Cascade Crew

fiveoformula · Posted: Tue Feb 28, 2012 8:04 pm Post subject: Wait isn't this bad?

Lets just say I just got around to putting an inline fuel pressure gauge on my TBI, prime the fuel pump, pressure goes up to about 11psi then bleeds off to zero almost right away, would that be bad or is this normal on TBI? the injectors don't visually leak and it idles at 15psi.

aaron_sK · Posted: Tue Feb 28, 2012 8:38 pm Post subject:

I have seen the check valve fail in older TPI pumps so that the line would not hold fuel for more than a few minutes. The only noticeable issue was a longer hot crank time.

fiveoformula · Posted: Tue Feb 28, 2012 9:15 pm Post subject:

Wierd.. the pump is not that old, it's an aftermarket airtex pump (stock TPI replacement). And it actually cranks over plenty fast.

fiveoformula · Posted: Sat Mar 31, 2012 1:17 pm Post subject:

So I have a couple weird things going on with the bird now... I installed an 18psi fuel regulator spring and cop car injectors then began tuning with the EBL. I had it dialed in to run OK. Is was not perfect but you could cruise around ok. Then I did one more tune trying to add a couple degrees of timing across the board and now it runs fine at idle then super lean once I start moving, if I'm not on the throttle hard enough, my W/B nearly pegs out lean... tried going back to a couple different bins but same symptom so I think its a mechanical problem. Anyone think the fuel pump got weak or something? It happened literally by shutting the engine off and starting it back up after a quick tune.

Dewey316 · Posted: Sat Mar 31, 2012 6:17 pm Post subject:

is it missing at all? Misfires will read lean on the WB, if you ran it really rich for a while, then tried to add timing, maybe fouled plugs and too much timing causing it to miss?

Twilightoptics · Posted: Sun Apr 01, 2012 8:49 am Post subject:

You need to isolate if its fuel pump, regulaor, or injectors bleeding down.

What's the fuel pressure.when you go lean?

fiveoformula · Posted: Sun Apr 01, 2012 12:57 pm Post subject:

I had thought the plugs fouled out too, since they didn't look so great, I got a new set and put those in... problem is still there. Didn't try driving the car with the fuel pressure gauge yet but it is rock solid at 18psi idling and when rev'd... I know I can ellinmate the injectors bleeding off since you can visually check but how can I rule out the pressure reg?

chevymad · Posted: Sun Apr 01, 2012 1:04 pm Post subject:

Block or crimp off the return line. If the fuel pressure doesnt drop then the regulator leaks. If it does then its on the supply side.

Careful though because with the line crimped you can spike the fuel pressure high enough to blow the pump off the line in the tank. Just cycle the key fast enough to build some pressure you can see on the gauge.

fiveoformula · Posted: Thu Apr 05, 2012 6:39 pm Post subject:

Well I just crimpped the rubber part of the line and hit te key, pressure went up and stayed rock solid. So that points at the regulator diaphram leaking?

fiveoformula · Posted: Wed Apr 11, 2012 8:07 pm Post subject:

Well I bought a new regulator and installed that, checked fuel pressure and still bleeds off. Pinching the return line and pressure staying pretty much rules out the fuel pump bleeding off, so I'm confused. Where else could the pressure be going?

chevymad · Posted: Wed Apr 11, 2012 8:55 pm Post subject:

If pinching the return causes it to hold then the regulator is leaking. No other way. The only way fuel can go through the return line is through the regulator.

fiveoformula · Posted: Fri Apr 13, 2012 1:22 pm Post subject:

that's what I thought... Is fuel pressure supposed to hold on a TBI motor with the engine not running? Because its fine when idling and when driving... just bleeds off imediately when you key on, engine off. Maybe this lean condition is a seperate issue.