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Tickerguy

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  1. So the new pump is here and guess what -- the fine folks who make these things came to the same conclusion I did above some time in the last however many years. Anyone with a vehicle in this age range that has a return line and the original fuel pump, or one of unknown vintage, if you have this sort of problem (high-altitude, high-temperature issues with fuel delivery) I'll bet its related. The new pump I received today (Delphi) has *two* chambers in the cup. The first admits fuel as the other one did with a silicone flapper at the bottom. The return also dumps into th
  2. Observation: These fuel pumps ("Cup style") all appear to return fuel to the cup and not the tank "at large." IMHO this is a generally-bad design because the fuel being returned (bypassed by the regulator) is going to be quite hot. In fact, in adverse conditions (e.g. very hot day outside, engine is working, etc.) that fuel could be VERY hot. Putting it back in the cup means it does not have the mass of the remaining fuel to dissipate the heat into, nor can it dissipate it through the tank wall; it will instead be immediately recirculated to the engine by the pump a second and su
  3. Oh there's a drain plug in mine. It was non-removable. Once I got the pan off and could put REAL torque (and HEAT on it) I realized they likely loctite RED'd it in the hole. Ain't coming out, no way, no how, and was obviously done at the factory to force you to drop the pan, which is ok generally in that you want to change the filter anyway. Kid just had the 4L60E blowup happen to her; almost 200k miles, smoked the 3/4 clutch pack. Limped it to a place in second. Nice surprise when you're on the road and it blows up in your face; not much you can do about it though as I'd driv
  4. Biggest bit of stupidity (other than the parking brake design which has been stupid on GM truck products for decades, simply because it never gets hot and thus turns into a ball of rust) is the impossibility of dropping the transmission pan without removing the shift cable bracket first (or the exhaust, which is even worse!) That wouldn't be such a big deal EXCEPT the bolts are Torx and on the TOP of the gearbox, and on a 4x4 the front driveshaft is in the way, so you get to take that out first. Turns what should be a 30 minute job to do trans fluid and filter into a couple of hou
  5. Who's the jackwad at GM who thought that tiny little feed hose from the tank bottom would be sufficient to keep the cup full under all load and environmental conditions? Specifically the most pressure differential (and thus flow potential) you can ever have on the "suction" side of a pump is 14.7psi, and as you go up in altitude that decreases of course. Run out of fuel in the cup if you consume it faster than the lift side can refill it and the high-pressure side sucks air - you're done. The obvious debris all over the in-cup strainer -- but none polluting the tank-bottom one -- is almost-
  6. I'm going to tear it apart and figure out why it failed once I get a replacement and put the beast back together. This is certainly an interesting one and since its original, and the kid's may be as well, I'm wondering if we share a common flaw in terms of design that may have been addressed down the road but neither was ever changed out.
  7. And the answer is.... with the pump sucking air two full 5 gallon cans siphoned out and a third that was 2/3rds empty (so call it 13 gallons so far) and there is still fuel in the tank! Sum-ting-wong with existing pump
  8. Well well now we got an interesting and new set of facts. Dropped the tank. Should have been empty. When I got the jack under it and took the straps off, well, it was rather too heavy. I got it out and.... there's a crap-ton of fuel in it. But the pump was pumping... nothing. So..... hypothesis (which I will confirm when I get the pump out after going to get a siphon to remove the fuel) is that there's a crack somewhere in the pump that lets air in intermittently but, it's not all THAT intermittent because here I am at sea level, I ran the pump until I go
  9. I may have found it. So I'm emptying the tank to drop it; there's about 5 gallons or so in it. Rigged my test gauge with a nice long hose into a 5 gallon can and jumpered the power terminals on the relay. After about a gallon had come out of the tank I still had good fuel flow out the hose but the stream was full of fine air bubbles and I could hear the pump change its sound as well. Of course you CAN'T hear the pump over the engine when its running. Looks like the pump gets warm and wherever it draws from stops getting clean fuel; perhaps a seal expands o
  10. Well, yeah, I know about the cylinder-deactivation garbage -- basically everyone who does it has had it blow up on people. No thank you. The shocker is that this thing has pretty-much stayed together, and my daughter's '03 Express is in pretty decent shape too. Then there's the '03 Jetta TDI she has (used to mine) with roughly 300k on the clock and other than an A/C compressor and a set of struts, brakes and such, three timing belt kits and miscellaneous suspension bushing stuff is actually OEM -- yes, including the CLUTCH and even the alternator! Next timing belt interval I'll swap the ca
  11. Nice..... yeah, as near as I can tell that's not the case with the '02; all I can find for regulation on that beast is a mechanical spill valve on the rail that has manifold vacuum as a control (an actual hose!) and that appears to be working properly. I could see where a stuck-open regulator could screw you hard (dump all the pressure, have a nice day!) but that doesn't appear to be at play here. One extremely annoying thing on these is no reasonable third-party scantools that can talk GM-ese. Ford and Mazda have Forscan which, with an OBDLink-MX, can do basically anything the
  12. I've already swapped it with the DRL relay and it did it again (twice) after I did that. But -- again -- only at altitude, and only when quite hot outside. Even beyond 5k' all the way through from the Grand Tetons to Casper Wyoming in the evening, no problems. It's heat and altitude that triggers it. There's another piece of information -- several years ago I lent the truck to a friend to move. She ran it out of fuel; it has long had a problem with the gauge sender in that when it shows 1/4 it's actually out. Well, she ignored my warning and called me to tell me it wouldn't st
  13. So new valve installed and drove it up to 6,500' altitude, no problems. But -- it wasn't over 80F, which I can't do anything about and which makes the test questionable. The long-term fuel trims did change with that new valve installed to some degree -- not a lot, but noticeable (positive deviation from what they were.) I also checked the fuel pressure, which I can't do while driving as the hose I have is nowhere near long enough to snake it somewhere useful; just over 50psi with the key on but engine off, right around 40-45psi at idle and spikes higher (mid 50s) when I blip the throttle go
  14. Ok, further update... the NEW purge valve will open and close under both positive and negative (mouth) pressure, where the old one will NOT open if power is removed and the pressure is positive. Guess what -- that's exactly what would happen if the valve was closed, you ascended in altitude (tank is now positive-pressure compared to the outside ambient) and then the PCM dropped power to it to command it open. Aha, says the dude. I'm about to install it but this fits exactly with what I observed and might well be a fix. Now it will be fun to find a place where I can actually test
  15. More data -- I started with the cannister purge (vent) valve, on the assumption that if it was commanded closed but actually was not that it would result in a wildly-off mixture since that is *after* the MAF and thus anything that gets into the intake (usually fuel vapor, obviously), if unmetered could throw the mixture lean enough to result in a lean-out to the point of a stall (it's a pretty large hose coming into that valve!) That is, I presume what the PCM usually does is to open the evap cannister intake to the manifold BUT at the same time make sure the cannister purge is closed (otherw
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