Part 2 of the PHAD Memorial Weekend Special…
This 1996 Ford F250 BIG BLOCK V8 is running like garbage after a recent engine rebuild to address a coolant leak at the head gasket. New pistons, rings, and camshaft were installed.
After a cold start, it runs SUPER RICH, floods out the cylinders, and completely LOSES COMPRESSION!! Why?
Let’s keep eliminating variables and see if we can pinpoint the root cause of the POOR ENGINE VACUUM causing a severe RICH condition…
IVAN’S PICO WAVEFORMS:
https://drive.google.com/drive/folders/1b3Mjmq3-gUVb9BcJ5FK5Jhl2AKt-N9LZ?usp=share_link
TOPDON TCVIEW THERMAL CAMERA: ***$80 OFF!!!***
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PHAD PRESSURE TRANSDUCER:
http://www.pinehollowdiagnostics.com/phad-pressure-transducer.html
Enjoy!
Ivan
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In the first video you mentioned the customer installed the distributor incorrectly and caused no oil pressure. Metal shavings could have gotten into the oil pump pressure regulator and caused it to stick closed. Also mention of a performance camshaft which will reduce vacuum at idle. That’s a weird one for sure.
any obstruction in the intake??????
Put some marvel mystery oil in the gas tank Lol, nah. I would tee in a Manual Vacuum Gauge, do a manual compression test on every cylinder then a wet test if any readings slightly low.
Also you can check the cam timing, turn the crank until the mark lines up with Zero on the timing scale for TDC. Remove the distributor cap, make sure the middle of the rotor is aligned with the #1 cylinder electrode. Pull the #1 spark plug and make sure the piston is all the way up.
If all of those basic tests check out then i'd be doimg a Cylinder Leakdown test with a Leakdown tester. Eventually you will find the cause/s of concern.
The timing chain may be a tooth off or somthing. Basically you are going over a complicated job that the customer did himself, i would not rule anything out.
If it has hydraulic lifters the oil could be badly diluted by now. That fits with a change in behaviour when engine warms up. Wouldn't account for original fault though.
This reminds me of an odd situation I had. The engine would start and run fine until you sped up and the it would run rough and quit. Then crank and it sounded like no compression. So I believed my experience that it doesn't have compression. Checked the oil pressure and it was over 100 psi. Pumping the lifters up and opening the valves. Changed the oil pump and oil and all fixed.
If you block the air intake it gives a symptom of little or no compression. We used to do it to help diesel engine get momentum to start. Don't know what happens if you were to restrict exhaust. Too much fuel gives the impression the engine thinks there's excess air.
1:31 thats not how the batman theme gos!
Hopefully he didn’t use a earlier style timing set with built in retarded cam timing.
I think it may be in the valve timing Ivan. When ever I built and engine I would always degree the cam specs to the cam card.
I m thinking valve timming or camshaft . then misfires can be caused by bad TFI ignition modules on ECC4
I think the wrong injector were used. That is causing excess fuel and cylinder wash during warm up (open loop) = low compression. When it warms up it goes in closed loop and cut back on fuel and cylinder cleans up restoring compression. The skew in vacuum is a result – not the cause – of poor running engine
I would check the junkyard to see how much they would scrap for it. . . …what a POS, sorry.
The only thing I can imagine that would cause all cylinders to lose compression at the same time is valves. Rings, washdown, any bearings, would not do it. Whoever setup that engine set the valves like you would set solid lifters. Valve all the way closed, tighten the nut while spinning the pushrod until it bound, then back off a half turn or so.
When the engine is cold, and all the oil has drained out of the hydraulic lifters, none of the valves will open. When enough oil pressure builds up while cranking, the lifters begin to pump up and open the valves.
If they were stuck open, even it its not an interference engine, you would hear air blowing out the exhaust and/or the intake.
Way too many variables, seems like the valves are stuck open.
have u tried blanking brake servo pipe off or brake booster can cause intake problems if servo faulty
They might have placed the order of the piston rings wrong?
My bet is on too little clearance on the valve rockers (haven't watched the entire video yet…)