Chevy Truck not starting

Hello everyone,

I owned this 1996 Chevy k1500 Vortex V6 4.3L manual since new. I love this truck, so I replaced the engine with a 65,000 miles one about two years ago. I am pretty confident that by now, I have replaced everything on this truck. A few days ago, the truck would have a hard time starting, and after so many times, it finally did start. But then it did the same thing a week later, and I ended up damaging the starter. So I replaced the starter and battery, and all was well for a few days. About four days ago, it did not want to start, but this time I used a starter fluid, and the truck started right away. Yesterday did the same and would not start even with the fluid… engine turns, and once I stop the key, the engine keeps turning slowly about five times… like bump, bump, bump, then stops. This time I only tried three times. Today I wondered if perhaps yesterday I used too much fluid, so I tried a couple of times again with no results. The fuel pump is about 1,000 miles old, the fuel filter is about 300 miles old, and the injectors are about 300 miles old.

Any suggestions would be greatly appreciated!

Ps. This is a truck that no matter what, it always started at the first time, so this is really a strange problem, at least to me.

I would pull a plug wire and check for spark. Just to rule ignition issues out.


and then verify the batt cables are clean and tight (common problem on Chevys with side mount posts.) then verify fuel pressure. and then verify cranking voltage. Then verify voltage at the fuel pump.

and be prepared for these all to be fine, and the truck start right up. So also be prepared to check these the next time it fails.

Chevy trucks/van of around this age eat fuel pumps for breakfast. Even though yours is new, you may have gotten a bad one. Verify the fuel pressure to be sure.

Either a battery drain, or bad connection or alternator. Were you able to catch the charging voltage when running. Had one side post battery the rubber cover on the terminal had stretched out so it was not making good contact as a thought. Clean and inspect cables and connections also. imhop

Since the engine apparently keeps cranking after releasing the key then I would say there is an ignition switch problem.

Just any FYI, but you should not use starting fluid. That stuff is ok for a cold diesel; in moderation anyway.
I’ve seen several cases where the heavy application of Ether would wash the cylinder walls down and drop compression to the point the engine is a no-start.


I think you need to hook up a fuel pressure gauge

Thank you guys for all your amazing suggestions. Before I had the chance to try any of your suggestions, I got the truck to start after a few times. Before this started to happened, I used to have a “lean mixture” error code, that I resolved by replacing the injectors with the upgraded version -I guess the old “o” rings were allowing air to get in. Now that I can start the truck, I have three new error codes that it is related to the turn and no start problem. They are;

P3151 Which is high voltage from the ignition central module. I did replace the camshaft sensor about a year ago, which could sometimes cause this error.

P0300 Random multiple cylinder misfire. Which I wonder if this error could be happening because of the P3151.

I have just replaced the fuel pump
I have replace the fuel filter two times in the past two months because I am still worried about any debris I may have left after I flush out the gas tank. Last time was about 2 months ago.
I did tested the intake manifold for leaks and that was not the case, no other vacuum leak
Spark plugs and wires were replaced about 2,500 miles ago. They are the simple cooper ones because of the higher spark, so they should have at least 8,000 miles of productive power.
Battery and starter were just replaced

P0155 o2 sensor heater circuit bank 2 sensor 1. I replaced all o2 sensors last summer and had no error codes from them, I am wondering if this o2 sensor is just dirty from the “lean mixture” problem I used to have.

A mechanic friend of mine took a few minutes to check the truck, and was impressed on how smooth the engine is running. He advised me to first check the wires form under the fuse box for corrosion that he said it is typical for GMC/CHEVY and I guess the age of the truck. He also suggested changing the knock sensor. Then, if there is no problems under the electric wires under the fuse box and still have the problem, to then replace the ignition control modular.

To any of this makes any sense to any of you? Any suggestions? Your suggestions are greatly appreciated,


Hello guys, so I ended up replacing the ignition central modular, and the truck was working fine… until I neglected to start it for four days, that is when I realized the pattern to the problem. If I do not start the truck for 3 or four days, I cannot get it to start it again! (without trying and trying, and then trying some more), and using starter fluid is not helping, and I am afraid I am going to damage the brand new starter. That seems like a very odd problem to have! Any suggestions?

Never mind. None of the other comments displayed for some reason.

Is it cranking as in the starter motor working and just not firing up? When you turn the key, listen for the fuel pump to run for a few seconds. If so repeat the key on key off (as suggested by others here) to prime the system. Could be losing fuel pressure due to sticking injectors, or by pass valve. If the pump is not running, bang on the gas pump to try and jar it to run. On the other hand, if starter fluid is not providing a pop, it may mean you have a spark problem, so test for spark. Crank sensor?

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Thanks, Bing for your ideas… keep in mind that the problem is now happening if I do not turn the truck on for 3 or 4 days. The fuel pump is new, the injectors are new, the starter is new, and the sparks plugs are new… When turning the key, I can hear the pump.

The engine will turn, and when I let go of the key, the engine kind of keeps very slowly going, like “pump,” “pump,” “pump,” making the whole truck shake a bit. Again, this only happens when the truck does not get started in 3 or 4 days, which kind of eliminates the thought of a spark problem or gas pressure problem. From all the effort I made to get started the truck this morning (after not turning it on for 4 days), I got some error code that I will try to read tomorrow.

Try the “key dance” described above. Fuel pressure can bleed off faster than you think. The key dance brings fuel and fuel pressure right up to engine just before you turn the key all the way to the Start position.

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Yeah I can’t think of anything else that would be time related besides the pressure bleeding off. There are things that would cause the chuga chuga chuga and then die, but not time related. Someone will chime in.

Hey guys, so as predicted I started the truck today at the first try and very fast, no hesitation or tardiness to start at all. So as I said on my prior post, yesterday I had to try several times with no luck, I left the truck alone for about an hour after trying so many times, and the truck got started. From doing that (I have no driving the P1351`EST Output High or Pulses Detected when grounded cylinder 1. The reason I disconnected the battery the last time was to replace the ignition central modular, which normally would be the culprit for that error code. When I inspected the old ignition modular, I felt it needed replacement because I guess the guy who replaced the engine felt that only one screw was sufficient, and the coolant silicone was almost not there. But the error code is back… also, I did replace the camshaft sensor that sometimes is associated with that error code.

Any thoughts?

No except that silicone stuff is a heat sink. Don’t use it or only marginal fastening and the thing can be fried. Now I once bought an after-market ignition module and it was bad right out of the box. So I used to have a junk yard coil and module just to swap in to test if that was the problem.

Good mechanics are under rated though.

Cranking robustly but the engine not catching and start running associated with the car sitting several days, my best guess is the fuel pressure is draining down . Likely causes are fuel pump check valve, in which case it is draining into the fuel tank, or leaking injector, in which case it is draining into one of the cylinders. Usually it is the first. But you could remove the spark plugs, if one or more is wet w/fuel, that would be a clue for the second. You could also try holding the pedal all the way to the floor when cranking. If that helps, good chance the engine is flooded due to the second problem. Or ask a shop to do a fuel pressure hold test.

Intermittent crank or cam position sensor failures are usually associated with heat; in other words it won’t start if the engine is hot. I don’t think that’s the problem here for the cranks but fails to start reliably.

Good idea when test-cranking the engine to crank for no more than 10 seconds at a time, then allow the starter to cool down for 3 or 4 minutes before trying again. Helps prevent starter motor damage. Best of luck.

Thank you, George, That makes a lot of sense, but I think I have something else going on because the truck started to behave differently now. Yesterday I got to work, and when done, without much thought, I turned the key as always and gave it some gas. The truck started right up, but then it went off after 4 seconds, and this time, it did not want to start. So after trying the “priming” the fuel with the key going and off, and after 20 minutes, I got the truck to start. So today, I have been looking into getting a new fuel pump but then decided to do some testing first. According to the Chilton manual, one of the tests would be to start the truck, and then remove the fuel relay, saying that the truck should stay on, and that if it goes off, then I have to check the fuel pump /oil pressure switch, and is wiring. Repair as necessary and repeat the test. Chilton does not have a page notation on where that switch is… To this makes any sense to any of you?

One more question, a few people mentioned checking into the ground of the pump, which is done to the frame nearby, and there is a good chance that it might need redoing. Would that explain why the fuel gauge is always showing way higher gas than it should (I did replace the gas sender unit as it came together with the fuel pump when I replaced it last year)

I am off to search for this switch on the web!

Thanks a lot

(EDIT) Ps. For what I am seeing so far, replacing that oil pressure switch does not seem to answer the weird behavior of the fuel pump, and perhaps I should change it anyway… Any thoughts?

Please don’t take offense to this . . .

In my opinion, you need to be very sure before you start throwing parts at the truck

That means using a digital multimeter to verify proper power and ground at the fuel pump and at the correct time

And it means hooking up a fuel pressure gauge to your test port

Whichever path you choose . . . good luck! :smiley_cat:

No offense taken, if you read my last message, I mentioned how I discovered that I have a bad fuel/ oil pressure switch by performing tests recommended in the manual. My wires at the relay area are clean, and I tested for power and ground. Leg 87 is always hot, 85 is hot for a few seconds after turning the key, and I have ground on leg 86. I can jump-start the fuel pump as I can hear it pumping when I do. The thing is that the pump seems to stop working randomly, and I am wondering if the bad fuel /oil pressure switch could be causing this odd fuel pump behavior. I also did a pressure test: 54PSI

I think the oil pressure switch wiring is run in such a way that it can shut the fuel pump off if you have zero oil pressure (or something like that). I assume it’s to save the engine - if the oil pressure drops to nothing, fuel shuts off, engine shuts off. Have heard that before, anyway.

If you’re looking for the oil pressure switch on your truck, it should be on the intake manifold- kind of back where the distributor is. Easier to feel it than see it, to be honest.

Some cars are wired that way. Circuit diagram would disclose that.