Weird LS startup issue - fuel or electrical?

#21
I copied what the OEM used with my 140amp alternator. (175amp Mega fuse). The fuse is rated for the maximum current carrying capacity of the gauge wire you are using.

If the internal tube is broken on the pressure side of the internal surge tank pump then the surge tank will build a slight pressure and the excess fuel will dump back in the main fuel tank at an accelerated rate. The regulator will never see enough pressure to reach it's set point. That may very well be your issue. Perhaps your replacement unit was someone else's return.
 
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#22
Thanks guys - I’ve gotten some good suggestions on next things to check. I’ll do another test to isolate the fuel pressure regulator - I still think there’s an issue with the return bleeding down, pressure should stay in the regulator with the pumps turned off if the check is located on the inlet side - but that’s an issue for later!

On the pump troubleshooting if the regulator is ruled out then I’ll pull the surge tank and take a look.

I found this photo of the internals and it looks like it’s a simple hose clamped on either end.



I didn’t think I’d need to consider this but it would also be good to know what kind of pump is installed in case I need to R&R the pump at a future date.
 
#24
Well, the fun just never ends ... I isolated the fuel pressure regulator today by looping it back onto itself (output routed to the fuel return port). So I basically created a dead leg coming out of the HP fuel pump, eliminating my injectors and the fuel pressure relief from the equation. Sure enough, the pump would only make 15 psi when it should have been making max pressure.

I couldn't open the case to verify whether the internal feed tube had gotten dislodged/disconnected as at least one, possibly 2 of the cap retaining bolts were cross-threaded. Jeg's is taking the pump back and I'm going to go down another path. Between my 2 units and 1 of Allan's, that's just too small a sample size for so many quality issues. The odds of all 3 of these units being random and I/we just got super unlucky are astronomically low, it suggests to me there are quality/workmanship issues at FiTech that still need to be sorted.

I have a rough idea of what I'll do next but I'm going to sit on the info for a few days until I can get it sorted out; don't want to make any suggestions that might lead folks down a path I'm no longer willing to take myself.

The count so far:

Bosch knock off #1: 2 miles
Bosch knock off #2: ~1000 miles
FiTech #1: 0 miles
FiTech #2: 20 miles
 
#28
Thanks for the recommendation Chris. I looked at Deatschwerks and their DW300 pumps. The surge tank specific part of their site looks to be down but I’m a bit surprised by how high the pumps sit in their cutaway view. It shouldn’t make much of a difference since the tank should always be filled by the LP pump but it seems like the pickup is about mid-height relative to the tank, anything below that point won’t be usable unless you’re running a hose or some other type of pickup. They state vertical or horizontal layout so I’m assuming you’re supposed to run some kind of hose.

It’s also interesting to note they’re going with a half-submerged design similar to the IE tanks.

Thanks!
 
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Howard Jones

Member
GT40s Supporter
#29
Where is the high pressure regulated. Inside the Fitec thing? Seams like a pressure regulation problem to me. Is it adjustable? And lastly can it be bypassed, If so, bypass it and see what happens.

By the way The Fitec thing has a 1 year warranty. Maybe just send it back and be done with it. They will either replace it, fix it, or tell you nothing is wrong with it.
 
#30
Hey Howard - I have an external fuel pressure regulator. It goes FiTech output ==> filter ==> fuel pressure regulator ==> fuel rail. The LS3 uses a returnless system so there's an additional port on the regulator that returns excess fuel to the surge tank. I had originally believed the regulator failed OPEN but with continued diagnosing discovered that's not the case. The regulator is adjustable but turning the adjustment screw did nothing for pressure (it had been registering 60psi the day prior). As part of my troubleshooting I looped the regulator back onto itself, essentially creating a dead leg at the fuel pressure regulator. I kept it in the equation because I needed the gauge (which is installed onto a port on the regulator), but wanted to eliminate a leaky injector from the list of possibilities.

I purchased the FiTech unit from Jeg's, received it not more than a week ago. I'm sending it back to Jeg's, a lot easier to deal with than going through FiTech. Yeah, I'm done with FiTech altogether. 1 bad unit for Allan and 2 for me, that's 3 too many in a population size this small. Irony of ironies, when I called them to get an RMA they checked on the status of my first unit and it was due to arrive the next day! The original unit hadn't even gotten back to them yet before I had to call them for this second unit.

You guys are going to think I'm nuts when I show you what I've come up with - but maybe with some explanation you'll agree it's not such a crazy idea. The wallet's lighter but hopefully my car will be back on the road shortly. Taking that short 20 mile loop was like getting up to the crack pipe and not getting a full drag, just enough to remind you of what you're missing. I need more ... o_O
 
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