Fuel pressure drop at 180

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Fuel pressure drop at 180

Post by Rad94 »

My Diamondback with an LSA 6.2 is throwing the check engine light every time it hits 180 degrees. As soon as the light comes on the fuel pressure drops from a steady 59 to 35 in a matter of seconds. It seems like it is starving for fuel and I have to shut down and let it cool. I've tried keeping it under that temp but being summer in Louisiana and carrying passengers keeps it running hot.

The codes are SNP-4236, 4237, 4238, and 4239. It says they are for Short and long trim in banks 1 and 2.

We have replaced the fuel control cell,the head the wiring went through, high and low pressure fuel pumps. Nothing has fixed the problem yet.

Any ideas what our problem could be?


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Re: Fuel pressure drop at 180

Post by unforgiven11B »

The newer PCM/Levitator engines go into “limp” mode to protect them when they reach 220* as a protective measure. The engine will be limited to 2000-2200 RPM once the engine drops below 1200 RPM it will allow you return to full power. Have you tried a new temp sensor? Might be faulted. Strange you aren’t overheating and it’s going into Safe mode. Do your plugs look ok? How about grounds? They will play hell on LS motors.

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Re: Fuel pressure drop at 180


Does the temp stay at 180 or does it shoot up?

Curious if you have checked the coolant or if steam may be a factor.

Unforgiven is 100% spot on with swapping out the sensor, and chasing that path.

I'm just thinking out loud ahead of that swap.

One Eyed Gator
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Re: Fuel pressure drop at 180

Post by One Eyed Gator »

Maybe PCM runs a different thermostat. I thought stock LSA thermostat was 190 degrees.

Codes are for adaptive learn and closed loop. Some systems will not run in closed loop without the motor being at the correct temp.

Could be sensor or voltage or ground to sensor. Also if it is running learn it will increase the temp quickly.

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Re: Fuel pressure drop at 180

Post by cadillacktm »

My boat was doing the same thing and I had to put a lower temp thermostat in my LSA and my issues went away. Not sure where I got the thermostat from.

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Re: Fuel pressure drop at 180

Post by Rickswamptours »

Im also working on this with Robert.
When the engine gets to about 180 (running 4500rpm or more), the fuel pressure quickly drops. I put it on the computer and had the fuel pressure gauge on it. Fuel pressure stayed around 59 till the temp started climbing then the check engine light came on and fuel pressure started dropping. I tried to hook up a volt meter to read if its a voltage problem. Other than the fuse panel, im not sure where to hook up cause the high voltage wires go inside the fcc

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