Recommendation for LUCAS engine ECU overhaul - Chim 400???

Recommendation for LUCAS engine ECU overhaul - Chim 400???

Author
Discussion

kramv8

Original Poster:

26 posts

115 months

Wednesday 6th August 2014
quotequote all
Hi to all fellow Pistonheaders and TVR folk alike!

I have a Chim 400HC suffering from a chronic overfuelling issue on one bank only (r/h bank). It's running the Lucas Hotwire system, as employed by Rangy classics & Disco's of the era, running 3.9EFIs. I'm close to the point of giving up as the following works have already been completed trying to solve the running issue:

- replaced plugs & leads
- replaced dizzy cap
- replaced rotor arm
- replaced AFM (with genuine new item)
- replaced ECU coolant temp sensor
- had all wiring from fuse box to ECU and injectors checked, tested and repaired
- known good injectors fitted - still overfuelling
- lambdas tested - all good

We've reached a stage now where the car will run pretty well from cold and then after 10mins or so, the hydrocarbons go through the roof, unburnt fuel pours out the exhausts and it runs very poorly.

I replaced the ECU with a used item which was sold by a TVR breaker as known good. The last thing me and my mechanic can now think, is that both ECUs have the same fault, as surely this can be the only component capable of sending the command to dump a load of unrequired fuel into one bank only?

Please can any fellow PHers, or TVR owners recommend a spot-on company who can test and repair (if required) my car's ECU.

This is driving me mad, and I've spent a lot of money and workshop time to arrive no further forward!!!

Thanks in advance for any help, or pointers.

cinquecento

553 posts

224 months

Wednesday 6th August 2014
quotequote all
A friend had a similar problem recently.. Turned out it was a single faulty injector pouring petrol into the combustion chamber. Disconnect each injector in turn and see if the problem disappears..also check all the exhausts are the same temp by spraying a fine mist of water and looking for a similar hissing sound in all header pipes

Colin RedGriff

2,526 posts

256 months

Wednesday 6th August 2014
quotequote all
Has it been connected up to any diagnostic equipment like RoverGauge or ECUmate, to see what is happening with the inputs?

I think it would be unusual for two ECUs from different cars to demonstrate the same fault.

Lesliehedley

238 posts

259 months

Wednesday 6th August 2014
quotequote all
My experience is with the flapper system rather than the hotwire system so I could be talking rubbish here. The flapper system has ballast resistors to drive the injectors. If the hotwire system is the same, one of the ballast resistors could be breaking down when it gets hot which could affect one bank of injectors.

rigga

8,727 posts

200 months

Thursday 7th August 2014
quotequote all
As said its extremely doubtful both ecu you have tried have the same fault, not impossible but no, also as previously mentioned have you tried some diagnostic testing or just replacing parts as you go, which as you have found gets expensive and doesn't really get you anywhere.

N7GTX

7,823 posts

142 months

Thursday 7th August 2014
quotequote all
As the fault only occurs on one bank that rules out almost everything you have tried so far. A simple test for the injectors and ECU that costs only around a tenner is this.

Either buy 4 noid lights or much cheaper is to buy 4 capless sidelight bulbs type 501 available at most garages, Halfords etc. Unravel the 2 wires from the base and separate them. Disconnect the injector plugs and insert the wires into the connector simply pushing them in. Start and run the engine for just a few moments and watch the lights. They should pulse on and off. If they stay lit constantly then they are not being earthed by the ECU. If they pulse then you need to see what the injector pulse width is on diagnostic equipment. If the pulse is too large, say 7+ m/secs, then fuelling is based on the coolant temp, airflow and throttle position so the ECU may still be faulty as it is not processing the signals.

I have used these 2 companies for ECU test and repair.

http://www.ecutesting.com/

http://www.bba-reman.com/index.aspx?ShowCountry=tr...

blitzracing

6,387 posts

219 months

Thursday 7th August 2014
quotequote all
You need diagnostics to check the ECU sensors and any fault codes stored to start with- RoverGauge or ECU mate. It will be dead easy to find once you have some sensible data at your finder tips for it as a whole unit. Swapping bits to try and fix it is a bad and expensive method of diagnostics.

Also there have been a couple of cases where the ECU loom has worn through, and caused a short on the injector ground rail on one back- this forces all 4 injectors to stick open....

Edited by blitzracing on Thursday 7th August 17:42

FlipFlopGriff

7,144 posts

246 months

Friday 8th August 2014
quotequote all
I had one bank drop out randomly while driving and it was lethal.
Turned out that the engine earth strap had almost worn through - out of the say 50 strands there were about 4 left.
Not actually sure where its located but as I couldn't see assume its either under the engine or towards the bulkhead and about 18" long.
Worth a check and a cheap fix.
FFG

kramv8

Original Poster:

26 posts

115 months

Friday 8th August 2014
quotequote all
Thanks for all of your feedback and advice.

Re the injectors, we've swapped a full (known good set) from another Chim 400 (which runs perfectly) and my car then runs with the same fault. Therefore, I don't think the issue lies with the injectors. Something is giving them the instruction to pour loads of fuel into one bank.

The earth strap is a good call and I will check that.

The full loom has been checked and tested.

I to believe it's unlikely for two ECUs to have the same fault however, I'm really running out of options!


blitzracing

6,387 posts

219 months

Friday 8th August 2014
quotequote all
Completely the contrary with some decent diags- if the ECU is dumping fuel in there will be a reason- you will see this with a shift of AFM voltage, temperature shift, or low lambda outputs, causing high fuel trim values, and fault codes. You can see shifts in map locations that control the fuel, you can see injector pulse widths. If the ECU sensors etc dont do anything crazy, then its the loom at fault grounding the injectors on one side. If you have a laptop, use RoverGauge, if you dont use ECUmate. No more guesswork.

N7GTX

7,823 posts

142 months

Friday 8th August 2014
quotequote all
kramv8 said:
Thanks for all of your feedback and advice.

Re the injectors, we've swapped a full (known good set) from another Chim 400 (which runs perfectly) and my car then runs with the same fault. Therefore, I don't think the issue lies with the injectors. Something is giving them the instruction to pour loads of fuel into one bank.
So why not take the advice either Blitzracing or I have suggested? My post is not about whether the injectors work - obviously they do from all your swapping - its about whether they are switching on and off. So by doing the light test which doesn't need diagnostic kit, at least you can see if the lights stay on, stay off or flash as they should. Then compare with the good side and you will be nearly there.
If they stay on all the time then they are not being switched off by the ECU or the earth return is broken.
If they switch on and off then you will need diagnostic equipment to see what the injector pulse time is and compare to the good bank.

Steve_D

13,737 posts

257 months

Saturday 9th August 2014
quotequote all
Your next question should be:-

'does anyone living near me have RoverGauge and can come round and test the car?'

Until you, or others, have seen the results you are just wasting time and effort swapping parts.

You don't say which bank is the problem.
If it is offside then I would go and check the injector hidden behind the coil mounting bracket. We have seen the injector wire worn through and shorting to the coil bracket. You will not find this if 'testing the loom' as you would have moved the connector away from the bracket in order to test it.

Steve

blitzracing

6,387 posts

219 months

Saturday 9th August 2014
quotequote all
Just to add- the injectors have a 12 volt supply on them all the time when the ignition is on- and are fired by the ECU by switching them to ground via a transistor in the ECU- so a ground short will do the same and bring all 4 injectors on at the same time. This would be clearly visible with a noid light or test meter when the fault appears. If you want to use a digital test meter across an injector , its likely to give odd results when the engine is running correctly as the DC signal is being switched so the meter cant sample it reliably- but it will show 12 volts the moment you get a short.

BTW, I have RoverGauge kits for sale in the classified ad's for a whole £35 inc postage if you want one.

http://www.pistonheads.com/classifieds/parts-and-p...

Edited by blitzracing on Saturday 9th August 09:54

kramv8

Original Poster:

26 posts

115 months

Saturday 9th August 2014
quotequote all
Thanks again for all your combined help.

I've decided to purchase a Roverguage kit from Blitzracing - crossing fingers and toes that this will provide the info we need and lead us to a solution.


Hoover.

5,988 posts

241 months

Sunday 10th August 2014
quotequote all
I'm no expert, but whilst chasing down issue on my car and talking to mechanics who work regularly on them the way the injectors are wired up if one sticks open this will cause the others to stick open in that bank....

turned out not be the issue on mine, as gone from over fueling to running very lean overnight..... had enough as been chasing this problem for 2 years and considerable expense and frustration and having MBE system fitted (drop of next Sat)

V8 Fettler

7,019 posts

131 months

Sunday 10th August 2014
quotequote all
kramv8 said:
Hi to all fellow Pistonheaders and TVR folk alike!

I have a Chim 400HC suffering from a chronic overfuelling issue on one bank only (r/h bank). It's running the Lucas Hotwire system, as employed by Rangy classics & Disco's of the era, running 3.9EFIs. I'm close to the point of giving up as the following works have already been completed trying to solve the running issue:

- replaced plugs & leads
- replaced dizzy cap
- replaced rotor arm
- replaced AFM (with genuine new item)
- replaced ECU coolant temp sensor
- had all wiring from fuse box to ECU and injectors checked, tested and repaired
- known good injectors fitted - still overfuelling
- lambdas tested - all good

We've reached a stage now where the car will run pretty well from cold and then after 10mins or so, the hydrocarbons go through the roof, unburnt fuel pours out the exhausts and it runs very poorly.

I replaced the ECU with a used item which was sold by a TVR breaker as known good. The last thing me and my mechanic can now think, is that both ECUs have the same fault, as surely this can be the only component capable of sending the command to dump a load of unrequired fuel into one bank only?

Please can any fellow PHers, or TVR owners recommend a spot-on company who can test and repair (if required) my car's ECU.

This is driving me mad, and I've spent a lot of money and workshop time to arrive no further forward!!!

Thanks in advance for any help, or pointers.
You probably have one signal wire back to the ECU from each bank of injectors, check the wire from the erratic bank

Sardonicus

18,928 posts

220 months

Sunday 10th August 2014
quotequote all
Hoover. said:
I'm no expert, but whilst chasing down issue on my car and talking to mechanics who work regularly on them the way the injectors are wired up if one sticks open this will cause the others to stick open in that bank....
Thats absolute garbage the mechanical part of the inj has no physical connection to the electrical side rolleyes meaning the circuit would not no if the inj is open or not and highly unlikely with the Lucas disc style inj IMO thats not a pop at you Hoover wink like mentioned already more than likely a chaffed cable grounding out the inj's on the faulty bank scratchchin

rigga

8,727 posts

200 months

Sunday 10th August 2014
quotequote all
The benefits or not of the 14cux batch firing one side then the next. When the grounding signal goes down it really screws the fuelling up.

Sardonicus

18,928 posts

220 months

Sunday 10th August 2014
quotequote all
rigga said:
The benefits or not of the 14cux batch firing one side then the next. When the grounding signal goes down it really screws the fuelling up.
The grounding duration is the only way the ECU can meter the correct amount of fuel so definitely wink

carsy

3,018 posts

164 months

Sunday 10th August 2014
quotequote all
Good move Hoover. You wont be disappointed.