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Noticed my front fuel damper was moist on top below the nipple (easy). I drew a vacuum and got no leaks. Started up the car..same no leaks.
I'm replacing it with a spare. No point in playing carbque roulette. Anyone seen this failure mode? Seem as if dampness outside the damper would mean a rupture membrane inside the unit.
Moist !
Dry inside vacuum and hold vacuum both car off and idling.
are you sure there is a leak there, and not just condensation, water pooling there and reacting with the fuel damper? can you smell gas there? if so, and it is leaking from the body , sure, replace, but the pics dont show a leak . maybe from that weld point where the nipple goes into the body?... even then, that should be on the dry side and you would get some gas smell in the vacuum opening too. you cant be too careful here, but you might not have any thing wrong too.
Wondering now if I have FPR failing and the damper is fine on inconsequential to my issue.
History:
Last week the pump is loud and causes idle fluctuation and cut out. I think because of the sound the pump which is original, is going out so I update the pump, tank screen, and short hose between the tank and pump. I also update the filter while I'm in here.
Out for first drive. Everything sounds good and I go get fresh gas at Chevron. Things sound good so I proceed. Fast forward a tense ten minutes of the sound returning and fluctuating idle. A few stalls at lights and pirate/sailorly language and I'm feeling like I worked at the wrong end meaning FPR might not be holding pressure when warm and likely have vapors in the rails.
Beside checking the vacuum hose any other checks or thoughts??
So the dampre isn't much more than a diaphragm under a spring,with the vacuum on top to slurp up any fuel that makes it past the diaphragm. For the most part, the car will run fine without a functioning damper. It's probably valuable at idle when pump flow is high and the FPR is struggling to balance pressures with 8 injectors firing simultaneously.
Meanwhile, the FPR adds a tapered needle in an orifice in the return line. Higher fuel pressure pushes on the diaphragm to lift the needle out of an orifice to allow fuel to flow back to the tank. A spring works hold the needle deeper in the orifice. High manifold pressure ('less vacuum') also closes the needle, so less fuel is passed back to the tank. Failure testing starts with the check of diaphragm integrity, testing to see if it will hold vacuum. The next test is running/idling fuel pressure to verify operation.
Vacuum update: dampers and FPR all hold vacuum both with engine off and on idling. I even left a vacuum on the FPR overnight with barely any seepage. Looking at ISV to see if that's sticky and/or have a air leak. Here's a video of why the fuel pump is sounding like.
Next up fuel pressure test. I don't sport the gauge on the rail regularly so will have to hunt down a new gauge because the oil leaked out of my original. Will post up another video soon.
Well after striking out with the dampers and FPR (all hold vacuum at least). I'm after an air leak I've heard under idle and think tis' been the issue all along. Following Dwayne's intake R&R (thanks!) I took off the intake. I also had to return to update some knock sensors I've had and been meaning to get to. Good a chance as any to hopefully fix the erratic idle.
I tackled the pump and bits because it sounded like a blender so naturally I thought bad pump. Mine was Czech built so not 27 years old but certainly assume vintage. New pump, filter, short hose and screen update but no change...
Off came the intake and voila! Voici le problem...crack in the smaller J hose on the ISV. It's not a gaping one but an inch long and likely enough for a sticky old ISV to have trouble adjusting for. Kinda makes sense in hindsight I noticed a few days prior to bigger idle changes that the idle seems higher. Should have focused here first but the very loud pump at the back distracted me. Hopefully helpful to others.
Last edited by Stromius; 11-05-2015 at 07:59 PM.
Reason: zee spelzing wast bat
A week or so ago I had thought my fuel pump was going. Very audible after a few minutes warming up followed by a very repeatable 6 second cycle (video in thread above). I changed the pump and front damper but no love. Strike one.
I knew I had an elevated idle prior to this so naturally thought a wosening idle and cutouts meant the ISV might be sticky and/or unable to stabilize the idle. Intake R&R, new ISV hoses and Y joint plus bonus knock sensors and generally tidying up..better idle as the smaller J hose had a tear, but still no love. New pump still cycling as before and cutting out. Tick foul, strike two.
I borrowed a fuel pressure tester and after hooking it up, I saw significantly higher (100!+) pressure so I shut things down knowing it was a failed fuel pressure regulator (FPR)!
Bosch part 0280160297 in case someone needs that detail down the road. I think the increased pressure probably wasn't that high but the relief that should have been going back to the tank IMHO wasn't working so hence original wetness spotted on the front damper on post 1. Not sure how this developed a six second cycle in the pump but assume there was some pressure relief every six seconds.
Anyway connected with the ball finally and didn't strike out! I was careful with fuel and making sure battery was disconnected and car was outside vs garage and fire extinguisher was nearby. Very helpful to have various write ups to guide me.
11-02-2015, 12:30 PM
Fuel damper failure mode?
Resolution!
