96 lt4 six speed. It has happened a couple of times and I haven't been able to sort it out. On occasion, the engine will just die. Sometimes it will start right back up, others it will just crank and crank as if it is getting no fuel or spark. It stranded me yesterday. I get a ride and come back an hour later with a fuel pressure guage and my service manual. It then starts right back up. I can't trouble shoot something when it is working perfectly.
I do know that the fuel pump is priming the rail when I turn the key on as I could hear the pump even when it does not start. When running, it does so perfectly. I also have no check engine light or codes set.

Any ideas?

 

If i read it right you are saying you scanned it and no codes, nothing even historic? The symptoms sound like an ignition module going south, but I think that should leave a code. Any good autoparts could test it for you though. Next time, when it does it just take a paperclip or whatver you have with you and push in on the fuel rail shrader valve to see if there is pressure on it. Thinking maybe bad connection to the fuel pump maybe giving intermittent loss of fuel.

 

How long since a fuel filter change or tune up?

 

I have no check engine light, and as I understand from the service manual, there are no codes for the ecm stored. Also I can hear the pump prime for 2 secs when I turn the ignition on. This does not mean I am getting fuel however, and I will have to check with the gauge when it actually won't start again. I will have to look into the ign. module.

I'm not sure on the filter, but the plugs and wires were done around 10,000 ago by a dealer. I don't feel this is the problem, because it runs so smoothly when it is running. Also the car has 67,000miles.

 

The fuel filter is a maintenence item and if you don't know when it was changed last, it would be a good idea to do so. The ignition contol module is another maybe. It usually fails when it gets hot. When it is going bad sometimes the car will start back up and sometimes not. You can remove it and take it to a place like Autozone and they will run a 10 cycle test (to get it hot) to see if it fails, and will do it for free.

 

That's good to know! Thanks.

 

i am having the same problem with mine right now. me and a buddy and everyone else i talked to were stumped so i brought it to a local mechanic, i will let know what the problem was when i hear from him.

 

Why not when it just cranks and cranks check for spark? Simple enough.

 

Getting it to not start on command is more difficult however.

 

Checking for spark is not the problem. It's not starting and it's getting fuel. So that means that it's not getting spark.
The problem is "why is it not getting spark"?

Scott and I both have about 50 hours into his car over the last 3 weeks. And now the problem we went in to fix is not fixed (turned out to be other then we thought) and we have a new and bigger problem. I wish I had the time to fix it. I feel bad that I worked on it and now it's messed up.
Don't worry Scott, Mike will hook you up.

 

dont worry about it troy. the price he gave me is not bad at all. and im sure he will find the problem with the ignition pretty quick. its gotta be somewhere around that coil.

 

got an update for ya. in our case it was a bad computer. kinda wierd that it never gave warning signs on its way out.

 

I finally got my car back after an accident, and it still did this. I was trouble shooting when I removed the harness to my coil. When I did, water came out. Somehow water got into my coil wiring harness connector and was intermittantly shorting out my coil. I dried it out and knock on wood so far so good.

 

Glad to hear it!

 

take a look at your crank sensor located behind the crank pully. this is where it all starts for the ignition system and injectors. Without this signal to the ignition module your not going anywhere. Also if this is something that happens when the engine is hot and you suspect that its the module gust get cold water and pour it on the module to shock it and try starting. If it starts you now know whats to replace. But always as a good diagnistic tech you always need to see if the computer is able to detect crank RPM with a scanner and fuel pressure. You can check the intergrity of your fuel pump with a Graphing DVOM and a Amp clamp. You do this to see the wave form from the pump. inside the pump and any rotatuing electric motors there are a set of carbon brushes and comutators. With a jumper wire from battery positive to the fuel pump prime wire, with the engine off, connect the wires to turn on the pump, take the amp clamp and put it on the jumper wire, set your DVOM to read and graph the reading. you should get a wave form that looks like a bunch of mmmmmmmm"s if you see and of the m"s spike down you have a bad pump. you could let this run for 20 min to get the pump hot, it wont hurt a thing doin this.


Terry Chaitas
Rolling Thunderz