I drove my car in an autocross Saturday night. I noticed in the later rounds that when I would corner hard, I would lose power for a moment when trying to accelerate out of a turn. I had no problems driving home later. Someone suggested it could be something with the TPI. Has anyone ever come across an issue like this related to the fuel injection system? The car is running a stock TPI system on an edelbrock base.

 

I'd bet money that you starved the engine of oil when turning, and the fuel pump stopped running for a second until the oil pressure came back up. There is an oil pressure switch that supplies power to the fuel pump whenever the engine has oil pressure. The ECM only tells the pump to come on for a second at key-on. That only exists to prime the fuel system. After that, the oil pressure switch determines if the fuel pump gets power or not (there is VATS, but that only disables the relay from what I understand). The oil pressure switch is either on the oil pressure outlet right next to the distributor towards the driver side, or down low by the filter. It has larger wires since it supplies ALL power to the pump, not powering the relay.

This happened to me all the time when my oil pump pickup fell off (long story that inevitably ended in a rebuild...again). I mainly autox my car, and it would cut out momentarily in hard turns and coming out of hard braking. Fuel pressure would drop and lean the motor out.

If you autocrossed with a stock oil pan and didn't overfill with oil (plenty of older cars just overfill the oil to keep this from happening), there is a solid chance you starved the engine of oil and likely took some bearing material out at the same time. I wouldn't lose too much sleep over it, but I would look to address it if you want to continue driving around on that same engine.

 

Just reread your post. Since your issue happened on later rounds, it could have been simply starving the fuel pump of fuel.

Tires get warm and give you more grip AND you likely get faster on a more familiar course. That can lead to a non-baffled fuel tank that lets air get into the pickup when the fuel sloshes to one side. I always autox with more than 3/4" full fuel tank to avoid this.

 

Thanks for the tips. I started with a half tank of fuel so I could well have starved the fuel pump. The car has a 7qt milodon road racing oil pan and high pressure pump on it. I’ll get at least 3/4 tank in it for the next event and see if that cures it. I appreciate the feedback!

 

Nope, nope. nope. That is wrong, wrong, wrong.



That's better. That's what was happening. Fuel pump was sucking air.

 

I doubt the car was starved for oil, if that was the case, you'd never have made it home. It only takes a seconds to toast the bearings. A high G, high RPM corner can do it. But its not nearly as common as starving the engine of fuel.

Below half tank, things get dicey the more lateral G you pull. At 1/8th of a tank, I'd say your guaranteed to experience fuel starvation every single corner. Its not a baffled tank, so it takes little to no time at all for the pickup suck air.

Only solutions I know of are a baffled tank, or a swirl pot for fuel.

Or you constantly keep the tank topped off so it never drops below half.

 

Agreed, and that is a common misunderstanding of the system, probably confused by the scheme that Ford used in their early systems. The pump relay is the primary power source for the fuel pump. In stock configuration, it will run completely normally with the auxiliary oil pressure switch disconnected, or not even installed.

Another potential cause could be wire harness flexing or displacement due to G-forces, but that would more probably cause a complete interruption of ignition and/or injection rather than just a partial loss of engine power output.

 

I'd bet a nickel you are correct, since that's probably the likely cause. I've wondered in the past if an accumulator could be added to the system to help prevent that, but there is not a lot of extra room between the tank and engine bay on a stock body to keep a pressurized half-gallon of fuel to feed the FPR and rails.

 

You guys are the best. Thanks for all the input and putting my concerns to rest.

 

I was definitely mistaken. Clear as day from this diagram for what appears to be a later model TPI. I'm curious why they chose to directly power the pump through the switch wiring instead of just using it as a redundant means to energize the coil on the relay.

Off topic, but my oil pressure switch failed about this time last year. Shot oil down the back of the engine, pooled up on top of the transmission, and poured onto the ground. Thankfully, I was only traveling a couple of miles away. I lost several quarts in that time, and dang near ran the thing out of oil. Gotta love pressurized oil leaks... Just had to tell the AAA driver to follow the oil slick back to my house, most of which is still visible on the road today.

 

Probably in case the coil in the relay failed, and/or the switch contacts w/in the relay failed.



That would be annoying. Close call.