I replaced the crankshaft and bearings in my 500L. New gasket set, new timing chain/pulley set, and new oil return tubes. Cleaned everything along the way. Now it is back together and I can't get it started. Checked fuel at the carb by pulling the hose off there. Got fuel. Checked spark at the spark plug leads. Got spark. Compression is worse now than before for some reason; 80 psi vs. 110 psi before. Not sure I have the timing right. I set the engine to #1 TDC and the distributor rotor is pointing at #1 and those valves are closed. I've gone one tooth above and below this location and adjusted the distributor fully in each direction while the wife cranks the engine. Best I got was a backfire. Nothing else.

So...anything else I can check? I set the new timing chain pulleys so the dots are facing each other. What else could I have screwed up? I'm second-guessing my valve adjustment but that seemed pretty straightforward.

Hi Marcus has the distributor been removed during the rebuild? Probably I would have thought, definately sounds like timing.

When you have the engine at TDC and rotor pointing to number 1. Do the valve on number one have a little movement up and down on the end of the valve stems? And the number 2 valves should be solid?

Tony

False alarm. If you put the plug leads on the distributor backwards, it won't run! Fixed that and I'm now running. Just got to adjust the timing. Whew...

I could use some advice on timing with a strobe. I've got the car running and idling OK. How do I set the timing at idle and at 3k? I've got one mark on the pulley for TDC and one arrow on the oil pump cover, which I'm assuming matches TDC. I have no other marks to go by. Pictures would be helpful!

From the mark on the pulley measure 13mm clockwise on the circumference of the pulley and make a mark with some white paint of file a little notch as you will need it in the future. That is 10 degrees BTDC. You can just see them on the pulley in the picture below.

Connect your strobe on cylinder number HT lead. If it needs 12v you can take the + from the coil + terminal and if you have an engine earth strap which you should have just connect the - clip to the engine cowling somewhere.

Point you strobe at the timing marks and turn the distributor until the 10 BTDC mark lines up with the little arrow. Tighten up the distributor, double check with the strobe to make sure it hasn't moved as you tightened.

I don't bother timing at 3000 rpm, mainly because I don't when I have reached it?

Tony

Very clear description from 'vitesse'.

It's not essential to check the timing at e.g. 3000 rpm, the setting at idle is more important. The check at 3k is to ensure the ignition is getting full advance from the auto-advance unit in the distributor as the engine speeds up, this rules out problems with the auto advance unit such as seized cam pivot, seized bob-weights etc. So setting the timing at idle is usually quite sufficient. If you want to check it use the same ratio that vitesse gives, so if 10 degrees is equal to 13mm on the pulley, then e.g.(idk the correct figure) 30 degrees full advance would be equal to 39mm i.e another 26mm further around the pulley from the idle timing mark. What you're looking for is a smooth advance in timing as you speed up the engine with the full ignition advance occuring by 3000rpm .Please keep in mind that strobe timing lamps make rotating objects appear stationary so mind your fingers etc, no loose shirt cuffs etc.

Al.

In my experience these engines are often out of sorts when correctly timed and run far better when done by ear / trial and error. I've never used a strobe on a 500 or pretty much anything else with a mechanical dizzy. I must be getting old....

Thanks for the timing advice. I got it set up this morning and drove it more than a mile for the first time ever. We made it about 10 miles before the oil pressure light came on. Stopped and had breakfast to let it cool, then drove it back home. Same story, about 10 miles in and the oil pressure light came on.

I'm running a new 126 oil pump in a used cover, new crankshaft, and new crankshaft and connecting rod bearings. All this because of low oil pressure and the pulley-end of the crankshaft was ruined when I got the car. All rebuilt now and still low oil pressure when warm and under load. I'm using 20W50 Brad Penn semi-synthetic oil and a little Lucas oil treatment (thickener).

When it was running it achieved a max speed of 40 MPH on the flat and maybe 25 on hills. Is this typical?

Sounds a bit sluggish Marcus. I have a speedo app on my iPhone, so I know it is accurate and I can get my bog standard 500F up to the low 50's MPH on the flat.

I use standard 20W50 oil no synthetic additives.

Tony

My 69 L with original engine does on average 62 mph on the flat and max 68 mph. Hills make it ping and keep it around 31 mph, and by hills I mean mountain hills.

None of the performance figures above seem particularly healthy - a good 500 should easily achieve 60+ mph on the flat and climb main road gradients without suffering noticeably. It does mean pedal to the metal driving, use of the gearbox and a decently set up engine.
If it pings / pinks timing and or mixture are out. If either of these are out then it will also overheat pretty quickly making things worse. Oil light at hot idle is pretty normal.

Do I sense a new thread needed?

Oil light flickers at hot idle, which I assume is OK. If I rev it, the light goes out. If I'm DRIVING, the oil pressure light flickers on and then appears steady when loaded. It will go out between shifts as the engine is unloaded and spinning fast enough.

Any advice on specific reasons for low oil pressure under load?

Just a guess but, at some point between pump and bearings there may be a way for the oil to bypass by a route that give less resistance than the bearings. This could be the pump itself being worn or maybe ill fitting or damaged gaskets. At least you identified a pattern that WILL make sense to someone.

marcus550 said:

Oil light flickers at hot idle, which I assume is OK. If I rev it, the light goes out. If I'm DRIVING, the oil pressure light flickers on and then appears steady when loaded. It will go out between shifts as the engine is unloaded and spinning fast enough.

Any advice on specific reasons for low oil pressure under load?

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The oil light should not come on when driving or under load!
I'd suggest you put an oil pressure gauge on this engine soon and see what readings you get at idle and when revving.
It's possible you have a faulty oil pressure switch, not expensive to replace if unsure of it's correct functioning or don't have access to a gauge.
Are you sure that the wire going to the oil pressure switch isn't chafing against something on the engine. If this wire is earthed it puts on the oil pressure warning light. It just seems strange that the oil light comes on when driving and goes off between shifts, sounds to me like the engine twisting one way under load maybe shorts out the o.p switch wire and off load twists the other way puttng off the light. I've seen this happen.

Al.

Just another thought - crankshaft end-float
When you shift gears, you press on the clutch pedal which pushes on the clutch pushing the crankshaft towards the rear of the car.
IIRC there is some sort of a plate sealed with piston ring type of seal/s on the nose of the crankshaft which is some sort of an oil seal in the oil supply system (haven't worked on Fiat 500/126 since the '70s, memory vague), if crank was moving perhaps it would affect oil pressure. Very strange that the oil light comes on under load but goes out as you change gear!! Maybe check oil pressure with a gauge with and without pressing the clutch pedal?

Another thing, IIRC the clearance between gears and gear to housing is only maybe 0.002in so if you machined 5 thou? of one of the pump gears, maybe you're losing pressure here?

Also would suggest you post a question on www.garagejournal.com in the 'Free Parking' section as you're in the USA, lots of very helpful, knowledgeable people there, might be able to point you in the right direction local to you re advice, parts, engine rebuilders/suppliers etc.

Al.

I'm scratching my head trying to think of what is left that can cause oil pressure to leak.

1. The oil feed tube for the rocker arm assembly. Does this have an O-Ring or a seal of any kind? At the rocker arm, it is a press-fit on to the aluminum collar in the middle of the rocker shaft. At the other end, down in the engine case, it just sits in a pocket there. No seal?

2. The cam bearing at the back (flywheel) end. This is just riding on the case itself. If the pocket is worn, it could leak pressure. But it doesn't explain why it is worse under load.

3. The cam bearing at the front (timing chain) end. This also rides right on the case, and the case could be worn.

Anything else I'm missing?

I'll re install the oil pressure gauge and take it for a ride. When I first fired the engine up and let it idle for 10 minutes, that gauge read 10 psi. I thought I was done so the gauge came out and the pressure switch sending unit went back in.

Under 'nothing is easy' on this car, the valve adjustment screw is stripped on #2 exhaust valve. New adjusters are on order. Once they come in I'll try a few of these experiments. The gauge reading with the clutch in and out sounds intriguing. There is an oil seal set of washers on the pulley-end of the crankshaft. I followed the manual when I installed this but it actually came out of the engine the other way around when I disassembled it.

Cam bearing/housing wear would likely result in low oil pressure all the time, i.e. low at idle and low at all speeds up the rev-range. Not saying you couldn't have this problem also but doesn't explain the variable figures you got, especially the drop to (near?) zero when hot.

As regards any seal on the rocker oil feed pipe,IDK, maybe check a parts/shop manual? (I no longer have any manuals for this car.)

The reason I mentioned the oil plate? on the front of the crank was I recall a very good Fiat dealer mechanic back in the late '70s having oil pressure problems on a partially rebuilt engine either 500 or 126 which he eventually traced to this plate (he was pulling his hair out with frustration!).

Just a word of caution, you need approx. 10 psi oil pressure per 1000 rpm,(although older Fiats generally run lower) so I wouldn't recommend going for 10 mile drives until you've fixed this oil pressure problem, otherwise it's likely to end in tears! It should be possible to carry out all necessary checks in your driveway/street outside incl. starting from cold and warming up fully while checking the pressure.

Al.

F123C said:

Very clear description from 'vitesse'.

It's not essential to check the timing at e.g. 3000 rpm, the setting at idle is more important. The check at 3k is to ensure the ignition is getting full advance from the auto-advance unit in the distributor as the engine speeds up, this rules out problems with the auto advance unit such as seized cam pivot, seized bob-weights etc. So setting the timing at idle is usually quite sufficient. If you want to check it use the same ratio that vitesse gives, so if 10 degrees is equal to 13mm on the pulley, then e.g.(idk the correct figure) 30 degrees full advance would be equal to 39mm i.e another 26mm further around the pulley from the idle timing mark. What you're looking for is a smooth advance in timing as you speed up the engine with the full ignition advance occuring by 3000rpm .Please keep in mind that strobe timing lamps make rotating objects appear stationary so mind your fingers etc, no loose shirt cuffs etc.

Al.

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Al....you're a genius.:worship: