'96 GMC C1500 305 Ext - Hard Starting

[Garage Mechanic's Companion]

Hi Gang,

 

Here's my problem:

 

About 6 weeks ago, while on my way to work, out of the blue, the truck died on the side of the road. I had the local garage tow it in. I picked it up that night. I was told that the crankshaft position sensor had gone (no spark), but it had not thrown a code.

 

I took it home that night. The next morning, I had to crank the engine for ~30 seconds before it would start. When I started it again to go home (9 hours later), it started fine. Would do this consistently.

 

After talking to a buddy with a similar truck, he had had fuel system problems (stemming from a clogged fuel filter) which had resulted in a similar starting problems. After 2 days of this BS, I took it back to the garage and had the fuel filter changed (can't remember when I last changed it). No avail.

 

Sidebar: I was told by mechanic that I should change O2 sensors, could improve gas mileage.

 

While under the truck looking for/at O2 sensors, noticed that the CPS sensor that had been "replaced" appeared to be used! Ordered new CPS, replaced it myself, hard starting problem went away. Won't be going back to that garage!!

 

Fast forward to this past Monday: I had been on the road and the truck had not run in about a week. Tried to start it, had to crank for ~1 minute (in the end, had to boost it off the car). Truck started fine that afternoon. Didn't try to start the truck again until today. Wouldn't go, didn't feel like messing with jumper cables, hitched a ride with the wife.

 

After all of the cranking, when it does start, it catches about 1-2 cylinders at a time. Once running, it runs fine. All of this time, it has not generated any fault codes. BTW, it has about 70k miles on it

 

Any ideas? Anyone encounter an issue like this?

 

Thanks in advance,

 

Derek

[02 Silverado Z71]

"Sounds" like a fuel pump problem.

 

When you know it is going to act up again, do this. Install a fuel pressure guage on the fuel rail. Have a buddy watch the guage.

Turn the key on; but don't start it. With the key "on", fuel pressure should jump to 60psi. If anywhere under 60 psi, could be a fuel pump.

 

Could also be any number of things. How's your cap and rotor? How are tune-up items? Worst thing we can do is guess; just trying to give a good starting point.

 

Could also be a few injectors sticking open, which would cause a loss of fuel pressure.

 

Gonna have to diagnose this a step at a time.

 

Also do a search on this site under "hard start" or "fuel" Lots of info.

[mcreyaufmiller]

Hi Gang,

 

Here's my problem:

 

About 6 weeks ago, while on my way to work, out of the blue, the truck died on the side of the road.  I had the local garage tow it in.  I picked it up that night.  I was told that the crankshaft position sensor had gone (no spark), but it had not thrown a code. 

 

I took it home that night. The next morning, I had to crank the engine for ~30 seconds before it would start.  When I started it again to go home (9 hours later), it started fine. Would do this consistently.

 

After talking to a buddy with a similar truck, he had had fuel system problems (stemming from a clogged fuel filter) which had resulted in a similar starting problems.  After 2 days of this BS, I took it back to the garage and had the fuel filter changed (can't remember when I last changed it).  No avail.

 

Sidebar:  I was told by mechanic that I should change O2 sensors, could improve gas mileage.

 

While under the truck looking for/at O2 sensors, noticed that the CPS sensor that had been "replaced" appeared to be used!  Ordered new CPS, replaced it myself, hard starting problem went away.  Won't be going back to that garage!!

 

Fast forward to this past Monday:  I had been on the road and the truck had not run in about a week.  Tried to start it, had to crank for ~1 minute (in the end, had to boost it off the car).  Truck started fine that afternoon.  Didn't try to start the truck again until today.  Wouldn't go, didn't feel like messing with jumper cables, hitched a ride with the wife.

 

After all of the cranking, when it does start, it catches about 1-2 cylinders at a time.  Once running, it runs fine.  All of this time, it has not generated any fault codes.  BTW, it has about 70k miles on it

 

Any ideas?  Anyone encounter an issue like this?

 

Thanks in advance,

 

Derek

 

<{POST_SNAPBACK}>

 

 

 

Maybe a little simpler that that, check your battery. without full voltage the coil will not fully fire the plugs until the engine turns enough to generate voltage from the alternator. Just a thought.

 

Mike

[Garage Mechanic's Companion]

Well, I had a go at it last night. After thinking about it all day, I figured I would at least determine whether it was a fuel problem or an ignition problem.

I got the wife to crank it over while I gave it a shot of quick start at the air filter to see if it would at least fire. While she was cranking it, I could hear a loud 'snap-snap-snap' sound coming from the rear of the engine. Closer inspection showed that the coil wire was arcing out against a bracket by the distributor (this was aided by the fact that it was dark out!!). I moved the wire away from the bracket, sure enough, it fired right up!!!

 

So I got a new set of wires for it. The old coil wire had an obvious pin hole where the wire was leaking.

 

Some problems are just never as complicated as they look!!

 

Thanks for the input,

 

Derek

[citydriver]

COOL

[Peter_C]

Good job on figuring out the problem

 

I do want to offer some words of protection though. A hot wire sensor is hot enough to ignite anything flamable that passes through it. These would be MASS/MAFF sensors. There have been many explosions from people trying to spray starter fluid down the intake tube.

 

At 70K I would start being very concerned about my fuel pump. One of the best ways to diagnose a failing fuel pump is to find a shop that can current ramp the fuel pump and look at the pattern it produces, to see if the brushes and commutaters sp? are functioning properly.