What Do You Make of This?

[christianb5s4]

I was scanning through some measuring blocks, specifically STFTs and MAF readings. Trying to narrow down an issue I have with starting the car as well as check the health of the Hitachi MAF that came with the car.

Issue I have is the car will take twice the normal amount of time to crank before firing, it probably happens 50% of the time vs. the other 50% being normal starting. I believe it's the 044 pump check valve going bad, I have a new one but haven't installed it. Also, around the time the starting issue started happening, the sound of the pump would occasionally change pitch when priming. Also, my thought process is that if it was a vacuum leak, wouldn't the prolonged starting happen every time vs 50/50?

Although the STFTs appear to tell me I have a vacuum leak, could it be caused by the fuel pump check valve not fully opening or closing that's causing the car to add extra fuel? Also, do the MAF readings look ok? The car was fully warmed up and at idle.

[MarlinFoundNemo]

I'd say replace the check valve now since you have it. Vacuum leaks will happen much more than 50/50, they dont magically seal themselves lol

[christianb5s4]

That's first on the agenda, next will be the fuel filter. Past that, the only thing changed when the car started to have the start up issue was I put in a used but supposedly good condition spider hose assembly. Wouldn't be surprised if that had a small leak, but that's next on the list after the check valve and filter.

[MarlinFoundNemo]

Oh that could definitely have a leak, why not diy one with silicone?

[Corradovolksb]

The fuel pump check valve is a good place to start because if your fuel pressure drops overnight or if the car sits for a few hrs the pump takes 2 atempts to prime. Your fuel trims are normal at idle (short term both both ok at +-5%) your long term is pulling fuel indicating that you may have a boost leak and running too rich. Did this all of a sudden start happening?

[rani_aridi]

Could also be one of the other check valves in the system if it isn't the one at the fuel pump. But it most likely is a check valve if it doesn't happen every time (because of pressure drop as said above).

[christianb5s4]

Oh that could definitely have a leak, why not diy one with silicone?

That's definitely an option, because all this stuff did happen after I installed that spider hose assembly. Do you know off hand what diameter hose is needed? I used 5/8" hose but it barely fits over some of the fittings.

The fuel pump check valve is a good place to start because if your fuel pressure drops overnight or if the car sits for a few hrs the pump takes 2 atempts to prime. Your fuel trims are normal at idle (short term both both ok at +-5%) your long term is pulling fuel indicating that you may have a boost leak and running too rich. Did this all of a sudden start happening?

So short term are ok then? I boost leak tested the car a few months ago and nothing has changed on that end, only thing that's changed is stuff on the vacuum side of the engine.

It started happening after I replaced the spider hose assembly with a new one, which tore the brake booster check valve hose in the firewall. I replaced that which solved that problem, but fuel trims still remain constant where they are at in the picture above.

Could also be one of the other check valves in the system if it isn't the one at the fuel pump. But it most likely is a check valve if it doesn't happen every time (because of pressure drop as said above).

It definitely doesn't happen every time, if the car sits for less than 30-45 minutes after running it starts right up. Anything longer than that, and it cranks. Also, when I clear the trims it sometimes starts more quickly sometimes doesn't.

[MarlinFoundNemo]

I'm not sure off hand but here's a few links that may work. One says that he got 1/2inch but it should've been slightly larger to get the fittings on. Putting a catch can in if you're redoing your spider hose could be a good idea too.

http://www.projectb5.com/product/pro...ne-spider-hose

http://www.audizine.com/forum/showth...-hose-assembly

[Corradovolksb]

Your short term trims are good the are the 1st and 3rd values. The 2nd and 4th are long term. If you have a bad. Check valve that is venting boost back into the ypipe or Pcv system that could also cause your long term trims to show rich. +-10% is spec for long term.

[christianb5s4]

Thanks guys, besides the check valve on the 044 pump itself, I'm trying to find a diagram that shows the rest of the check valves to look at. This is the one I've used in the past but are there addition check valves beyond the ones in this diagram?