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Old 10-05-2006, 10:36 AM   #1
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Well, since my car is having so many problems, pretty much every day.. I thought I'd start my own thread

Todays problem:

Yesterday braineack and I checked my fuel pressure.. 80 PSI max.. and thats WITH the inline pump supplementing the stock. So we changed out a walbro 190hp. Right off the bat I was able to get 120psi of fuel upon testing. Taking the car out for a test run the FP rose fine until about... 5k rpm. The pressure rose great until at 5k RPM the pressure went from 80 and just DIED.
My two options:
FPR is broken?!
HKS VPC is just jacked up? (MAP sensor is dead? anyone know how to test?)

Any opinions? Fuel setup now consists of the walbro 190, pierburg inline (not really needed anymore), Cartech AFPR, and 1.8 injectors, HKS VPC controller
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Old 10-05-2006, 10:50 AM   #2
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check for a leak at the fpr. also did you check the fpr itself with a boost source to see if it is tough enough to figth the pieburg and walboro by itself maybe you have a week diaphragm?
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Old 10-05-2006, 11:03 AM   #3
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I'd pull the Pierbug out. If it didn't work before, maybe it is screwing up the flow from the 190.
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Old 10-05-2006, 11:11 AM   #4
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can't hurt to try a new fpr. Also if i were in your position i swear i'd borrow someones ecu and afm just too see what happened.
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Old 10-05-2006, 11:12 AM   #5
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The FPR will be checked tomorrow using a compressor, I have a spare vortech to swap. As for a leak, there is no leaks in or around the FPR, since I just replaced all the fuel lines and pressurized the system to 120 PSI just to be sure.

Olderguy, my question is this.. If I was able to pressurize the system to 120 PSI using the walbro/pierburg combo, would that not prove the pierburg worked?

Thanks for your input guys
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Old 10-05-2006, 11:23 AM   #6
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well technically you would be able to hit the 120psi with just the Walbro.

Verified:
75-80psi max on stock pump and Pierburg
120psi on 190HP and Pierburg (I have a feeling both the stock pump and Pierburg are shot)
Max pressure with load was 80psi then a drastic drop in pressure (just after hitting 5k & around 5psi)

Here are my thoughts:

1. The Pierburg is shot and is to blame. We can try cutting power to it at least and try again, easy test and easy way to rule something out, but with the 190HP there is no need for it.
BTW, we couldn't find the Pierburg before because it was mounted by the muffler on the driver's side; Saw a speaker wire sliced off the pump's power and followed it.
2. The Cartech unit might be failing. The diaphram could be ripped, the shim might need replacement, or the piston might need lubing. Since it is the old Cartech unit, it's gotta be as old as the car itself. Since we pressure tested by clamp the return we never veified the unit's working condition.

Simple test, running 10psi of air into the vacuum line of the unit and verifying the fuel pressure levels.

3. The HKS VPC unit. Just because it's a confounding variable and something unknown.
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Old 10-05-2006, 11:33 AM   #7
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Quote:
Originally Posted by Newbsauce View Post
Olderguy, my question is this.. If I was able to pressurize the system to 120 PSI using the walbro/pierburg combo, would that not prove the pierburg worked?

Thanks for your input guys
The 190 should give you all the pressure/flow you need. It may be possible that the Pierburg is bad and randomly blocking your flow. Just something else in the equation to worry about.
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Old 10-05-2006, 12:04 PM   #8
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Bruce is right, pull the Pierburg out. Since you don't need it anyway why leave another variable in there?

Is the fuel pressure dropping off because you are falling out of boost? Or are you falling out of boost because the fuel pressure is dropping? Things happen pretty quick and it might be difficult to tell what's going on. If for whatever reason your car falls flat on it's face you'll see FP and Boost take a nose dive, and if it happens really quick it all seems to happen at the same time. So which is it?

If your pump can handle 120psi when manually pinching the return, it's likely ok. I'd suspect the BEGI. I've got an old one myself and just rebuilt it, has made a significant difference in adjustability and consistancy.

Once you pull out the Pierburg, I'd look at swapping the Vortch FPR in. Eliminate one thing at a time if possible.

Jay
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Old 10-05-2006, 12:17 PM   #9
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Quote:
Originally Posted by jayc72 View Post
Bruce is right, pull the Pierburg out. Since you don't need it anyway why leave another variable in there?

Is the fuel pressure dropping off because you are falling out of boost? Or are you falling out of boost because the fuel pressure is dropping? Things happen pretty quick and it might be difficult to tell what's going on. If for whatever reason your car falls flat on it's face you'll see FP and Boost take a nose dive, and if it happens really quick it all seems to happen at the same time. So which is it?

If your pump can handle 120psi when manually pinching the return, it's likely ok. I'd suspect the BEGI. I've got an old one myself and just rebuilt it, has made a significant difference in adjustability and consistancy.

Once you pull out the Pierburg, I'd look at swapping the Vortch FPR in. Eliminate one thing at a time if possible.

Jay
I was watching the FP gauge and brad was driving and watching the Boost gauge. It would pull makes boost and gradiually increase FP and then it literally dropped off, as soon as it did I yelled cut it.

I think we are all on the same page as what to start doing next.
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Old 10-05-2006, 01:43 PM   #10
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Quote:
Originally Posted by braineack View Post

I think we are all on the same page as what to start doing next.

Start smashing my car with a hammer?
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Old 10-05-2006, 02:48 PM   #11
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you're really good at reading between the line!
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Old 10-05-2006, 05:58 PM   #12
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I had an old school Cartech/BEGI 2005 model (not the year) I took it apart once and found some little black ***** of FM inside(others have mentioned this as well) I cleaned it up and it worked fine. (I might have made a new shim out of a beer can too, but it's been so long I can't remember).
Is it always at 5K rpm? it might be the rpm signal to the HKS?
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Old 10-05-2006, 08:11 PM   #13
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Quote:
Originally Posted by braineack View Post
Verified:
75-80psi max on stock pump and Pierburg
120psi on 190HP and Pierburg (I have a feeling both the stock pump and Pierburg are shot)
Max pressure with load was 80psi then a drastic drop in pressure (just after hitting 5k & around 5psi)
Just a few thoughts:
1) Yes, the Pierburg is either shot or not wired in correctly as the stocker + the Pierburg should put out well above 120psi. In fact from statement #1, it looks like the stock pump was fine, but the Pierburg was not working.

2) While I agree with pulling the Pierburg out, even if it was not working, it should not be causing a restriction in flow as IIRC it has a bypass that makes it "invisible" to the stock fuel system when not needed. If the bypass was not working then you would always have a restriction of flow, not just at high rpm but all the time.

3) Test #2 of the walbro + pierburg was again probably all walbro and the pierburg is basically not working and out of the equation.

4) While I also agree that the afpr may need reconditioning, if the diaphram was leaking, I don't think it would increase pressure and then suddenly cut. It would probably have a slower rate of rise and cease to rise at some point.

5) Even with just the stock pump functioning at 80 psi max, you technically should have been able to support 5psi assuming a base of 45-50psi + 6 psi of fuel pressure per psi of boost = 75-80psi of fuel needed.

Thus, it almost sound like you have a fuel cut above 5k rpm under heavy load...so I'm putting my bet on the HKS unit as the original AFM also controls the fuel pump on/off. Maybe at 5k rpm under load, it has a poor signal that causes a fuel cut? I think that mach929's idea of swapping in a AFM and stock ecu (if feasible) would help rule that out. Just my 2 cents...
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Old 10-05-2006, 09:26 PM   #14
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From what I've read up on the VPC, the only function is has to it replace the AFM. It does this by using a MAP and Temp sensor and converting the signal. It can also fine tune the AFR by 2% increments up to -+16%. Ths only way it would cut fuel is from an output to an F-con unit which can program a fuel cut.
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Old 10-05-2006, 09:52 PM   #15
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Quote:
Originally Posted by braineack View Post
From what I've read up on the VPC, the only function is has to it replace the AFM. It does this by using a MAP and Temp sensor and converting the signal. It can also fine tune the AFR by 2% increments up to -+16%. Ths only way it would cut fuel is from an output to an F-con unit which can program a fuel cut.
I'm not saying it'll adjust fuel via a fuel cut, but I do know that one issue beyond temp sensor and flapper door conversions is that if the stock AFM is disconnected, the fuel pump will not run as the stock AFM will cut off the fuel pump if there is no airflow so.....if the VPC is putting out an odd signal, it might cause the fuel pump to shut off. Just a though as a dead fuel pump and leaking afpr wouldn't tend to cause a fuel cut...

Heck, solving these problems is half the fun...
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Old 10-05-2006, 11:08 PM   #16
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Think a failed MAP sensor could be a plausible culprit? They have the voltage outputs listed, might as well test it.
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Old 10-06-2006, 10:51 AM   #17
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Another option...

If your FP is good @ idle, but worse above 5K, maybe it's a fuel filter? When's the last time you changed it?

I 5000th -- pull out what you don't need in the system.....

Dave,
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Old 10-06-2006, 11:20 AM   #18
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He just changed it.
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Old 10-06-2006, 11:57 AM   #19
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Well the plan of action is this:

1> Remove the pierburg
2> Test the AFPR
3> Eat Chipotle
4> Test the MAP (hopefully brain will learn how)

However, I'm stalled by the weather, since its like monsooning out today :(
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Old 10-06-2006, 12:19 PM   #20
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Just another thought to try before tearing into things:

1) Get the car running and then jumper the F/P and GND in the diagnostic box. That'll keep your fuel pump running no matter what while the ignition is on.
2) Re-test the fuel pressure at 5 psi of boost.
3) If the car holds a steady fuel pressure this time then fp is okay but control/power to the fp is not.
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