I have a 2002 Eco with a Hahn Stage 2. I seem to have a problem that Hahn has never heard of and no one else I talk to can figure out either. Problem is that when the car runs a while and gets hot, the fuel pressure begins to fluctuate randomly. This makes it hard to start the car and hard to idle when stopped. Mainly, my problem is when racing the fuel pressure will suddenly and without warning, just not rise with boost. It stays pegged at about 40psi. So I have replaced everything in the Hahn fuel kit including the pump, wiring, relay, and all connections. So the only thing left I can think of is the stock in-tank pump. I just don't understand how the pump runs normally most of the time but then could just die. Does this sound like the stock pump to anyone else? Or has anyone else ever experienced this?
I'd like to eliminate the in-tank pump all together and go purely with the external pump. Has anyone ever made or seen a decent fuel pickup line used for J cars? I couldn't think of a reliable and effective way of making one for the stock pump assembly. Any info or suggestions on this matter would be great. I feel like my car is possessed or that I'm going crazy!
"If you aren't shifting, then you certainly aren't driving!"
Let me add that I would be willing to replace the in-tank pump if I had good reason to assume that is the problem. I'm just sick of throwing money at this problem and never getting any positive results!!
"If you aren't shifting, then you certainly aren't driving!"
Yes FMU is installed correctly. The failure only occurs after its hot and is somewhat rare depending on use. But it has let me down at very crucial moments and I no longer trust the car. Not a good combination. But, I don't see how the FMU can cause this.
"If you aren't shifting, then you certainly aren't driving!"
wow that sounds like an FMU where the thing inside gets @!#$ when the car gets hot... relocate it, problem solved
LE61T PTE6262 Powered 
What do you mean the "thing inside?" Do you mean the aluminum shim? No one else with the Hahn kit seems to have this issue. Have you known anyone to experience this?
"If you aren't shifting, then you certainly aren't driving!"
So this doesn't sound like a fuel pump issue to anyone then?
"If you aren't shifting, then you certainly aren't driving!"
silvercav02 wrote:So this doesn't sound like a fuel pump issue to anyone then?
No, not if its intermittent.. Just my personal opinion.. you should always upgrade your pump to suit your fuel needs!
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Sorry about the late response. The system was upgraded by installation of the in-line pump. The stock fuel pump was retained in the gas tank. I have put more thought into eliminating the stock pump. I figured I could just buy a connector to plumb the pickup line to the out line. Then I could just run the system from the external pump. Has anyone done this before?? I would love to hear any suggestions or comments on this since I have a very limited time to fix this when I start. Thanks guys!
"If you aren't shifting, then you certainly aren't driving!"
why not just stop beating around the bush and just change the fuel pump to a walbro. Its not that hard.
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Yeah I had seen posts that those pumps had pick up problems. For the type of racing I do I can't afford for this to happen.
I am going to try replacing the shim in my fuel regulator to see if that helps, but I doubt it will.
"If you aren't shifting, then you certainly aren't driving!"
John Higgins wrote:Lefix wrote:Buy this Walbro In-tank Pump, problem solved...
http://www.autoperformanceengineering.com/
Part# FPG003 Kit, and buy a Flex Hose...
Easy!
Yeah so he can have fuel cut issues.
If you can afford to spend thousands on a turbo kit than I dont want to hear you whining because you have to keep more than a 1/4 tank of gas in your car.
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cavmania(Keeper of da Sleeper) wrote:John Higgins wrote:Lefix wrote:Buy this Walbro In-tank Pump, problem solved...
http://www.autoperformanceengineering.com/
Part# FPG003 Kit, and buy a Flex Hose...
Easy!
Yeah so he can have fuel cut issues.
If you can afford to spend thousands on a turbo kit than I dont want to hear you whining because you have to keep more than a 1/4 tank of gas in your car.
What does how much we spent on a turbo kit have to do with it? Maybe some of us only run our cars with 3 gallons of gas in them for a reason, WEIGHT and CONSISTENCY. Maybe we can't afford to run our cars down the track with the tank at various different levels. I keep everything the same for every run as much as possible, including only keeping a 1/4 tank of gas in the car TOPS while running it.
I used to race cars, now I race myself.
5K PB: 24:50
10K PB: 54:26
Team Vision Racing (aka hypsy) wrote:cavmania(Keeper of da Sleeper) wrote:John Higgins wrote:Lefix wrote:Buy this Walbro In-tank Pump, problem solved...
http://www.autoperformanceengineering.com/
Part# FPG003 Kit, and buy a Flex Hose...
Easy!
Yeah so he can have fuel cut issues.
If you can afford to spend thousands on a turbo kit than I dont want to hear you whining because you have to keep more than a 1/4 tank of gas in your car.
What does how much we spent on a turbo kit have to do with it? Maybe some of us only run our cars with 3 gallons of gas in them for a reason, WEIGHT and CONSISTENCY. Maybe we can't afford to run our cars down the track with the tank at various different levels. I keep everything the same for every run as much as possible, including only keeping a 1/4 tank of gas in the car TOPS while running it.
Thank you!!! Plus if the mod you do does not 100% fix your issue why do it?? We should be able to get a fuel pump option that does not give us fuel cut.
FU Tuning
John: People don't realize how few of us are willing to except fuel cut as a side-effect. I would think no one would take that as a side-effect they'd allow, but yet here we are.
I used to race cars, now I race myself.
5K PB: 24:50
10K PB: 54:26
the fuel cut is easily solved.... hell it was solved a long time ago, there are various options, one was some comapny who does performance stuff for GTP's, you buy the GTP install kit it has a little fitting that flows fuel into the cup, someone not to long ago made there own solution to the problem and it worked, peopel make the fuel cut problem seem like alot bigger deal then it is, its a cheap easy fix
Darkstars wrote:the fuel cut is easily solved.... hell it was solved a long time ago, there are various options, one was some comapny who does performance stuff for GTP's, you buy the GTP install kit it has a little fitting that flows fuel into the cup, someone not to long ago made there own solution to the problem and it worked, peopel make the fuel cut problem seem like alot bigger deal then it is, its a cheap easy fix
Actually the fuel cut issues has never been 100% solved. Even in that thread you posted he came back and was still having issues. I seen Raven post about the T-ing off thing, but I have not heard of any J-body's doing that yet. I would do the T before the drilling. I do like this option and I'm considering it
fuel pump
FU Tuning
I'm sorry for the confusion I caused!! What I'm attempting now is to get RID of the in tank pump by bypassing it completely. I will use the external pump from Hahn to run the whole system (it is capable if no restrictions from the stock pump). What I could not find was any previous attempts to make an effective feed/pickup doing so. I plan to leave the stock "housing" of the pump and try using the stock feed line and connect it to the stock out line of the pump. Then my external should be able to run the whole system from outside the tank by sucking throught the stock fuel pickup. I still need to get a signal from the stock wiring to run the external, but that shouldn't be a problem.
Thanks to those who responded. I knew about the Walbro pump post, but I would like to retain the external pump for ease of replacement/maintenance reasons. And fuel cut would be detrimental to my car since I use it for autoxing and track events.
I'm not trying to start a war about pickup issues, I'm just looking for anyone with experience or ideas on a decent way to solve this problem. Thanks again.
"If you aren't shifting, then you certainly aren't driving!"
silvercav02 wrote:I'm sorry for the confusion I caused!! What I'm attempting now is to get RID of the in tank pump by bypassing it completely. I will use the external pump from Hahn to run the whole system (it is capable if no restrictions from the stock pump). What I could not find was any previous attempts to make an effective feed/pickup doing so. I plan to leave the stock "housing" of the pump and try using the stock feed line and connect it to the stock out line of the pump. Then my external should be able to run the whole system from outside the tank by sucking throught the stock fuel pickup. I still need to get a signal from the stock wiring to run the external, but that shouldn't be a problem.
Thanks to those who responded. I knew about the Walbro pump post, but I would like to retain the external pump for ease of replacement/maintenance reasons. And fuel cut would be detrimental to my car since I use it for autoxing and track events.
I'm not trying to start a war about pickup issues, I'm just looking for anyone with experience or ideas on a decent way to solve this problem. Thanks again.
You did not start anything.
I do not think you can do what you are talking about (at least in the way you are talking about). I think you would need to make a custom tank were the feed lines are at the bottem of the tank, and then the external pump could pull the fuel needed.
FU Tuning
the pump form the Hahn kit is meant to be a booster pump, not the only pump, I don't see it working out
To help you from running into more issues than you are currently having I want to lend you some suggestions...........
The inline pump that hahn has supplied you with is NOT designed to be a standalone fuel supply pump hence it being an inline pump. The pump is designed as a "PUSHER" which limits its ability to "SUCK" . The in-tank pump is designed to suck the fuel and exert it into the fuel system. The inline further helps to pressurize fuel beyond the stock or at least maintain I should say constant pressure without over exerting the in-tank pump as the in-tank is able to supply much more volume than it is pressure. Personally you don't really need to upgrade your in-tank however "IF" it is going bad why not upgrade. You keep throwing money at it because you aren't finding the problem first!!!!!!!! You are just throwing parts at it and that becomes expensive.
Could be an electrical short in the in-tank circuit........ could be a lot of things but you need to try and eliminate somethings first.
I will tell you from experience that if you run a low tank of fuel the fuel will quickly become HOT because there is no time for it to cool before it heads right back into the HOT engine bay and rail. When this happens the fuel thins and is obviously pumped easier and the extra heat begins to create much resistance in the motors of the pumps, over working them. Usually why the inline is screaming its lungs out when on a low tank. Also because the in-tank supplies the inline with a low tank it is certain you will at times more often than desired suck AIR. This is further exaggerated by the inline which causes you to lose fuel at critical times, usually under wide open throttle at full injector PW. Dropping the fuel PSI in the rail considerably. This also creates less than desirable spray patterns etc. that lead to fluctuated A/Fs and Fuel PSI spikes and loss. if you monitor your fuel PSI while driving around it can help eliminate many problems just in the way the needle moves. Repair problems with your head NOT YOUR WALLET
ASE Master Certified Automotive Technician
