Is my engine getting enough fuel?
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Is my engine getting enough fuel?
89 460 EFI in a rock buggy, I have a fuel cell -> aftermarket high flow filter -> stock high pressure pump -> motor. The fuel cell is located above the engine height, and the fuel pump is at the lowest point of the frame.
I tested the fuel pressure at the test port and got 38 PSI IGN on, 30 PSI at idle, when I revv the engine to WOT, the pressure slightly goes up to 36 PSI and then drops to 30 without me letting off the throttle. Is this normal, or should I need to put a low pressure pump right after the fuel cell.
I tested the fuel pressure at the test port and got 38 PSI IGN on, 30 PSI at idle, when I revv the engine to WOT, the pressure slightly goes up to 36 PSI and then drops to 30 without me letting off the throttle. Is this normal, or should I need to put a low pressure pump right after the fuel cell.
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From: Colville, Washington
Those pressures sound fine for a stock 460 EFI system, about the only thing is the distance between your pump and tank. An electric pump makes a lousy puller of fuel, it would be best to be as close to the fuel tank as possible or use a low pressure pump at the tank. The pressure change is related to vacuum, the acceleration causes lower vacuum which the regulator responds to by increasing fuel pressure. It goes down once RPM's stabilize and vacuum goes back up.
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Thanks for the responses. My thinking, which might be flawed, is that the pump doesn't have to pull much since the fuel cell is the highest point of the system, once fuel starts flowing from the tank, it won't stop (like when you're siphonning gas). My main concern is why the pressure drops down to 30 PSI, after it has spiked up to 36 PSI, while I'm at WOT (the vaccum has not changed), isn't it suppose to stay at 36 PSI? The engine revvs fine at idle, but I'm trying to diagnose lower power upon acceleration, I'm only down to 2 options: either lack of fuel, or bad MAP.
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From: sunny fla sometimes windy
The pump is pulling too good could also be the problem if it is mounted far from the tank!! It is actually CAVITATING it lowers the pressure in the line enough to actually
cause the fuel to boil!! either get a low pressure pump near the tank or move the
pump you have closer to the tank ( that is why single pump systems are actually in
the tank!!) Make sure that if you add a pump it can supply the high pressure pump
what it needs flow wise. I would try moving the pump you had as opposed to adding
more wiring, breaks in fuel line another pump etc. KISS keep it simple especially on a buggy!! Put a bigger line feeding the pump input or make two lines going to it and
keep it under say 2 foot from the feed in the tank.
cause the fuel to boil!! either get a low pressure pump near the tank or move the
pump you have closer to the tank ( that is why single pump systems are actually in
the tank!!) Make sure that if you add a pump it can supply the high pressure pump
what it needs flow wise. I would try moving the pump you had as opposed to adding
more wiring, breaks in fuel line another pump etc. KISS keep it simple especially on a buggy!! Put a bigger line feeding the pump input or make two lines going to it and
keep it under say 2 foot from the feed in the tank.
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Thanks all for the replies, I tested the volume of fuel at the return line and it was .5L per 20 sec at idle, which is within specs by Chilton.
I pinched the return line and pressure went up to 60 PSI and the motor ran better.
It turned out that my injectors were bad, I put on a new set, and the motor is running top notch now.
I pinched the return line and pressure went up to 60 PSI and the motor ran better.
It turned out that my injectors were bad, I put on a new set, and the motor is running top notch now.
