I say this as a joke cause some friends and I were working on my fueling issues and some of the wierdest stuff happened.

First off, With my rising rate reg, we hooked up a bike pump to the vac line(on the reg) and pumped in about 40 psi which takes my FP up to 100. You would think this ould choke the engine out right? Well it didn't. Absolutely no change in idle. We even later on drove with the FP that high and it drove like normal. Even with rice_etr behind me, he said that my pipes looked clean and no smoke coming out.

Secondly, at one point we removed the reg and just ran the fuel line stright to the rails. The first time we did this without the gauge hooked up(as my gauge connects to the FPR). So we pull the fuse to the Fuel Pump and let the car run so the pressure is relieved. Over a minute later, the car is still running. So we disconnect the power lines to the top of the fuel tank. The cars still ran!!! WTF!?!?!?!

How can the car run when there's no power going to the fuel pump?????

Later on we did the same test, but we hooked up the fuel pressure gauge. Pump was putting out at least a 100psi. We cut the power to the pump, and the FP dropped slowly. The engine idled fine till about 10 psi of fuel when it finally cut off. So this time it acted normally. We tried it again and again, when the gauge is hooked up, the car dies out like it's supposed to.

We checked the lines for restriction and there is no obvious restriction. Granted we didn't have the tools to simulate heavy flow.

Summary: The pump can't keep up. At WOT it's lucky to maintain 60psi(sometimes dipping as low as 40). I have a Walbro GSS340. Mightymouse, Rise-Etr, and myself racked our brains Saturday trying to hash this one out.

There are two issues: One the pump doesn't seem to have the flow. Is it restriction in the line? Is the pump defective? It shouldn't be voltage as the pump is seeing 12.9V when the car is on.

The second issue is tuning. Why isn't my car dying out when I up the FP? The computer has no control over FP. How is it compensating for the immediate rush to a super rich condition?

I know this is a lot to read, but thank you.

Mike

 

what fuel pump do you have?
and what regulator?
is your pump gettng the corect voltage?

 

*Walbro GSS340

*Aeromotive Boost Reference FPR(but we also tested MightyMouses' CAS FPR and the same things happened)

*12.5 volts engine off, 12.9V engine on

 

Issue One: Either you have a restriction in your line, or your pump is not moving enough volumn. If you give me some numbers I can whip out the calculator and tell you whether or not you have maxed the flow of the pump (HP, Torque, Fuel PSI, Boost, Injector Size, a/f ratio, MAF reading if possible).

Issue Two: Your car can compensate for changes in fueling....LTerms. As you increase your fuel pressure, more fuel is delivered into the cylinder. You oxygen sensors sense the richening condition and reduce the injector pulsewidth. I bet if you were monitoring Lterms when you were doing this, they would start going waaaaaay negative.

Good Luck,
Kevin

 

and you should never "dead head" a pump. It will blow your pump seals. Pushing a pump above its rated pressure is bad mojo (read: new pump).

 

i know...i know...ding...ding!

i have been going through this issue for awhile now.

racetronix GSS340M system
cas fpr

at idle with the fpr engaged, i was at 62psi..under moderate boost the fp would rise about 3-4psi and under heavy load..the fp would drop to about 40 psi

3 weeks ago...i wired in two STOCK PUMPS and without the fpr engaged, the fp was at 64psi. i hit wot...not drop in fp. not 1 psi!

drove it like that for 2 weeks...no problems. even in 100 degree weather..no problems.

last weekend, i removed the intake regulator and used the cas fpr and set the base pressure to 58psi...hit wot...fp rises to about 70psi..i get close to ~12psi.

drove it all day yesterday..no problems...fp looks good..o2's @ 6.3k are at .910

now..i was originally gonna do a hobbs switch to turn on the second pump...but didnt like the idea of running a wire in the gas tank...so i shot that idea down...it was just easier to do the fpr way.

hope this helps!!

 

Can you explain how you ran two stock pumps in parallel? Wiring, plumbing, mounting etc?

thanks

 

This is the kinda stuff that scares me. I hope I don't run into any more fuel problems.

Good luck.

 

he he he... yea the newest weight saving mod... remove the fuel pump lol

That's the weird thing NoGo, we verified his fp was going up.. at 80psi+ at the rails, his L-trims should have dropped like a rock... although they didn't move, and the car's idle never changed.
I can tell you guys, his workmanship and installation of this fuel system was done VERY cleanly, just doesn't make sense.

I think the only possible issue could be his fuel filter is too restrictive or something is defective with the pump. I know walboro makes a few 255lph pumps.... but not all of them are hi pressure/hi volume which the GSS340" signifies.... are all 340's high pressure AND high volume?

Thanks,

-Jarrod

 

Hey RICE_ETR I believe the high volume, low pressure model is called like a 307 or 310 or something like that. I'm pretty sure all 340s are high pressure, high volume.

As for computer tuning I was under the impression that O2 behavior was learned over time. I mean the STFT are short term, and I don't think even they work fast enough to compensate for a bike pump jacking the FP up to 100 psi in a few seconds. Maybe they can. That's what I'm trying to figure out.

SC-MECHAM-WS6 I'm also curious how you set your pumps up. What year is your car? Got pics? Very interested in what you did. I've never heard of a 340 getting out flowed(especially down to 40 psi).

As for my setup, it's a 2000 M6. ATI tuner kit, D1SC 8# pully, 42# SVO injectors, Edit, single Walbro GSS340 intank. I don't have dyno numbers, mostly cause my fuel has never worked right. But I was at 352 before the blower. I have my timing retarded back to 16* at WOT. I'm probably seeing around 390 rwhp/tq. I have less knock now than when I was N/A. I realize my timing is way far back, but until I have my fueling issues solved, and run through a wideband dyno to see exactly where I'm at, I'd rather be safe than sorry.


Mike

p.s. What's dead head mean? Please forgive my ignorance.

 

Hey man, sorry I couldn't get there Saturday, although it sounds like that might have been a good thing for me, . I don't have any info, but David said something about using my file. If you want I can email you the latest one, but it's always a work in progress , so I can't say everything will be right for you.

 

casey i dont think he will be able to read your file (98)

yes the ltrims and strims didn't budge reguardless of fuel pressure.

 

ok...no pics. but my car is a 98 WS6.

oh..ok. here is an example of how i outflowed the fuel pump

http://drivefaster.net/~mecham/vehicles/ta/dynoaf.jpg

see after 5k rpm? that was where the fp would drop from 60ish to 55...50...45...40 psi it wasnt the programming or the injectors.

i will draw up a psuedo diagram of how i did two fuel pumps...hmm..actually..i got the idea from seeing another ls1 member do it.

here is a drawing of how i did the fuel pumps...
http://drivefaster.net/~mecham/vehic.../dualpumpz.jpg

 

as far as wiring...all i did was splice into the + and - of the other pump. just got one of those splice connectors that u put two wires in..and press down the metal thing and the current is on both wires.


i would take a pic..but i just put everything back together last weekend. although i've taken the pump assembly out so many times now...it take me longer to remove the carpet and other stuff than take the assembly out.