I have a 96 Tahoe that is giving me a lot of trouble starting. This is an ongoing issue that I put on the back burner for a while and just drove my other truck. Now I need the Tahoe running. I have replaced the fuel pump and have the proper fuel pressure. About 55-60 psi. I have replaced the fuel pressure regulator, the plugs, the wires, the cap and rotor button, the coolant temperature sensor and it has a new battery. It will crank and crank but will not fire up. Meanwhile the engine is being flooded with fuel fouling the plugs. All the plugs are soaked with fuel. It now refuses to run at all. The temperature here is around 34 degrees now. If I try to start it in the cold weather it wont start but if it were around 60 or 70 or higher, I can eventually get the engine to start. Then, after I get it running, it will run fine as long as the engine is warm or the temp outside stays warm but if the engine gets cold or the temp drops it will not start at all. When it does run it runs great. Any ideas what could cause these problems? I figured the coolant sensor would have fixed it for sure. I just changed it today but it still will not start. Any help would be appreciated!!!!! Thanks.
1996 Tahoe Wont start/Hard start
- Thread starter JC77
- Start date
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MO Viet Vet
Full Access Member
If in fact you are getting fuel fouled plugs after long cranking then you have no fire. Since you threw all the parts at it I would now recommend replacing the module, cam sensor and crank sensor. Hopefully you already got a quality cap and rotor. I have seen the cheap ones have no spark through them right out of the box.
How long does the fuel pressure hold when you let the fuel system prime?
I agree with issues with the ignition, have you had the lower intake manifold off?
Where did you check for fire at?
Might see if you have someone can put a scantool on it and see if the PCM sees ambient temps from the CTS or if it is showing -44 (then the circuit would still be open, i.e. bent pin or something... been there done that...)
I agree with issues with the ignition, have you had the lower intake manifold off?
Where did you check for fire at?
Might see if you have someone can put a scantool on it and see if the PCM sees ambient temps from the CTS or if it is showing -44 (then the circuit would still be open, i.e. bent pin or something... been there done that...)
The battery was out of the vehicle for a year and it has not run as of yet since putting it back in so I would say any codes set are long gone now. The only part that I changed since working on it this time is the cooling temp. sensor until today. I have fuel to the point of soaking the plugs and have fire at all plugs while cranking. Took plugs out one by one and inserted them into the plug wires and grounded to the manifold. It has a strong spark. That is why I cant understand why it will not even hit at all. Not even when I sprayed a shot of ether in the throttle body. So, I figured it may be the crank pos. sensor. Changed it. No difference. Had a new cam position sensor already from working on it previously so I put that in also. The cap and rotor are new Duralast brand. It still refused to even hit, backfire, or show any signs of life. The fuel is there, the fire is there. Never seen one that had fire, fuel, and air that would not run unless it was so far out of time it couldn't. The timing chain is not broken and I have never moved the distributor. I have not checked the exact fuel pressure yet I have to get a gauge but at the valve on the rail it has decent pressure. Enough to spray violently against the hood. I will get a gauge tomorrow and check the pressure and check for leakdown. Not really sure where to go from here. I work on mining machinery for a living so I understand the term parts changer or throwing parts at it until it works, but I don't generally do that but troubleshooting something that no matter what you do shows no change or no improvement is really frustrating.
No lesterl I have not had the lower intake off, just the upper when I changed the fuel pressure regulator. Also, I got the pressure readings when I installed the pump about a year ago. I have not driven or started it since. I am going to get a gauge tomorrow and recheck it again. I also have a scantool coming tomorrow and I will check the CTS.
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Nice on the scantool, they can be a BIG help, I have a couple...
Pull the fuel pump relay and leave the plugs out of the engine and turn it over a few times to clear the fuel from the cylinders.
Replace plugs with new ones, get an OEM ACDELCO cap and rotor.
with the FP relay still out and engine aired out, try to start it with a shot of your starting fluid.
Make shure your fuel pressure on prime isnt bleeding off fast (aka a FPR seal leak or a crack in the injector pod), also with the scantool on the engine off igntion on check the CTS value vs actual outside temps..... should be close...
Pull the fuel pump relay and leave the plugs out of the engine and turn it over a few times to clear the fuel from the cylinders.
Replace plugs with new ones, get an OEM ACDELCO cap and rotor.
with the FP relay still out and engine aired out, try to start it with a shot of your starting fluid.
Make shure your fuel pressure on prime isnt bleeding off fast (aka a FPR seal leak or a crack in the injector pod), also with the scantool on the engine off igntion on check the CTS value vs actual outside temps..... should be close...
Ok, scan tool didn't show up today. My friend did not have the time to bring it to me. He has a garage and a wrecker service that keeps him pretty much tied up. I had no ride to get it either. So, that being the situation, I went ahead and changed the plugs out with new ones I already had. Tried to start it with the starting fluid after clearing the cylinders of fuel like you suggested. No go. Nothing. Not even a sputter. Since I had no scan tool, I wondered if I could take a meter and check the resistance on the CTS as compared to the old damaged one. At 200k the old one read around 4-4.5 ohms. The new one read the same. Should the CTS read this way if it is good? That is putting the leads on both prongs to try and read the thermistor to make sure it was not open or damaged. The readings are with the new one in the engine and the old one in my hand. If they are good should they read this way? Every other thermistor I have tried to read with a meter would read a specific ohmic value based on the rating of the resistor +/- whatever the temperature is. Do you know what the value of the thermistor is for the CTS? Minimum or maximum? I don't know any other way to check this part without the scan tool. The fact that they read very close to the same, can I ASSume that both are good, or both are bad? I also put a 3ohm resistor into the plug from one wire to the other and tried to start the engine. If I am correct, that should have fooled the computer into thinking that the ambient temperature was around 70*F and stopped dumping excess fuel into the engine. It did NOT. Still flooding and not hitting. Nothing I do seems to make any difference to this stinking engine. I have never ran into a situation quite like this one before. No progress what so ever. Hopefully tomorrow I can lay my hands on the scan tool and a pressure gauge and eliminate the pump and CTS. If those check out, what next? The timing chain is not broken, The gear on the distributor is not stripped or broken, All vacuum lines appear intact. Could the injectors be damaged and causing this? I mean, surely whatever the problem, it should at least hit, backfire, backlash or show some type of life if I have fuel and have fire. I know I have both so what is the issue? Please make me understand what it is that I am missing.:help:
:whymewhyme:
:whymewhyme:If it is dumping fuel into the engine, it will foul the plugs and they will not fire if they are wet. You already know that, but until you get it figured out, you are going to have to continually take the plugs out and try to dry them off after each trial start if they are wet. You may have fixed the problem along the way but the fouled plugs might keep it from starting.
You might want to try your starting fluid experiment again. Dry the plugs out and put them back in, DISCONNECT the fuel pump so it will not run, and then try a couple of squirts of starting fluid and see if it tries to run. If it does, then you know your main problem is overfueling for some reason.
You might want to try your starting fluid experiment again. Dry the plugs out and put them back in, DISCONNECT the fuel pump so it will not run, and then try a couple of squirts of starting fluid and see if it tries to run. If it does, then you know your main problem is overfueling for some reason.
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