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I had family day yesterday. All plugs are firing. It ran today for 20 min. and then died. I thentested the plugs and they all fired. I also tried putting a little gas in the throttle body and cranking it. It TRIED to start. My thought is something's closing the injectors, since it would not run with the pump jumped and it's firing on all plugs. What do you think and what's the next move?
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Patience is sometimes hard for me. Persistance? You convinced me. Talk to you tomorrow.
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Texas Panhandle. I will give that a shot first thing in the morning. But with the history, it'll probably start up and run for a while. I'll just have to drive it and get stuck. Maybe not to far from my house this time :>). Anyway I'll give it another shot in the morning and let you know.
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Sounds like this is going to take more than I can do. I'll just have to bite the bullit and take the truck to a mechanic. Wish you were close, since you already have a history with it, I'd bring it to you. Thanks for all your help!!!
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No hostility, just letting you know that I made sure it was plugged in right. It's just I'm usually good at troubleshooting problems with my vehicles but this one's got me confounded. I still haven't found the problem. After I emailed you last I took the truck out for a drive to see how it would go and it quit again. I took the jumper with me and followed the steps you gave me to hook it up. I heard the fuel pump running, but this time the motor wouldn't start. I turned off the key and disconnected the jumper and went through the steps again. Fuel pump ran the whole time I tried cranking. It tried starting a few times but wouldn't run this time. The friend that towed me home suggested that the pump may be running but not pumping. I don't know. I'm stumped. Do you have any more suggestions. I'm greatful for ALL your time and suggestions.
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I will change the oil, though it's not that old and does not smell gassy. There was only one plug of the type that would fit the sending unit, and it IS plugged in right. I am a little suspicious of the new unit as the oil pressure does not change that much while running through high and low rpm's. What I mean is that when I start the motor the oil pressure is 20lbs at idle and when I take it up to 2500 - 3000 rpm's it slwoly moves up to 30-35lbs. When I let off the gas it slowly comes back down to 25-30lbs at idle. I'm used to the gauge reacting a little faster and haveig consistant high's and lows. I don't remember if they asked me if I had a gauge or light, I bought it 10 days ago, but they are shaped the same and have the same three prong plug style. Should I replace it?
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Funny you should say something about the oil pressure switch. Where is that located? Is it integrated into the oil pressure sending unit? The reason I ask is that my sending unit went bad a few weeks ago (reading high). I just replaced it a few minutes ago and when I went to restart the motor it started and died. It did this a couple of times. Finally it ran consistantly through high and low RPM's. Is this the end or do I need to look for a seperate oil pressure switch? BY the way, the oil pressure on the new unit was reading 20lbs idling and 30lbs @ 2200 rpm's.
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OK, here's what I did, after I emailed you this morning (while I was waiting for your reply) I went ahead and got a new fuel pump relay and installed it. The truck is 12 yrs old and has 240k miles on it so I thought it couldn't hurt. the truck started fine and idled for 13 min. I decided to rev up the engine and as it was idling down it died and wouldn't restart. After I got your email I tried what you told me. With the new relay in I put a jumper from the gray wire on the relay to the + post on the battery. I could hear the fuel pump running I started the truck and let it idle for 5 min.. I decided to rev up the engine and it kept running. I let it warm up to running temp and did it again and it kept running. So I decided to disconnect the jumper and the truck kept running. I rev up the engine, it ran. I let it run a little while longer and then shut it off. It started right back up. I did this a few times and it kept restarting. The only thing I didn't do is drive it. I don't know what happened or why it's running now. I'll listen to any suggestion why. I'm going to let it cool down and see if it will keep performing well. I will let you know. thanks for your help so far as I'm not convinced that this problem is cured.
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I followed the harness from the fuel pump relay and the first female only connector was under the air filter on the lead to the coil. I traced from the relay every direction multiple times. The only lead that was taped to the harness by the relay had two ends plugged together.
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Answer to first question: I disconnected the return gas return line connectet a clean hose to it and ran it into a bucket. When the engine would start, the short time it was running it ran a full stream back into the bucket, but I did not pressure test it. Second: I had the transmission rebuilt about 13k miles ago (in march). before that was the fuel pump. I tried cycling the key 3 times and starting on the 4th, it idled for 10 min. and then died. Engine temp. was about 140 deg.
Thanks
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I have a 92 GMC 1/2 ton 2wd w/TBI that stalls when you let off the gas. And then it's hard to start again. I've replaced the fuel filter. Fuel pump is about 40K miles old and seems to be working fine. What's next? Thanks for the advise.
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You stated: "seems to be working fine".
Question: How did you determine this ?.
What was the LAST repair on the vehicle ?. ANY repair of any nature ?. In most cases problems that arise days, weeks or even months later can usually be traced back to the previous repair.
Try this TEST:
Cycle the ignition key from the OFF position to the ON position 3 times, Do NOT try and start the engine during this test.
On the fourth cycle try and start the vehicle and let me know.
autohelp
autohelp
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OK. Locate the fuel pump relay of which is usually mounted in the engine compartment. Look at the electrical harness jsut before the relay and you will see a female connector taped to the harness that is NOT connected t anything. This female connector is the FUEL PUMP TEST LEAD.
Using a standard 12 volt test light, probe this connector and turn ON the ignition switch and observe the test light, It should illuminate for 2 seconds and then go out.
If it does this, We can proceed.
Leaving the test light installed start the engine and observe the test light, It should stay illuminated all the time that the engine is running.
If it DOES, We can proceed.
Take a TEN (10) AMP FUSED jumper wire and attach one end to the battery POSITIVE terminal and the other end to this TEST CONNECTOR, Thus providing battery voltage to the TEST CONNECTOR at ALL TIMES as long as you have your TEN AMP FUSED jumper wire installed. You can hear the fuel pump running constantly.
Leve this TEN AMP FUSED jumper in place and start the vehicle and see if your problem is resolved.
let me know so we can proceed.
autohelp
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OK, Then locate the fuel pump relay and here is what you should have at these fuel pump wire locations at the relay:
Turn the ignition key to the "ON" position ONLY. DO NOT try and start the engine. OK, With the ignition in the "ON" position via the key:
Locate the GRAY wire at the fuel pump relay and using your 10 AMP FUSED jumper wire, Connect this GRAY wire to battery voltage and you should hear the fuel pump run constantly as long as you have battery power to the GRAY wire.
Now see if the vehicle will start and remain running.
let me know.
autohelp
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A bit SKEPTICAL is a GOOD thing.
OK, Here is how the fuel pump operates:
1. When you turn the ignition (key) past the ON position to the start position, There is a 2 second fuel pump run as soon as you turn the key to the ON position on it's way to the START position.
This 2 second pump run is provided by the fuel pump relay.
Once the engine starts, The fuel pump relay is no longer needed and battery voltage is supplied to the pump via the vehicles ECM (computer) and on SOME engines, Through the oil pressure switch, Then back to the fuel pump.
Let me know.
autohelp
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Are you POSITIVE that the oil has not been diluted with gasoline from this problem ?, As this can cause the oil pressure NOT to close thus shutting off battery voltage to the fuel pump.
There also is the possibility of a faulty NEW oil pressure switch.
Usually the factory wiring harness has 2 (TWO) connectors for the oil pressure switch.
One connector is for if you have an oil pressure LIGHT and the other is for an oil pressure GAGE. Make sure you have the right one plugged into the oil pressure switch.
When you bought the new pressure switch did they ask you if you had a LIGHT or a GAGE on the dash ?, As the pressure switches are DIFFERENT and NOT interchangeable.
I would change the oil and filter FIRST.
Second would be check that you have the correct connector plugged onto the pressure switch and that is is plugged onto the pressure switch CORRECTLY.
autohelp
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Do I sense some hostility per your statement: "and it IS plugged in right."?.
I would install a known good external oil pressure tester just to see EXACTLY what pressures your engine is doing, Before I return it and buy another one.
autohelp
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When it quits running and you are trying to get it started are you getting sufficient ignition to ALL the spark plugs ?.
What I am leading up to is a possible CRANKSHAFT SENSOR intermittent failure, IF applicable to your vehicle and type of engine.
autohelp
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Hang in there a little longer and just check the spark plug wires for ignition when you are trying to start the vehicle after it quits.
We almost have a diagnosis here.
I am in New mexico, Where are You ?>
authelp
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Haul that vehicle out here to Grants NM and I know I can diagnose and resolve your problem.
I have a 1 ton 1994 Ford dually and a flat bed trailer and on several occassions I have picked up vehicles and brought them back here and within a day or two, depending upon parts availability, The owner came and drove the vehicle back home.
I have even made house calls up to 150 miles from my home. But I am NOT cheap, But I do have 20+ certifications from GM, FORD, CHRYSLER and JAGUAR and also held several ASE certifications prior to retirement.
A couple of more tests won't kill you, Patience and persistance is the key.
autohelp
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I am teaching this trade to my son who has ZERO patience until I showed him what he would be making in a few years. I think he changed his attitude. You don't have to get dirty diagnosing electronic problems and it pays extremly well.
autohelp
AnswerOK, If you think something is turning OFF the injectors, here are the possibilities:
1. Faulty intermittent failure of the fuel pump.
2. Faulty intermittent failure of the Crank sensor.
3, Faulty intermittent failure of the cam sensor (if
applicable to your vehicle.).
4. Faulty intermittent failure of the ECM (computer)
5. Faulty intermittent failure of the Ignition module.
6. Faulty intermittent failures of the numerous electrical
connections.
7. Faulty intermittent failure of the Pressure regulator.
8. Foreign debris in the fuel tank plugging up the micron
filter at the bottom of the fuel pump.
And many more possibilities.
I am NOT going to start guessing and have you replacing part after part after part in hopes of finally getting lucky.
I am NOT a parts replacer. Your either going to do the diagnostics or your NOT.
What do you want to do ?.
I can't help you if you can't help me in performing the diagnostics.
autohelp
