Specific engine issue 4.0 OHV 1994


Tater Tot

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It ran just as crappy with the new ones as it did with the old ones lol
 


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rusty ol ranger

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Your 29 PSI fuel pressure seems low.

Have you changed the filter and pump?

Im not sure how you would diagnose an ECM issue in this situation.

@RonD
 

Tater Tot

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Your 29 PSI fuel pressure seems low.

Have you changed the filter and pump?

Im not sure how you would diagnose an ECM issue in this situation.

@RonD
I’ve changed the fuel filter like 3 years ago, no to the pump. Fuel pressure seems a little low but barely, not seemingly enough to cause this issue. I mean when I rev it it’ll go up past 30 psi on the rail and stay there. So I don’t understand how that would be the problem. Haynes says 30 psi min. I’ve seen 30-40 psi on several threads for my engine, seen others with like 28 psi than ran fine. Fuel injectors can be opened for longer to account for the minimal pressure differential by the pcm.
 

Tater Tot

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If it was the fuel pump, then I don’t see how it would work better at high rpms.
 

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#9 " Done vacuum tests, vacuum (if idle stays up) is like 19 Mercury. It stays there, goes to 20 or so when revved. Drops down low when it idles low, but when it’s idling high, the vacuum seems alright. Like when I rev the engine, the vacuum is fine. "

When you rev a engine the vacuum pressure on the intake should drop. not stay the same or increase. check the brake booster for air leak, vacuum leak, if you are sure all other lines are fine.
 


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