99 Chevy Blazer hard starting when cold

toasted311February 14, 2006

My mother's 99 chevy blazer(4.3 V6/auto with 83k) has a hard starting problem if it has set for a day or two. The longer it's set the worse it is. I went ahead and did a tune up(wires, plugs and cap/rotor) and the fuel filter was due. Dad had run the batt down on it trying to start it before I tuned it up.

Truck boosted off then and ran that day fine. Next day it wouldn't start at all, crank but not start up. Batt did test bad this time, replaced batt with a 900 CC batt.

It starts easier now but it still has very long start times if it has set over night or long enough to totally cool off. Any idea what else I can check out. Fuel pressure was spot on with key on and then with truck running too. Love pesky problems. Thanks

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mxyplx

Tried ether? Works like a charm.

    Bookmark   February 14, 2006 at 7:33PM
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toasted311

Funny mxyplx, that's not a fix and not an answer to a honest question. Anyone got an honest idea that would really fix it and not be a smartalic.(sp?)

    Bookmark   February 14, 2006 at 10:41PM
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john_g

Isn't this kind of work fun? The only time you can measure and test for the problem is while it's happening. Any other time that the car actually starts, everything you test will be "spot on" as you put it. Which is a reference to the most likely suspect for your mothers car's symptom. Low fuel pressure I.E. a bad pump. These things will not start with 54PSI of fuel pressure, they must achieve 56PSI! Your gage has to be accurate within 1PSI in that range to actually see this occuring. The thing is, hitting this with a little ether (I prefer propane) will give it some fuel to burn and increase manifold vacuum, and often times allows the car to start, because the vacuum actually helps open the poppet injectors. The poppet injectors are why this thing needs a minimum of 56PSI to start.

Other things to consider. "Spark volume" I know you replaced secondary ignition, did you clean the breathers in the base of the distributor? They tend to clog, and then crankcase gasses will collect in the distributor causing corrosion, and then the spark will short to ground inside the distributor.

Fuel: It takes more than just fuel pressure to ensure the engine is getting fuel. The injector must be triggered on by the PCM. I have had the two wire connector between the engine harness and the injector corrode and cause a loss of injector command. Plus you need to have a good crank signal trigger to not only tell the computer to drive the injector, but to command the module to trigger the coil.

Tell me, when the car acts up. Key on, you hear the pump run for two seconds. Start cranking the engine, do you hear the pump turn back on? This would tell me if the PCM sees the signal from the crank sensor.

    Bookmark   February 15, 2006 at 9:29AM
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toasted311

Yeah when I turn the key on the pump runs for a couple of seconds and the it does kick back on again when I turn the key to crank it. I replaced the rotor and cap, plus wires and plugs. Breathers at the bottom of the distributer? I did use a little degreaser on a rag to wipe off some carbon/soot buildup on the base of the dist.
It's funny how some vehicles give you no problems while others nick pick you crazy. Dad said the truck had been had to start for about a year now, wish he'd mentioned it earlier. He did have the injectors cleaned at a local shop day before yesterday and it seems to be a little better, but still hard to start the first time.
I had the truck over night and hooked up my fuel gauges before I had a friend start it, when he turned the key it hit 62 psi and when he cranked it over it only dropped to 57psi, so I thought that would rule out the fuel pressure issue but it was still slow to actually turn over the first time.

    Bookmark   February 15, 2006 at 10:42AM
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john_g

Plug an ST-125 into one of the plug wires the next time you try to start the truck. If spark jumps it, you have good spark. If spark DOES NOT jump that tool, even if the truck starts you do NOT have good spark, and diagnose as "no-spark".

An ST-125 looks like a spark plug, with no outer electrode, and an alligator clip that holds it to ground. It takes 25kv, (25,000 volts) to fire that tool. The adjustable ones can be innacurate and have led to some false good spark conculsions.

    Bookmark   February 15, 2006 at 12:52PM
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earthworm

How about getting back to us, Toasted ?
Some awfully good advice from John G. - as usual ...
It would be good to know what the fix was.

Is the truck still slow to "turn over" (starting RPM) ?
Could just be a corroded connection at the starter....

    Bookmark   February 25, 2006 at 2:33PM
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toasted311

It ended up dying on her in Memphis the other day. Got it home and the fuel pump was totally dead. Guess the two times I tested the pressure it had enough life in it to show good then. Oh well it's fixed now and running like a champ again.
Thanks

    Bookmark   March 4, 2006 at 9:15PM
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earthworm

That is good news.
Maybe the fuel pump test should be both pressure and volume...
These things can be very difficult to diagnosis....

    Bookmark   March 5, 2006 at 2:54PM
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john_g

When it comes to testing these pumps, you should be checking;
Pressure, Volume, and using a low amps probe and an ocilliscope to see both the current draw, and the pump RPM. Even then you can still have an intermittent slip by and bite you. One common failure point often overlooked is the wiring connector from the vehicle harness to the pump sender assembly. Plus the little harness that goes from the top of the pump sender to the pump itself. A poor connection at any point in that circuit gives you low or no pump output.

    Bookmark   March 5, 2006 at 7:42PM
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tjr348_hotmail_com

Try replacing the engine temperature sending switch.
NOT the one for the temp guage.
i had a cavalier same problem not starting when cold.
was fine after replacing.

    Bookmark   August 3, 2009 at 8:50AM
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arkansas_girl

Though it is extremely informative to get ideas of what can cause this issue...the OP did say it turned out to be the fuel pump.

    Bookmark   August 3, 2009 at 6:11PM
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