1993 s10 blazer dies and wont restart

[markmclaurin2007]

I have a 1993 s10 blazer 4x4 with a 4.3L vortech v6.the problem is the vehicle will start and run 5-20 minutes and dies and wont restart for several hours or days it will spin over and will not even try to start.there are no trouble codes stored in computer.fuel pressure is a steady 56 lbs ( which is high enough for vehicle to run because i have a 92 s10 blazer with the same injection system and it runs at 52 lbs just fine).i have replaced fuel pump,filter,cpi unit,ecm unit ,coil,ignition module,distributor cap,rotor,plug wires and checked all the fuses all with the same result.when engine does run it sputters and misses but not badly .i did have a trouble code one time for the egr and iac valves but it cleared and has not returned.parts are getting expensive what am i missing?

[GirlBear]

possible fuel pump. Not definate but u might wanna test ur pressure.

[MT-2500]

When no start check for spark to more than one spark plug.
Also check fuel pressure when a no start.
If the 4.3 W engine you need 60 lbs of fuel pressure on a cold start.
Specs are 55/61.
You need full pressure to squirt injector on a cold start.
They will run all day on lower pressure but will not start cold.
MT

[markmclaurin2007]

fuel pressure is good,spark is good I have swapped parts that were suspect off my other blazer they work fine on it.still have same problem.possibly the new cpi unit may be problem?

[MT-2500]

If you have good spark and fuel pressure check for injector pulse.
Also check EGR valve for being stuck open or a carbon ball under plunger.

[markmclaurin2007]

good spark and fuel pressure checked egr valve no obvious problem .i swapped egr and cpi unit on my 1992 blazer it ran fine.the same parts off the running blazer did the same thing on the non running blazer.it would start up and run 5-15 minutes die and would not restart.does this vehicle have a low oil pressure shut down switch? the oil pressure is not abnormally low but it does run slightly lower when running than that on my 92 blazer.

[MT-2500]

Some do have a oil pressure switch for fuel pump.
But they are not a shut off switch but are designed to keep the fuel pump running if the fuel pump relay quits.

At the time it quits or no start recheck for spark and fuel pressure.
If you have spark and fuel then check for injector pulse.
MT


The dist module or pick up coil can be fading out.
Or the pcm can be losing injector pulse or rpm signal.

Give the pcm the old tap or twist test.
And get a injector noid test light and check for injector pulse.

[kevnchelle]

Hi, just wanted to let you know your not alone I have a 96 s10 with the same engine and the same problem..Good Luck..

[Spectria, L1 MT]

[quote=MT-2500]Some do have a oil pressure switch for fuel pump.
But they are not a shut off switch but are designed to keep the fuel pump running if the fuel pump relay quits.quote]

I think the Oil Pressure sensor sends a signal to the FP relay to indicate that the engine is running (oil pressure sufficient) and is to cut the fuel pump if oil pressure drops below a safe level to protect the engine.

Try Spraying Carb Cleaner (Chemtool) in PCV Breather tube at Intake while someone cranks the engine and see if it starts and runs. Do this test after your standard failure period.

If it still won't restart then you don't have a fuel problem but an ignition problem and most likely it is the pick-up coil which has a tendency to fail as it heats up (with age).

[MT-2500]

[quote=Spectria, L1 MT]

Originally Posted by MT-2500

Some do have a oil pressure switch for fuel pump.
But they are not a shut off switch but are designed to keep the fuel pump running if the fuel pump relay quits.quote]

I think the Oil Pressure sensor sends a signal to the FP relay to indicate that the engine is running (oil pressure sufficient) and is to cut the fuel pump if oil pressure drops below a safe level to protect the engine.

Try Spraying Carb Cleaner (Chemtool) in PCV Breather tube at Intake while someone cranks the engine and see if it starts and runs. Do this test after your standard failure period.

If it still won't restart then you don't have a fuel problem but an ignition problem and most likely it is the pick-up coil which has a tendency to fail as it heats up (with age).

Quote
I think the Oil Pressure sensor sends a signal to the FP relay to indicate that the engine is running (oil pressure sufficient) and is to cut the fuel pump if oil pressure drops below a safe level to protect the engine.
Quote


The oil pressure switch is not a cut off or saftey shut down.

It works in series with the fuel pump relay and only powers fuel pump if the fuel pump relays failes.

On cars and light trucks with gas engine the pcm/vcm does not read oil pressure.

MT

[Spectria, L1 MT]

[quote=MT-2500]

Originally Posted by Spectria, L1 MT

Quote
I think the Oil Pressure sensor sends a signal to the FP relay to indicate that the engine is running (oil pressure sufficient) and is to cut the fuel pump if oil pressure drops below a safe level to protect the engine.
Quote


The oil pressure switch is not a cut off or saftey shut down.

It works in series with the fuel pump relay and only powers fuel pump if the fuel pump relays failes.

On cars and light trucks with gas engine the pcm/vcm does not read oil pressure.

MT

Could you direct me to the place where this oil pressure switch info is located. I have read your posts and you are clearly an expert, soooo I am not trying to make anybody wrong here. I just want to reconcile my training with your info.

It doesn't make any sense to me that there would be a back-up to the fuel pump relay. Isn't it receiving info from multiple sources, including the rollover switch and the pcm to cut power in certain circumstances.

I am probably more familiar with Bosch systems, and in every one that I know of, if the oil pressure sensor reads low, the fuel pump relay cuts.