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1998 blazer 2 dr

Last week I went to gas station and filled S.U.V. got back in and would not start. I towed it home and found that fuel pump was not working. I also did not have spark. Was told if fuel pump failed ,spark would also stop due to lack of pressure. I replaced fuel pump and problem still exists.Today I replaced cam position sensor.Problem still exists.Any body got any ideas???

How did you conclude fuel pump not working? How did you conclude no-spark (both times)? Have you checked for correct DC voltages? Have you done a complete underhood inspection (looking at wiring connections) have you tested with starting fluid?

What you probably heard was no oil pressure no spark not no fuel pressure no spark and that probably was the crankshaft position sensor not camshaft position sensor.

You actually lowered the tank and relpaced the pump? sure you got the right pump?

On what basis are you replacing these parts? Have you tested them?

You say “Was told . . .” By whom? Is this information reliable?

Why would a manufacturer design a system that cancels spark just because there is not enough fuel pressure? Sounds like a nightmare to me.

Is GM that bad? I find it difficult to believe.

Do you have a service manual for this vehicle, with instructions for testing of individual components, or are you just guessing?

It’s the other way around. If you don’t have spark, the fuel pump won’t run.

98 Chevy? Crankshaft Position sensor.

Tester

I have definitvly heard no oil pressure no spark (the logic is clear,prevent engine damage) but whats up with no spark, then fuel is inhibited? why would that design be of benifit?

You have been told wrong about the automatic fuel and spark shutoff. That is so bo-oh-oh-oh-gus! Stop wasting your time and money by replacing “guess” parts. There is a way of troubleshooting this problem (and, it is not by changing parts helter skelter). Take your vehicle to a repair shop.
[ I know this isn’t what you wanted to hear, and you have done a job on your treasury; but, what reasonable thing are you going to do?]

I am seeing in my 95 FSM in the driveability section for Fuel Cutoff Mode a statement “fuel is not delivered if no reference pulses are seen from the Ignition Control,which means the engine is not running”

And in 3A chart A5 a fuel pump relay inhibit circuit for a faulty oil pressure switch.

Now that being said I am totally against using a FSM from the wrong year,but it is all I have. Do you have the 98 FSM that indicates these features are ommited for 98?
This is a 95 S/T Truck FSM (with both TBI and Central MFI diagnosis) so there is room to question if it applies.