No fuel

[GarmrYuk]

More likely, it just takes a few seconds to drop the oil pressure; so the oil pressure switch keeps the pump running.

But I would have expected that with the key "off", there'd be no connection to battery power. I'm somewhat surprised the pump runs with the key "off".

No matter what, there is no "un-prime". The fuel system should be holding pressure.

I think that you are correct on this 99 percent of the time. What you are saying is typically true. But on occasion they put hot fuel modules in these things. I believe that is what I have. So I agree with you 100 percent. Most people say what you are saying. But I think that I have some out of the ordinary device in mine.

 

[Donald Mitchell]

How old is the fuel pump?

 

[Supercharged111]

Playing with TBI just mentioned a hot fuel module. Look that up and read a description of what it does. Based on my research it would not matter what pcm you have. It overrides the pcm and runs the fuel pump after shut off to keep the fuel cool as temperatures rise under the hood. I suppose that with manual fans this makes sense. You shut off the motor and you shut off the fan.

If it does take a dump check this out, a member here makes replacements.

Possible replacement for Hot Fuel Module

One of my recent projects started as a fix for a problem I was having with my Airstream. If the MH sat for a while without being started I found that it would crank FOREVER before it would finally start. I did find that it would start quickly if I turned the ignition ON/OFF/ON a few times. After...

www.gmt400.com

But it sounds like the hot fuel module just gives you a long prime before you start, not keep the pump running after you turn the key off.

 

[PlayingWithTBI]

But I would have expected that with the key "off", there'd be no connection to battery power. I'm somewhat surprised the pump runs with the key "off".

I've long wondered if it was a relay sticking, but it's fed by ignition power isn't it?

The Oil Pressure Switch is fed from fusible link "F" and is "Hot At All Times" so, that's a possibility of a stuck or slow OPS. Here's my 88's diagram.

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[Schurkey]

But it sounds like the hot fuel module just gives you a long prime before you start, not keep the pump running after you turn the key off.

1. That's my understanding of the HFM.

2. I thought only the TBIs got the HFM. Not used on Vortec. Am I wrong?

 

[GarmrYuk]

How old is the fuel pump?

5 years. It pumps fuel and runs all day. It just doesnt prime. Could it just be a bad pump?

 

[GarmrYuk]

More likely, it just takes a few seconds to drop the oil pressure; so the oil pressure

More likely, it just takes a few seconds to drop the oil pressure; so the oil pressure switch keeps the pump running.

I can see that being an issue however I have been running this thing with a bad oil pressure switch for a long time. I replaced it a few weeks ago to get this thing where it stays running once I get it running. It does the same thing and runs the pump after shut off. On rare occasions that I have communication from the ecm it runs the pump for 5 seconds after I shut it off with or without a working oil switch. It did that twice today. Normally it doesnt it everytime. It even does it if I dont start it. Turn the key to run. 10 sec prime. Turn the key off. 5 second prime. No start. Cold motor. It does it religiously and consistently

 

[GarmrYuk]

If it does take a dump check this out, a member here makes replacements.

Possible replacement for Hot Fuel Module

One of my recent projects started as a fix for a problem I was having with my Airstream. If the MH sat for a while without being started I found that it would crank FOREVER before it would finally start. I did find that it would start quickly if I turned the ignition ON/OFF/ON a few times. After...

www.gmt400.com

But it sounds like the hot fuel module just gives you a long prime before you start, not keep the pump running after you turn the key off.

This is interesting. If I long crank like he said it will start eventually but if I do a series of short cranks it usually fires up much faster.

 

[GarmrYuk]

1. That's my understanding of the HFM.

2. I thought only the TBIs got the HFM. Not used on Vortec. Am I wrong?

I think you are right. I cannot find info on any 98 truck or 99 yuk/hoe having any kind of control module. However I have a 10 second prime. No doubt about it. And a 5 second prime after off even if I do not start it so the oil pressure switch is never activated. So what else could cause this if not ops or hfm

 

[Donald Mitchell]

I would check the ground inside the frame rail for corrosion before spending any money.