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I was finally able to get the vehicle to die on me again. I had my fuel pressure tester on me and as soon as it died on me I tested the pressure. I was only getting 30 PSI max. After about 5 minutes I tested again and I was getting 60ish PSI. So I now know that it's a failing fuel pump. I've never heard of a fuel pump intermittently failing like this. If somehow dies on me again I will be checking all of the other suggestions!
Thank you everyone
When you tested the pressure was it after a new key on event? Assuming yes then you have either: a failing fuel pump, debris randomly blocking a filter/sock, a failing pressure regulator or a bad injector(s). How many miles on the fuel pump? Is it original?
So the original problem was my vehicle died when it was hot. I was driving around yesterday for around 2.5 hours and it finally started to sputter and died on me. This was the same scenario as last time. I originally thought that the engine was dying when it was hot but I could drive around for 30 mins and it would run fine. As soon as it died I checked the fuel pressure and that was when it was reading approximately 30 PSI. The only thing I have done to the vehicle since it died the first time was cleaned the distributor rotor and cap.
As for the fuel pump I am not sure if it is original. I am the third owner of it. It has 232k km's so it very well could be. I changed the fuel filter a couple of weeks ago and I can't check the sock unless I remove the fuel pump so I have no idea about that. The pressure would hold at 30 PSI when I removed the key so I don't think it is the fuel pressure regulator.
Based on the fuel pressure I got would you suggest it's the fuel pump? My guess is that when the fuel pump gets hot from operation for an extended period of time it starts to fail? I'm not sure why it doesn't completely fail however.
What I am trying to understand is when the truck died did you just hook up the pressure gauge to the schrader and get 30 psi or did the key get cycled off then on and then you measured 30 psi? IOW did the fuel pump get a chance at a recycle at least once (even though it would not start) before you measured the fuel pressure?
The engine was able to run long enough for me to pull the fuel pump relay to bleed the pressure off before I connected the gauge to the schrader. I reconnected the relay (correctly) and cycled the key several times. Each time the gauge maxed out at approximately 30 PSI and held there. I waited for about 5 minutes and tried again and the engine turned on and held at about 55 PSI. I was able to drive home. I had a dentists appointment today and drove for about 10 minutes each way and I didn't have any problems. The problem I am having seems to only happen when the engine has been on for a couple of hours. The original time the engine died on me, I had been driving for around 2 hours as well.
Another thing I forgot to mention is the fuel gauge is faulty. I know this is a common Chevrolet problem especially with older vehicles. I would guess the fuel pump is old if the sending unit is faulty.
You definitely have a fuel pressure problem. What you don't know is if its the pump, the filter, the regulator, leaky injectors or leaky plumbing. The whole point of the fuel pressure test being repeated at the filter output under the truck if it fails at the schrader is to further subdivide the problem. A failed result as you have had at the fuel rail schrader sends you down to repeat the test at the filter output. If you fail there then the pump or filter (not likely) is bad. If you pass there then the problem is back up top.
Your choices are to get set up for the other fuel pressure test with the correct fittings and get the filter output pressure when failing to narrow this down. There is a test for leaky/clogged injectors called an injector balance test which requires a pulse box that goes for $32. that works with your fuel pressure gauge. The last option is to make an educated guess and throw some parts at it. Since your fuel gauge is dead there is a good chance that its the fuel pump but you need to use an AC Delco or Delphi and its a little bit of a job. I would rather see you get more info first so you don't risk wasting your money but the best guess at this point is the fuel pump.
Is there a difference in how long the truck runs depending on the fuel level in the tank?
I have actually went out and bought a new pump this morning. It's a Sprectra Premium fuel pump. The man (who is trustworthy) I get parts from the auto store here assured me they make quality pumps with a lifetime warranty.
I haven't noticed any difference in running time depending on the fuel level. The first time it died the tank was probably around half when I started driving and yesterday I had a full tank when I left and it died at around the same time.
Can an issue with the evap system cause problems with fuel delivery? I have had troubles fuelling up since I bought this vehicle last year. The nozzle shuts off frequently which, from my research, tells me it's the evap vent solenoid.
Slow tank filling can indicate a blockage in the filler neck/evap system hose or a failed vent solenoid. A malfunctioning evap system can cause improper pressure/vacuum in the fuel tank/vent/purge system but I don’t know if this can be dramatic enough to cause the fuel pressure to become limited to half of its normal value. Apparently this blockage can cause a partial collapse of the fuel tank from the tank draw down and subsequent vacuum which is pretty dramatic. It would stand to reason that under those severe conditions the fuel pump might have problems developing proper pressures but I have never seen this myself and I don’t know how likely it is that this is your problem. Correcting that issue first might make sense. A quick check would be to open the gas cap during the failure and see if that changes anything.
I don’t know if Spectra or any of the other particular after market fuel pumps have dependable reliability and if so, which ones. What I do know is that after market pumps have a terrible reputation for reliability in general and the recommendation all over this forum is AC Delco or Delphi only. A good pump is expensive and the job is involved so I personally would not take the chance. Not saying that your parts guy is wrong but there is a lot of Blazer/4.3L experience here. One member here went through I believe three after market pumps in a matter of a few weeks. Trust me, after dealing with a tank full of gas on your back in the driveway dropping the tank, properly cleaning said full tank, replacing and re-installing, etc - if you have a new fuel pump fail, the warranty won’t prevent the severe frustration and finely woven tapestry of profanity laced language that will follow. I look for LLW on my parts as well because a free replacement part is always better but on tough jobs I prioritize known good parts so I don’t have to do it again any time soon. I realize that it’s hard to swallow that $160 AC Delco pump vs that $35 Spectra pump but only you know your budget, time constraints and tolerance for reworking the same problem.
A failed crank sensor can indeed cause a no run or no start condition but then you would have no spark. We may or may not also have no spark but we know we have inadequate fuel pressure and now we also know that we have an evap system issue as well. Everything that we know is faulty is fuel related not spark. If we verify no spark during a failure then we can go down that path.
George
Last edited by GeorgeLG; Jun 18, 2020 at 10:45 AM.
I replaced the pump today anyway. I guess I'll find out in the future if it's a good pump. It was $250 vs $400+ here in Canada (we get hosed on everything). Needless to say I will be buying known quality in the future for any vehicle.
I took apart the whole evap system today and blew into every nozzle and there was lots of flow. I did clean out the solenoid which had a decent amount of debris in there. Do you know how to diagnose a bad charcoal canister?
An ODBII system does a self test every drive cycle and sets a code if the system malfunctions. Evap systems vary across makes but this generic picture and description captures the essence of the basic function and faults.
The gas cap is sealed. The purge valve is normally closed. The tank is vented through the charcoal canister and the normally open Evap vent solenoid. This captures fumes temporarily but still allows tank venting for filling and drawing down from the fuel pump. Normal function is to occasionally purge the stored vapors from the charcoal canister into the throttle body by leaving the vent solenoid open and opening the purge solenoid so that the stored vapors are sucked into the throttle body from the vacuum in a controlled manner. Then the purge solenoid closes.
The system is tested routinely by closing the evap solenoid and either applying a vacuum or pressure to the system either through engine vacuum or a dedicated pump then leaving the evap and purge solenoids closed and see how well the system holds a vacuum/pressure. Codes are set if the system is leaking or cant get charged for the test.
The charcoal canister, hoses and vent solenoid can either be cracked and are leaking or are blocked and can't vent to the atmosphere. The most common failure after a leak from cracked hoses or canister is a faulty evap solenoid that either won't closed for the test or is always closed and won't vent. When you cant fill your tank then then air cannot escape from the top of the tank as the fuel level goes up because the vent path of tank/hose/canister/hose vent valve/hose is plugged somewhere and not normally open as it should be.
