Vacuum Leak or Fuel Pump

I recently had a Jasper rebuilt engine installed in my Ford E150. Since than my check engine light keeps coming on and the computer is saying my cas air mix is “lean”. The instaler says i need a new fuel pump.
Another mechanic says it is more likely a vacuum problem.
I know it’s possible that the fuel pump is bad bur since this has just started since the install, I don’t believe it can be the fuel pump unless it’s just one hell of a coincidence.

Anyone have any thoughts?

Have the fuel pump pressure checked. If it falls within range then have them look for a vacuum leak or a small vacuum hose that was not reconnected. Make sure they check the cheap plastic “T’s” as well. They crack easily.

Test the fuel pressure.

I would be leaning toward a vacuum leak.

Since replacing an engine involves alot of work… removing the old engine/installation of the new eninge, disassembly and transfering of parts, there is a good chance of a vacuum leak. I would start there.

If it is a fuel pump… a good technican can easily diagnose that with a fuel pressure gauge.

And if it’s a vacuum problem, a technician can check that with a vacuum gage.

I’m curious… is this rebuilt engine a direct replacement? Is it stock configuration? Nothing that might require a change in fuel pump?

As noted, there is no need for anyone to stand around and guess. Fuel gauges, vacuum gauges, smoke tests…there are all sorts of ways to figure it out.

What are the exact codes? P0171? P0174? One or the other or both? Or something else? There are more causes than an actual lean condition. Has anyone cleaned the MAF sensor? Are the O2 sensors new or old? Specify, including the codes.

If the code is PO171, I had that code about a year ago on my '02 Ford Escort, I changed the 02 sensor and resolved the problem.