Paging Red - dad's truck

[Aerovette]

1995 Chevy K1500 5.7 4WD Z71

My dad has trouble relaying events to me so bear with me because I have gotten a couple variations on the details below ...

Dad drove it to the parts store for a new temp sensor because the gauge wasn't working.
He pulled the temp sensor and replaced it with a new one. The new one was wrong and he could not plug the connector in to it. He said he tried to start it (no idea if this actually happened or not) and it would not start.
He put the old one back in and it started.
He drove to the parts store and got the correct one.
He put the new one in and plugged it in and the truck didn't want to start. It acts like it jumped time but the timing set is only about 2 year sold.

I came home from work and here is what I did.
Listened for fuel pump at the fill neck.... Check
Checked spark at distributer... Check
Checked spark at a plug...Check
Took the fuel line loose and turned the key to check for fuel... Check
Sprayed the TB with starting fluid while holding the throttle open. It sputtered and coughed and tried to start but even with either it was not going to run.

Any ideas? It has gas, it has spark, it won't run. It acts like timing is off but it has not been touched. It got dark on me and late so I didn't swap the temp sensor back out for the old one. Could that really make it not start?

I did hear spark leak (snapping) so I turned out what little light there was and had him turn the key. Two cylinders for sure have arcing wires.
Would this keep it from starting / running suddenly though?

I bought new wires, but I have a feeling it will still not start after they are replaced.

Thoughts?

[Kerrmudgeon]

Did it backfire at all in all this trying? Tell you why.....my truck same as that had some bad gas and kept backfiring and wouldn't start. Took the valve cover off and it had blown two rockers off the pushrods. Bent two pushrods.

It's easy to pop the covers off to have a look if you can't get it going.

You could check to see if the chain jumped but I doubt it. Did you say a new chain 2 years ago? Do you know how to get the marker up to TDC on the compression stroke to see if it's close?

Good luck.

[Aerovette]

Originally Posted by Kerrmudgeon

Did it backfire at all in all this trying? Tell you why.....my truck same as that had some bad gas and kept backfiring and wouldn't start. Took the valve cover off and it had blown two rockers off the pushrods. Bent two pushrods.

It's easy to pop the covers off to have a look if you can't get it going.

You could check to see if the chain jumped but I doubt it. Did you say a new chain 2 years ago? Do you know how to get the marker up to TDC on the compression stroke to see if it's close?

Good luck.

I'll be damned, he did mention a backfire BUT it ran after that.

[Kerrmudgeon]

Originally Posted by aerovette

I'll be damned, he did mention a backfire BUT it ran after that.

It might run for a minute or two until the pushrod breaks or rocker comes right off, but it will run shitty.

I'm not saying it's the answer, but it's a possibility.

With the cover off you can also see if the cam is turning by the rockers going up and down.

[Steve Austin]

Did he ask for the correct sensor ? They generally have one for the dash and one for the ecm. The one for the ecm is an important part to make the motor run right.

[RED-85-Z51]

The one in the intake up front is for the ECM, the one on the left head is for the gauge...One does not effect the other.

Im guessing he is losing a ground somewhere, such as on the front at the thermostat water neck, check those grounds.

Its a TBI, so you should be able to watch the injectors spray while cranking it over, should get 2 conical fine mist patterns.

Another thing to look at is the ignition module in the distributor, these were known to fail randomly, I had a similar part on my 97 C3500 go out..I pulled it into the driveway...shut it off, ran great...came back 20 minutes later to move it...no joy, would crank, but no spark...or intermittent spark...tested everything, it all pointed to module..put in a new one, vroom...

But make sure he wasnt messing with that front sensor on the intake...thats the one the ECM uses to adjust fuel trim to keep up with the change in engine temps.

[Aerovette]

Originally Posted by RED-85-Z51

The one in the intake up front is for the ECM, the one on the left head is for the gauge...One does not effect the other.

Im guessing he is losing a ground somewhere, such as on the front at the thermostat water neck, check those grounds.

Its a TBI, so you should be able to watch the injectors spray while cranking it over, should get 2 conical fine mist patterns.

Another thing to look at is the ignition module in the distributor, these were known to fail randomly, I had a similar part on my 97 C3500 go out..I pulled it into the driveway...shut it off, ran great...came back 20 minutes later to move it...no joy, would crank, but no spark...or intermittent spark...tested everything, it all pointed to module..put in a new one, vroom...

But make sure he wasnt messing with that front sensor on the intake...thats the one the ECM uses to adjust fuel trim to keep up with the change in engine temps.

I knew you'd be the one to ask. Thanks and thanks to Steve Austin. The front sensor is what he changed. I'll bet that is the problem, but why? Swapping one for another should be fine, no?

[RED-85-Z51]

Not really...

Often, the parts drones give you the sensor for a dash light..which is either ON..or OFF, not a gauge...which sends a variable value to the gauge depending on temp...

If he has a sensor for a light..where his ECM input is..its possible it is not fueling enough. or overfuelling...

Its like...when its cold, the ECM tells the injectors to pulse longer, for mopre fuel...a cold engine needs more fuel...and as it gets hot, it pulls it back.. Also your idle speed is affected by this sensor...as a cold engine will idle higher for warmup.

Put the old sensor back in...top off the coolant....

Get a "sensor, for a gauge"....for the one in the head...

ALternate and OEM part numbers are (as per rock auto) 25037332, 5744032, TU152

I beleive, looking at osme online...if the sensor has 1 terminal in the plug It sends the lead to ground, to turn on a light...using the base as a ground...if it has 2 terminals...it uses 1 as power in (probably 5v reference) and then sends power back based on temperature, to the gauge, or ECM...

[Aerovette]

The sensor he bought is a BWD brand and the number is WT3000. The description is "Coolant Temperature Sender" but I don't know how to determine if it is a gauge sensor or ECM sensor.

He installed it here...

[RED-85-Z51]

Wt3000 or wt3000P

[mike100]

Originally Posted by aerovette

The sensor he bought is a BWD brand and the number is WT3000. The description is "Coolant Temperature Sender" but I don't know how to determine if it is a gauge sensor or ECM sensor.

He installed it here...

that's the ecm sensor for sure. GM cars from the 80's and 90's often have a separate 1 pin sensor for the gauge or for an electric radiator fan control input. Since it is a truck, there isn't an electric fan. Try looking on the passenger side cylinder head toward the back.

sometimes sending unit is here (but it is sometimes located elsewhere):

[Aerovette]

Originally Posted by RED-85-Z51

Wt3000 or wt3000P

No "P" on the end of the part he installed.

[Aerovette]

He put the old one in and it fired up. Put he new one back in just to be sure and nothing. Put the old one in yet again and it started.

[RED-85-Z51]

Yep...now have him swap out the sender..for a sensor, and put it on the drivers side head, have him check that wire too.

[RED-85-Z51]

This is my 94...

1st pic is the engine...
2nd pic is the sensor he has messed with.
3rd is the one he needs to look at, between the 2 plugs

[Aerovette]

Originally Posted by RED-85-Z51

Yep...now have him swap out the sender..for a sensor, and put it on the drivers side head, have him check that wire too.

So it was his fault at least partly. He asked for the sender for the gauge. He got it but screwed it into the ECM sensor hole in the manifold. Realizing it was wrong, he returned the part for a matching ECM sensor. Then it would not start.

What I am still unsure of is why a replacement ECM sensor would keep it from starting. It was put in the right place, it just wasn't a needed repair.

As I type this, they were going back for the original sending unit they bought and will put it in the head as the pictures indicate.

[Steve Austin]

If he put teflon tape on it that could create a bad ground or he may have just gotten a bad one. If its not right, the car will run bad, for sure.

[Aerovette]

Sonova b$#@

He replaced the thermostat and now the damn thing won't heat up. Temp gauge stays low and I can put my hand on every hose. It's either in upside down, or bad. No heater and no reading on gauge.

[Aerovette]

Originally Posted by Waco

Did you boil it first to make sure it would open properly? It might just be bad.

It is a failsafe style thermostat and I am afraid it failed and is free-flowing.

[RED-85-Z51]

Dont use failsafe, they are the worst gimmick going...they can fail either way, and are apt to fail for no reason.