2007 Impreza won't start until bumped or jolted

[robrob]

My girlfriend's son has a 2007 Impreza. The last few months it will randomly not start.

1. One day he drove fine, stopped at a park. Hour later goes to leave, wouldn't start. I jumped it and it started fine. It occurred a few days later. Another jumped worked. We had battery/alternator/starter tested. All were good.

2. It happened a third time. We got a new battery, just in case.

3. Several days later it occurred again. We changed spark plugs.

4. Several days later it occurred again, this time in a parking lot. We had it towed to a mechanic, explained the issue. It was loaded on a flatbed truck. When the mechanic unloaded it, it started right up. And continued to start throughout the day. The mechanic found no codes, cleaned the throttle bottle thinking that might be it. It seemed fine.

5. A week and a half later, it occurred again, this time at home. Attempts to move/shake it to start were made, nothing. It was finally towed to another mechanic who has experience with Subarus. As before, once off truck started fine, repeatedly. They never encountered it not starting, no codes found. Just in case a new started was installed. It seemed fine. This was last Monday.

6. Last Friday son goes to leave school, wouldn't start. He eventually put it in neutral, it slowly rolled and bumped into a curb. It then started.

My question - is this a fuel pump issue? If so, should it be throwing a code? Both mechanics said no codes were thrown and couldn't figure out any problem.

I appreciate any feedback.

 

[Ecmbuster]

By random, is the stater cranking? Is the starter cranking and the engine not start during that failed event?
There is a profound difference between the two events
Did any one check the battery negative connection to the body? Did anyone check the ground straps between the engine block and the body?

 

[robrob]

When attempting to start, it does crank. You hear the engine trying to engage. It sounds like it **almost** wants to turn over.

The battery was checked out, when engine idling and when engine is off.

I am unsure about the ground straps.

 

[Ecmbuster]

If it cranks over, check for spark and fuel pressure, providing the ignition key is recognized.
Look at the "key reader" at the ignition switch and make sure that are NO fancy "bling bling" stuck on near the ignition cylinder.
Other keys or "transponders" on the same key ring is also another issue.
(throttle bottle = throttle body)
At the same tine, with a scan tool, read the cranking RPM. No RPM, no start.