V6 Massive interference from distributor

[timhum]

The original distributor in my Bongo gave up the ghost on the first damp morning about a month ago. As a non starter I got the AA to come round. The distributor was worn out but with a clean, the engine started and ran until a new distributor and rotor arm was sourced and fitted. The coil lead was burned onto the cap so had to be replaced also.
The LPG conversion, just out of guarantee, behaved strangely from the AA came around but I thought I would be OK once the new cap was on.
Not so! Good running on petrol but LPG was not functioning at all.
Gave up quickly and took it to a good LPG place to sort out. They reported that the ECU was burned out and needed replacing. I opted for a new and different model of LPG control, with guarantee.
When they started the engine for the first time, they could not get the LPG to work and found the new ECU was burned out. The problem was "massive interference" from the distributor cap. It also messed up the computer which was coupled to the ECU at the time. They are shielding the leads and distributor cap which is having the desired effect but it is not ideal to say the least!
The distributor cap and rotor arm is a new blueprint one, likewise the coil lead.
Does this scenario sound familiar to anyone, the LPG place is good and they certainly know their stuff. I have suggested getting in the Mazda parts, none in the country when I needed them, surely this interference, which only extends to within the engine compartment, is not being caused by the new parts, or is it?

Sorry about the long post but telling the whole story seems necessary.

Any comments gladly received as always.

Tim

[haydn callow]

Think this is one for Paul & LPG Imports >>

I had "rough" running when I first got my V6 on LPG only.....thanks to Paul and others it was eventually fixed with new leads/cap/rota arm....the rota arm was the main culprit.
It seems that the ignition system has to be 100% to work properly on LPG where as when on petrol it is more forgiving...
I cannot comment on the ECU problems...Perhaps Paul will be along....Mine now runs fine

[lpgimports]

Hi

Was it the distributor or distributor cap that the AA cleaned? very rare for anything other than the centre contact point and tip on the rotor arm to need more than a clean and replace is worn, the cap if the pickup point are worn away/eroded then replace a clean will sometimes help but if eroded then your not likely to get a healthy enough spark at the plug for LPG which requires a strong spark to ignite due to differing properties than unleaded. I imagine they gave everything a blast with a water dispersant as well.

The AA would have cleaned all contact patches and terminals and probably unplugged leads and gave a squirt of water dispersant.

The original LPG ECU should be under a 2 year warranty if from a reputable installer/supply company but you have moved on from there now anyhow. What make was it by the way?

Parts replaced to this point

Rotor (blueprint)
Cap (blueprint)
Distributor??? Source?
Coil/King Lead ?? source?

It doesn't say coil/king lead has been replaced has it? if not I would recommend that it is if it was fried onto the cap.

OK the second company are having it sounds huge interference from the HF side of the ignition system, this should not occur any HF should go straight down the lead to the plug and to earth via the plug inside the combustion chamber. HF releasing into the engine bay points at.

Bad earth for the engine? has this been removed or damaged? check and fit a good earth strap from the bellhousing to the chassis.

HF tracking to earth through old or bad leads, replace the king lead as a matter of course it could be this was damaged either by AA or subsequent replacement of cap.

Plug leads, have you access to a meter with resistance, if so remove each in turn and measure resistance, one may be breaking down.

Where is everything installed on the LPG side, especially the LPG ECU, it should be mounted away from possible HF sources but should deal with reasonable levels by being encased in metal.

The LPG systems wiring could be somehow coming into contact with a breaking down spark plug lead and directly tracking into the LPG ECU.

Did the second LPG company replace the LPG wiring or just another brand of ECU?

Other than that hard to comment more without seeing pictures.


Paul

[apole]

Only think that springs to my tiny mind is the non genuine parts fitted to date, are you sure they are correct/up to the job?

Had issues with other non genuine parts, if the system ran on lpg before all this kicked off then you have to look at the bits you just fitted.

Good luck and keep us posted.

Andy

[timhum]

Hi

Was it the distributor or distributor cap that the AA cleaned? very rare for anything other than the centre contact point and tip on the rotor arm to need more than a clean and replace is worn, the cap if the pickup point are worn away/eroded then replace a clean will sometimes help but if eroded then your not likely to get a healthy enough spark at the plug for LPG which requires a strong spark to ignite due to differing properties than unleaded. I imagine they gave everything a blast with a water dispersant as well.

The AA would have cleaned all contact patches and terminals and probably unplugged leads and gave a squirt of water dispersant.

The original LPG ECU should be under a 2 year warranty if from a reputable installer/supply company but you have moved on from there now anyhow. What make was it by the way?

Parts replaced to this point

Rotor (blueprint)
Cap (blueprint)
Distributor??? Source?
Coil/King Lead ?? source?

It doesn't say coil/king lead has been replaced has it? if not I would recommend that it is if it was fried onto the cap.

OK the second company are having it sounds huge interference from the HF side of the ignition system, this should not occur any HF should go straight down the lead to the plug and to earth via the plug inside the combustion chamber. HF releasing into the engine bay points at.

Bad earth for the engine? has this been removed or damaged? check and fit a good earth strap from the bellhousing to the chassis.

HF tracking to earth through old or bad leads, replace the king lead as a matter of course it could be this was damaged either by AA or subsequent replacement of cap.

Plug leads, have you access to a meter with resistance, if so remove each in turn and measure resistance, one may be breaking down.

Where is everything installed on the LPG side, especially the LPG ECU, it should be mounted away from possible HF sources but should deal with reasonable levels by being encased in metal.

The LPG systems wiring could be somehow coming into contact with a breaking down spark plug lead and directly tracking into the LPG ECU.

Did the second LPG company replace the LPG wiring or just another brand of ECU?

Other than that hard to comment more without seeing pictures.


Paul

Hi Paul and thank you for the time you have devoted to your reply.

To answer your queries in order, here goes...

I understood that the AA cleaned the distributor cap, the leads to it were untouched as far as I could tell. The Bongo responded to the clean and ran well for another few weeks before another damp morning stopped it again. The mechanic left a bunch of blue cleaning roll wedged under the engine so I get the impression he was not out to impress.

The LPG ECU was a few months out of warranty so had the option of starting again with a new system and guarantee. The original LPG ECU and system was Landi Renzo which is not well represented now and the new one is Romano.

The distributor cap and rotor arm was from IgnitionCarParts.co.uk half the price of the Mazda badged and in stock which is why I ended up with them. The distributor was not changed and the coil lead ( I bought a full set but only changed the coil lead) was probably from the same source via a Bongo dealer.

The interference wiped the memory of the calibrating computer and can be picked up on the trailing leads of a multimeter without any contact with live terminals.

The coil lead was changed by me and I will change all the spark plug leads since they are available. I will check for the earth strap in daylight tomorrow. The new ECU has been mounted as far as possible away from the distributor and the control wires to the injectors and other wires have been wrapped up in aluminium foil since the interference was getting into those as well. The wiring has been changed due to the new location of the ECU and the different brand of injector.

I am concerned about what will happen when the aluminium foil becomes oxidised and brittle with age and vibration so the cause of the HT leakage needs to be addressed and I will have a look at this as a matter of urgency. I will try to add a picture when I send an update.

Thank you again for your response,

Tim

[timhum]

Only think that springs to my tiny mind is the non genuine parts fitted to date, are you sure they are correct/up to the job?

Had issues with other non genuine parts, if the system ran on lpg before all this kicked off then you have to look at the bits you just fitted.

Good luck and keep us posted.

Andy

I agree Andy, though I will make sure I have a few other checks carried out before going on another buying frenzy though.

[lpgimports]

Hi

Romano great system we install those and have on a number of bongo's with no issues.

Try to obtain a loan set of cap rotor and leads even a old set swapped off a members bongo who has serviced and kept them.

Paul

[haydn callow]

When I was having ignition system problems I bought a set (£65) of aftermarket HT leads...they were worse than useless........

[timhum]

When I was having ignition system problems I bought a set (£65) of aftermarket HT leads...they were worse than useless........

In what way "worse than useless"? I wonder if the choke lead which is an aftermarket jobbie, is to blame.

I would be very interested in knowing more on this.

Cheers,

Tim

[haydn callow]

I goy a full set of 7 x after market leads......the insulation was breaking down when on LPG and shorting to the dizzy cap....they were o.k.when running on petrol

[dandywarhol]

Ignition leads are either copper cored and UNINSULATED and used suppressed plug caps OR the whole lead is screened by using a high resistance carbon lead and UNSUPPRESSED caps - get it mixed up and you'll get massive interference/misfire problems