1998 Chevrolet Express No start

ROBERTBUBBA2

MEMBER
1998 CHEVROLET EXPRESS
4.3L
V6
RWD
AUTOMATIC
190 MILES

Express van 2500 4.3 vortec engine 1998 no start has 67 psi fuel pressure looks like compression is good fuel pressure stays above 50 psi when cranking [no start] took mass airflow oss throttle body left wiring on mass air flow sensor, sprayed starting fluid down throttle body did not even try to hit any cylinder. Seems to have spark but under compression I wonder it jumps plug gap on plug outside of chamber and I got bit a couple of times not shocked big time through my body does GM have a igntion. Coil problem like old style Chryslers had on there 318-360 engines v8 and the v6 engine 3.9? No codes as of yet in engine cotroler

6 Replies

WRENCHTECH

MECHANIC
20,761 POSTS

You don't have enough fuel pressure when cranking. This engine usually won't run with under 55PSI. Try priming it with some fuel or starting fluid and see if it starts.

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Wednesday, December 16th, 2015 AT 9:28 AM

ROBERTBUBBA2

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4 POSTS

Thank you I did that a day ago and it still would not fire

If you read my post I said I took the mass air flow sensor off but left it wired up shot startting flluid right down throttle body with no response of it even trying to start.

And according to the book on this truck fuel pressue should be above 50 psi when cranking motor over which is well above 67 to 70 psi

ps and if I leave pressure gauge on for 1/2 hour pressure is 40 psi

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Wednesday, December 16th, 2015 AT 1:57 PM

WRENCHTECH

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20,761 POSTS

I don't know what book you are reading but the fuel pressure spec for this engine is 60 to 66PSI and that is non-negotiable. This engine is very pressure sensitive.

You also can't start the engine with the MAF not connected to the throttle body. You have to put it back in place before starting the engine.

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Wednesday, December 16th, 2015 AT 2:53 PM

ROBERTBUBBA2

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4 POSTS

Test was right off the internet either way the fuel pressure was above 66psi when cranking but I did not know about the mass air flow sensor having to be put back on

Thanks either way I think its got a spark problem but will find out tommorow and I will also be able to check it for trouble codes because I now have a scanner

Thanks Bob

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Wednesday, December 16th, 2015 AT 4:10 PM

WRENCHTECH

MECHANIC
20,761 POSTS

It's probably time to go back to square one and run all the no start diagnostics.

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.