Symptoms of cam timing error

I am fault finding a persistent but intermittent 328 problem that is being discussed in another thread. A possible cause that has been suggested by a couple of 328 specialists in the UK is that the cam timing is out. What would be the symptoms to look our for if the belt(s) were misplaced by a notch?

The car appears to run normally most of the time but can start backfiring on deceleration with noticeable loss of power during a long run if it gets hotter than normal. This can be difficult to reproduce at will. Could cam timing cause this? If so, any other clues that might lead to this diagnosis would be extremely helpful.

GG

 

You need a good Ferrari specialist. In Manchester there is Marios Kriticos shop, Maserati official service point that can solve your problems. Maybe I write his name not correctly, but I met him in person and he knows how to work

Ciao

 

The appropriate timing marks on the flywheel/cams can easily determine if the cam timing is correct or not. Any mechanic should be able to make that check.

As far as whether the timing could cause the problem - my gut reaction is no. Cam timing doesn't change when the engine is hot/cold - IOW, if cam timing is off, it is off at all times, the effect t doesn't come and go depending on engine temp or the length of the "run." I'd be inclined to think it is an ignition-related problem

 

Albert-LP -- the car is in France, not the UK and has already been to a couple of competent garages, one a specialist Ferrari shop the other Lamborhigini, and neither tracked the problem down.

Mike996, yes, the mechanic looking after the car can do this but I have several avenues to explore and would rather prioritize the most likely. Are there any signs to look for that would indicate the cam timing is out?

Ignition has always been a likely culprit for this but so far nothing untoward has been found that relieves it. It is probably something simple, but what?

GG

 

Agreed.

 

You can do an easy test. If cam timing is off, a compression test will read consistently low on one bank but the leak down numbers will be uneffected.

 

That's true, of course but to me just checking the cam/flywheel timing marks is quicker/easier than doing the compression and the leak down test. But certainly a compression and a leak down test together are an extremely valuable engine evaluation tool.

As far as symptoms - I don't know how many degrees of advance/retard a one tooth change in the 3x8 cam system produces. But assuming it's not too dramatic, the symptoms would not be all that obvious. If it is retarded, you would expect noticeably reduced low end power; if it is advanced, it would be the opposite. BUT, if you don't have anything to directly compare it to, you might not realize it's wrong. IOW, the engine could run OK just not with as much power/flexibility that it is supposed to.

Let's say, for example, that if the engine is timed correctly and in good condition, it puts out 250 HP. If the cam timing is a bit off the engine might produce 200 HP with no particularly noticeable problems. There wouldn't be any misfiring or other indications that something is "wrong." Now, if the timing is far enough off, there could be backfiring through the carb, etc but again, cam timing errors would not vary based on temperature or length of time the engine has been running.

 

I am trying to make a mental comparison with my 2.7 Cayman which lives in the UK and the 328 in France. I think that when running smoothly the 328 is slightly snappier than the Cayman under most conditions, though there is definitely less snap at low revs. However that is a very qualitative assessment.

GG

 

Cayman and 328...very different (I have both, too).

If timing is off enough (~2+ notches off on belts?), temp could affect (dissimilar metals expansion); this is not likely, since performance would be off enough to irritate enough to fix at any temperature. I would think fuel more than timing (FYI, WUR on US 328 has 2 bimetal strips; when I rebuilt mine, I could not replace these; works fine to warm up the car on a cool day, but on a hot day, I need to manage more on startup; when to normal temp, you would think the WUR would not adjust fuel concentration much, but with two 30yo bimetal strips...who knows).

If concerned about timing, I recommend a timing alignment (not just a belt replacement, but remove the valve covers, check clearances, and align cam positions (flywheel is at TDC on #1). Compression/LD tests are easy enough; might as well include with timing align.

Good luck.

 

Has the ignition timing curve been checked when the problem is present?

A faulty vacuum sensor in the Digiplex unit could affect timing as could flaky flywheel sensor.

 

No, the timing curve has not been checked with the fault present. It has never been possible to present the car with the fault at a sensible time of day. I will bear than in mind for next time.

Fuel is one of the areas we are examining at the moment. My mechanic has seen the car once with the fault and he is convinced that what he hears is the result of a lean mixture. That is consistent with the other main symptom, a heat buildup between the engine and cabin bulkhead -- likely from excess heat from the exhaust manifold. The WUR has been mentioned before but under normal circumstances starting and warming up are fine under both hot and cold conditions. However there may be potential for excess heat in the fuel line that goes from the filter to the metering device (21 in the Eurospares 012 diagram for 1985 328) as this is against some secondary aluminium heat shield material on top of the normal foam which could transmit heat to it (see attached image.) I'm not sure what effect that might have.

One feature of this problem is that once it starts the symptoms do not seem to go away until the car has been allowed to cool for a long time. Backfiring on engine deceleration will continue for up to an hour, even with the car idling, once it has been triggered. There may be some feedback mechanism that keeps it going, but even so it suggests that something with a large heat capacity that holds excess heat for a long time is involved, somewhere.

GG
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You do not need to take cam box covers off on a 3.2 motor to check cam timing.
I know from experience that being 1 tooth out, the engine will run fine.

 

You mentioned backfiring. If you are getting popping and banging going on this is not a fuel issue, it is a timing or intermittent no-spark issue.

An easy first step would be to fit neon spark indicators to the plugs and then catch it when the fault is present and check they are all firing in a regular pattern. This wont tell you if the whole timing curve is wrong but will indicate something flaky with the ignition and whether its one bank affected.

 

2 teeth off and I would think you would easily be smacking valves into pistons...

Compression check is easy to do...

 

You can bet poping and banging from the fuel system on the injection engine but it usually has the engine running rough all the time, but here it is intermittant.

When the diaphragm on the fuel distributor block has a hole in it, it supplies excess fuel to a particular injector, the engine has a job burning it and causes backfires. What is missing here is the engine is showing no sign of fuel passing the piston and the sump oil level increasing.
Makes me dismiss it being fuel related.

 

I've had a similar condition on my 1980 "i" 308. The car runs great and strong 'till a few minutes after full warm-up. Then during acceleration it starts sputtering ( makes a noise like when you stick your tongue out and blow). Still accelerates but misses a few beats. On a cool day, say less then 65 degrees F, I can't reproduce the condition. Literally the ambient temperature is enough to make it tip over into this condition. On a 90 degree day it will happen.

Like your condition the car has to cool down for several hours to run right again.

I've replaced plugs, wires, extenders, fuel injectors, one suspect speed sensor, flipped the coils and digi boxes and added grounds, but have not fixed the situation. So for now, cool days are the ones I take long drives on.

 

The popping from the car is only audible on deceleration. Under acceleration there is no audible popping, just a loss of power. I am assured from a variety of sources that the popping on deceleration is a classic symptom of lean fuel mix. Of course it could also be something else and ignition is a likely culprit too. However we have had no luck there so far.

Where do I find suitable neon spark indicators?

GG

 

https://www.amazon.co.uk/Laser-2780-Ignition-Spark-Tester/dp/B003AN1VPW

 

I agree with this.

cam covers off will allow valve clearance checks.

 

Thanks for the support re cam timing.

The motor runs fine generally so valve clearences must be reasonably ok.

 

Thanks for the link to neon spark indicators.

Any thoughts on a hot fuel line?

GG

 

Send the car in Italy, it's impossible to say what the car has staying behind a laptop!

Very likely it's not anything referring to the cam timing.

There is a superb vintage Ferrari electrician specialist here around: instead of wasting money in France, send the car here in Italy (it's not so expensive).

ciao

 

This is one of the possibility, but a fuel line should be where it shouldn't be.

ciao

 

If there is excessive heat in that area is there an exhaust leak maybe?

 

There has never been any evidence of an exhaust leak but it is an area that needs examining again. However my thought -- unlikely though it might be -- is that the secondary aluminium heat shield material that has been added to the back of the cabin bulkhead is helping create an unusual heat buildup somewhere, perhaps against the fuel line it seems to touch. If the temperature rises high enough this could eventually trigger a problem leading to a lean mixture (vapourisation perhaps). The thing is, once it starts, fuel burning in the manifold as a result will create a nasty feedback loop, keeping the problem going.

I should add that most people I have tried this on think it highly unlikely. But so far the likely causes have led nowhere.

GG