Mechanics

HEATER CORE NOW NO ENGINE STARTING

1997 Chevrolet Blazer • 160,000 miles

1997 Chevy blazer 4.3 160000 miles will the oil pressure switch cause a no start condition if it fails and what checks could be done on this problem.

Okay. Car ran fine before replacing heater core now a no start condition. Put dash back together hook battery. Back up. Now thecheck engine ligt abs batt andairbag is on no tart codition engine turns over but wont start.I have checked fuses and relays seem to be working I now dont here the fuel pump kicking on when I turn the ign. On.I AM in the process of going through ignition sytem.I have replaced the switch harness under the steering column. Any input or advice to point me in the right direction would be great thanks
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Dodgeboy71
March 4, 2012.




It can only cause a "no start" if the fuel pump feed is shorted out. All you have to do is unplug it to eliminate that possibility.

All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.

Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.

2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.

3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.

Wrenchtech
Mar 4, 2012.
I did a fuel pump test it did not hold when I turned the key off so I will try unplugging the oil pressure switch and see what happens thanks so far. But it almost sounds like a bad ground dont no how t o check that

Tiny
Dodgeboy71
Mar 4, 2012.
It's neither of those. It's not electrical in nature at all. You have a leakdown problem. This can happen at a leaky injector, pressure regulator or bad check valve in the pump.

What is the fuel pressure at peak?

Wrenchtech
Mar 4, 2012.
It was 60psi and this will cause all the warning lights to light up on the dash? Ok I will do the checks. It sounds like it might be more than one thing. Will check back after the ign. Testing side of it. Thanks, it just makes me feel silly it ran fine before the heater core replacement and now nothing works didnt expect that, will keep u posted thanks again

Tiny
Dodgeboy71
Mar 4, 2012.
No, the fuel pressure is an issue but not preventing it from starting. As long as you can keep it up around 60PSI when cranking, it will run. Make sure that pressure that you are losing isn't an internal leak fouling the plugs. The dash lights have nothing to do with that but being on when the engine isn't running isn't unusual.
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Wrenchtech
Mar 4, 2012.
Kool thanks will keep u posted

Tiny
Dodgeboy71
Mar 4, 2012.

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