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My 98 F 150 with 60K miles was in storage for a year and started right up with no problem until I drove it about 5 miles and then it would not start at first. It took about 20 tries to get it to start. I drove it back home and tried to start it again and same problem. After it started I turned I off and on several times without a failure over several days. I took to a shop and they have not been able to get it to fail either. They found codes for lean fuel mixture and want to replace the relay, fuel filter and fuel pump. Do you the way to go?
Tests have to be made when the issue is present to see if it is fuel, ignition, or power in some form.
Of course address the codes first.
If the codes are 171/174, don't go for a fuel pump unless it is proven.
These codes are shifted fuel tables that could be from Rodent damage or just rotted rubber in the PCV line. Look behind the upright intake manifold where the PCV hose terminates.
Sounds like to much guessing at this point and not enough testing.
Good luck.
The battery relay assembly was out of stock a few months ago when I had a similar issue. I went to an old school auto parts store and he made me one from 2 separate assemblies. When installing the relay, I pulled off the passenger tire and inner liner. I found the ground points were bad where it attached to the frame and the starter as well.
On a separate note, there is a wire bundle running thru there. When the battery ends get replaced a few ties, the relay cable assembly gets shorter. This causes the wire bundle going to the trans and parts aft to ride on the exhaust manifold. Cleaned, replaced relay, threw in a new starter, repaired the wire bundle and have zero issues.
The burnt bundle explained why the PO had run jumpers back to the OD on the trans as well. Just throwing it out there for you to consider. Cleaning grounds and checking out your battery relay is cheap enough.