25thAnn_RS

Car dies after driving 50 miles or so. It will start back up if I let it sit for about 20 minuets, but then I can only get maybe another 5 miles out of it before it dies again. Otherwise it runs great. It's a 92 RS originally with the TBI305 and 5 speed. I finished my LS1/T56 swap back in '09. I used a Walbero 255 LPH fuel pump. I've only put 10k miles on it sense then. It's been doing this for about a year now. I just drive it local so I don't get stranded, but it's getting worse. When I did the engine swap I removed the EVAP canister and left the vent line open so it vents under the hood, so there should be 0 pressure in the tank. I haven't herd any air escaping when I open the filler cap so I don't think my lines are clogged. However when I turn the key on after it stalls the fuel pump sounds like it is struggling. I herd somewhere that there should be about 1psi of pressure in the tank due to a valve that is on the EVAP can... that I threw away. Does anyone know if that pressure is required to help the fuel pump or are these just bad fuel pumps that don't typically last more than 4 or 5 years? Or maybe my fuel pump is fine and there are other problems.

I have found several threads about vent lines, excess pressure and boiling fuel. But no mention of their car dieing. That and I don't seem to have excess pressure or boiling fuel. What have you guys done with the vent lines and has there been any similar problems amongst the LS1 swaps?

QwkTrip

iTrader: (22)

I wonder if the fuel pump is over heating.

How did you do the return line and pump wiring?

25thAnn_RS

The pump over heating sounds like a good possibility. The wiring is all stock. It was a kit from Hawks that plugged into the factory harness. I got the wiring upgrade kit but never got around to installing it. The return line comes from the Aeromotive fuel pressure regulator I used and is otherwise stock at the tank.

The wiring upgrade kit is basically so you have a heaver gauge wire to supply the power to the pump but it only upgrades it to the plug that is over the rear axle. The wiring remains stock from there. The whole thing seems pointless to me. It uses the factory relay to power a new relay that doesn't upgrade the wiring 100% of the way to the pump. Maybe I'm wrong and it really makes a difference.

Pocket

iTrader: (24)

That's why I think hotwire kits are pointless

Stock wiring is fine for a 255, when not pushed to the limit

Try leaving your gas cap off for a drive. You might just have a dud pump too

25thAnn_RS

Well, I plan on cleaning all the lines and replacing the fuel filter. If that doesn't do it then I guess I will replace the pump. Still looking for any thoughts on weather or not I can leave the vent line open or if I should find a check valve to keep that 1psi of pressure in the tank. Has anyone else left their vent line open, and have you had any problems with it?

Lonnie P

An easy way to see if it is temperature related is to compare the time it takes to act up vs. the amount of fuel in the car. If the fuel is getting hot, it should take longer to heat a full tank of fuel than a nearly empty tank.

The open vent should not matter.

I would look for fuel lines close to exhaust etc. that may be picking up excess heat.

Does the pump sound louder when it starts to act up? This is a sign of cavitation due to heat or a restrictive fuel sock.

Flip 2

iTrader: (1)

Just removing the old EVAP canister will not do the job…I HAVE TRIED. Seems like it should, but no. For some reason, that hard line will not pass enough air to balance out the tank.
The ONLY way I get mine to work- this without the 4th gen tank, fuel gauge, etc- is to have an (shhh!) open vented tank. I do it by putting a small K&N filter where that one way air valve is on the fuel tank. Works 100%. I have sleeved the vent down by tube inserts, but air can pass unimpeded.
Last year, I tried a one way vented gas cap (let air in-supposedly), and valve in place of the filter------NO WAY, started not running right really quickly. Went back to the filter, and no issues, whatsoever.
I DO advise keeping your fuel filter with the best, and change it at least annually. The Ethanol in the gasoline can jelly up and clog the filter if left TOO long. Happened once, a year and a half ago. That was shortly after sitting up for the Winter.
So, get a fully vented gas cap, or try my method. You should have no time/distance limits on using your car.
Good luck.

86White_T/A305

I can say from when i had issues like this on my swap I learned a few things. I have a walbro 255 also..but i made a access whole in the trunk to check the pump after several times needing to remove it.Once it was the rubber line in the tank from the pump to the feed line deteriorated and the pump was literally laying in the tank.I sought out a submersible fuel line and clamps.Another time the Factory wiring in the tank at the connector was jelling up with gunk from sitting and this caused the pump to run HOT! The whine that came from back there sounded like I had a areomotive 1000lph pump. I replaced the assembly and upgraded the wires from the tank to the hotwire kit. And my on doing..I had a slight fuel vapor leak from the vette filter/regulator to my feed line wasnt fully snug. I advise if your regulator doesnt have a gauge on it then put one on the fuel rail.Its a cheap easy way to make sure you have adequate pressure at all times.My vent line I literally did as mention..its cut all the way at the tank with a small k/n filter and rubber line.No issues with the tank when I fill up and never noticed any smell of fuel.

25thAnn_RS

Thanks for all the input. I haven't been able to actually get to it with going back to college and family taking up a lot of time.

You pretty much hit the nail on the head. It does take longer to act up when the tank is full, and the pump is louder when it starts acting up.

I'm finally getting started on it this morning so hopefully I have some answers soon.

Pocket

iTrader: (24)

New pump time, hopefully your tank isnt full

If the old pump has any life left, use it to pump the tank as low as possible so the tank isnt crazy heavy. Not the easiest to maneuver out of the car anyhow

alex722607

iTrader: (3)

Hi Guys I was wondering something. (Before I start, I know next to little about the EVAP on TPI and LS1's)

On my car, its an 88, 5.7, tpi, whenever I open the gas cap air escapes. I get lousy gas mileage and the car stalls on start (no cold start injector). I am going to LS soon, but I wanted to ask if these issues are related. My dad did a fuel pressure leak down test and it indicated fuel was leaking internally at some point in the system (or he didn't clamp the lines tight enough) I just replaced the injectors with Bosch III ones. Is the air escaping related to any of this? I know I should have probably posted this in the TPI forum, but I like the LS forum better. (Atleast here I don't get criticized for wanting to ditch TPI)

Flip 2

iTrader: (1)

I had this problem when I had my 383 SBC in. This was when I thought the old line to the charcoal canister would vent the tank. Like you, I was continually mystified. I drove the lousy Super Ram(ed) 383 so rarely, I could never see any pattern. It would just quit. Wait a half hour, and it ran.
When I went to my LS1, I put in a vent on my tank, and there is NO problem with this setup. I can drive anywhere, for as long as I want; 1/2 hour, 2 hours, 5 hours.
Plus, WHEN I tried another way of venting the tank- it acted up right away- started running funny- amazed me at how sensitive it was, really. Needless to say, I put it back.
My 2 cents, BEFORE you get into the costly cures you could try the simple one.
Good luck.

25thAnn_RS

I'm getting better at this. This is the third time I've had the axle down and the second time for the gas tank. I just refuse to cut a hole in my trunk.

I figured that out yesterday when I had it all down. There's a valve in the tank tor the EVAP vent line that's supposed to close when fuel hits it. I think They clog real easy. That and the newest of these cars is 22 years old. There's a second vent line That goes into a valve over the axle. This one is supposed to let air in but not out, it is also wide open in the tank. I just disconnected the line from the valve over the axle and now it should breath properly.

Alex I would try the same thing. you can get to the valve without removing anything. just undo the line. I have no idea if any fuel will spill out or not. I haven't had the time to really drive it yet.

25thAnn_RS

The vent line seems to be fine. I don't smell gas and there's no pressure in the tank when I open the gas cap. However I still have the same problem. I forgot to mention if I push the car real hard (pounding it up passed 100mph and shifting above 6000rpm) it dies shortly after. It just did it again about 20 minuets ago. I guess the fuel pump is the last thing I can think of. I'm using a Walbero. Does anyone have any better suggestions? This pump barley made it 10k miles. I don't really want to buy another one.

Lonnie P

A fuel pump does the same work whether you are idling or running full throttle. It always pumps the same amount of fuel. It either goes down the return line or in the engine.

With this being said the only difference with running it hard is the amount of fuel drawn from the tank. This is likely a venting issue causing a vacuum in the tank.

cam-

Have you logged fuel pressure cold vs hot(when it dies)? 58psi or so is normal range +-3psi

Alice89

iTrader: (6)

Out of curiosity, Did you ever figure out what was wrong 25thAnn_RS?

25thAnn_RS

Unfortanantly I have not done much of anything with it yet. And now that it's winter it will sit in the garage untill spring. When I dropped the tank everything looked pretty good except my fuel filter was pretty clogged. It's probably been like that for a while now. Thats probably what took out the fuel pump. Like I said though, I haven't replaced it yet. The pump has been sitting in the center councel for about two months now. I will post again when I get it changed in case people are still courious. Probably not for a few months though. Sorry.

Lonnie P

A clogged filter will definitely increase the load on the pump.
This increases the current draw & therefore the heat it produces.
Typically you either end up with a vapor lock condition or a burned up pump.


It is amazing how something so simple can cause so much of a problem.
Hope you found it.