'94 350: good cold starts, struggles to crank when restarting or still warm

[usar17]

1994 Stock TBI 350 w/4L60E

So this summer i noticed that if i shut the truck off to go in and shop it would struggle to turn the engine over when i got back in, like it was fighting some massive compression now. Once it got to the 2nd crank rotation it fired right up. If it sat for 2+ hours it starts fine again. I also noticed twice during the summer that while sitting idle for maybe 30 minutes, at a boat ramp with the AC on high, I went to move the truck and boat and she stalled. Only ever happened twice, same conditions. I did have an issue in the spring where the truck wouldn't crank at all. Battery tested fine, installed a new starter, still wouldn't crank right until i added a ground cable from battery to a starter mounting bolt and replaced the positive cable.

I have felt or noticed no other issues when driving this truck, except what sounds like maybe an exhaust leak. She runs great, accelerates great.

Now i have forgotten nearly everything i learned about reading ALDL data haha. This is what I pulled from sitting in the driveway cold start -> warmed engine in maybe 30 minutes.

Knock Counts: 415
Spark Advance: Jumps around 18-22.9
Block Learning Multiplier: 152
Block Learn Cell: 18
Integrator: 131
MAP: 30.6
IAC Position: 8
TPS: 0.6v
Battery: 13.4v
Engine Temp: 182.8
Barometric Pressure: 98.9
O2 Sensor: smooth sweep from 150 to 970 and back

Shut it off, restarted it: knock when to 651. all other data remained the same.

Any thoughts? One person told me, without knowing my truck or seeing any diagnostics, that it sounds like my timing is getting too advanced and making the restarts harder to crank.

 

[thinger2]

The slow crank sounds like classic chevy starter heat soak. Sometimes on a really worn starter the windings get too hot but more often it is actually the wimpy little wire on the solenoid.
When it gets hot, the resistance in the wire and the windings spike and will crank really slow.
I always put a "hot start" kit on Chevys.
Make sure you didnt pinch the knock sensor wire when you put the starter in and make sure the knock sensor isnt falling apart.
The centers of them come loose and wiggle around and the connectors are a crap design.
They sell the sensor pigtail and its easy to replace

Its one single wire right above your starter and goes to a sensor that is threaded into a water jacket on the side of the block so just know if you go to replace the knock it will pee coolant on your head.
If it doesnt, its plugged full of crud.
Poke a screwdriver in there and the crud will blow out then just be quick about threading the new one in and you wont loose much

 

[usar17]

The starter isnt a year old.

I can crank the motor easy, shut it back off, then struggle to restart it. Otherwise I was thinking heat soak originally.

I plan to replace the knock sensor being the easiest think to start with. Then verifing base timing.

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[98 Nitro]

When my 94 started up cold but not so much when warmed up it was a failing fuel pump.
Also can be cts.
BTW when the pump was giving out it ran good, until I tried towing my bass boat.

 

[DerekTheGreat]

Like you said in your first post at the end, your timing might be too advanced. Especially with the knock counts being so high like that. I'd verify that first before firing the parts cannon and replacing the knock sensor, as it costs zero dollars to do that if you already have a timing light. To do it, get the engine up to operating temp and then shut it off. Make sure the ignition is off and unplug the tan wire with black stripe located under the cover panel on the passenger side firewall. Re start the engine and check the timing. SHould be set to zero. If it isn't, put it there. I don't care what some Jim-Bob tells you about advancing the timing, just put it to zero. These are happiest there and the computer will pull the timing out anyway once it sees knock. Once you're done, shut the engine off, reconnect that connector and button everything back up. Observe any changes/improvements.

 

[PlayingWithTBI]

Make sure the ignition is off and unplug the tan wire with black stripe located under the cover panel on the passenger side firewall. Re start the engine and check the timing

^^^What he said. Only IIRC 94 - 95 has the wire under the glove box.

Edit: it's not uncommon for you to get KCs while cranking, as long as you don't when running you're good to go.

 

[usar17]

Timing is at zero...maybe 1° if anything. It's damn near center of the big notch.

Shut it off. Went to restart it while sti at base timing, still hard to get that first 2 crank rotations.

Rehooked the tan/blk wire. Floored the gas pedal and cranked it. Didn't help to start the motor...but ...after the first 2 revolutions the starter had no problem cranking it faster. So it's like the initial crank or 2 after the motor has been running. Am I some how pressurizing the cylinders and the starter can't move the fly wheel till the valves open? Running rich and extra fuel vapors are what the starter is fighting? Lol I'm getting lost in my head now.

So next thought?

 

[PlayingWithTBI]

Am I some how pressurizing the cylinders and the starter can't move the fly wheel till the valves open?

I'd hate to say it but, maybe it's hydro-locking? Are you loosing coolant too?

 

[usar17]

No coolant loss.

And wouldnt that be a constant start issue. Not just warm starts

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[PlayingWithTBI]

Maybe unless after it sits for a while the coolant leaks down out of the combustion chamber - just throwing out out there.