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Low compression on my Spartan rebuilt engine

1994 F150, 215k mi, ~3k mi on rebuilt engine.

I purchased and installed a rebuilt 4.9L I6 engine for my F150 after a massive oil leak trashed the factory engine. I had been driving it for a few months, and had got nearly all the bugs worked out, except a fuel odor, and a low-speed miss that seemed to be getting worse.

Thinking the two were related, I suspected a fuel injector leak, only a fuel pressure test showed no pressure drop, and no anomalous plugs noted. I now suspect a leaky Schrader valve in the fuel line is responsible for the fuel odor, and I have ordered a replacement.

I then moved on to compression. Alas, my compression readings are as follows:
1–145 PSI
2–90
3–147
4–165
5–168
6–170

No 2 compression increased to only 98 after spraying in oil.

Anybody have any feedback about warranty claims on a rebuilt engine?
Should I have a leakdown test performed?
If I pulled the injector to the #2 engine, would it pass emissions, or would the unburnt O2 richen the overall mixture?
What if I pulled the pushrods out of #2?

Is there any paperwork with the engine? I assume from your post that’s you installed it and did not pay to have it installed.

Here is the warranty page of the Spartan Engines web site. You might also check with the Advance Auto Parts store where you probably bought the engine.

http://spartan-engines.com/warranty.html

Yup. It’s exactly what the paperwork says it is.
However, that should not prevent you from contacting the seller and demanding a refund. Or a replacement.

I doubt it. Besides the metering getting messed up, you’ll have a glaring CEL. And a host of codes.

At this juncture I’d recommend documenting everything clearly and contacting the rebuild company and the company you bought the engine from (if other than the rebuild company). Hopefully they’ll work with you to get to a resolution.

That would seem to indicate top end problems

What is the compression supposed to be for your engine?

It would probably only confirm top end problems, in my opinion

That’s what I would think. The pcm would read excess oxygen and compensate by commanding a richer mixture, which would certainly not help your chances for passing the emissions test

Personally, I would contact Spartan . . . or whoever you purchased the engine from . . . and try to get them to swap out the motor for yet another rebuilt. That’s what I would do, before pulling an injector and/or pushrods

If you pulled the pushrods AND unplugged the injector, there would be no oxygen sucked into or exhausted from that cylinder. But since you’re now only running on 5 cylinders, the engine would have to work harder to maintain the set speeds . . . should be 15mph and 25mph in your area . . . which would mean increased emissions, versus the same engine running properly on 6 cylinders.

And that’s not mentioning any lit check engine light for the misfire and unplugged injector. And don’t forget if the inspector sees the unplugged injector, that should constitute an automatic failure right there.

An unplugged injector might result in an incorrect idle speed. There is a section of the smog inspection, where if the idle speed isn’t correct, you can’t even perform the dyno run.

Sorry if I sound pessimistic, but I think your best next step is contacting Spartan

I think the first step would be to check the valve adjustment on the #2 cylinder. Did you do the required valve adjustments as laid out in your warranty? Don’t answer that please.\ unless you did it.

1 Like

Old-timer,
AFAIK, the 4.9 has hydraulic lash adjusters, and the rockers bolt directly to pedestals in the head. No valve adjustment procedure other than correct torque values for the bolt holding them in place.

That is good, I think you are all set to make a warranty claim, if I read your warranty correctly they will pay you $300 to put your new engine in.

Concur w/ @oldtimer … if it is possible to adjust the valves, that’s the first place to check, the valve adjustment on all of cylinder number 2’s valves. Some hydraulic lifter systems still have an adjustment mechanism, but others – like my own Ford 302 truck believe – are not adjustable.