THSCC Forums

I had trouble with the gauge sender one day. The one that went to the ECU was fine, so I never had a CEL or other problem... just the temp gauge reading too cold all the time.

Jim Pastorius wins the prize It was the fuel pump. Thank goodness we were able to get the car out again today. So the cutting out was "softer" than I remembered it ... in fact the first indication that something is wrong is that the car was only getting to 90 on the straigh at VIR-S where on previous laps 95+ was easy. But it was hard to feel. Then the power began to surge, then it would stop revving all the way up.

The car ran great for one session, and I was able to get the cutout on the 2nd session after about 3 laps of really driving hard. So we jumped out of the car, put on a fuel pressure gauge, and went out for another stint. Good pressure was 38-40 under load. Over a few hard laps the pressure dropped to 25-30, then the power loss became obvious.

Came in again and threw a new fuel filter on it. Went out, same problem. Came in again and put on a spare fuel pump from the parts car. Went out, problem solved -- fuel pressure stayed at 40 psi consistent.

Thanks to Jim for advice today, Ron for helping and lending tools, and Colin for riding along to help diagnose. I had a list of 15 different things to try/swap, but talking with Jim led me to look at fuel first, glad we did.

We're READY for the Lemons race in 2 weeks!

_________________
Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

Glad you figured it out. Out of curiosity, where is the fuel pump located? And what was heating it up?

_________________
Richard Casto
1972 Porsche 914
2013 Honda Fit Sport
2015 Honda Fit EX
http://motorsport.zyyz.com
Money can't buy happiness, but somehow it's more comfortable to cry in a Porsche than a Kia.

Pump is right in front of the driver's side rear wheel, accessible from under the car pretty easy.

So I wasn't exactly correct about the head-related assumption. It was just load and duty cycle. The weak pump has enough oomph to get the rail pressurized to 40psi at lower duty cycles (street, pits, slow laps) but eventually couldn't keep up with high duty cycles (balls-out laps).

It could be the pump was internally heating up and contributing to the problem, but I think the main issue inside the pump is probably leaky check valve, blockage, or maybe a diaphragm leak. I was thinking about taking it apart but it's got this massive crimped aluminum can on it that I'd have to cut or grind away -- with sparks - which I decided was a bad idea.

_________________
Mike Whitney
whit32@gmail.com, 919-454-5445
V10, V8, V8t, I6, I6, V6, F4t, I4, I4, I4, I4, I2, 1, 1

We're READY for the Lemons race in 2 weeks![/quote]


You hope you are ready! Remember, "Rubbin' is Racin'".

_________________
Rubbin' is Racin'