91 no start after sitting.

[Leper]

Was going to drive the Blazer around for old times sake and it would not start. Turns over fine, but no fuel from the injectors. When the key is cycled on you can hear a buzz from the fuel tank for a few seconds.With the line off at the fuel filter, and the key cycled on, fuel will run out of the line, but not under much pressure. With the lines off at the throttle body, nothing comes out. The truck will run with gas put down the throat of the throttle body. I put another five gallons in the tank just to make sure the pickup was under the fuel line. No change

The truck has sat on an incline for the better part of a year and I am thinking that the fuel pump has gone bad. I think the fuel should be shooting out of the line at the filter instead of just running out.

Is there anything else that would cause my problem? A ground I have overlooker? An ignition component that relates to the fuel pumps function?

Can you think of anything that would cause this?

TIA
Leper

 

[dyeager535]

I would agree with your diagnosis.

I'd probably run 12V to the relay bypass (the single red wire) with the line disconnected just to ensure that it's not a voltage to the pump issue. Since it's me, I'd also run 12V directly to the pump itself (To eliminate the wiring between the relay and tank as a cause), and also check the tanks ground wire. Never know, a rat or mouse may have decided to chew on some wiring while it sat.

But more than likely, it's the pump if it operates with little pressure. Injectors won't fire if the ignition module doesn't tell the ECM the engine is turning over, but since it fires with fuel dumped in the TBI, that would tend to rule the module out. Since you aren't getting fuel to the TBI in the first place, it makes sense. You did disconnect the line going TO the fuel filter, so that rules it out as well, correct?

And it may not be the pump, but something like the sock pre-filter, or hose from the pump to the fitting on the sending unit. But either way you'll have to drop the tank to look.

 

[Leper]

Where is the fuel pump relay? I didn't even know it had one.

I did pull the line before and after the filter. The ground wire is good also. I may go and supply batt voltage to the pump and see if it makes a difference.

I am thinking about getting a generic inline pump and plumbing it inline at the filter. If I did that and it still didn't run, it would mean that there was a problem with the pickup inside the tank. If it ran, I would be good to go. I guess you can tell I really don't want to drop the tank. 31 gal and 3/4 full. lol

 

[dyeager535]

Relay on TBI is underhood, somewhere around the booster I believe.

If you can get it to flow, just hook the thing up to 12V and let it pump into a gas can, and fill up whatever you need to. About a 1/4 tank is manageable, but still fun when it starts to shift.

Drop the tank, it's better to make sure everything is alright in there first, and I'd argue internal pumps are better than external...but you have to get a good one, like AC Delco. One time in 17 years (assuming yours is original) is not asking to drop the tank too many times.

 

[kennyw]

I'd agree your pump is not working... the fuel running out at the filter is likely just from gravity (should be nearly the same with the key on or off). Check the relay first with a test light to be sure the signal wire is turning on with the key as well as checking the function of the relay itself.

 

[Leper]

Found the problem. The thick rubber hose between the fuel pump and the feed line had turned to mush and had a hole in it. It was bleeding off most of the fuel back into the tank and only allwing some fuel to flow with no back pressure on the line.

 

[Blue85]

That's what I was going to suggest, because that happened to me once. My first clue was that the pump seemed to run fast and didn't sound like it had any load on it.

Fortunately, I run Megasquirt, so I just told it I had super tiny injectors and then it was able to deliver enough fuel that I could idle the truck home (there was like 2psi in the fuel rails).