Jump to content

Killing Fuel Pumps?


Recommended Posts

I haven't confirmed a second dead pump yet, but the car falls on it's face as soon as it gets boost above about 4k rpm.

 

I'm running a Mitsubishi 4G63 turbo with ECMLink, Walboro 255 on a Z31 fuel "bowl" setup, -6AN lines to and from, Denso 660cc injectors, and Aeromotive FPR.

IMG_0668.jpg

IMG_0671.jpg
IMG_0670.jpg
IMG_0669.jpg

 

Several months ago, I brought my car to my friend's shop to help get a basic road tune to make it safer to drive and get to know the software a bit. We determined that it was running out of fuel under boost and checked the fuel pump. The pump was spraying fuel from a relief valve on the pump body itself, so we swapped it out along with the fuel line from the pump to the fuel pump "hat" that contains the hard lines and electrical connectors. After doing this, everything seemed fine, but my recent trip to the dragstrip was disappointing because the car didn't want to rev over 4-5k rpm. So I swapped the pump again thinking that was the issue. A quick spin around the block and I was back to boosted glory.

 

Fast forward a couple of weeks to today. I was pulling away from a light in first gear, and the car fell flat when I tried to give it more than "cruising" load. This is the same feeling I was getting at the dragstrip. I can't imagine that I killed 2 pumps (maybe 3) from what little I drive it. The car has a total of about 1700 miles on it. I can activate the fuel pump with the motor off, and I get my set fuel pressure at the rail. I also get a noise in the fuel tank that sounds like returning fuel. Maybe more fuel than it should. It's possible that the relief valve is spraying fuel again, but what would cause these failures? The fuel sock looks good. My inline filter looks good. It makes the appropriate amount of fuel under cruise and throttle. What would cause a "partial" pump failure?

 

I'm posting here for general help and knowledge, but will be posting in several places where people might have more specific knowledge of my components.

  • Like 1
Link to comment
  • Replies 23
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Hope you aren't buying the chinese knock-off Walbros.

 

They copy them right down to the box, stampings on the pump, and instructions.

The only way I ever buy a Walbro is through the US distributor, FuelPumps.net

They have a whole page telling about the rip-off pumps out of chinkland.

  • Like 2
Link to comment

Power supply wire to tank too small a gauge? Electric motor is on all the time trying to make minimum full pressure. Not sure if your fuel pump is intermittent duty or not. It should build pressure and then 'rest' till it drops below it's regulated pressure. Unless it is continuous duty it's pounding away all the time.

  • Like 1
Link to comment

A true Walbro 255 can take continuous running.

 

The current pump in the car is from Titan Motorsports.

 

I'd call FuelPumps.net, and see if Titan is actually buying pumps from them.

A lot of big name on-line people supplement their income by selling crap.

FuelPumps.net would be a good place to ask about your problem.

 

Oh, and I am less than impressed with a single plastic tie holding the pump on.

You are asking for trouble.....

  • Like 1
Link to comment

Power supply wire to tank too small a gauge? Electric motor is on all the time trying to make minimum full pressure. Not sure if your fuel pump is intermittent duty or not. It should build pressure and then 'rest' till it drops below it's regulated pressure. Unless it is continuous duty it's pounding away all the time.

My fuel pump has a dedicated power and fuse directly from the battery. It also has a dedicated ground to the battery along with several other grounds on the fuel cell.

  • Like 1
Link to comment

Oh, and I am less than impressed with a single plastic tie holding the pump on.

You are asking for trouble.....

 

The zip tie is mostly for piece of mind. The pump itself is stable with just the hose on there. However, it is also held into the fuel bowl and there isn't much room for it to move around. I suppose I could throw another zip tie on, but I don't see the purpose. I could also use a worm clamp, but again, not sure why I'd need it.

  • Like 1
Link to comment

My fuel pump has a dedicated power and fuse directly from the battery. It also has a dedicated ground to the battery along with several other grounds on the fuel cell.

 

Not what I said. The gauge of the wire is the queation. Too small for the current drawn through it, and there is too much voltage drop. Running a long ground wire is also bad. Use the body, can't get bigger than that.

  • Like 1
Link to comment
It is confirmed that the fuel pump has blown the "relief valve" just like the first one. My Aeromotive FPR can't lower the pressure below about 23psi. I am definitely getting return fuel into the fuel cell, so that eliminates a restriction that would cause high pressure.
 
My thoughts are either the FPR is bad (not likely since my fuel trims look decent) or there is a restriction in the fuel line. Which is also not likely. Other thoughts are that the fuel pump is actually getting too much current since it is directly wired to the battery with an inline fuse and using the stock ECU wire as a trigger. Basically it's just the standard "fuel pump rewire" if the battery was in the trunk.
 

 

What else would cause the pressure to be so high that it would blow the relief valve? I assume that's the correct term and diagnosis. It's the small hole next to the feed outlet. I'll attach a picture of the previous pump for reference.
C7_BB51_B9-_BA08-4_B7_C-9086-87798_FEF82
8_BDFC502-42_D4-40_AA-8_C08-_E7_A31_AA21
BBA1_E102-33_A7-453_A-_BA62-11_A9874_D47
  • Like 1
Link to comment

Not what I said. The gauge of the wire is the queation. Too small for the current drawn through it, and there is too much voltage drop. Running a long ground wire is also bad. Use the body, can't get bigger than that.

Wire gauge is 10ga to and from the relay. The ground wire is only 16-18ga, but is only about 18" from the battery. The fuel pump hat also holds another 3 ground wires with 2 going to the battery and one going to the relay. It is possible that there is an issue there, but I would think it's causing too much current and causing the pump to run too quickly.

  • Like 1
Link to comment

Seems like the power wiring would be sufficient but as current is the same in all parts of a circuit the ground must also be equal to the power wire. 

Impossible to have too much current flow but easy to get less.. Current (I) flow is a function of voltage (V)  divided by resistance ®. Think of voltage as the thing that pushes current through a load. As the voltage is 12-14, and the pump (load) does not change then an increase in current cannot happen.
 
FormulaOhm01.gif
 
The pump is designed to run on a car's power supply which is 12 up to 14v when running. The best you can do is ensure that it is getting the maximum voltage to it.
 
To increase current flow you would have to increase the voltage or decrease the resistance.

  • Like 1
Link to comment

I put a small 3mm machine screw in the relief valve of the old pump just to see if I could make it work.
IMG_3525.jpgbackground
It works. For about 2 seconds until the pressure is too great and it bogs down the pump. I took a quick video. This was after it had already build some pressure, so it bogs down even faster.
https://drive.google.com/file/d/0B9b...ew?usp=sharing

After that, I pulled it back out, and benched tested both the old and new pumps. I was surprised how much fuel stays in the pump itself. The old pump spit fuel from the feed like it's supposed to since the relief valve was blocked. However, the newer pump only spit fuel out of the relief. This leads me to believe either the feed is blocked in some way. I'm actually surprised that it could send 40psi to the rail with how little it tried to send fuel without pressure on it.

  • Like 1
Link to comment

Is the pump bottomed out blocking the sock over the inlet?

 

 

IMG_0669.jpg

 

Assume this is the 'surge tank'? How does the gas get in?

 

There is a rubber dampener that helps space the sock up from the bottom. That being said, it could possibly still be bottoming out. I'll try to do a better job when I install.

 

The "surge tank" from the Z31 has a couple of holes around the parameter to allow fuel in. It also fills from the return line. The "maze" shape also acts like a baffle to hold fuel in the pickup area.

  • Like 1
Link to comment

Hope you aren't buying the chinese knock-off Walbros.

 

They copy them right down to the box, stampings on the pump, and instructions.

The only way I ever buy a Walbro is through the US distributor, FuelPumps.net

They have a whole page telling about the rip-off pumps out of chinkland.

Fuelpumps.net domain is up for sale so I do not think it is the go to place any more.  Unless the Chinese hacked the domain.

Link to comment

The Chinese have a 4 thousand year history of graft and bribery. There's nothing like ' fragrant grease' to smooth things over. Remember when Carter was president and the Iranian hostages? Remember the seal ? teams that were helicoptered in for the rescue? One helicopter had to be abandoned. It was the failure of a counterfeited part. Just look up Chinese counterfeit parts, and their government's failure to crack down on it. You wonder why replacement parts fail or are 'bad in the box'?

  • Like 1
Link to comment

I'd move the return line away from the pickup.  Its likely pushing fuel away fro the pickup, creating an eddy in the tank.  I like the kick in your return line, but shorten it up to about half the depth of the tank OR extend it a few inches longer away from the pickup.  

Are you sure you're not just starving the fuel pump?  What's your duty cycle like on the injectors at 4k?  It may be a programming calibration and the pump is fine.They shouldn't be past 70% even with boost at 4k.  

Link to comment

I'd move the return line away from the pickup.  Its likely pushing fuel away fro the pickup, creating an eddy in the tank.  I like the kick in your return line, but shorten it up to about half the depth of the tank OR extend it a few inches longer away from the pickup.  

Are you sure you're not just starving the fuel pump?  What's your duty cycle like on the injectors at 4k?  It may be a programming calibration and the pump is fine.They shouldn't be past 70% even with boost at 4k.  

I can move the return line a little. I don't know that it would cause too much of an issue, but that's a good thought.

 

I haven't checked a log with the fuel pump to see what the duty cycle is. Immediately after replacing the last fuel pump, I did some pulls to redline, and it ran great. It seems to be starving for fuel when boost comes on, and the relief valve shouldn't be spraying fuel at idle. I don't have a way to check fuel pressure while driving. I'm checking for restrictions in the line right now. The new pump should be here by Friday, so I want to make sure everything is in order before then.

Link to comment

I've inspected the lines and blew them out with compressed air. I'm not finding any issues. The only thing I could think of is a clogged fuel filter. I'm running this one:

I thought someone told me years ago that I'd have issues with it, but I can't imagine why. It is advertised as fuel injection compatible and the housing is supposed to be good for 300psi. I don't see a rating or restoration for the filter itself other than stating it is 40 micron. I got a replacement filter today to see if there was an issue there. I also got an Autometer fluid filled pressure gauge in case the old one was bad. I had a crappy generic one that was falling apart. The new fuel pump should arrive tomorrow so I can do some testing.
Link to comment

I'm still "testing". It did make a round trip from Vegas to LA on Sunday (around 500 miles) with some low boost uphill pulls (about 7psi). I haven't looked at the logs yet, but it seems to be working so far. I'm planning to get another fuel filter with a larger element. I'll be working with a friend on Sunday doing some road tuning to see if we have it ironed out.

 

Edit: No updates. The system still seems to be working fine. I still plan to run a bigger fuel filter, but I haven't had any issues since the last pump replacement.

Edited by jeffball610
Link to comment

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.