Engine shutting down when I don't want it to, then won't restart.

[Wags391]

I've been having this problem of my engine shutting down while first starting, and when driving. I can't figure this one out. The gas pump seems to be pumping and no trouble codes. It will start, then shutdown, and I will try and try to start it. I'll pump the gas and then once it starts you can definitely smell the gas. Could this be a grounding issue with something electrical??

[rayhalks72]

It could fuel or spark, LOL. A faulty fuel pump will produce lower pressure if it is on it's way out and heating up. This can be looked at with a fuel pressure gauge taped to your wiper and drive. Also, if no spark when it heats up, I'd point at the ignition module, it's one of the symptoms. Either no spark at start, or no spark once it heats up. Check for spark once it dies and you try to restart. If there is spark and good pressure, check the distributor cap and rotor. Mine was toast on my no start blazer. I got spark, it was just shorting too. Cam sensor can be grimey. They cause no spark while the crank sensor produces no fuel. But I'd check the above first. Test and inspect before replace, don't throw money away. I think Autozone can test the ignition module too. Pour cold water on it when you die and see if it starts up sooner.

G/L!

[cspring]

It would help to know the vehicle, but it sounds like it could be your IAC valve ( Idle Air Control valve ). When they go bad your vehicle usually won't want to stay running when it is cold. after it warms up the vehicle will run fine. Hope this might help

[cspring]

Just saw that it was a blazer

[Wags391]

Originally Posted by cspring

It would help to know the vehicle, but it sounds like it could be your IAC valve ( Idle Air Control valve ). When they go bad your vehicle usually won't want to stay running when it is cold. after it warms up the vehicle will run fine. Hope this might help

Is there a way to test the IAC? I've replaced it before and would rather not waste the money on a new one if it's not bad. I'd say I replaced it with the last two years. Always a possible bad one of course. Any other items I should check while I'm at it? Could this be a fuel pump problem? I bet if it was, I'd have problems while driving also, huh? What about a sloppy timing chain? That's on my list of to-do for this truck. Fuel filter?
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[Wags391]

Originally Posted by rayhalks72

It could fuel or spark, LOL. A faulty fuel pump will produce lower pressure if it is on it's way out and heating up. This can be looked at with a fuel pressure gauge taped to your wiper and drive. Also, if no spark when it heats up, I'd point at the ignition module, it's one of the symptoms. Either no spark at start, or no spark once it heats up. Check for spark once it dies and you try to restart. If there is spark and good pressure, check the distributor cap and rotor. Mine was toast on my no start blazer. I got spark, it was just shorting too. Cam sensor can be grimey. They cause no spark while the crank sensor produces no fuel. But I'd check the above first. Test and inspect before replace, don't throw money away. I think Autozone can test the ignition module too. Pour cold water on it when you die and see if it starts up sooner.

G/L!

Cap and rotor are brand new. Distributor is a new reman. Only a couple of months with it. Dist came with the module so I'll have to get it checked. Could this be a computer problem?
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[CalifOkie]

Since you didn't say what year or what engine is in that Blazer helping out is tough. If it is 1995 or newer it would have a 4.3L CPI engine inwhich the CPI (Central Port fuel Injection) unit ( also known as a spider unit) could be failing and cause just that. If it only acts up when the engine is cold then an ECT (Engine Coolant Temperature) Sensor would be my first guess. On the older TBI engines it could be a bad throttlebody or leaking throttlebody baseplate gasket.
In either case the first thing I would do is change the fuel filter just to make sure that the whole thing isn't caused by fuel restriction.

I really need more info to help out.

[Wags391]

Originally Posted by CalifOkie

Since you didn't say what year or what engine is in that Blazer helping out is tough. If it is 1995 or newer it would have a 4.3L CPI engine inwhich the CPI (Central Port fuel Injection) unit ( also known as a spider unit) could be failing and cause just that. If it only acts up when the engine is cold then an ECT (Engine Coolant Temperature) Sensor would be my first guess. On the older TBI engines it could be a bad throttlebody or leaking throttlebody baseplate gasket.
In either case the first thing I would do is change the fuel filter just to make sure that the whole thing isn't caused by fuel restriction.

I really need more info to help out.

Here ya go. 1992 S10, 4x4, 4.3L, TBI. It generally acts up after it has been running then allowed to cool for a short period of time. Sometimes acts up on a cold start. Hadn't thought about ECT sensor causing this. My next step was to check the fuel filter. Should be good. Less than a year old, but who knows.

[CalifOkie]

It is quite possible that a faulty ECT sensor could cause your problems but inorder to test it you would need access to a OBD1 scanner with the capability to read engine data. Then before coldstart ( first thing in the morning) scan the engine data looking for the Engine Coolant Temperature and the Idle Air Temperature. The two should read within a few degrees of each other and comparably to the actual outside temperature.

However by your description ( except for the gas smell) that it is most likely to be a failing fuel pump. However, if the gas smell is there everytime it restarts after stalling or after sitting for a short time then that would point towards a leaking throttlebody. While sitting after a run cycle the fuel pressure will bleed off through either the injectors or through the outside body of the fuel pressure regulator. The leaked fuel will accumalate on top of the pistons and cause a flooding condition when you try to restart. Another sign of this condition is when it does start and until it clears out the cylinders there should be a noticable gray smoke from the exhaust pipe that goes away after the engine starts running smoothly again.

[Wags391]

There's no smoke. And I believe the "gas" smell is from when I pump the gas repeatedly just to get it started; as if it's coming from the exhaust. Almost flooding the engine, trying to get it started. I really have to pump and rev the engine to get it to go. It's almost as if, something needs to warm up before it wants to work correctly. I need to look at the fuel filter first though. Anymore thoughts?

[blazes9395]

This sounds like its running to rich. First it would be a good idea to make sure the two throttle body injectors are not leaking and that the fuel system is holding the proper pressure. If that checks out, check your coolant temp sensor. If that checks out and there is no vacuum/gasket leaks like CalifOkie mentioned, then I would be looking very carefully at the ECM( Electronic Control Module). The ECMs of this vintage had a tendancy to cause problems when they were on their way out.

[Wags391]

Originally Posted by blazes9395

This sounds like its running to rich. First it would be a good idea to make sure the two throttle body injectors are not leaking and that the fuel system is holding the proper pressure. If that checks out, check your coolant temp sensor. If that checks out and there is no vacuum/gasket leaks like CalifOkie mentioned, then I would be looking very carefully at the ECM( Electronic Control Module). The ECMs of this vintage had a tendancy to cause problems when they were on their way out.

How can I get an ECM/prom checked?

[blazes9395]

The only to check it would be to connect a scanner and watch what the ECM is doing, what the readings are with different sensors etc. You have to know what ranges to expect from each sensor at different points of engine operation to get a good idea if your ECM is going bad. The PROM rarely goes bad at all. Checking it requires special diagnostics/tools, I wouldn't worry about the PROM being bad.

Getting a scanner might be a good idea on this one. Have you checked and made sure there are no vacuum leaks, injectors are good and not leaking etc first? Is it holding the proper fuel pressure?

[Wags391]

Originally Posted by blazes9395

The only to check it would be to connect a scanner and watch what the ECM is doing, what the readings are with different sensors etc. You have to know what ranges to expect from each sensor at different points of engine operation to get a good idea if your ECM is going bad. The PROM rarely goes bad at all. Checking it requires special diagnostics/tools, I wouldn't worry about the PROM being bad.

Getting a scanner might be a good idea on this one. Have you checked and made sure there are no vacuum leaks, injectors are good and not leaking etc first? Is it holding the proper fuel pressure?

I think I'll go for the ECT sensor first. Cheap and easy. I'll let you know.

[4x4 blazerguy]

Originally Posted by Wags391

There's no smoke. And I believe the "gas" smell is from when I pump the gas repeatedly just to get it started; as if it's coming from the exhaust. Almost flooding the engine, trying to get it started. I really have to pump and rev the engine to get it to go. It's almost as if, something needs to warm up before it wants to work correctly. I need to look at the fuel filter first though. Anymore thoughts?

I have been wrong before but as I understand Fuel Injection pumping on the gas does nothing but open & close a throttle plate that controls only AIR. The gas is controlled ELECTRICALLY or MECHANICALLY in the case of older diesels through the injectors.