4.3 vortec (cbi) the problem is that the truck will not start on its own when the engine is cold. it started getting hard to crank so i did a whole tune up (plugs,wires,cap,rotor) and not long after this started. the truck will start by spraying a little gas into the throttle body but can still be a hard start. after it starts it runs perfect no lag nothing out of the ordinary. and after it warms up it will start on its own every time. so i changed the air charge temp sensor and that didnt help. still running about 53 psi fuel pressure when the key is turned. i asked one of the parts houses and he was telling me that it could be the pick-up in the dist? that just doesnt make ne sence to me but hey what do i know. id really like some help on this before i try that because its going to be a pain and a half. thnx ahead of time. P.S. truck is a 4x4 4.3 v6 cbi
There may be a check valve in the fuel pump that is leaking and allowing the fuel to back flow into the tank. I would see if the is the case since it seems to start by adding some fuel.
now how exactly would u check that?
Monitoring the pressure while the vehicle is parked should reveal if the fuel is leaking back
Click here and see if tester’s post may apply to your symptoms:http://community.cartalk.com/posts/list/662016.page You could have fuel draining back into tank from the fuel pump which is also in tank, but not as bad as the scenario in above link- the fact that engine starts when it’s already warm means it could be the heat that’s creating enough fuel pressure. (heat=pressure) Try tester’s trick. I have to admit the 53 PSI you noted is a fly in the ointment of all this.
good thought but nope it didnt work tryed it about 4 times
I know the gas spray worked but please don,t put gas into any FI car. you could have a back fire any cause a fire. di you try a little starting fluid? but fisrt check label on can to see if it will harm any of plastic sensors. then it will cost you alot more. not srr the car this is something fromout space.thinking back to old carbs with vacuum leaks just place some thing over the throttle opening about two thirds
don,t spray any thing into it don,t hold it with your hand tape it if it starts you have a vacuum leak. and the exta gas even,s out the mixture after the engine is hot and medal exspanes and with ever hot the engine will start. you could have leak under intake gaskets just I wild thought . you could have a bad TPS and it is telling the computer the car is in motion and pedal is pushed down and engine needs more fuel. check this item first. does this car have MAP sensor this tells computer how to mix the fuel also. it is somthing telling the computer to change timing or fuel pressure . did you look at injector too see if just turning ke to start if fuel is spraying out. it should do with pushing on gas. if tps is it tells computer car is running no FI car will start with this wrong info to it. I tried for you if you do not find
the problem advance auto is having a sale on stater fluid . ggod luck it is every hard to fix a car over the web.
sorry this boxwrench again not map sensor but mass air flow sensor.
Tomorrow morning when you go to start the car, put the key in the “on” position for a few seconds without putting it in the “start” position. Do this a couple of times. If the fuel is draining back into the tank, this will pressurize the line and the car should start promptly. If it still does not, then I’d look elsewhere for the problem.
Post back with the results.
i dont think u get the picture it isnt getting enough gas to start on its own and yes i have been using starting fluid
already tryed it dont work
Since you’ve tried this, and you’ve checked the fuel pressure and already changed the temp sensor, and it starts by spraying gas into the throttle body, I’m out of ideas at the moment, but I’ll “bump” the post while I ponder some more. Perhaps someone else here will have another idea.
You say in your original post you replaced the air charge temp sensor. Did you also replace the coolant temperature sensor? It will be screwed into the intake manifold near to the thermosat housing and close to the gauge temperature sensor. If you have replaced the CTS, check for a ground or short in the wiring to the CTS because that would be intrepreted by the computer as a warm engine condition. OBDI systems do not set trouble codes for shorts or opens.
One diagnostic test is to disconnect the CTS plug and try to start the cold engine. If you get a start, you have a positive sensor diagnosis. Measure that exact resistance of the CTS and see if it fits the resistance to temperature tolerance. If you do not get a start with the CTS plug removed, you can suspect a ground or short. Measure the positive voltage at the plug with a DVM. It should be approximately 5 VDC to ground. If it is other look for grounds or shorts.
Let us know the progress or what solves this condition.
All of that troubleshooting stuff is just too much trouble, isn’t it jimmymac? So, just change the engine coolant temperature sensor.
it has not been changed or tested but i have noticed that after it started all this mess that it takes it alot longer to warm up than it should would that have ne thing to do with it?