I have a 1995 blazer with 115k miles on it. A month ago it starting having problems starting. After sitting for a while... sometimes its 4 hours, sometimes its overnight it has problems starting. I crank for about 5-6 seconds, stop, then try again and it slowly sputters to a start. After that it runs great, no problem at all. When it does have a problem starting, i do smell gas so I am not sure about the fuel pump. I put in a can of seafoam and it seemed to help a lot when it was in the tank, but after we put new gas in, it was back to its old ways. I replaced the fuel filter with no affect. We took it to a shop, and the two days they had it they tested the fuel pressure and it was fine every time and of course it started fine everytime too. They gave us a laundry list of things that needed to be done that could fix the problem. Anybody have any ideas?

 

Sounds like you are losing compression. I'm not sure. You need lastcoupe for this...


LASTCOUPE!!!!!!!

 

Hmm... Lost compression wouldn't go away like that once running... You'd feel the power loss. Compression is easy enough to check for though. A good tester should run ya $40 at your favorite parts store. They're good to have around.

Almost sounds like bad gas, but even bad gas would result in power loss to a certain extent. Have you tried a different station yet? Used any water removal products (IsoHeat)?

Not to scare you, but this could the early stages of an internal fuel leak. Have you tested your fuel pressure? Does it start right back up after it's been running? Does it typically get harder to start the longer it has been sitting? If so, you may want to try holding the key in the 'run' position for 5-10 seconds, then turning it to run and holding the throttle to the floor atleast initially. This will pump up the fuel system and help to disipate any fuel vapors from the intake more quickly. If the engine catches, let off of the throttle so as not to rev it up too high.

 

I just though of something.

We have the same problem with the 4.3L Silverado at the school shop, ant it rufuses to start occasionally. We'll click the ignition on and of about 5 times and it'll straiten up. I know for a fact that the O2 sensor is screwed up... but if your O2 sensor is bad, you will notice a big loss in power..

Seafoam should deal with a problem of mildly watery gas...

Sounds like if you are smelling gas it could be and internal fuel leak as Kyle said. If the shop tested the fuel pressure at the injectors, a clogged injector isn't the problem, but if they checked it at the rail, it very well could be a contributor.

 

Seafoam isn't really a fuel dryer, it is more of a cleaner/lubricator. But the fact still remains that if he's getting bad gas, then it stands to reason that his next fillup brought him right back around to the problem.

Once the PCM throws the code for the O2 sensor, it effectively ignores the sensor data and goes to a predetermined fuel map. This is why vehicles always seem to run better right after an O2 sensor code is triggered. The PCM starts ignoring the sensor and relies on the other sensors to determine the 'proper' IPW. I put quotes around proper due to the fact that this method will not result in the most efficient running of your vehicle. That is why fuel mileage suffers, but it does allow you to get around with it without hurting anything but your wallet.

On your school truck, it sounds more like something going wonky with the ignition switch than an O2 sensor.

 

Yet again Kyle, you prove you know morethan I do! LOL

O2 sensor is only one of many problems with that truck... The ignition switch works and it trys to crank, it shudders and shakes, but clicking the ignition resets something in the computer that causes it to do something that causes some kind of problem in fuel delivery... I dunno, that's all I got out of Mr. Braswell explainations anyway...LOL

I think GM was gonna give us a newertruck to mess around with this year...

 

Thanks for the responses!

When it was in the shop they checked the computer codes and there was nothing stored. The 02 sensors should be ok as we had it emissions tested about 4 months before the problem started and it passed with flying colors.

I was thinking the fuel smell was from fuel being pumped into the cylinders and out the tailpipe and not combusting due to lack of spark. We fill at different gas stations and it doesnt seem to matter.

I have tried turning the key to hte on position for 5-10 seconds several times and it doesnt seem to matter, however I did not try pushing the fuel pedal in. I will try that tomorrow morning.

 

How long has it been since your tune-up? If you had it at a shop recently I would check all your connections (ie plug wires, and the like) also as strange as it sounds it could be a vacuum line somewhere that has come off (someone correct me if I am wrong). Have you noticed any difference if you try to jump start it? Did the shop check the whole ignition system (ie alt, battery.....)or just the fuel pressure?

And for a shot in the dark you can always talk to a Chevy certified tech and see if he/she has seen this before.

Also with it having problems starting but not running, I almost wonder if it is the starter. Maybe the starter is just beginning to go bad so it doesn't quite register yet. But after sitting for a while tends to seize up a little.

 

Very true! If the plugs are dirty or the gap has worn large, you could have troubles starting the truck. Its also possible that the cap and rotor have built up with deposits effectively advancing the timing while decreasing the overall spark intensity which will make it more difficult to start as well. If its been awhile since you've done a tuneup, I'd recommend plugs, wires, cap and rotor. But you can check the wires easy enough with a spray bottle of water and a dark night. Get it started and just let it idle. Spray the water over the wires and look for leaking spark. The cap can be removed and checked as well. If you see buildup on the pins in the cap and/or a worn flat button in the center of the cap, it's time to replace it. Same for the rotor, if there are deposits on the rotor tip, you'll want to replace it.

I'll also agree with the vacuum leak causing issues.

On the starter getting weak, well that may be, but if it spins over the engine pretty consistently, then I wouldn't suspect a weak starter. Even if it spins it over kinda slow, advanced timing through the carbon buildup in the cap/rotor terminals will also cause this.

 

Ive got somthing similar on my 91. Heres what i did.
Take off your distributor cap, thepoints are probably all corroded and nastry. Just clean 'em off with some sandpaper and it should fire up no problem. The gas smell is probably from all the unburnt gas that pours in when you try to start up and arent getting any spark (from dirty points).
What i still cant figure out is how to keep water from getting in ther and making a mess. Ive tried that plastic spray, even tried making a gasket, No luck.