I had an odd problem that I thought was behind me crop up this morning. See the specs below for context of just what this thing is. I didn't build it and fuel injection is rather new to me so keep that in mind.

6 months ago when first driving the car I proved Mercedes right for not trusting their customers with a dipstick when I overfilled the oil. This resulted in gradually worsening loss of power until the thing just wouldn't go at all. No white smoke, nothing, just refusal to respond to the throttle. I thought it was a miss but finally realized the oil situation and once I drained out the excess it righted itself and I drove another several hundred miles without a hitch. Now this engine has a vacuum pump which as I understand it is supposed to do great things to improve ring seal. Its little catch-can however seems to fill with oil rather quickly. Is that normal?

This morning it was deja vu all over again. At first I chalked it up to the cold morning but it soon dawned on me that it was the same symptoms as before. The thing is I haven't added a drop of oil recently and it has been running well enough until this morning when I had to turn around for home it got so bad. What I wonder is, could the catch can be filling with oil and then preventing the vacuum system from doing its job? Thus the crankcase builds up pressure (there is no other vent) and blows oil into the combustion chamber? (Or something else as there is no visible smoke) This would seem to be supported by the fact that letting it sit for a minute fixes the problem temporarily (pressure bleeds down?) Could also explain the excessive rear main seal dripping in the garage as oil is forced out. Furthermore today I saw that the serpentine belt is split, perhaps overheating on a vacuum pump that refuses to turn?

Anyone familiar with vacuum pumps that can point me in the right direction?



From the ad when I bought it:

• Original 4-bolt LT-1 block bored .040 with a 3.75" stroke forged Scat crank, Scat 6" forged H-beam rods, and forged SRP flat top pistons (0 deck height)
• ARP main studs, head studs, and bolts used throughout
• Pro-Action (now RHS) aluminum heads (63cc chambers) with 2.10" intake valves and Isky springs
• Comp Cams solid roller cam (Intake = .577/.248 @ .050, Exhaust = .583/.254@.050 w/112 degree lsa)
• Cloyes billet timing set
• Edelbrock Victor Jr. "E" intake with a FAST 1350 cfm throttle body
• Accel Gen VII Direct Fuel Injection (DFI) ECM running sequentially through 42lb Ford Motorsport injectors
• Moroso crank trigger to alleviate harmonics commonly found when using "Dual Sync" distributors
• Hooker Super Comp headers with custom 3" exhaust all the way out the rear
• Meziere electric water pump (controlled by the DFI ECM)
• Aeromotive fuel filters and regulator with a Mallory electric pump

 

Hopefully you can go back to the engine builder with these problems and get some answers. Here's my take: The vacuum release valve is malfunctioning (not opening when you exceed the desired vacuum setting ~ 10" Hg for a street engine). The more the pump tries to suck air from the crankcase, the more power is diverted to turning the pump. Finally the vacuum pump starts dead heading/seizing causing damage to the serpentine belt.

A contributing factor is the amount of windage oil you're pulling from the engine itself while driving. Unless your pump has incredible suction and is pulling oil out of the sump (unlikely), the crankshaft is whipping up the oil inside the crankcase which, in turn, is sucked out of the engine. Does the engine have a windage tray or crank scraper installed? How much liquid does your catch can hold when it's full? The catch can should contain just a smattering of oil under normal use on the street.

Again, these are just my take on the problem, YMMV. Good Luck!

 

Nevermind the vacuum pump hypothesis (though I still have that to look into also.)

Here is the culprit of the rough-running, a dead pushrod:







Not sure what the cause of the failure was. It's rev limited to 7k and I don't hit that hardly at all. Everything in there is relatively new, just a few 1000 miles. Will take a better look at what's available but it may have just been a bad one in the batch. Looks like I can replace the one rocker without having to buy a whole set though I'll be replacing all 16 pushrods.

 

Frustration: Rocker, all pushrods, and all spark plugs replaced ... symptoms remain unchanged!

The demolished pushrod is clearly too much of a coincidence to be unrelated, but the amount of debris in the oil pan and filter is exactly what I'd expect from what is missing from the pushrod. So I have a hard time imagining a destroyed cam lobe or lifter without there being more debris. I haven't rigged up a dial gauge to check that the lift is correct yet but visually it is moving a reasonable amount.

Could the mashed pushrod have done further damage to some other component? Broken roller lifter that didn't drop any parts into the pan? Could there have even been valve to piston contact? I'll check valve lift and cylinder compression, anything else I can test before being forced to dig deeper?

 

Without any pressure on that push rod the lifter more than likely will bounce on the cam lobe. My guess would be either cam lobe or the roller on the lifter or both damaged. Probably be best to pull the intake & see if you can pull the lifter out of it's bore. Inspect lobe for damage. Good luck....

P.S. If you plan on spinning it up to 7k I would also install a rev kit. http://www.iskycams.com/pdfcatalog/2004-05/page21.pdf

 

Thought I'd resurrect this thread as there has finally been some development. Ran a compression test and leakdown and the suspect cylinder is fine by both measures. Cam and lifter check will be next weekend, off comes the intake, likely out comes the radiator and red goes the bank account for a new cam and lifter set! Still better than a piston/valve clash by far!

The only other thing I can think of is that maybe the O2 sensor was fouled while the pushrod was broken, I'll probably pop that out just to have a look before tearing things apart.