CutLS

iTrader: (6)

Doing a little searching back on my build page, I have a Walbro GSS-340 pump. It is meant for higher horsepower (than what I make) setups but I didn't know what I was going to put down and if I upgraded to some power adders in the future, it would suffice. I can't find anything that says that this pump has a check valve but their site says that most do.

mstansbury0704

You mean to tell me you had a fancy digital fuel pressure gauge and you’re just now breaking that out!? Lol.

That pump Sounds like a damn jet engine about to take off lol. It looks like it builds about 36psi before priming ends and motor fires up around 20-30.
One thing you can do is try to put an inline check valve in the line near the tank. In between the tank and the filter

I think the fuel pump prime time is hard coded on our cars so idk if we can change that.

I thought all walbro internal pumps had check valves in the outlet. Pressure is falling really FAST and doesn’t quite reach what it should, but I’ve had two gauges read 5 PSI difference back to back so idk.
a quick google Shows there’s been quite a few people reporting of split check valves in walbro pumps

CutLS

iTrader: (6)

Haha. Yeah I hadn't really thought about checking fuel pressure since listening to that pump prime, I figured it was good. Decided it was a good time to borrow works fancy gauge. I tried cycling the key on and off real quick. I can get the gauge close to 38-45 but that is cycling like 8 time real quick. I think I will place an order for a replacement pump and look into that check valve. I did see they sold them for inline applications. I might have be able to burn up some fuel before I get the new one, since I just filled the tank the other day.

mstansbury0704

Maybe try to do that fast cycling thing again and try to start it during the last prime and see if it comes to life any faster.

CutLS

iTrader: (6)

Yeah It seems to start faster when I did that rapid cycling. I didn't try it cold but if I let the vehicle sit for awhile, it would crank a few times, so I figured it would be the same test parameters. It does make sense that the extended crank is due to the low fuel pressure. I'm going to order my pump and try looking more into how to tune better and figuring out those low spots you were mentioning. Thanks for leading me into the right direction.

mstansbury0704

It would be a good idea. You may even be able to just order another check valve for them. I’ve never gone into a pump but maybe they’re replaceable?
Also for your tuning Can you log your wideband? If so a fellow named chopperdoc has some really good videos on YouTube about VE tuning. And then Goat Roap Garage has some on tuning the MAFs. I still watch chopperdocs to remember what crap I have to turn off to force open loop. Lol
However if you can’t log your wideband you can still fix that low portion of the VE table with just your short terms.

CutLS

iTrader: (6)

I don't think the internal check valve is replaceable. I tried searching but I can't find anything other than valves for carburetors.
finally figured out how to log my wideband into HP Tuners using my Pro Link. I have mainly been watching Goat Rope Garage's videos about tuning and setting up graphs. He talks fast but seems to know what he's doing since he's said the same things that a few other people have said. I have my MAF and SD Tunes created but I have not driven much and what I have logged I haven't gone in and changed anything yet.

mstansbury0704

Does your tune file have a secondary VE table? Make sure if you do you read the proper procedure on tuning our stupid 2000 OS. Not sure why GM decided to give us two but it makes tuning a bit more extra leg work. When I first started tuning mine I read a tutorial and it mentioned nothing of the secondary VE table is used when MAF is failed out. So here I was making all kinds of changes to my primary and not seeing any change at all. Lol. Had to start all over again.

CutLS

iTrader: (6)

Yeah it has a secondary. Looks like the only difference is the primary is more detailed down to every 5 kpa change, while secondary does every 10 kpa

mstansbury0704

yes. When you fail your maf to tune VE your car reverts to using the low octane table and ALSO the secondary VE table.

I log both my secondary VE and Primary VE in my histograms.
The very first logging session if I find I’m way off like +10% in cells, I tune the secondary first, copy my new data over to the primary and interpolate vertically to populate the 5 kpas. Then I do my smoothing in 3x3 groups of cells on the primary and copy all the new data back to my secondary.. After that first initial tune though I just log my primary via the histograms, do my tuning in the primary, smoothing and blending in 3x3 groups of cells and then copy the new data over to the secondary, rinse and repeat until you got it to your liking. At that point I’m usually about sick of driving lol. But you SHOULD try to tune the maf the same day you nail your VE down.
As I said there’s ALOT of tutorials out there, but I think the one by chopperdoc is the best. Idk if he touches the secondary VE subject or not. But I just did for you so you should be set. Lol