Greetings chris032188,
Looks like the OP's first and last visit to this forum was back on May 4th. But elsewhere in this
forum we've troubleshot a similar issue, so we'll just pick up this thread and run with it.
From your description it sounds like you have to employ the "Clear Flood" mode (ie: holding the
gas pedal to the floor while cranking) in order to get your vehicle to start once it's warmed up?
When you do this you are telling your TBI computer to override it's fuel delivery calculations and
instead meter a very lean ~20:1 A/F mixture in order to help clear a flood condition.
(I'm assuming that this is for your '94 5.7 K3500?)
The short story is that the ECT has a lot of authority over the quantity of fuel being delivered
when the engine is cranking over. And if the sensor goes out of calibration / fails open (or there's
an open in the wiring harness to the sensor) ...then the TBI computer will think it's -40° out,
and responds by delivering an impressive amount of fuel, leading to a crank/no start at normal
temps and rough running for a short while afterwards.
In order to get yourself up to speed on all this, here's a thread where we troubleshot a vehicle
with starting issues very similar to yours. In response to the OP's description of only being to
start his vehicle by holding the gas pedal to the floor, I posted the following:
https://www.gmt400.com/threads/truck-wont-start-need-suggestions.65257/page-2#post-1370733
You might want to read the entire thread from the beginning in order to get a good feel for
troubleshooting this kind of problem, but at the very least go to reply #
43, open the video,
and fast forward to ~13:15, and watch how much fuel his truck was spraying while cranking.
(The manual mentions that the cranking A/F ratio goes from 14.7:1 at 201 degrees all the way
to 1.5:1 at -33°F. (!)
Note: The OP was having trouble getting a good, stable reading with his multimeter during testing,
but persevered, changed the faulty sensor, and got his truck starting as it should. After the fix I
asked the OP if he would mail the old sensor to me, which he did, and I was able to verify the
sensor had failed in reply #
71.
****
Elsewhere on the interwebs people will suggest throwing parts at a problem (parts cannon
in Ready, Fire, Aim mode :0) ...but doing so can lead to a GMT400 owner to dig an expensive,
deep hole with the original problem remaining, but now joined with additional ones. Yikes.
Instead, you will find that the folks who hang out here will ask yout to troubleshoot first, and
replace parts based upon test results.
As always, the above is just food for troubleshooting thought, and no guarantees that the solution
shared is the correct one for your issue. YMMV. But it's something to consider.
Check it out and be sure to let us know what you discover.
Best of luck --
