in line with the HT leads will give you a rough visible indication of spark strength. If it's fading when the problem happens, that's a clue.
A NOID lamp across an injector will give you a rough visual indication of injector duration. If this is OK you can rule out a whole host of potential problems relating to the engine management sensors and wiring.
A fuel pressure gauge will tell you whether the fuel supply is sufficient. If it is, you can rule out pump and pump supply problems.
A wideband lambda sensor will tell you whether the engine is heading towards a lean misfire.
The point is that by having a theory and getting evidence to support or refute it, you can track the problem down methodically. The alternative approach will take more time and money.
Some of these techniques need equipment which isn't cheap, but some can be done very cheaply. And the money you spending getting set up, and the skills you acquire, will transfer to every engine you work on subsequently.
AW111 said:
If you have a way to fit a wideband Lambda sensor, even temporarily, it would help with diagnosis.
If it's a fuelling problem, you should see it go lean when it misfires.
If it's lack of spark, it should go rich.
Thanks for the suggestions. I have solved this eventually by replacing the aged original Lucas fuel pump and cleaning the petrol filter prior to the pump. After lack of use over the years, I assume there is some surface rust in the tank. I had removed all the old petrol but clearly not the surface corrosion. John If it's a fuelling problem, you should see it go lean when it misfires.
If it's lack of spark, it should go rich.
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