Quote:
Originally Posted by LakeErieFishing
The fuel pump is mechanical and new this year. It's not the fuel pump.
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Here's a mildly related story... which happened to me.
I had a car that did the same sort of thing. When cold, it would run fine. But when warmed up, it would lose power and sometimes I couldn't start it again if I shut it off until it was stone cold.
We checked everything that you can think of. It seemed like it wasn't getting any fuel, so we replaced the mechanical fuel pump.
The problem continued, so I ended up solving the problem at the time with an electric fuel pump. This seemed to solve the issue, and we couldn't find out why the mechanical fuel pump would stop pumping fuel when the engine was hot.
One day when I had nothing to do, I decided to try to find out why the replacement brand new mechanical fuel pump did not solve the issue.
I removed it and analyzed it very closely to fully understand how it worked. It was a very simple device, so I couldn't understand how it wasn't working when the engine was warm. As long as the pushrod that was activating the mechanical fuel pump was pushing in on the pump's lever, then it had to work. There was no way that it couldn't function when warm if the lever was being depressed.
That was the clue! This car had well over 170,000 miles on it (closer to 200,000). I removed the pushrod and found a replacement, mostly as a comparison as the end of the original one seemed to have a bit of wear on it. It turned out that the old one was just a bit shorter than the new one due to wear (it probably wasn't getting enough oil, or was a bit softer than it should have been, perhaps due to a manufacturing defect).
Evidentially, over the many miles, the push rod had some wear on it. And as the engine warmed up, some tolerance would change due to the heat, which would cause the mechanical fuel pump to not pump the fuel because the push rod that activated wasn't pushing fully enough on it's lever.
At the time, the replacement pushrod cost me about $5 to replace.
I replaced the old pushrod with the new one, and was able to remove the electric fuel pump.
So don't just think that because you replaced the mechanical fuel pump that the problem is solved. You still need to verify that the engine is getting enough fuel when it's warmed up and under load.
I can't tell you how many hours we spent trying to find the source of this issue.