truck starts only intermittently

[Redog]

I have an 08 ranger 4.0L 4x4 sport
I've just replaced the timing chains and after putting the engine back into the truck the truck starts only intermittently, if I remove the ground cable and put it back on it starts.

 

[enjr44]

You mean that if you remove the battery neg cable and then reinstall it the truck will start and run once?? But, if you shut it down, it won't start and run until you again remove and reinstall the negative battery cable???

Just trying to understand!!

 

[Redog]

that is exactly what is happening....

 

[enjr44]

Man, this is beyond my pay grade..... But, it has to be something simple!!! It spins; but, won't start??

Can you hear the ECU and fuel pump relays click when the key goes from off to run? Swap them with the WOT relay, they are all the same.

When it does not start can you spray starting fluid into the air box and get it to start??

Does the fuel pump run for two seconds when you turn the key from off to run. It will run for 2 seconds each time you cycle the key.

If the fuel pressure is below say 30 psi it will not start, not enough fuel pressure and until rpms are over 300 the computer will not turn the fuel pump back on. If the rpms drop below around 300 the computer shuts off the fuel pump (safety) and maybe spark (don't remember).

Do you have spark? Use a timing light to check if you can. Pulling a plug and grounding it may or may not work with the waste spark sys.

 

[Redog]

it doesn't turn over, it only turns on the dash lights and head lights and when you turn the key its like its dead, it doesn't even click its just not doing anything unless I remove the ground and put it back then it goes no problem, but I've just put in a brand new battery, because I thought it was shot, as it was a three year old battery.

 

[enjr44]

Go Here and study the wiring diagram.

http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80e64262

It looks to me like with an automatic transmission the starter relay and the PCM gets power on the orange/green wire when the key is in start. The ground for the starter relay comes from the PCM on the yellow wire. A manual trans has a similar route with the blue wire in the mix.

So for some reason, when you disconnect and reconnect the negative battery cable the circuit works as it should when the key goes to start. But, not on subsequent tries.

I think I would try measuring voltage on orange green wire with the key in start, you should get 12 volts. Then measure the voltage on the yellow wire with the key turned to start. The voltage should be zero with the key off and zero with the key in start. If you get 12 volts in start the PCM is not applying the ground for some reason. You can use a straight pin to pierce the wire to check the voltage. When done clear rtv or ever clear nail polish will fix the hole. Make your measurements with the meter on the 20v dc range and the black lead on a good ground.

If the orange green and yellow wires check out, I would pull the relay and jump pin 30 to pin 87 in the relay socket. The engine should turn over, so don't have it in gear or anything in the way. After thinking about it, if you do this first and the engine turns over, you will have tested most of the system and then you can go figure out what is going on the with the orange/green and yellow circuit.

http://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0996b43f80e64262