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Car cranks but wont start!!

15K views 14 replies 4 participants last post by  FloMaster 
#1 ·
So let's establish that I'm an idiot for rushing into things, I got it. This morning I decided it was time to upgrade my throttle body and plenum. Everything was going fine, plugged everything back in, and went to start the car. Now that brings me to my dilemma. Car cranks, but wont start. Here's the part where I explain as to why I'm an idiot. The whole time I was unplugging and plugging in stuff, I still had my battery hooked up, so my ECU must have started to freak out on me. Could that be my problem? It's cranking like it's thirsty and hasn't had any gas in days, and my fuel pump doesn't seem to be helping out much. I don't hear it when I turn the ignition to On. I checked the fuse and fuse is fine. I have a tuner with a few tunes, I restored the ECU back to factory settings (according to my tuner) to see if that helped any, but no luck. As I said, everything was plugged back in the right spot so that shouldn't be an issue. I even checked my coils and fuel rails and they were all plugged in and everything. Anyone?
 
#2 ·
spay some starting fluid in it to see if its fuel issue. Make sure all sensors are plugged in like maf and tps
 
#4 ·
I did my tb/plenum without unhooking the battery, everything went fine.

Go back over everything you did. EVERYTHING. Again. Chances are you missed something somewhere. If all else fails, disconnect the battery for 10 minutes and try again.
 
#5 ·
The OP did not mention the model year of the car. However, for the 1999-2004 MY, the fuel pressure sensor is a NO START sensor. That is if the PCM does not receive a valid fuel pressure signal, the motor will crank but won't start.

Based on the work done, I would start there. Check the electrical connector to the fuel pressure sensor. Confirm that the intake vacuum reference line is connected and leak free.

Since you own a tuner, consider using it to monitor the fuel pressure. What is it? Also use the ODB2 scanner to monitor RPM's. Do they change during cranking? If so, that means the PCM is receiving a good CKP signal.

Next check the MAF value. Does it change during cranking?

Here's some more information:

http://www.allfordmustangs.com/forums/4-6l-tech/336452-1997-mustang-wont-ignite.html#2984838
 
#9 ·
For the 1999-2004 MY's, the fuel pressure sensor is located on the left hand (driver's side) fuel rail. It will have a small vacuum line that is the intake manifold reference line.

If still unable to locate consider posting pictures of your engine bay.

Also note that a vacuum leak between the MAF and throttle body could cause a crank with no start.
 
#10 ·
Battery died in the process of trying to crank it. I tried cranking with the throttle halfway and open, also tried unplugging the MAF with no luck.
 

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#11 ·
I put tape around all the vacuum hoses to make sure there were no leaks or got detached in the process. I tried unhooking the battery for 30 minutes like twice, reset my ECU back to stock, also loaded an updated tune, no luck. Fuel pump is on and can hear it when the car is on the ON position, checked for tripped fuel pump in the trunk and that is fine as well.
 
#14 ·
What does the theft light do at initial key on? After the 3 second prove out?

When did you do the field repair (splice) to the fuel pressure sensor? Why don't the wire colors match? I can also see exposed wires on the picture.

Were you CRANKING the motor while reading the RPM's? If so, this would indicate a problem with the CKP sensor. What about the fuel pressure?

Where does the red vacuum line from the fuel pressure sensor go? Were there changes made?
 
#15 ·
Disregard everything I just said. It started right up. The solution?

I checked my TPS, and looked at the way it was supposed to go in. When I originally put it back on, I was unsure of how it was supposed to go in, so I just sort of winged it and put it in whatever way, totally ignoring the fact that it can only go one way. I heard a pop when I originally put it on but I didn't much of it. So I took it back out after hours of thinking and narrowing down the symptoms and stuff, and found out that the spring inside the TPS was broken, being the reason why my ECU didn't know if I was holding down the throttle or not. So I ran to AutoZone and bought one for about 25 bucks, popped it on and fired right up. This could easily have been avoided if I had just paid attention and not rushed into things like I did, would've been a 30 minute job instead of a 2 day job. Thanks wmburns you helped out a lot and all the other guys that gave me a better understanding.
 
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