Technical Lets Play a Game, Engine diagnostics

Maybe we'll have some interest here.
Maybe this will give us some mental tools the toolbox by sharing these experiences.
I'll start first. All I ask is we solve one scenario at a time.
Also, the scenario must have a resolution that is not open ended. This is not, unsolved mysteries. If you post a scenario, you must know the answer. After a time, give another clue if no one can guess, give the answer after 3 clues.
As always let's keep this HAMB era.

I'll go first.....


Small Block Ford
When driving, it loses oil pressure going downhill.

 

Front or rear sump?

 

Front sump.

 

Clue # 2
This was an older engine, a good runner. It was inspected on the stand and a gasket set was installed.
The timing cover would not fit. A small bit of material had to be removed from the inside of the cover to get it to fit.

 

Have you pulled the oil pan to see if either the sump is clogged or perhaps the sending unit is leaking?

 

Too big of a gap between the pan and the pickup screen is my guess, or the pickup tube had a crack toward the bottom near the screen so when oil went to the front of the pan when going downhill it stopped ****ing up oil.

 

The sending unit was checked. everything seemed fine as far as the gauges.
One correction....
The reason the timing cover was off was due to an oil leak. The timing cover and pan were removed and new gaskets were applied.
When the pan and cover gaskets were put on, the oil input was clean.
The only issue was the timing cover would not fit back on.

 

Clue #3
My brother removed the engine because eventually it lost oil pressure all the time going down hills.
It would drop to zero......
On level ground or going uphill the pressure would come back.

When we had it on the floor, I was helping him move it around.
I grabbed the damper to move it.
The damper/bottom pulley, the crank slid out 1/4 to 1/2".

 

I had a similar issue on my flathead. I bought an inspection camera for my iphone (sorry @Moriarity doesn't work with flip phones), drained the oil (obviously) and stuck it in the drain hole (just like the Doctor's office). My pick up screen was higher than my dip stick so I was getting a false reading. I didn't have time to drop the pan and correct the pickup tube/screen so I cut off the aftermarket dipstick (the end inside the handle) so they sat at the same level. Problem solved for $25.

 

Can you post some more specifics about the engine, such as year and model so I can look up some phantom views, exploded views of the internal components, I am curious about the oil pump itself.

 

It was a 1970s 302.
The oil pump was fine.
All that stuff was good.
The engine would run all day, just fine on level ground. It would drive all day on level ground or going uphill. Go downhill, oil pressure would drop to zero.
Back on level ground, oil pressure comes back.

 

With better than a 1/4" of crankshaft end play, I would suspect that the thrust bearing is out of it, or non-existant. Could that movement of the crank be enough to uncover an oil port and allow all oil flow to dump out of the crank - into the sump, essentially dropping oil pressure to 0? Not sure why that would only happen going down hill though, and with no thrust bearing, the engine should fail, likely catastrophically, quickly.

 

Was the vehicle the engine came from a stick?

 

Automatic

 

BINGO!!!!!

The thrust bearing was gone/severely worn.
Clue #1 Losing pressure going downhill, the crank would slide forward covering the oil ports. On level ground it would slide back uncovering the port, restoring oil pressure.

Clue#2 The difficulty replacing the timing cover. The crank was out of position.
Clue#3 Being able to pull the damper/crank back and forth was a sure clue the thrust bearing was worn.

 

I see it all the time on engines being returned for warranty consideration at work, especially on medium duty diesels equipped with an Allison automatic. Replacement engine fails within the first 1000 miles and the thrust bearings are toast. Dealership Tech installed the replacement engine but didn't get the trans mounted up correctly. Tech used the big impact to draw the engine and trans together and bam! There goes your thrust bearing and no warranty for you. Dealership gets to eat the cost of a $25,000+ engine and hopefully figures out how to hire better techs.

 

Awesome!!!!!
This is what I'm talking about, learning stuff.
The basic lesson, if stuff does not fit, it does not fit.
Alignment....
From a brake line fitting to mating a transmission. If it's not in alignment, forcing it breaks stuff.
For a young mechanic there's tight and then there's hillbilly tight. Hillbilly tight breaks stuff. This is why torque specs exist.

Mmmmmm
If I remember right, my uncle did have that truck at a transmission (maybe a home shop) shop a couple of years before my brother got it.
My uncle knew a guy.

Frozen Merc
Your turn if you wish....

 

Ok, I can play along. This occurred on my '51 Ford F-1 a number of years ago. It drove me nuts trying to figure out the root cause.

Vehicle: 1951 Ford F-1, 351W, 5 Spd manual trans. Engine is equipped with a stock Ford DuraSpark II Ignition and Distributor with vacuum advance, Holley 600 cfm 4 bbl, Edelbrock intake and cam, iron heads.

Problem: The engine would sputter and misfire under hard acceleration, sometimes... Under light throttle, it would never skip a beat. This was a new problem, and the truck probably had 30,000+ problem free miles on it before the misfire started. New plugs and wires did not solve it.

 

Anytime I see a weird ignition issue and the term "DuraSpark" is involved, I'll always go for the module being the likely culprit.

 

I would start with all the connections, paying special attention to the coil wires and making sure all connections were clean.
I would look for wire insulation failure especially at connections.

 

Also....
I would check the advance.

 

In this case, the module was not the problem. But, yeah I can't begin to tell you how many I have smoked due to simple things like welding on the ch***is, or even just hooking a high amperage battery charger up. Standard Electronics replacements used to be like $19 at the local Auto Value. Always kept a spare or two on the shelf.

 

Your are getting warmer. The vacuum advance was working properly, but that action was also the cause.

 

Wire cracked due to the movement of advance plate?

 

Yeah, I had a motorcycle that did that, drove me crazy for a while...

 

BINGO!

The hook coming from the vac advance canister to the advance plates under the rotor had snagged one of the ignition module wires, this led to an intermittent short that only occurred when the vac advance was operating and tugging on the wire.

 

Wow!
I wonder if I would have found that?
I would like to think I would have.

I’m trying to think realistically and go over in my head what I would have done.

Hard acceleration and stumble….
Light acceleration, no stumble…..
This points me to the advance.
Honestly I would not rule out the carburetor.

I would go to the tune up data….
(I’m more familiar with points than I am Dura Spark…)
I would check the timing….
I would have checked the advance by a static test (revving)
I would check advance, vacuum advance plugged
I wonder if it would have shown here doing a mechanical advance check with the vacuum canister plugged?
Also, I would have checked for vacuum canister function. Hopefully I would have found this then.

Truthfully, I would have probably adjusted idle and mixture on the carburetor during this process.

I’m trying to be honest, it may have taken several rounds of this and maybe driving to completely clue in on the distributor.

I don’t know if I would have found this with the distributor on the car?
If I missed it on the car, next step would have been to mark and remove the distributor for a close clean and inspection.
Hopefully I would have found this then.


Very Good
Thanks Frozen Merc!

 

Should there be a "rule" added that whoever solves the problem goes next? I can see this thread lasting forever and being beneficial to the community...

3blap.

 

Only problem with that is the only good one I have was the same issue Three weeks of evenings and weekends trying to figure it out.

 

I have a ton of off-topic ones I could throw up, especially around diesels and 2 and 4 stroke small engines. Some of it is relative to our hot rod engines, but very off topic.