problem with P505, 32/35 tmima carburettor.
- Thread starter 2pac
- Start date
Csmshaft is original. I have an m78 dizzy from a 2.0 engine but it's with contacts, how does it connect?
Could be incorrect spark plug gap? They are now 0.6 as per the book, do you have a good experience with a different gap?
Could be incorrect spark plug gap? They are now 0.6 as per the book, do you have a good experience with a different gap?
Last edited:
I'm definitely not an expert but one who often just follows the book. If I'm understanding the situation, it backfires using either the 123 distributor or the M78? The camshaft is the original one and it's installed correctly? The only thing changed from standard on the engine is the 123 distributor?
2pac,
Like others I've gone back to the beginning of the thread looking for inspiration. No inspiration, but perhaps a few points to clarify:
1. The "banging" in the exhaust on overrun -- how loud is it? Could it just be a leak at the exhaust manifold? Have you tried driving it yet, or does it not seem happy enough?
2. You found that the cam timing was late. In particular, that the inlet valve was opening AFTER TDC. Reporting back you said the chain was right but the sprocket had a different offset so you replaced the sprocket. Perhaps it'd be worth checking that the valves are now both rocking when the piston is at TDC.
Going on from this, it might also be worth checking that the piston is really at (or very close to) TDC when the pulley mark lines up with the TDC timing mark. If a sprocket had the wrong offset, maybe the pulley does too?? Worth a check.
Finally, no fun changing the distributor back if you have to rewire things. You might instead check the advance curve against spec. by using a timing light while revving the engine (with vacuum advance disconnected). If your timing light doesn't have adjustable advance you might just dab a bit of liquid paper every 5 degrees clockwise from the timing mark on the pulley. Note that the curves are often stated in distributor RPM, so double them for crankshaft RPM. If the timing is retarded at 4000rpm, that could give you banging on overrun; it'd also be down on power.
Have fun,
Rob.
Like others I've gone back to the beginning of the thread looking for inspiration. No inspiration, but perhaps a few points to clarify:
1. The "banging" in the exhaust on overrun -- how loud is it? Could it just be a leak at the exhaust manifold? Have you tried driving it yet, or does it not seem happy enough?
2. You found that the cam timing was late. In particular, that the inlet valve was opening AFTER TDC. Reporting back you said the chain was right but the sprocket had a different offset so you replaced the sprocket. Perhaps it'd be worth checking that the valves are now both rocking when the piston is at TDC.
Going on from this, it might also be worth checking that the piston is really at (or very close to) TDC when the pulley mark lines up with the TDC timing mark. If a sprocket had the wrong offset, maybe the pulley does too?? Worth a check.
Finally, no fun changing the distributor back if you have to rewire things. You might instead check the advance curve against spec. by using a timing light while revving the engine (with vacuum advance disconnected). If your timing light doesn't have adjustable advance you might just dab a bit of liquid paper every 5 degrees clockwise from the timing mark on the pulley. Note that the curves are often stated in distributor RPM, so double them for crankshaft RPM. If the timing is retarded at 4000rpm, that could give you banging on overrun; it'd also be down on power.
Have fun,
Rob.
It's not the plugs.
no, i didn't try the conventional dizzy, only the 123 and that's i think the only thing not standard.
the banging is quite loud, i'm not sure if it happens only after i leave the pedal or also when it's revving.
there was a tiny gap between the manifold and the downpipe which i sealed with a victor rheinz sealnt, can it cause the banging?.
didn't try to drive yet.
the crankshaft pulley is ok, i checked it. as for the valve timing, maybe i was wrong, it's hard to tell the right moment when the valve begins to open without an indicator gauge.
To me, it really sounds as though the timing is out. I know nothing about 123 distributors but maybe it's not set up correctly. Also, it could be a hassle but I'd try the old distributor and see if it makes a difference.
Not of the sort you describe here. Exhaust leaks can give some banging/popping on overrun due to letting air in with hot unburnt fuel.
I agree with Peter Chisolm that the timing is top suspect. Just testing as I described yesterday at 1-2-3-4000 rpm should let you know if the 123 dizzy's advance curve is something like it should be.
A short test drive -- even 20m on a driveway -- can tell you things about how the engine is behaving under load that you can't get free revving in neutral. Obviously don't do it on my say-so. You have to judge whether you might end up stranded.
Have fun,
Rob.
i tried today to use different ignition curves but nothing helped.
noticed that when the engine revs at about 1500rpm steady the exhaust spits and caughs, and the engine doesn't work very smooth.
i will try to install a standard dizzy from an XN1 engine, but it's a classic type with points. the car it came from had a ballast resistor- do i need it to use it and how does the wiring go? it has now a 12v coil.
noticed that when the engine revs at about 1500rpm steady the exhaust spits and caughs, and the engine doesn't work very smooth.
i will try to install a standard dizzy from an XN1 engine, but it's a classic type with points. the car it came from had a ballast resistor- do i need it to use it and how does the wiring go? it has now a 12v coil.
A 12V coil won't want a ballast resistor. For wiring, the +ve coil terminal will stay as it is. You just need to run a wire from the coil -ve to the points terminal on the distributor. I'm assuming the condenser is still there on the dizzy. Make sure the points are clean, and gap them as per the book. At a minimum, do static timing with a test light. Time with a strobe timing light after that.
However -- the symptom you describe above doesn't sound like timing. Bad coil, dirty/cracked distributor cap or rotor button, perhaps shorting plug leads; could be water/dirt in the carburettor. Sorry to be spraying theories at you, but timing problems don't give misfires. Other ignition problems can, and so can a lean mixture. This web diagnosis game is not easy.
I'm a little surprised you have a 12V coil -- but checking the 123ignitions website shows it's expecting a 12V coil. I guess that's to keep the "standard" look. Anyhow, a failing coil will often be ok at low RPMs but become patchy as the revs get up. If you have another coil, try substituting it. If that doesn't get you anywhere, I think I'd start looking at the carby.
Have fun,
Rob.
However -- the symptom you describe above doesn't sound like timing. Bad coil, dirty/cracked distributor cap or rotor button, perhaps shorting plug leads; could be water/dirt in the carburettor. Sorry to be spraying theories at you, but timing problems don't give misfires. Other ignition problems can, and so can a lean mixture. This web diagnosis game is not easy.
I'm a little surprised you have a 12V coil -- but checking the 123ignitions website shows it's expecting a 12V coil. I guess that's to keep the "standard" look. Anyhow, a failing coil will often be ok at low RPMs but become patchy as the revs get up. If you have another coil, try substituting it. If that doesn't get you anywhere, I think I'd start looking at the carby.
Have fun,
Rob.
Actually, with that behaviour at just 1500rpm, I think I'd go straight to the carby.
Might be that the popular "tune up" trick -- revving the engine and then, while keeping the throttle open, putting your hand over the carburettor throat for a moment -- might draw a blockage through one of the jets. But even if this works, it'd be wise to take the lid off to see how much dirt is in there. And fitting/replacing the fuel filter mightn't be a bad idea. If there's water that's more bother.
Have fun,
Rob.
Might be that the popular "tune up" trick -- revving the engine and then, while keeping the throttle open, putting your hand over the carburettor throat for a moment -- might draw a blockage through one of the jets. But even if this works, it'd be wise to take the lid off to see how much dirt is in there. And fitting/replacing the fuel filter mightn't be a bad idea. If there's water that's more bother.
Have fun,
Rob.
i got a Bosch blue coil to suit the 123 dizzy.
before that i had the standard transistorized ignition system, doesn't it have a 12V coil?
so how to use the contact breaker dizzy- with or without resistor?
Last edited:
I need to recalibrate my brain. I know it's a 505, but my XN experience is 04 vintage with points, so I wasn't thinking you were coming from an electronic setup.
Your 505's original setup would almost certainly have had a high energy ignition coil which would overheat and fail if run in a points setup. I get mixed messages from the 123ignition website. On the page with the recommended Peugeot dizzy it says it expects a 12V coil. On the support page on "what kind of coil do you recommend", their generic advice seems to be "what your car came with".
Perhaps the distributor is running too short dwell times for the 12V Bosch Blue and might work ok with the standard HEI coil. Perhaps test your standard coil with an ohmmeter. According to them, they can deal with any resistance >1.0 Ohms across the two primary terminals. If your standard coil has a significantly lower resistance than your new Bosch Blue, it will likely deliver a good deal hotter spark. That might fix your problem. But that's not the end of the story. If the 123 distributor's dwell time is like a points distributor's the coil will be overloaded at low rpm -- will tend to get hot and, sooner or later, fail.
It'd be good to check this with an oscilloscope, but that's probably a tall order. If you have an ohmmeter, compare the two coils and, if it looks promising, try the standard coil. Feel with your hand whether the coil's getting hot. It should get pretty warm, but shouldn't get so hot that you can't keep touching it for a few seconds.
Have fun,
Rob.
Your 505's original setup would almost certainly have had a high energy ignition coil which would overheat and fail if run in a points setup. I get mixed messages from the 123ignition website. On the page with the recommended Peugeot dizzy it says it expects a 12V coil. On the support page on "what kind of coil do you recommend", their generic advice seems to be "what your car came with".
Perhaps the distributor is running too short dwell times for the 12V Bosch Blue and might work ok with the standard HEI coil. Perhaps test your standard coil with an ohmmeter. According to them, they can deal with any resistance >1.0 Ohms across the two primary terminals. If your standard coil has a significantly lower resistance than your new Bosch Blue, it will likely deliver a good deal hotter spark. That might fix your problem. But that's not the end of the story. If the 123 distributor's dwell time is like a points distributor's the coil will be overloaded at low rpm -- will tend to get hot and, sooner or later, fail.
It'd be good to check this with an oscilloscope, but that's probably a tall order. If you have an ohmmeter, compare the two coils and, if it looks promising, try the standard coil. Feel with your hand whether the coil's getting hot. It should get pretty warm, but shouldn't get so hot that you can't keep touching it for a few seconds.
Have fun,
Rob.
No. A 12V coil can handle 12V continuously across it's primary terminals. That would burn out an HEI coil pretty quickly.
The "12V" is not the key thing. Both coils are insulated against far higher voltages. The failure is due to too much current.
Optional boring reading:
Working back from its purpose in life, here's what goes on in a coil:
Spark in the secondary occurs when the current in the primary is interrupted. The greater the primary current, the stronger the spark.
The primary current depends on how long the voltage is applied across its terminals. It starts at 0 and ramps up as time goes by. Depending on the coil, target current might be 6A to 12A. Coil will burn out if current goes much above this target. It typically takes about 3ms for an HEI coil to reach this current. A 12V coil doesn't let primary current get so high. This weakens the spark, but means you can have ignition on and points closed and not burn out the coil.
The 123ignition distributor will work with any 12V coil. It can also work with many HEI coils because it includes current limiting. It watches the current in the primary as it ramps up. When it reaches the limit (which I guess is around 6A) it holds the current at that level. This means it is tolerant of long dwell periods like a 12V coil, but can deliver a much stronger spark. If used with a 12V coil, the 123ignition current limiting won't be used.
So, once you've verified that your original coil has > 1.0 Ohms resistance (and < your Bosch Blue), I'd try it.
However, the weak spark of a 12V coil will mostly affect high rpms. Your description of rough running at a steady unloaded 1500rpm doesn't suggest this as a cause. But it won't hurt to have as strong a spark as possible.
Have fun,
Rob.
The "12V" is not the key thing. Both coils are insulated against far higher voltages. The failure is due to too much current.
Optional boring reading:
Working back from its purpose in life, here's what goes on in a coil:
Spark in the secondary occurs when the current in the primary is interrupted. The greater the primary current, the stronger the spark.
The primary current depends on how long the voltage is applied across its terminals. It starts at 0 and ramps up as time goes by. Depending on the coil, target current might be 6A to 12A. Coil will burn out if current goes much above this target. It typically takes about 3ms for an HEI coil to reach this current. A 12V coil doesn't let primary current get so high. This weakens the spark, but means you can have ignition on and points closed and not burn out the coil.
The 123ignition distributor will work with any 12V coil. It can also work with many HEI coils because it includes current limiting. It watches the current in the primary as it ramps up. When it reaches the limit (which I guess is around 6A) it holds the current at that level. This means it is tolerant of long dwell periods like a 12V coil, but can deliver a much stronger spark. If used with a 12V coil, the 123ignition current limiting won't be used.
So, once you've verified that your original coil has > 1.0 Ohms resistance (and < your Bosch Blue), I'd try it.
However, the weak spark of a 12V coil will mostly affect high rpms. Your description of rough running at a steady unloaded 1500rpm doesn't suggest this as a cause. But it won't hurt to have as strong a spark as possible.
Have fun,
Rob.
now i'm completely lost in the coils subject...
the original coil is stamped 12V, it has about 1.6 Ohms although the book says it should have less than 0.7 Ohms as it's transistorized system.
anyway i tried this coil and it didn't fix the problem.
don't know if it's related, but oil is coming out of the air filter intake (it's the oil bath type of filter).
the original coil is stamped 12V, it has about 1.6 Ohms although the book says it should have less than 0.7 Ohms as it's transistorized system.
anyway i tried this coil and it didn't fix the problem.
don't know if it's related, but oil is coming out of the air filter intake (it's the oil bath type of filter).
Sorry. I do go on. At least I warned you it was optional.
1.6 Ohms sounds low for a 12V coil and reasonable for an HEI. An ohmmeter only gives you a ballpark figure anyway since resistance isn't really what makes a coil tick.2pac said:
Bummer, but at least I was right about something for a change.2pac said:
2pac said:
Overfilled the oil bath perhaps? Backfires on the intake side? If much air is actually blowing backwards through the filter that'd be a real puzzler. Crankcase breather problems can lead to oil before the carby, but you'd need tremendous blow-by to send it any further. Alternatively, you'd have plenty of other symptoms if this was due to inlet valves being open when they shouldn't.
All seems a bit unlikely. I think you should check for gunk in the carby.
Have fun,
Rob.
Okay, it sounds as though trying the original standard distributor is more complicated than expected. You've checked the timing chain etc and you reckon that all is well. Getting back to the carby, you say you rebuilt it so maybe the problem does lay there? The easiest thing to do would be to try a different carby but you may not have another to use.
Maybe we need to clarify exactly what the engine is doing. Does the engine idle smoothly? If not, exactly what does it do? Does it go up through the rev range smoothly? If not, exactly what does it do? Does it seems to lack power (assuming you've driven it)? What are the exact symptoms?
Maybe we need to clarify exactly what the engine is doing. Does the engine idle smoothly? If not, exactly what does it do? Does it go up through the rev range smoothly? If not, exactly what does it do? Does it seems to lack power (assuming you've driven it)? What are the exact symptoms?
the engine idles at 900-950 and revs smoothly, although in constant speed it wasn't so smooth.
exhaust sounds smooth at idle, no hissing, puffing etc. but while driving in the yard it quite stinks.
the mixture screw has to be out about 5.5 turns and the idle screw has to be almost closed in order to get the smooth idle.
if i open the idle screw more than that it starts to idle slower until it dies.
only when driving it sounds like the valves are ticking, although i adjusted them, but when the car is standing the valves sound ok.
exhaust sounds smooth at idle, no hissing, puffing etc. but while driving in the yard it quite stinks.
the mixture screw has to be out about 5.5 turns and the idle screw has to be almost closed in order to get the smooth idle.
if i open the idle screw more than that it starts to idle slower until it dies.
only when driving it sounds like the valves are ticking, although i adjusted them, but when the car is standing the valves sound ok.
Okay then. When you say "it quite stinks" I assume you mean that it runs very badly rather than someone has planted a dead fish in under the drivers seat?
Someone will probably chop it off but I'll stick my neck out and suggest that it's running lean - if timing etc is okay. Blocked jet, a different blockage in carby, fuel delivery problem such as blocked fuel filter, faulty fuel pump etc.
Someone will probably chop it off but I'll stick my neck out and suggest that it's running lean - if timing etc is okay. Blocked jet, a different blockage in carby, fuel delivery problem such as blocked fuel filter, faulty fuel pump etc.