Cutting out after hard acceleration?

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adamskibx
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Cutting out after hard acceleration?

Post by adamskibx » Sun Apr 09, 2006 5:31 pm

Having got an MOT on the BX I am using it as my everyday car. One problem I have is that when I use the engine reasonably hard; ie accelerating up a hill for a period of more than 20 seconds, it will start to splutter and there is nothing I can do to save it except to turn the ignition off then immediately back on again. I did suspect a fueling problem, but now im more inclined to think that its an ignition problem; perhaps the module or coil? The reason I have almost ruled out a fueling problem, is that: a) if I engine brake for a long period when it starts to splutter, the problem is still there, and B) Because I cant see how a quick off and on of the ignition could resolve fuel starvation. I have no problems if I labour the engine and use the torque, but if I take it to say 4500 RPM plus a couple of times, while driving the car (not when in neutral), it is likely to give trouble after I have done this.

Was hoping someone might be able to shed some light on this as I dont want to replace everything needlesly.

Cheers, Adam

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Post by Stewart (oily!) » Sun Apr 09, 2006 6:13 pm

Although the symptoms seem like fuelling it is worth checking the ignition system over, I have had the same symptoms turn out to be coil problems and ballast resistor problems.
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Post by sleepy0905 » Sun Apr 09, 2006 6:19 pm

I agree with stewart those Ballast resistors can be right troublesome Bliters and do give this exact problem had a friend with a Reliant based trike do this last week till it eventually died altogether it was traced to a dead ballast reistor.
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Post by adamskibx » Sun Apr 09, 2006 6:58 pm

Aha, so thats what they are called! Ballast resistors. Cheers guys. Umm. Its funny you know; ive just been out to check the car over and I sudenly rememberd that when I put the new engine in, I used the original carb to that engine. If the ballast resistor, is the part im thinking of, then the new engines carb has two, the old engines carb had one, and that of course, meant that there is only one conection to attatch to a balast resistor in the GT's wiring loom. I just attatched this connector to the "ballast resistor" that was in the same position as the one on the old carb. I just tried unplugging the wire completely-result, engine will not idle. Then I attatched it to the other resistor, result- problem still present but possibly less persistant.

The question now of course, is what to do? lol. I wanted to use the current carb because its very clean and only done about 10,000 miles since it was replaced aparently, but if I have to stick the old carb on then thats what I have to do. I remember that the GT would idle at about 1500 RPM only, but then I suppose the broken head gasket could have caused this.

I know very little about carberettors as you can probably tell, but can anyone tell me what these "ballast resistors" do etc?

Cheers, Adam

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Post by richard » Sun Apr 09, 2006 7:06 pm

I think the 'ballast resistor' on the carb you are refering to is the idle cut off valve unless i am mistaken. Remove power from this at idle and the engine will die!

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Post by adamskibx » Sun Apr 09, 2006 7:50 pm

Cheers Richard. I didnt know that. However, im still confused as to why the car idles fine if I connect the one wire I have to the other ballast resistor? Does that mean they are both idle cut off resistors? Its odd as when the problem occurs, the engine doesnt always cut out completely; it revs fine and idles with stability, but is totally useless as you cannot drive off otherwise it just dies.I might as well swap the carbs over and see what happens.

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Post by Stewart (oily!) » Sun Apr 09, 2006 7:55 pm

Before you go swapping carbs, have a look at the coil, the ballast resistor is likely to be attached to it or wired close to it, swap the coil before the carb.
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Post by sleepy0905 » Sun Apr 09, 2006 8:16 pm

After looking at the wiring diagram the ballast resistor could be in the ignition module on the gt as there is no reference to it seperately on the GT wiring diaghram. But i will keep looking for you.
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Post by richard » Sun Apr 09, 2006 8:27 pm

I think coils come in two flavours. Ballasted and un-ballasted. I may be wrong, but most cars with electronic ignition have un ballasted. Anyone know any different?

The point you are possibly connecting your wire to may be a a 'live' connection, therefore opening the idle valve and allowing the engine to run.

I have found that you can 'bypass' the valve by slightly opening the throttle. this causes the car to run slightly above idle.

As Stuart mentions, change the coil before the carb. New carbs are bloody expensive!!!!! esp webbers.

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Balast resistors.

Post by Geoffrey Gould » Sun Apr 09, 2006 11:31 pm

Hi all.If I may put my 2 p's worth in, I think that there is a degree of confusion creeping in. On a car with a balast resistor this is used to provide a really good spark under starting conditions.
Starter pulling battery voltage down.
Cold engine.
Slow cranking.
Weak spark.
This was done by having a coil that ran on something like 7 or 8 volts, obviously this coil would not last long being driven by the battery voltage of 12 V+, so under normal running conditions there was a balast resistor in series with the coil that dropped the voltage down to the working voltage of the coil ( 7or8 V ).
There was a lead from the starter circuit ( usually a tag on the solenoid ) that had the full 12 V battery voltage on it ONLY when the starter was actuated. This was fed to the coil and overloaded it on STARTING only, thus giving a very strong spark. This was a special coil.
A normal 12 V coil does not have a balast resistor, as this would of course mean it was working under voltage so would have a very weak spark under normal working conditions.
The canister with a single connection screwed into a carb. is a fuel cut off solenoid. When fed with 12 V a plunger is moved to allow the slow running or idle circuit in the carb. to work. No supply and the plunger cuts off the fuel and the engine will not idle.
This was done to stop engines "dieseling" or running on.
After saying all this I dont know if the Citroen has a balast resistor as mines a diesel and I dont have a wiring diagram for a petrol one.
I hope this has helped.
Cheers.
Geoff.

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Post by jeremy » Mon Apr 10, 2006 12:11 am

I entirely agree with you Geoffrey in your excellent account of that unlovely device - the ballast resistor.

On British cars it was iintroduced at the end of the 60's and originally was a resistor wired in series with the coil, which was shorted out when the starter was operated - then they had the brilliant idea of incorporating the resistor in the wiring, and again it was shorted out for starting purposes. I mention this as if you have one you should also have a mysterious shorting connection to the coil which may be the giveaway.

Some coils had a cut out which operated when they got too hot and using a ballasted coil without the resistor could cause the ignition to cut in and out - great fun tracing that one! The give away is that the coil runs very hot!

Ballast resistors etc will NOT be found anywhere near the carburrettor.

From looking at the wiring diagram in Haynes for the 19GT I can't see a ballast resistor. I'm not 100% sure the control module doesn't function as one but I don't think it does. The diagram I'm looking at shows a magnetic tickup in the distributor instead of conventional contact points.

have you access to a gasalyser (like the diy models Gunson used to make - or even their colourtune?) - if so looking at the mixture while you fiddle may be revealing.

The diagram does show an idle cut off. The small automatic wiring diagram does also list a float chamber electric ventilation. Could these be the units you have?

jeremy

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Post by ellevie » Mon Apr 10, 2006 7:11 am

Well done on your MOT !
In your previous post http://www.bxclub.co.uk/forum/viewtopic ... ght=#18842
You wrote:The only problem I noticed was after sustained uphill sections it seemed to suffer from what felt like fuel starvation and would be fine again once the engine was switched off then immediately back on again? No idea what that could be but I know the ignition timing is just guessed. It performs very well, and there is no sign of pinking from what I can tell, so ill leave that till I get a timing light.
How did you get on with the timing ? Did you get a timing strobe and set the timing correctly ?
In your position, I would be strongly inclined to eliminate incorrect timing as a possible cause.
David

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Post by ernst stavro blofeld » Mon Apr 10, 2006 8:54 am

It is most likely to be the ignition module itself. This is a solid state box that just gets old. Replacement is the cure as a rule. Cleaning the contacts, removing it from the bulkhead and cleaning it, then reapplying the thinnest possible smear of heat sink compound will all make you feel better but it won't fix the problem. It is not likely to be the coil, either so start saving for a new module. For a second opinion, find a reputable auto electrician with the right frut machine to test the coil.

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Post by Jaba » Mon Apr 10, 2006 10:57 am

This is a long shot.............................but if the air filter is partially blocked then the engine will cut out when it is working very hard i.e. high revs and or uphill and would restart immediately after the ignition was turned off and on.
Its easily eliminated anyway. Apart from this I am with the rest of the team. You have an ignition component - ht coil or module or connections that is begining to fail.
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Post by richard » Mon Apr 10, 2006 6:55 pm

It may be a possibility of a bad connection on the ignition module. I had that problem on mine a while back.

A more recent problem i had was the connection from the pickup on the distributor was a little dirty. This caused cutting out, but with no set pattern.