GM '93 5.7L-dies then no hot start

[whiterice]

This is a GMC C1500, 130k that has be running great. Last week it dies while at idle in the driveway and wouldn't restart. It would crank over but no fire. That was at 9:00 at night, so I let it sit overnight. The truck fires right up the next day, but dies about 2 miles from the house and will not start again. I come by where is it parked a few hours later and it fires right up.

Now for what I have done. I have replaced the fuel pump with no better result. Changed the fuel pump rely, same no help, also have changed the fuel filter. No help.. But get this, I am trying to figure this thing out as to way it won't start. I drive it into the driveway, running great. Turn it off,(the truck is at normal temp) and it won't start. It cranks but no fire. So I hit it with some go juice(ether) and it fires and runs fine. Turn it off and it doesn't start, cranks fine but that's it. Spray ether into throttlebody and it fires right up and runs and idles fine. I repeated this about 4 times, each time it wouldn't start without spraying in the ether.

It hasn't died on me today, but at warm up it did miss a little and the tack needle jumped around abut 500 rpms. It was running rough at that time, but didnot die. Then it ran fine...
What would not let it get fuel when hot and not running? The truck is all OME no add on's at all.

 

[crash2]

weak fuel pump--or burnet dist cap....


When it does it again---spray some carbcleen down the throttle body and see what happens bruce.....

 

[whiterice]

I sprayed down the carb yesterday while it was running. What am I looking for it to do with carb cleaner?

 

[crash2]

I sprayed down the carb yesterday while it was running. What am I looking for it to do with carb cleaner?

Run for a few seconds till the crab cleaner is burnt--And do it for like 5 seconds of spray time to ensure you get enough to fire off.

 

[whiterice]

Still not following you?
Do you want me to spray down the throttle body while it is not running or while I am cranking it and it isn't starting, or get it started with and then when it is running spray the throttle body down. The last is what I did yesterday. With it running I hosed down the throttle body with about 1/3 can of carb cleaner. I thought about the dist, cap but since it starts and runs I kind of just passed on that. How would that not let it start but run fine?

 

[crash2]

Next time it doesn't start bruce--follow these steps :awesomework:

1. remove the air cleaner assembly from atop the throtle body(single t-handle bolt thingy)
2. with right hand open the throttle body to wide open
3. with your left hand take the can and spray it for 5 seconds
4. close the throtle body
5. reinstall the air cleaner
6. crank and see if it starts and runs for a few seconds

Try that bruce :awesomework:

 

[whiterice]

All steps complete:
No start, no pop or fire, nota,, zipo, no start

It is just outside in the driveway.

 

[Zoediak]

just a thought.... and it may not even be the problem, but have you thought about taking the ignition module down to the parts store and having it checked out to see if there is any problem there?

it would only cost you the time to remove and the gas to go to the parts store and back...

just a thought....

I only mention this because, recently, we had a problem kind of similar... except ours would die about a block down the road and not want to restart... then hour or so later, could hop in it and fire it up.. then it would get to temp and crap out again...

 

[crash2]

All steps complete:
No start, no pop or fire, nota,, zipo, no start

It is just outside in the driveway.

You need to see if your getting spark

How old is the dist cap?

 

[whiterice]

mike:
Not sure, only have had the rig a little over 6 mths.
Way will it fire right up with ether, is it just because it doen't need as strong of spark?
I'll go pull the cap and see how it looks. Just from the looks of the engine it seems to have had normal service.
Be right back,

 

[crash2]

mike:
Not sure, only have had the rig a little over 6 mths.
Way will it fire right up with ether, is it just because it doen't need as strong of spark?
I'll go pull the cap and see how it looks. Just from the looks of the engine it seems to have had normal service.
Be right back,

If its a stock cap--it will have a bar code sticker on the back side of the cap...

 

[whiterice]

So it's been a looong time since I pulled a GM cap. Last one had the coil in the cap. This one is more normal. There is wear, brass ends, no crack lines or crossfire tracks. Cap is same, I would replace it just on looks alone, min 30k at least. Rotor shaft has rust on it, not much else in there..

Should I go get parts and see if that helps?

 

[crash2]

So it's been a looong time since I pulled a GM cap. Last one had the coil in the cap. This one is more normal. There is wear, brass ends, no crack lines or crossfire tracks. Cap is same, I would replace it just on looks alone, min 30k at least. Rotor shaft has rust on it, not much else in there..

Should I go get parts and see if that helps?

They are 100k caps

I would check to see if you have spark at the plugs..

 

[whiterice]

Wow,
So first off it was starting because it cooled down, so I hot rodded it around the block in first gear(auto) it ran up to 4500 and shifted, smooth running.
Pulled into the driveway and no start, pulled a plug wire and cranked it and I couldn't get it to jump to the plug. So to ad to the test, I sprayed it with ether again and bamm it fires up,, weird,,,,,,,,,
So I didn't see spark on the no fire
What's up

 

[GaryTJ]

sounds like weak spark. Take a good look at the coil wire. If either end is corroded, replace it. If it is OK, replace the coil.

another possibility is lack of fuel due to wires arcing inside the tank. Did you replace the pump itself, or the whole module?

We always replace the wires to the top of the module from the pump, and if any of the pins that the wires attach to are brown from heat, we replace the whole thing.

 

[whiterice]

When I replaced the fuel pump, it came with a new wire harness. Four wires, two to the gauage and two to the pump motor. The old ones looked fine, but I replaced them with the new ones anyway. Also cleaned by light sanding the pins that they pluginto on top of the pump assy. housing. I hope I don't have to go back into the tank,, dam 42 gal pig.. I had drained the tank first, but since then I have filled it up, thinking maybe bad gas.. No luck, still has the no start when hot..

 

[Zoediak]

have you checked for the spark yet???


I know that coils, and as I mentioned before, ignition modules will lose spark (get much weaker or none at all) when they get hot.

I would check them out.

because generally when they cool down they will throw a hotter spark...


just the nature of the beast, and I have gone through it all before... thinking I wasn't getting fuel and replaced everything... then plugged in a different module I had laying around... and that was the prob.

 

[whiterice]

It just hard to figure, it runs so well once it is starts. I am calling it a night and will sleep on the idea of buying anything else. Coil? Sure seems like a temp sensitive problem. Why will it go from a no run to run great once started if it has a weak coil, it revs fine under load while running. Anyway, thanks for the tips.

 

[Binder]

When it dies try to verify that it is or is not getting fuel. Maybe hold a piece of paper under a injector and crank it to see if there's fuel on the paper. Be carefull not to suck the paper into the intake.