With gas prices what they are I typically would let my gas run down to fumes prior to this problem. I would buy enough gas to get me through Friday evening. About a month or so ago I went out on a Sat morning and it would not start. I poured some gas in it from a can in my garage and it started and I drove to the gas station and put gas in it. Then it got to 1/4 tank and it would not start!? I put more gas in it and it once again started. Since (1.5 months ago) I have been afraid to let it go below 1/4. If it starts to get close to a 1/4 it gets hard to start. I told my problem to a mechanic and he said that is not the symptoms of a fuel pump (FP) going out. He said the FP just flat go out and the fuel level in the tank has no bearing. He did agree that GMC FP are known to go out early and the FP on the later Colorado are even worse. He also said the GMC FP assemblys are known to also give false readings for fuel levels on the dash and that it may be out of gas at the 1/4 mark. He also said there is a filter sock over the end of the FP and he thinks that mine came off or came apart then when I let the fuel get low it is being pulled into the FP pick up. Which kind of made sense to me since a FP can’t half work it either works or it does not right? He also said that at hwy speeds I would notice low fuel pressure not at start up. Here is what I have learned so far. A) GMC fuel pumps are known to go out early B) they are very pricey C) the symptoms are very missleading. Once started my truck has been running down the road fine. However, now w/i the past 2 weeks of this 6 week troubleshoot I now at idle I have noticed a one hit miss. A few times it has done it a few times in a row but not close enough in a row to call it a stutter. It would be like miss…wait…miss…wait…then fine. I now wonder if I have one of those dual problems all at once happening that can really throw a troubleshoot off. I have 82K at 75k I changed the plugs. One of the plug wire ends come off with the plug and to fix it I just crimped the end down hard back into the wire and put it back on. It ran fine like that since 75k but now I wonder if the stumble is a spark issue and poss. related to that wire. Either way I am at wits end here. I have a 3 month old I have to start picking up from daycare soon so I need this all ironed out so I can depend on the truck again as I have for the past 82K. Thanks a bunch
Automotive, in-tank fuel pumps are designed to be excellent gasoline “pushers” but since they are located in the tank, they don’t need to be strong “pullers”. When the pumps get weak, they start showing it at their weakest point. The pump gets weaker at lifting the fuel from the tank. The fuller the tank, the more easily it can pump fuel from the tank because the weight of the fuel is helping the pump.
By consistently running on “fumes” you are shortening the lifespan of your fuel pump. They require fuel to both lubricate and cool the pump. Starving them is not good. Therefore, it is a false economy to run very low on fuel as you risk damaging a very expensive to replace component.
It’s always a good idea to test things before replacing them to insure it is a likely culprit. When short on cash, it’s imperative. If it were mine, I would do a fuel pump pressure and volume test with the tank level below 1/8 full. If the pump is weak, it will likely show up in this test.
If it hasn’t been done recently, you might want to start with replacing the fuel filter. It’s cheap and easy to do and could be the cause of, or a contributor to the problem.
Before I actually replaced a pump that tested bad, I would make sure that the electrical supply to the pump was not compromised by corroded connections or a failing fuel pump relay that isn’t delivering the rated voltage and current.
Thanks a lot for the advice. I had the same question myself. If my tank is lets say 18’ deep and my pump is toward the top of the tank then with 1/4 tank of gas would it not have to work harder to start to move the gas lets say 9’ rather than if it where 1/2 a tank and only had to move it 4’? I felt that this was a indication of a fuel pump that was starting to fail myself. I am going to chagne the filter and keep the tank as full as poss. and see how long that gets me. Maybe it will get me to that check from my favorite Uncle (Sam) and then I could better afford a $400 fuel pump or if I do not feel comfortable enough with the repair after getting in there and changing the filter poss. the $600 needed to have someone else change the pump.
Yep, that would be another good way of looking at the limitations. By and large, the pumps are usually located lower in the tank with the outlet pipe longer than the inlet pipe. That way, they have the least difficulty pulling fuel in and they tend to be submerged in the fuel more than one that’s located higher in the tank. This helps to dissipate heat and keep the pump cool.
Sounds like you have a good plan. One investment in fuel to get the tank 1/2 full and then your regular routine to keep it from getting below that point.
I’m not familiar enough with that model year to be certain but most GM pickups can be easier to lift the bed than to drop the tank to gain access to the pump when/if the time comes. Something to consider…
Not to pick a nit but one tick = foot, two ticks = inch. 18’ = 18 feet, 18" = 18 inches.
Best of luck to you!!