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[yamagrant]

i have a 91 safari 4.3l tbi cranks but will not start. if i prime it it will run,shut it off and it will not start untill it has been primed

[GM-Tech]

i have a 91 safari 4.3l tbi cranks but will not start. if i prime it it will run,shut it off and it will not start untill it has been primed

 

Marginal fuel pressure may make for difficult starting but run fairly okay once it's running. So, a fuel pressure test would be the first place I'd start. These don't have a fuel pressure test port, so you'll have to T a gauge into the pressure line, usually, right at the fuel filter.

 

These usually run around 11-12 psi, some a tad higher. If you're down around 9 psi or less, you have a problem.

[yamagrant]

i have a 91 safari 4.3l tbi cranks but will not start. if i prime it it will run,shut it off and it will not start untill it has been primed

 

Marginal fuel pressure may make for difficult starting but run fairly okay once it's running. So, a fuel pressure test would be the first place I'd start. These don't have a fuel pressure test port, so you'll have to T a gauge into the pressure line, usually, right at the fuel filter.

 

These usually run around 11-12 psi, some a tad higher. If you're down around 9 psi or less, you have a problem.

 

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i pulled off the dog house to ck fuel pressure ok at 13lbs, would now not start on prime . does ignition module control injector pulse (no spark now) i was using quick start to prime so maybe a weak spark would have let it start and run on added voltage due to alt charging?

[GM-Tech]

i pulled off the dog house to ck fuel pressure ok at 13lbs, would now not start on prime . does ignition module control injector pulse (no spark now) i was using quick start to prime so maybe a weak spark would have let it start and run on added voltage due to alt charging?

 

Fuel pressure is excellent. Does sound like you might have a bad ign. module or pickup coil, with the latter being the most likely of the two.

 

Here's a little trick that sounds goofy, but it does work. Might be hard on an astro though due to the location of the battery vs. the distributor. Key ON. Coil wire off. Pickup coil disconnected from the ign. module. Lick the index finger on both hands. Hold one finger on the positive battery post, swipe the other finger over the two terminals where the pickup coil was connected. You should get a spark out of the ignition coil. If you do, you know the module is okay.

 

You could do this with a test light too. The idea is, your providing a slight voltage just like the pickup coil would do, triggering the module, firing the ignition coil.

 

Resistance of the pickup coil, as I recall, is around 800 ohms, though I think the allowable range is something like 600-1300... but don't quote me. Even though resistance is correct, it could still be bad.

[GM-Tech]

Oh, and by the way, if you use a test light for the above mentioned test, it'd be connected to positive, not negative like if you were checking for voltage.