timing

[adsm08]

So the purge is on the throttle body? What does tfi stand for? Thanks

No, the air line for the purge valve is on the TB, I don't know where your purge solenoid it, but it's probably somewhere near the carbon canister.

TFI stands for Thick Film Ignition, but you don't have it anymore. It was part of the 2.9 ignition system, but is not part of the 4.0 system.

I'm not sure if the purge solenoid would cause your hard starts, but I want to say no. I'd still get that plugged in though because it will mess up your mileage.

 

[kimcrwbr1]

So the purge is on the throttle body? What does tfi stand for? Thanks

the purge solenoid allows the engine vacuum to pull the fuel vapors from the cannister into the combustion chamber to be burned while the engine is running if you smell fuel in the engine compartment the carbon cannister is saturated with fuel vapors trace the vacuum lines from the cannister mine is mounted on the front left of the radiator there should be a solenoid with two wires and the other side goes to the throttle body. The TFI is the ignition module on the distributor but I just checked and you dont have one so nevermind. But anyway make sure all the vacuum lines are good and connected check the nuts are tite on the throttle body and get it started and spray some carb cleaner around all the intake manifold connections if the idle rises that is where the leak is if you have one.

 

[adsm08]

Does it help it start if you give it a bit of throttle?

 

[kimcrwbr1]

when you go to start it turn the key and let up after a second and see if it catches instead of cranking on it give it short bursts It still sounds to me like the ignition is not retarding to count for the low rpm but it starts when you let off the key. I have a schematic for a 90 4.0 and there is a start wire going to the computer but it gets all mixed up with the park neutral switch,clutch multifunction and neutral sense switches. I`m gonna see if there is a start mode for that ignition similar to the TFI

 

[litlred]

It doesn't really help to hold the throttle open, it seams like it starts the best after the battery has been on charge all night, but that could have nothing to do with it. As far as the short burst, when I do that it acts like it wants to start, then usually dies. So what your saying makes sense. I did go from an automatic to a manual where I spliced my transmission harness, if the start wire goes threw that then its possible I messed something up, ill trace them wires to make sure. On the automatic there was two connectors, one blace and one gray, on the manual there was also one black one gray when I traced all the wires I needed for the manual reverse, nuetral safety, and three sensors all ran through just the gray connection. I'm wondering now if there should have been a splice to the black connection that might be the wire your mentioning.

 

[litlred]

I'm sorry, there was only two sensors, the third that ran through the manual harness now is in the engine harness.

 

[litlred]

Okay traced wires from automatic trans harness, there is a green/yellow strip wire on the black connector that spliced in with the pink wire that goes to the neutral safety switch on trans to the gray connecter at the main harness.

 

[litlred]

After spicing it into my current harness, it seems to be helping, I don't know what that wire goes to though, I can't find it in the wiring diagram. There are still 3 more wires from the black connector that I'm assuming are part of the automatic trans that I don't need but I can't find them either.

 

[AllanD]

Don't worry about "TFI" a 4.0 doesn't have one...

AD

 

[kimcrwbr1]

Looking closer at the diagram It kinna looks like the start circuit throws the emissions into a closed loop using the white and black wire thru either the clutch or neutral sense to a black and white but dont know if you can put battery voltage to the sensors safely on mine the sensors had 5 volts going into them in normal operation but what I understand the computer runs in an open loop until it warms up then it closes the loop. Is the computer you have for a manual transmission or does that make a difference.
white/black to the computer and the two switches neutral, clutch
black/white to the sensors from the switches all five sensors
see if you are getting voltage to the sensors with the key in start that would be the black and white common to all of them.

 

[litlred]

Wouldn't the loop be closed if the clutch is in or in neutral?

 

[kimcrwbr1]

yes that is the goal how many connectors does the neutral switch have on it on the tranny find the two that are closed in neutral those go to wht/blk and blk/wht and all ways check for shorts also the other ones are for the backup lights unless that is a different switch the clutch switch is another thing it is actually a triple function switch do you need to push it fully for the starter to work. And I was reading a little closer you mentioned it worked a little better when you had charged the battery that could be very well the problem if your battery is low you should have around 12.5 volts on a charged battery take it in and get it checked replace it if it is bad as soon as you start it make sure the charging system is working correct clean all the grounds the tech library has a good section on charging you should be getting around 14.8 to 15 volts at 1500 rpm no more than 2.5 volts over battery and with the lights on high beam and the heater or a/c on high no less than .5 volts over battery at about 2000 rpm. Just a thought

 

[litlred]

Yea, ive had the battery and altenator tested, both are good. It wasnt charging when I first swapped the 4.0 in. But all it was was a fuse. Its starting better, but not like it should.

 

[kimcrwbr1]

Is your battery fully charged you can test the other thing by unplugging the start wire on the starter and have someone turn the ignition to start while you test the black/white wire on one of the engine sensors for voltage the water temp would be the easiest in neutral clutch in

 

[kimcrwbr1]

start wire on the start relay