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manifold pressure and transfer pump


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Hi, I have a 2000 CX 460 etech and for the last month it's been stuttering of and on and the manifold pressure varies a lot with the footpedal down. Sometimes pressure increases sometimes no response to throttle. Most pressure I ever get is 25 psi if I get any. Could it be fuel transfer pump not working like it should? It got new fuel filters n no difference . Sometimes my truck runs 75 with a tailwind, other days it barely pull 55!

I have been checking the forum but haven't been able to solve problem yet. Looked at check valve n it looked fine. Took for T27 screws of transfer pump n didn't see anything concerning, but hiw do you know if that thing is bad? I haven't checked the fuel pressure but to me that could be the problem. When I try to accelerate the manifold pressure might rise in spurts to 25 psi n without warning drop back to 10 psi. It's just like driving with a part time turbo, lol.

Thanks for any answers to my problem

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It does sound like low fuel pressure, the engine needs fuel to make boost. With the cover off the supply pump, see if the gears in the pump will turn by hand, if they will the drive gear is slipping the shaft. There is a plug in the front of the block just above the timing gear cover that can be used to hook up a gauge to check the fuel pressure if you find the pump is OK. There is also a plug below it behind the cover, sometimes that plug will come loose and cause low fuel pressure and leak fuel into the engine oil.

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Thanks for your answer Sir, I will check gears again, but last time I touched them they didn't seem to have slack. But what I forgot to mention in my question also is that sometimes my truck yerks like it doesn't get any fuel at al, for like a split second, but I can not reproduce that by turning the key off cuz that lasts longer. I will post if I get my problem resolved

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  • 4 weeks later...
  • 2 weeks later...

Can you actually check fuel pressure at the pump delivery? And I assume you checked for leaks already.

As Rick said, pressurize and test all the CAC/tubing for leaks, and while you're at it, check the turbo. Excessive play in the turbine shaft or damaged compressor wheel could cause it, and make sure it doesn't bind when you spin it. Check the air cleaner..the obvious stuff. Feel free to whoop 30PSI of air to the charge air system, it'll take it and it better not whistle. Soap and water helps finding leaks in the cooler itself.

Eliminating any air-related faults, you're back to fuel. Any smoke? Lightning bolt light coming on? A misfire can cause boost to drop off.

Full load @ rated speed should be 35PSI, in the real world we'll see 28-32 and that'll be OK with some miles.

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