problem with P505, 32/35 tmima carburettor.

Ah, my experience with the pushrod engine is 404/504; didn't know they'd abandoned the index hole. Well, it's not likely that the marks on the case are off by much if at all. Didn't mean any offence on which timing mark -- it was just a remote possibility.

There's very little active in the carby when you shut the throttle. The air flow is cut and fuel should only be coming through the idle jet. If extra fuel is being drawn in somewhere else, that wouldn't usually tend to cause backfiring. Extra AIR being drawn in might though. Just perhaps, the higher vacuum of overrun means air is drawn in at (say) the carburettor base, but when engine speed drops and the vacuum eases, it can no longer draw the air in, so you still get a decent idle. I guess it might be worth looking for vacuum leaks after all -- but I feel I'm clutching at straws.

Have fun,

Rob.
 
They did away with the holes in the bell housing by 1980 as my 1980 504 didn't have one.
 
2pac,
It would appear all bases have been covered.
However, when you adjusted the valve clearance did you follow the "road map" as shown in the manuals. Mr Peugeot uses this method for a reason I'm sure. My simple understanding is because of the rocker shaft design and the angle of the pushrods for the hemispherical head design. Others may like to elaborate here?

Also I have always found it necessary to go over the clearances twice. Sometimes finding some have closed up or loosened.
 
I reckon you need someone over there to check your work, 2pac.

It's easy to get into a closed mindset about things....similar to when you lose something and think you have looked everywhere. Someone new will often check places you think you have thoroughly checked, and find the thing you have lost.
 
Didn't you have an odd problem at one stage with fuel coming out somewhere ? Somewhere in the cooling system ?
Click to expand...

yes, fuel was entering the coolant, but since than i replaced the inlet manifold and rebuilt the head again, so this problem is solved now.

i do the valve clearance exactly in the right order, but after running the engine always one or too change.

what can cause cross-fire?
 
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I can't think of exactly what happens. But because of some kind of mis-alignment (between sprockets and gear between the cam, dizzie drive gear (underneath it) and/or the way the dizzie cap sits relative to the dizzie itself), the spark does not fire when the rotor button is pointing exactly at one of the 4 electrical terminals inside the dizzie cap (as it should).

Instead, the spark fires when the rotor button is facing somewhere between two terminals. So that spark goes to two of them, instead of one.

Robs thinks that this is not your problem though. Still, who knows ? You are the guy who is physically there !
 
Sorry, I've been barking up the wrong tree. It's not really possible to have a phasing problem with a standard distributor. I have had to grapple with phasing problems in both cars I have fitted Megasquirt to. In that case, external electronics decide WHEN to spark, and the distributor only decides WHERE the spark goes.

WIth an ordinary distributor setup, the low tension side decides when, high tension decides where, and the whole thing is built so spark will only occur when the rotor button is pointing at a terminal.

Apologies again for the red herring.

Have fun,

Rob.
 
It's still a "standard" distributor in that it's intended as a drop-in replacement. Its built-in electronics *could* do all sorts of things, but I'd take them at their word that they do the same job as the standard dizzy, just better.

One thing I've been meaning to ask: you say you have the valve clearances inlet 0.1mm, exhaust 0.15 (having started with 0.15 and 0.30 before retorquing the head). That exhaust clearance sounds tight. I remember 0.25 in the 504 days. Did they reduce the spec? You indicate this isn't related to the banging, and fair enough, but too small a clearance may lead to burnt valves over time.

Looking at that part of the conversation, you said the banging only started after "refilling" the head. By "refilling", do you mean machining the gasket surface, or is it filling corrosion or whatever with weld?

In any case, if it was fine before this and the cam hasn't been disturbed, that'd pretty much eliminate cam timing as a problem. Which leaves me clutching at straws again...

Have fun,

Rob.
 
If you want to positively eliminate the 123 distributor then drop in the old one and see if it makes a difference.
 
Peter Chisholm said:
If you want to positively eliminate the 123 distributor then drop in the old one and see if it makes a difference.
Click to expand...

Just re-read the whole thread and I concur with Peter's comment.

Change back to a standard distributor and see what happens.

Cheers
Roland

:banana:
 
robs said:
One thing I've been meaning to ask: you say you have the valve clearances inlet 0.1mm, exhaust 0.15 (having started with 0.15 and 0.30 before retorquing the head). That exhaust clearance sounds tight. I remember 0.25 in the 504 days. Did they reduce the spec? You indicate this isn't related to the banging, and fair enough, but too small a clearance may lead to burnt valves over time.

Looking at that part of the conversation, you said the banging only started after "refilling" the head. By "refilling", do you mean machining the gasket surface, or is it filling corrosion or whatever with weld?

In any case, if it was fine before this and the cam hasn't been disturbed, that'd pretty much eliminate cam timing as a problem. Which leaves me clutching at straws again...

Have fun,

Rob.
Click to expand...

a slip of the pen, 0.25 for the exhaust valve...

by filling the head i mean adding material to bring it back to normal height.
i'm not sure if the banging was there before or not.

changing back to standard dizzy won't be easy as i think i cut the wires...

in haynes they give some data of valve opening and closing with angles on the crank (after setting the valve gap to 0.35), will try to check this way.
 
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Well, in haynes the data is for fuel injection engines, but i found the attached data in a french manual. The abbreviations are french for inlet opening lead, inlet closing lag, exhaust opening lead and exhaust closing lag, respectively, which is afaik the points when the valves start to open and when they are fully closed, isn't it? So i've checked #4 valves after setting the gap to 0.7 as required, by measuring the distance of the notch on the pulley from the tdc mark. It turned out the valves are retarding by about 10-15 degrees. Maybe it's not accurate, but no doubt that the inlet valve starts opening only AFTER tdc instead of BEFORE.
so does it mean the valve timing is wrong?
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2pac said:
no doubt that the inlet valve starts opening only AFTER tdc instead of BEFORE.
so does it mean the valve timing is wrong
Click to expand...

Yes, unfortunately. At the top of the exhaust stroke both inlet and exhaust should be rocking. 15 degrees sounds about right for one tooth too. Well, at least it explains the banging.

Have fun,

Rob.
 
so now we know what it's got...
any chance the valves bent?
 
It won't have bent the valves. Just reinstall the timing chain and it should be ok. Hope so.

Have fun,

Rob.
 
well, i checked the timing chain and it was ok, but the camshaft sprocket was from a 1.8 engine, the 2.0 engine sprocket sets the camshaft in a slightly different angle relating to the crankshaft so i replaced it. there are also new ignition wires, rotor and cap, and a new diaphragm to the economizer in the carb.
after all that, the banging from the exhaust is still there.
checking with a vacuum gauge shows normal readings, expect for the needle is shaking in idle.
any ideas?
 
So, just to recap, exactly what isn't standard on this engine?
 
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