2G Walbro fuel pump cutting out / engine bucking or missfire.

[Brad Bell]

I've been having this problem for a few weeks but it seems to only happen under extreme load, or starting from a complete stop in some instances. it's a walbro GSS 342, 255LPH. Engine primes and starts fine, but after running for 15 minutes the I can hear the pump sputtering. Walbros as we know have a distinct whining sound, which mine makes fine when cold starting. The engine however will randomly start lossing power and misfiring when under load. Such as trying to go up a hill in 5th gear and you step on gas. It also happnes periodically when starting from a complete stop, the engine will start spitting rapidly and buck hard. My A/F gauge totally goes lean at this moment too. Is my pump dying on me? My sparkplugs bad? I have a rising rate fuel pressure gauge also, and it will not raise the fuel pressure past 60psi, which I need to run my 8psi efficiently.
Please help!

 

[kmetiuk]

Kind of sounds like a loose connection or a bad ground on the fuel pump or the MPFI relay maybe? The fact that its random makes me initially think electrical issue.

 

[Brad Bell]

Kind of sounds like a loose connection or a bad ground on the fuel pump or the MPFI relay maybe? The fact that its random makes me initially think electrical issue.

No idea, I made sure the connections are good. Its not necessarily random, It runs almost perfect warming up, but after like I said 15 minutes it starts to happen pretty bad. I can normally predict when it will happen and at what rpm, depending on what gear I'm in. It happens more in the higher gears under load. It's like the fuel just gets cut off, my fuel pressure gauge doesn't drop however, but my AF gauge says lean.

 

[kmetiuk]

Is your fuel pressure gauge oil filled? Most are and it dampens the needle speed so if it happens really quickly then the gauge might not show it. I'd trust the AF gauge in this case.

What your describing is weird....the fact that you can't get over 60 psi of fuel pressure kinda makes me think maybe it is your fuel pump then....or your AFPR maybe? Or maybe the gauge is busted or wrong?

Just thinking about the fact that it happens after its warm though.....when a relay is bad or is going it sometimes acts up only after its warm.

 

[Brad Bell]

Is your fuel pressure gauge oil filled? Most are and it dampens the needle speed so if it happens really quickly then the gauge might not show it. I'd trust the AF gauge in this case.

What your describing is weird....the fact that you can't get over 60 psi of fuel pressure kinda makes me think maybe it is your fuel pump then....or your AFPR maybe? Or maybe the gauge is busted or wrong?

Just thinking about the fact that it happens after its warm though.....when a relay is bad or is going it sometimes acts up only after its warm.

Gauge is brand new auto meter electric gauge. With brand new fuel pressure regulator, its a rising rate fuel pressure, so under boost it will rise from pre set fuel pressure 45psi, to around 80-85psi. It will rise but stops at 60psi, however, sometimes it will only go as high as 50psi. A Waldro pump should go a lot higher.

A sound that I can describe coming from the pump is when the car is warmed up and I come to a complete stop at a stop light, a wall or should be making a steady whining sound which it does when cold, but here it makes sort of like a pulsing sound, not a steady one. Sort of like the pressure it is putting out is going up and down.

 

[Brad Bell]

Gauge is brand new auto meter electric gauge. With brand new fuel pressure regulator, its a rising rate fuel pressure, so under boost it will rise from pre set fuel pressure 45psi, to around 80-85psi. It will rise but stops at 60psi, however, sometimes it will only go as high as 50psi. A Waldro pump should go a lot higher.

A sound that I can describe coming from the pump is when the car is warmed up and I come to a complete stop at a stop light, a wall or should be making a steady whining sound which it does when cold, but here it makes sort of like a pulsing sound, not a steady one. Sort of like the pressure it is putting out is going up and down.

I feel I should just replace the pump but I'm worried that's not the entire issue I'm having.

 

[kmetiuk]

I feel I should just replace the pump but I'm worried that's not the entire issue I'm having.

Ya man, that's a tough call.

I wonder maybe if you have a blockage in the suction end of the pump or in the feed line between the pump and the rail.

I'm just throwing things out there that you could check before swapping in a pump.

 

[Brad Bell]

I have a Walbro GSS 342, 255LPH (it's an old one, around 2006), stock injectors, and a BEGi rising rate adjustable fuel pressure regulator. This has been happening for a while, but I noticed while running my eclipse GS, the fuel pressure will not go above 60psi. I'm running 6psi on the turbo, so the pressure should be around the 80-90psi range. The base fuel pressure is set to 45psi. I tried turning up the fuel pressure at the FPR just to see how high the fuel pressure would go, but it stops rising at the 60psi mark, the FPR is not bottoming out.

I believe the problem is my Walbro pump, because while driving under heavy load such as a hill the engine misfires like crazy. I sometimes cannot hear the pump while waiting at red lights. Is my pump dying on me? Or is this something else. I simply can't get the fuel pressure high enough, even with this high-pressure fuel pump. The car starts up fine no problem and will stay constant 45 psi. the only problem I'm having is that it won't reach high enough pressure, even with the regulator maxed out.

 

[Brad Bell]

Ya man, that's a tough call.

I wonder maybe if you have a blockage in the suction end of the pump or in the feed line between the pump and the rail.

I'm just throwing things out there that you could check before swapping in a pump.

The fuel pressure reaches a max of 60psi while driving with the afpr, even with it maxed out, it just won't go past that point.

 

[bradcurtis15]

Hey If you think your pump is bad why don't you replace it to rule it out. have you checked injector seals? do you have vacume leaks and do you have your afpr connected to the proper vacume source? what is your fuel pressure at without a vacume source connected?

 

[ceedawg]

Hows your battery voltage and did you do the fuel pump rewire upgrade?

 

[Brad Bell]

Hows your battery voltage and did you do the fuel pump rewire upgrade?

Battery is 13.8 while running. And the pump was pretty much plug and play. not a hot wire or anything.

 

[Brad Bell]

Hey If you think your pump is bad why don't you replace it to rule it out. have you checked injector seals? do you have vacume leaks and do you have your afpr connected to the proper vacume source? what is your fuel pressure at without a vacume source connected?

Not sure of vacuum leaks. And I've tried vacuum source in two different places with no luck. Fuel pressure raises to max of 60 psi like I said, won't go any higher.

 

[blktalon3]

A rising rate regulator will rise 1psi for 1psi. So if your running 45psi base pressure with the vacuum hose disconnected and 6psi of boost the regulator will only rise to 51psi at full boost

 

[bradcurtis15]

Maybe I am not understanding you clearly, with no vacume source your at 60psi?

Make sure your fpr is set up correctly sir.
http://www.dsmtuners.com/threads/aeromotive-afpr-install-with-install-kit.338084/

If your injectors aren't working properly you will lean out car will buck and get fuel cut under boost. I see you been posting on here since Nov 3rd and you are still struggling. check for vacume leaks I've had bad injector seals and would fuel cut at 10psi. hope this helps you.

 

[We're on Boost]

..... it will not raise the fuel pressure past 60psi, which I need to run my 8psi efficiently.
Please help!

What is this "8psi" that you are talking about? Is that the boost you are running at? If your fuel pressure reaches 60 psi at full boost, that would be the correct fuel pressure for about 16 psi of boost, given the normal 43.5 psi fuel base pressure. So I don't know why you are expecting to see more fuel pressure than ~60psi. Is that a typo? Did you mean 18 psi of boost? Still then, 60 psi of fuel pressure is about right when you are WOT and spooled up, within the margin of error of all the gauge readings.

Just as a suggestion, it kind of helps to post in your profile all your mods so people have some basic idea about your car. If you do that, it will show up as a "DSM Profile" by your user name.

 

[Brad Bell]

A rising rate regulator will rise 1psi for 1psi. So if your running 45psi base pressure with the vacuum hose disconnected and 6psi of boost the regulator will only rise to 51psi at full boost

Yes but it runs leans and misfires at such a fuel pressure at the 6 psi of boost. It should be more.

 

[Brad Bell]

What is this "8psi" that you are talking about? Is that the boost you are running at? If your fuel pressure reaches 60 psi at full boost, that would be the correct fuel pressure for about 16 psi of boost, given the normal 43.5 psi fuel base pressure. So I don't know why you are expecting to see more fuel pressure than ~60psi. Is that a typo? Did you mean 18 psi of boost? Still then, 60 psi of fuel pressure is about right when you are WOT and spooled up, within the margin of error of all the gauge readings.

Just as a suggestion, it kind of helps to post in your profile all your mods so people have some basic idea about your car. If you do that, it will show up as a "DSM Profile" by your user name.

Yes I'm running 8psi of boost. I'm running a walbro, so shouldn't I be getting a larger fuel pressure than just 60psi with the FPR turned all the way up? The engine needs more fuel pressure for this boost, it just misfires , and bucks like a horse under boost or even approaching boost.

 

[Brad Bell]

Maybe I am not understanding you clearly, with no vacume source your at 60psi?

Make sure your fpr is set up correctly sir.
http://www.dsmtuners.com/threads/aeromotive-afpr-install-with-install-kit.338084/

If your injectors aren't working properly you will lean out car will buck and get fuel cut under boost. I see you been posting on here since Nov 3rd and you are still struggling. check for vacume leaks I've had bad injector seals and would fuel cut at 10psi. hope this helps you.

When I disconnect vacuum line it reads 60psi, with it attached it reads 45psi. If I try to turn up the base pressure while the vacuum is disconnected, it won't go any higher than 60psi. It will screw in and rise pressure but will max out pressure at 60psi.

 

[We're on Boost]

Yes I'm running 8psi of boost. I'm running a walbro, so shouldn't I be getting a larger fuel pressure than just 60psi with the FPR turned all the way up? The engine needs more fuel pressure for this boost, it just misfires , and bucks like a horse under boost or even approaching boost.

Well normally, with 8 psi of boost, you would set the fuel base pressure to the normal 43.5 psi. Not higher. Then when you are actually at 8psi of boost while driving WOT, then you should see about 52psi of fuel pressure when the boost gauge reads 8psi. I don't know what you have going for engine management (ecu mods) or what injectors you have (stock or what). So without knowing anything about your car, there are a few possibilities. But it sounds to me like you are probably sending way too much fuel to the engine because you have the fuel pressure set way too high. At low loads when you are running closed loop, the stock O2 sensor and the ecu figure out how to correct the A/F mixture back closer to what it should be. But when you get on it and it goes into open loop, there's no correction, and it just plain runs way too rich.

If you have some time, probably you should put a profile up that says what mods you have made and everything else is stock, something like that. If you have trouble figuring out how to post up a profile, take a look at mine or somebody's but ask for help and don't worry about it. I had a hard time figuring out how to use the profile here too . My profile that is labeled "14b manual" in the tile below is a nice example for a car that is not radically modified.

Anyway, no, you shouldn't have such high fuel pressure just because you have an upgraded fuel pump. With 8psi of boost you should probably just have the base fuel pressure set to whatever the stock base pressure is from the factory, and since I don't know much about 2g's, I don't even know what that number is. It might be 43.5 or it might be a little less.

 

[Armando Elepan]

I had a similar issue when I first got my 95 TSI. Given I did have some boost leaks, but the bucking continued after that was fixed.

I spoke with a reputable Dsm guru, Miles Denton not sure if he is on here or not.

Set the fuel pressure with the vac line OFF, to 42 psi.
When you do this, plug the vac line with your thumb so the rpms don't rise. Set the pressure to 42. Then tighten down what you have. Plug the vacuum back in and you should be reading 33 psi at idle.

This is how my car is set and I run 15psi. Aem wideband never leans out.

Too much fuel could be causing the bucking as well. I'm going to assume you have ran a boost leak test?

 

[We're on Boost]

Set the fuel pressure with the vac line OFF, to 42 psi.
When you do this, plug the vac line with your thumb so the rpms don't rise. Set the pressure to 42. Then tighten down what you have. Plug the vacuum back in and you should be reading 33 psi at idle.

Yes, that's what the Chilton manual says too. Chilton manual for 1990-1998 Eclipse, on page 5-8:
For 1995-1998 2.0 liter turbo engines,
Pressure should be 33 psi at idle with the vacuum line connected.
With the vacuum line disconnected, pressure should be 42 to 45 psi.

Apparently on the 2g it doesn't make any difference whether you have a manual or an automatic transmission, for this setting.

 

[dsmcrzy]

OP what are you using to tune? Please start a build profile so everyone knows what your current mods are.

 

[Kal2gEclipse]

Hello all
Hi Brad I have the same exact problem going on, I'm on my 2nd pump, the first a very enexpensive pump this one is a walbro and I have had problems with both.I really think its electrical, its after the car has warmed up. a couple of times with the old pump it just cut out not even 10 seconds after I started the car. I'm perplexed, maybe the voltage becomes unstready after warming up maybe the alternator is causing it or maybe the ecm or relay idk but I'm trying to get to the bottom of it this post helped me to realize I'm not the only one experiencing this problem so if I can do anything to help let me know
Thanks

 

[Brad Bell]

Alright I fixed it, it was just the sparkplugs, I think they were gapped too wide and also they were pretty old. Runs great now! Thanks everyone for the help!