teknics

iTrader: (4)

ok maybe someone can help me here.

I just finished converting from a single pump with kgrails, 850/1680 and an aeromotive FPR. Had no problems setting fuel pressure.

Went to a full parallel setup with CJ Walbro holders, -6 lines from pump to rails. Primary line connects to the small metal hose setup on top of the block then goes to primary rail. Seconday line goes directly to the secondary rail.

I then have both lines come out of each rail, directly to the FPR. The FPR then has a -6 return (which first goes through that metal hose on top of the block) and then back to the stock metal return line.

Ever since i converted my lines like that, if i let the car idle, take the vac source off the FPR and block it, when i try to set fuel pressure to anything of 32psi it just wont hold. The needle on the gauge will be steady at 30/32 psi then once i turn the adjustment down it looks like its going up then it falls down to about 25psi and starts shaking/jumping a lil up and down. No matter what I do i can't get higher then a base pressure of 32psi. I tried using a new aeromotive FPR i had around for my other car, no change. Different gauge, no change.

Now if i disconnect the secondary lines fuel pump, and disconnect it from the FPR and plug the secondary port (so it's like im only running the primary rail) the FPR works perfectly, the needle is steady and i can raise fuel pressure as high as I want.

Please someone help me out, Im at my wit's end, the only other thing i can thing of is get a y-block to combine the 2 feed lines and run my rail lines stock-style/series at the engine.

Kevin.

killahrx7

on the return lines from the fuel rails, do they go to sides ports of the regulator and the return from the bottom port of the regulator? just checking, it seems as if the way you route the lines to the regulator is causing the problem. oh also, if the lines are routed correctly then the secondary rail fuel pump isn't working, the fuel is going back in the secondary rail and not returning to the tank. just my 2 cents as i'm no guru on this site.

teknics

iTrader: (4)

Yea both lines come from the rails and go to the side ports and then the bottom line (FPR #13109 IIRC) goes to the return.

I know I'm outputting Fuel from both pumps, removed the lines to check, I dont have a way to check volume of course tho.

I'm thinking im going to unplug the secondary line from the FPR and plug it. Then I can run one pump at a time to check and see that both can go to and hold 40psi by themselves. I hope its just a bad pump as I have a known good spare one of those I can use as well.

Any other opinions/insights on this?

BTW it's an FD. I also tried unscrewing the return at the CJ Motorsports flange in case there was a resistance causing a buildup or something, even with the return line pouring gas out onto the floor pressure couldnt be built over 30/32psi.

The weird thing to me is that *without* the VAC line attached to the FPR you'd think the needle would remain steady, this one does not, it will raise steadily as i adjust it to 32psi, as soon as i turn it a bit more to go to say 34psi the needle starts having a seizure and falls to 20-25psi.

kevin.

teknics

iTrader: (4)

any ideas on this yet?

kevin.

afterburn27

iTrader: (5)

Try bypassing the fuel pump resistor by jumping the fuel pump relay at the front of the engine bay. I bet your problem goes away.

BTW, a spare fuel pressure gauge and a few fittings goes a long way for diagnosing problems like this. Take your pressure gauge and block the line before the rail to measure the max pressure, it should be over 75 psi. That will tell you if the pumps are good or not.

teknics

iTrader: (4)

Yea the resistor is gone already, pumps hardwired.

i've got a full pressure test kit...just nothing to adapt to AN/braided.

If i pull the AN fitting off can i just slide in a pressure tester adapter and hose clamp it? (before fuel rail, so its just straight line-> pump pressure?) I have a Master Universal fuel pressure tester and I know my way around working on them (used to work at an independent shop been a senior tech at mazda for a while now) this problem just left me scratching my head tho.

Youre saying i should see 75+psi?

I will definitely try that out. I'm also planning on disconnecting the secondary line from the FPR and plugging the port. I know the primary pump can be used and adjusted to proper PSI like that, so i'm going to simply swap fittings at the tank so the secondary pump will be the primary for the test and see if i can set it to the proper psi by itself.

For whatever reason i'm thinking the secondaries pump is bad, brand new bad walbro not cool, luckily i have a spare (and a spare FPR, just about a spare everything, just wanted to try to avoid just swapping parts constantly, already swapped FPR's with same result so I eliminated that as well as the gauge i have on the FPR being switched with no change)

Thanks for the help, anyone else have more ideas to try?

kevin.

afterburn27

iTrader: (5)

So much for that idea.

My dual pumps (denso) wouldn't put out more than 30 psi with the resistor in place. I removed the resistor and bang! 100+psi. I had done a full re-wire job, but I tried leaving the resistor in place to keep everything as "factory" as possible.


Yes, you can just use a hose clamp with the braided line. If you cap the feed line before the rail the pump should produce over 75 psi (probably closer to 100 psi). You will have to do this twice, once for each pump, although it sounds like the primary pump is working just fine. I would suggest that you keep both pumps running for each test.

The FSM suggests the same test for the stock pump.




Sounds like a good test. Just keep eliminating items and you will eventually find the problem. So far it sounds like you have eliminated the FPR & primary pump.

teknics

iTrader: (4)

thanks for all your help, probably going to start tackling this issue tomorrow, been so busy since this problem arose, and of course its been beautiful weather since this happened.

hmm looking back over the info I used to hardwire my pumps I think the fuel pump resistor may still be having an effect so I guess i'll add that to my double check list ( i used chuck's notes which have you leave the wire in place for the resistor and run a wire from the relay back to the pump, gonna try disconnecting the now parallel stock wire (W/R) and see if anything changes.

kevin.

teknics

iTrader: (4)

WOW, solved it a few minutes ago.

Lesson learned? A single 12 gauge wire from the Fuel Pump Relay to the Fuel Pumps which splits to 2 feed wires, one for each pump, does not provide enough electrical power to produce real fuel pressure.

Not even sure how I got to that I was testing each pump individually, Unplug one connect it to primary rail's line, plug the secondary port of the FPR and run it. Each pump was able to achieve 50-52psi at the FPR before the gauge's needle fell to 35-40psi and began shaking. So i knew each pump was working identically, no chance of a double failure of the same type. So i reset the pumps to the full dual parallel system as it was. Then I tried cutting the stock W/R wire out of the situation, no change. Measured voltage at each fuel pump terminal with relay grounded so they were running, both had full voltage.

Then however/wherever it came from I decided to cut the one pump off the current wire and run a whole seperate wire to the battery for that pump, set it all up (literally ran wire around outside of car just to test it). Start the car, check Fuel Pressure...dead on 40psi. Try to crank it up...50psi...60psi..steadily easily rising before car starts bogging so i simply set it back to 40psi and basked in my moment of joy.

Going to setup a full second/seperate relay for the 2nd pump tomorrow and then it's time to wire the Methanol controller, then off to the dyno for some 25+psi runs, woo woo.

BTW, car feels a lot better driving now with both pumps (took it for a quick run to make sure pressure rose 1:1 appropriately)...not sure why, didnt expect to feel a change without tuning.

kevin.