94 Truck problem solved

[TK]

This one goes in the book!


-----Original Message-----
From: EFISYSTEMS at aol.com <EFISYSTEMS at aol.com>
To: diy_efi at efi332.eng.ohio-state.edu <diy_efi at efi332.eng.ohio-state.edu>
Cc: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: Wednesday, May 26, 1999 8:09 PM
Subject: 94 Truck problem solved


>HI Everyone,
>        I first want to thank everyone that took the time to help diagnose
>this thing.  What struck me was someone who said to check the
>basics.......Sometimes people like us get so involved in finding an efi
>problem that we do forget the basics......my biggest problem was I did not
>talk to the customer long enough,,,,,,to  find out the problem started
almost
>a year ago but just recently became severe.......well I did find the root
of
>the problem during my initial scan.....when key on was applied with engine
>not running and fuel pressure came up...fuel was blowing by one of the TB
>injectors and after disassembly discovered bad o-ring.....replaced and no
>more fuel leak.....still engine would run ok for a few seconds but would
>start running rich......had already done a compression test but turned out
>ok........I won't bore you guys with the details but I had to start
thinking
>back what I would do if this had a carburetor on it,,,,and since I had
>verified fuel and spark it must be mechanical......so looked back over my
>compression chart and noticed #3 was the lowest cylinder so I checked it
>again and now was even lower, so checked the one next to it to verify it
>wasn't lower due to temp,,,,,no it was the same so re-checked the #3 in
case
>I just hadn't cranked it enough times......guess what now it's 0
>pressure......now can assume broken valve spring or sticking
valve.....remove
>valve cover and check....no broken valve spring but intake valve is stuck
>down.....remove rockers and tap top of valve with hammer and... "pling"...
>valve comes up......solution, leaking injector, over a period of a year,
has
>built up excessive carbon on top of intake valves and is now causing them
to
>stick open randomly.......so anyway,,,those that want can sit back and
point
>at the screen and laugh.....I am.......it was actually a good road trip
>looking back on it......cya later
>-Carl Summers
>