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My 94 Suburban K1500 is floodng itself out again when trying to start. If I unplug one of the injectors it starts up and idles and I am able to plug the injector back in and it will idle as normal. If I try and start it with both injectors plugged in, it just cranks and cranks without attempting to start. I have tested the coolant temperature sensor. It was showing 2.6 at cool temp and went down to like 0.2 ohms at around 190 degrees in boiling water.
I also replaced the fuel pump relay and the oil pressure sensor. Fuel pressure shows approximately 14 psi at the filter when the pump is running. As soon as the relay kicks the pump off the pressure drops to zero quick. I think this is normal as some TBI systems have a built in release.
Can someone tell me where to go from here. Throttle position sensor? ECM? I am lost here with this one.
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I got some data here that hopefully you can make heads and tails out of. I google how to test the map sensor, coolant temperature sensor and throttle position sensors. This is the results.
Map sensor is showing…
4.78 Volts with 0PSi vacuum applied
3.89 Volts with 5 PSI vacuum
2.78 Volts with 12PSi vacuum
2.08 Volts with 15 PSI vacuum
1.15 Volts with 20 PSI vacuum.Sensor maintained the 1.15 psi for over 2 minutes and the voltage went up to 1.17 towards the middle of two minutes, however the voltage never dropped until I released the pressure.
Coolant temperature sensor showed…
approximately 2.5 ohms at room temperature and went down to 0.21 ohms in 190 degree boiling water. It started to go back up slowly once it was removed from the hot water.
Throttle position sensor shows…
0.51 volts on the signal wire, a good ground and the power wire shows 5.07 volts. The signal wire goes from 0.51 volts at an idle to 4.56 volts at wide open throttle.
Oil pressure sensor tan middle wire shows a good ground. Grey wire show 8.75 volts and the red wire shows 12.37 volts. If I jump the two end wires together the fuel pump runs constantly however, this time is wont start. I had this same issue about a week ago where the truck was flooding out and not starting. Once I jumpered the two wires on the oil pressure sensor, the truck started up on its own. I think it was a coincidence though.
Truck was showing three DTC’s however the light was not on the last time I drove the truck. I think all three are from me disconecting sensors and cranking the engine over trying to start it. It shoued DTC 15 open circuit in coolant temp sensor, 22 something about the throttle position sensor and 54 which is fuel pump circuit low voltage.
BTW, I found out the truck will start if I keep the gas pedal to the floor when cranking, however the engine just dies as soon as I let off the pedal.
I just started the truck up by starting it with the pedal to the floor. Once it started up, I reved it a little and slowly let of the accelerator. It ran on its own but rough for awhile. The longer it ran the better it seemed to run. I shut it off and tried to restart it. It wouldn’t start without me holding the gas pedal to the floor. I restarted it holding the gas pedal to the floor and once it would idle I got out and checked the injectors to see if one looked like it was spraying more than the other. They look the same to me. Than I started spraying starter fluid around the upper intake looking for leaks but it apparently found none. I shut it down and the third and fourth times I was able to start it without holding the pedal to the floor.
It seem like you have to much fuel pressure. when you put
the pedal all the way down. You are in clear flood mode. which
will turn off the injectors.you may need a tbi rebuild.especially
the fuel pressure regulator.Have you also checked timing? not saying
you have to modify like this guy.But but the fuel gauge was a nice touch.
Your injectors should have a light spray pattern.not heavy or dumping.Once again thanks college guy. I think I got the problem figured out. I replaced the fuel pressure regulator and that still didn’t fix it, but I had the engine running and I accidentally bumped the wire that goes to the coolant temperature sensor and I noticed the engine idle changed when I did it. Further wiggling and I could get the engine idle to change as I moved the wires. I also noticed that the oil pressure gauge would fluctuate when I jiggled the wires to it. So, I replaced both the oil pressure sensor and coolant temperature sensor pigtails and so far so good. Also I am now able to unplug the fuel pump relay with the truck running and the oil pressure sensor keeps it running. Last time I thought I had this fixed when replacing the oil pressure sensor, it would still die when I unplugged the fuel relay. So it seems like the problem was a combination of bad connections at the coolant temp sensor and the oil pressure switch. Thanks again.
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