1997 Ls 400 Won't Rev Beyond 4000

[MUDGUTS]

****UPDATE****

The problem is now resolved and I can confirm the car performs as it should do, right through the range, transmission operating correctly, etc.

Today the technicians at Thor Racing, Coventry, had a look at the fuel pressure and confirmed it was low, so had a look in the tank at the pump with the intention of replacing this, they also had a look at the fuel filter (which was clear) and after a good look around, discovered a fuel clamp, hidden away on the fuel pipe by the differential. Once removed, the fuel pressure was confirmed at correct, the car road tested and as I say above, it is 100% now.

Thanks to everyone who contributed to this thread, as SRK said the fuel pressure should be looked at. I think the voltage rise to the pump had been checked when the car last went in but we ran out of time to persue this any further and I have been living with it since I bought the car. The increased noise from the pump recently is still a mystery but the pump is now silent.

Somewhere a mechanic is missing a fuel clamp...

[SRK]

That's great news! If the pump is silent, it's happy. The reason for the noise is that the clamp would have produced very high pressure on the discharge side of the pump, but reduced pressure at the fuel rail. The pump was under a huge load in other words, and removing the clamp allowed it to run at the designed pressure.

And that's a cheap fix, which is good too!

SRK

[landar]

Wow, thats 'freakish'. So the pump was ok but the rubber fuel line was pinched, restricting flow. Still do not see how the RPM was limited to the same amount with and without load. Oh well, glad you got it sorted out and thanks for the 'closure'. ;)