Vortec Owners: Weird Mechanical Issue (1 Viewer)

[Idaho Savage]

My daughter and I drove up into the hills, roughly 1500' of elevation gain from our house--5K to around 6500' at right around 90F. Right before we turned off the highway, my 1969 with 5.3L Vortec simply shut down. I pulled over to the side of the highway and tried to restart it--nothing doing--the starter engaged but the motor made some unhappy sounds. I waited maybe a minute, tried it again. Got it to turnover, only to die immediately.

At this point I'm thinking fuel supply. All gauges are normal and happy--Coolant temp, oil pressure and voltage are all happy. I pop the hood, everything looks fine. So I unscrewed the gas cap to let the tank breathe just in case it was a vapor issue. I had a about a 1/2 tank of gas in it. No hissing or the like, but I left the cap off and took my daughter for a 20 minute walk. We came back and it fired right up--drove the campsite another 10 or so minutes, shut her down for the night.

This morning it fired right up, no issues all the way home (45 minutes or so).

My spidey sense tells me fuel supply, and either the fuel pump got wonky or it was a vapor issue. There is NO charcoal canister on this truck and I'm not even sure the tank breathes in any way shape or form--going from memory, I think there's a hose going from one vent port to the other. Two main variables were heat (around 90F) and elevation gain.

I wanted to get your collective thoughts on the issue. If the fuel pump were indeed failing, I feel like it probably would not have started again, let alone run flawlessly. Do fuel pumps ever overheat or succumb to other temporary pressures? The fuel pump has always been loud, for what that's worth.

Thanks in advance.

 

[peesalot]

Wierd, the only time my LS did that it was in fact fuel or lack of it, I run an in cab fuel pressure gauge and every time the motor acts up I look at gauge and sure enough fuel pressure is down. Are you running stock tank ? I run a frame rail e2000 pump and yes, they are a bit loud, tends to be air , I have grown to enjoy the sound as it fluctuates with blinkers and lets me know all is well. I put a venting cap filler from a dodge dakaota and I ran a vent up high, I run 2 tanks, both vents T together and go to the high point, never had any vapor lock issues. Does your return go to filter or back to tank ? Might try changing filter.

 

[h82crash]

Sounds like fuel to me, as well, since it fired on that early attempt. Fuel pumps can fail abruptly or they can slowly reduce pressure over a short period of time. It can cause hard starting, then run for a while and eventually die. You should put a gauge on the bleed port and see what you're getting. That's a good place to start.

And I've seen the term "turning over" a bunch here and the other groups and forums. Many times I have to have the person asking to clarify the symptoms. People seem to use the term for cranking and starting, depending on what they think the term means. Generally, when diagnosing a starting problem, it is either a "no crank" condition, like a bad starter or dead battery or, a "crank- no start" condition. When I started wrenching over 40 years ago, we used turning over to mean cranking, because if it does what it is supposed to, it starts or it runs.

 

[Idaho Savage]

Sounds like fuel to me, as well, since it fired on that early attempt. Fuel pumps can fail abruptly or they can slowly reduce pressure over a short period of time. It can cause hard starting, then run for a while and eventually die. You should put a gauge on the bleed port and see what you're getting. That's a good place to start.

And I've seen the term "turning over" a bunch here and the other groups and forums. Many times I have to have the person asking to clarify the symptoms. People seem to use the term for cranking and starting, depending on what they think the term means. Generally, when diagnosing a starting problem, it is either a "no crank" condition, like a bad starter or dead battery or, a "crank- no start" condition. When I started wrenching over 40 years ago, we used turning over to mean cranking, because if it does what it is supposed to, it starts or it runs.

Yes, fair. I'd say it ingnited and cranked but then died nearly immediately. So a crank, no start.

I checked the tank (yes, stock) and it is vented up to the filler neck. My question here is--that fuel cap is TIGHT so I can't imagine any actual venting taking place--Is that ok?

My money is in a dying fuel pump at this point but I'll get after it and report back.

Thanks for the input so far!

 

[mattressking]

Put a fuel pressure gauge on the feed line to inspect fuel pressure when the issue occurs and make sure the tank is venting - whether it be a venting gas cap or plumb the vent from the tank to atmosphere or to a charcoal canister. Then repeat testing scenario that initially caused the trouble.

Factory gas caps are sealed and the tank itself has a vent that is plumbed to a check valve and/or charcoal canister.

 

[Idaho Savage]

Put a fuel pressure gauge on the feed line to inspect fuel pressure when the issue occurs and make sure the tank is venting - whether it be a venting gas cap or plumb the vent from the tank to atmosphere or to a charcoal canister. Then repeat testing scenario that initially caused the trouble.

Factory gas caps are sealed and the tank itself has a vent that is plumbed to a check valve and/or charcoal canister.

I think I need a venting gas cap.

 

[h82crash]

Yes, fair. I'd say it ingnited and cranked but then died nearly immediately. So a crank, no start.

I checked the tank (yes, stock) and it is vented up to the filler neck. My question here is--that fuel cap is TIGHT so I can't imagine any actual venting taking place--Is that ok?

My money is in a dying fuel pump at this point but I'll get after it and report back.

Thanks for the input so far!

The fuel cap should not be vented, that is what the evap system is for. That hose that runs from the tank to the filler is for displaced air/vapor to escape while filling.

 

[Idaho Savage]

The fuel cap should not be vented, that is what the evap system is for. That hose that runs from the tank to the filler is for displaced air/vapor to escape while filling.

There is no evap system.

 

[h82crash]

There is no evap system.

I know, but your cap is not vented like the ones in the 1960s. So, without an evap system when it is hot you have high pressure in your fuel system and when it is cold you will have low pressure or a vacuum in your fuel system.

 

[peesalot]

Thats why I got the filler neck from a 90's dodge dakota, 3 bolts line up, vent tube, and size all work, got it at pick n pull. Just for the vented cap. FWIW I put a T in the line from tank to filler vent and ran that to a high point with filter and check valve. My return for that tank T's into same line but lower right off tank. I needed the vented cap to give it a second vent just in case the return flow blocked that vent. I have dual tanks with a Ford switching valve that switches returns as well, been runing the 6.0 on the original ( 16 years ) e2000 external pump so far so good.