Scangauge alarm? Where, how, what? Expensive?

 

ScanGauge - Trip Computer + Digitial Gauges + ScanTools

Cheap. Can monitor tons of sensors through small gauge and can pre set alarms for any gauge. Bought it simply to get an accurate coolant temp reading but helps finding problems by knowing what the computer thinks is going on (maf throttle position speed intake temp etc) also can use on any obd2 car to read and clear codes.

 

Pulled out my tire gauge and checked the pressure on the fuel rail. After the truck had been sitting a couple hours, I was seeing 9ish PSI at the rail. I started up the truck while it was idling I was getting 29.5 or so PSI at the rail. If I understand the system correctly, I should not be loosing much pressure while it is sitting so that seems consistent with a leaky fuel injector.

Other symtoms include:
- occassional need to crank a few times after the truck has been sitting overnight, no issues starting otherwise.
- poor fuel economy - hovering around 10 MPG
- the p1179 code that came in pending yesterday and has gone away on its own since.
- short-term fuel trims fairly consistently in the negatives
- long-term fuel trim = negative 8.6.

I will swap my MAF to my other one just to see but to me the above speaks to a leaky fuel injector(s). Fuel pressure leaks out and pushes fuel out leaky injector while sitting, leading to drop in pressure over time while truck isn't running, resulting flooding leads to hard start after the fuel pressure has pushed fuel from lines into combustion chamber(s). The leak(s) result in more fuel getting into combustion chambers than the computer thinks the injectors are putting in/need to put in. The 02 sensors therefore tell the computer to lean and it compensates accordingly. The worst the leak, the more short-term trim is affected until it gets to the extent of its range (which finally triggered code). The consistent negative short-term values has resulted in the adaptive long-term trim being fairly negative.

Unless anyone has any thoughts of things I am missing. Plan of action is:
- clean other MAF and swap for good measure
- hook fuel lines to my other intake manifold/injectors and turn on key to pressurize and monitor for drop in pressure/leaks.
- jump each new fuel injector to check for good spray.
- if all checks out, purchase new o-rings and put my 2nd set of injectors in the intake/fuel rail on the truck.

Not sure if I will need to get the adaptive memory cleared by someone with testbook or if it should adapt on its own (assuming the above fixes the issue).

Interested in any feedback on my thoughts.

 

Bought a proper fuel pressure gauge. Was around 30 psi while idling. After shut off seemed to go up to as high as 36... After 2 hr pressure was around 30 Psi still. After 5 or 6 it was around 10. Does this seem normal?

 

Yes but no, supposed to remain high indefinitely. The fuel pressure regulator at the end of the fuel rail is closed with engine off. Might be leaking down from there, not an injector leak. Techron is what I use to clean the fuel system with, works pretty good. Try that and see if it changes within a week. It might take a couple of bottles. On a newly rebuilt engine it's not a bad idea to have the injectors sent out to be cleaned if high mileage not a bad idea to replace the FPR too, they do get weak and worn.

 

Fuel injectors... Fuel regulator ... What about the fuel pump? I can replace both injectors and regulator if those are the issues but don't have another pump... I guess Iguould install some t valves on the fuel lines and shut them at full pressure to isolate the leak to the fuel rail?

 

Shoulda, woulda, coulda. Up to you how far you wanna go. I personally wouldn't worry about it and just let the circuit come to full pressure before starting the engine but I'm not restoring anything, just running it till it's worn out.

 

Fair enough. I still think my pressure might be a bit low and wonder if the cause of the dropping pressure while off could be a symptom of the same issue. And also could have caused the p1179 pending code which periodically came and went away before triggering the CEL.

Given the parts I have on hand, I will swap injectors and fuel pressure regulator and see if any difference.

 

The FPR leaking doesn't trigger a CEL itself but will help other sensors do so.

 

Yeah. If it was resulting in low rail pressure, fuel injectors injecting less fuel than they should, mixture lean, o2 sensors tell computer to richen mixture and if too low pressure and computer can't keep up it spits a code. Perhaps? Just trying to figure out if I indeed have slightly low pressure (it appears so) if it is in fact abnormally dropping while the truck is off (I think so) and if so where the pressure is lost from (best guesses for fuel injectors or check valve in fuel pump).