1989 5.7 TBI

[Duffyjr]

I have a question about the spark and fuel. Say the engine wasn't getting any spark would that keep the injectors from spraying fuel? So in other words the engine is turning over but it wouldn't start, I tried pumping the accelerator and and at no time did I smell fuel. Now I know from past experience when this thing is flooded it reeks of fuel.

Here is the kicker, a couple weeks later the day before I'm going to tow it to the mechanic I went out to make sure it wasn't going to start but to my surprise it started right up like nothing was ever wrong. Been driving it since last Thursday with no issues.

 

[OVERKILL]

Could be the fuel pump on its way out, hence the intermittent operation.

 

[Duffyjr]

Could be the fuel pump on its way out, hence the intermittent operation.

So far it's just been the one time and I'm certainly not ruling that out. Here is why I was asking about the fuel being delivered if there is no spark. The night before it rained really hard and the wind blew so I was thinking the distributer or coil may of got wet, would that keep it from sending juice to the plugs and if so would that keep the injectors from working.

 

[mk378]

No, wet wires or other problems on the high voltage side wouldn't stop it from spraying fuel. A bad ICM might-- but that is permanent.

Since you never tested the spark I agree with OVERKILL that at this point the incomplete diagnosis would tend toward it being purely a fuel problem.

Actually you never checked if fuel was coming out, you only expected to smell it.

Pumping the gas pedal does nothing to help start an EFI system, except that cranking with the pedal held to the floor usually *turns off* the injectors to help clear a flooded condition.

 

[Duffyjr]

Even thought it only has 82k on it the fuel pump could be 31 years old as far as I know. Better make sure my towing is paid up.

Thanks guys.

 

[Donald]

When the engine is running with air filter off you can see the gas being sprayed from the TBI. Maybe even at startup.

If the fuel pump has never been replaced you will probably end up replacing the fuel sensor assembly which has the fuel pump mounted on it. The connectors will snap trying to remove them even with a flare wrench. Use OEM or you will do it again. Never run out of gas or get close. Fuel pump is cooled by fuel going through it.

My comments come from a 1993 Suburban with TBI. Three fuel pumps I replaced over about 10 years.

 

[BrianF]

Oil pressure switch on the way out maybe?

 

[Donald]

Oil pressure switch on the way out maybe?

Or a fuse or relay (I am pretty sure).

 

[Dinoburner]

Interesting problem, maybe 1,000 possibilities to bee narrowed down with diagnostics before buying parts.

 

[clinebarger]

No Spark & No Injector Pulse would be from a missing Reference Pulse from the ICM, Whether is a failing ICM or Magnetic Pickup/Pole Piece is the question.

ICM's rarely come back to life/Intermittently fail.....But I have seen it! With the age of these TBI trucks....The whole distributor needing replaced is quite common.
RamJet 350 distributors from Chevrolet Performance Parts used to be the best bang for the buck, But they're on back order last I checked

 

[joegreen]

My truck has tbi. When the icm was failing it would work fine for a while when the distributor was still cool but once everything heated up the truck would just shut off until the icm cooled back down then it would function fine for a little. So they can fail intermittently.