Hey y'all

I've read into this problem but none of them seem to be the exact.same as I'm having...well, sorta.

Basically on a cold night my friend and I were putting up a car port and while doing so used the jeeps lights to help us see. My battery got.low enough to now want to start the vehicle, so we jumped it, then brought it close to the house where we put it on a trickle charge for about an hour

After the trickle, we tried to start it...fuel pump made no noise, and has/ has not intermittently since. If I gave it some gas she would perk right up and stay revving along without my foot on the gas, but now we can't get it running for **** unless I hold the starter down and push the gas pedal.

I've come up with 3 possible culprits
1) fuel pump- I have pressure at the rail after trying to start it, but not as much as I think I should have

2- iac- we did clean this off without removing it by using some Carb / TB cleaner sprayed in the TB, seemed to help but still no fuel pump actuation is heard- relay does click

3- pcm- a longshoremen but apparently a leader in the search for culprits as per Google.

 

You are going to need to adopt a "testing" strategy to figure out your problem. And you need to look at "cause and effect" first of all.

1. The fact that you used Jeep lights for a project makes me very suspect of your battery. Trickle charging for an hour which you did is not nearly enough to recharge a battery. You MUST verify your battery with a LOAD TEST. Any parts store will do this for you for free. The #1 symptom of a marginal battery on the 4.0 is stalling. Sound familiar? And yes, you can have a battery that is strong enough to start the engine, but marginal enough to give the engine management system fits. At the very least, put your battery on a charger overnight (not a trickle charger) and see if that helps. But even if it doesn't, still load test your battery. Sometimes a solid discharge is the last straw on the life of an automotive battery.

2. Test fuel pressure. With a gauge. No shortcuts; gauge is the only way to know. Your fuel pump is working somewhat or the engine wouldn't be running at at all. For a 90, you need 31 psi to fire and run the engine. Then disconnect the vacuum line leading to the fuel pressure regulator and the pressure should jump to approximately 39 psi. Be sure that the vacuum line is pulling good vacuum and is not wet with fuel which would indicate a ruptured fuel pressure regulator diaphragm. Many parts stores will rent you a gauge if you don't have one.

3. Test your throttle position sensor. And adjust it.

My guess at this point is that this is battery related. Good luck and be sure to update us!

 

Do remember/ note that the pump only runs for a few seconds after you turn the ign. on. (then when it starts). Also after a few times it may not. The rear orange wire off the ceramic ballast resistor there on the inner fender by the air cleaner goes directly to the pump I think. The resistor is mainly to quiet the pump, it can be bypassed or eliminated. Idk! But theirs that!

 

Battery is noted as a culprit. I did only test the voltage, 12.5-.7 volts...but ill get it load tested tomorrow.

Just in case it comes to it, can I have a link or explanation of Toshiba adjustment? I know cruiser has posted it

 

Have you ever changed your fuel filter? Had the same sympthoms on plow-truck ( -88 MJ ). Started and reved up when turning key. Changed fuel filter and now it works again. Problem was a nearly total clogged fuel filter and water in it. This can be part of your problem if you never had changed fuel filter.

 

I never have changed the filter but at the same time wouldn't I still hear the pump trying to prime

 

Update-
Tested everything. Iac is clean as a whistle, ecu is fine, Tps is adjusted...
Battery tested and came out 237 cca @ 12.4 volts

 

So next step is to place that FULLY CHARGED battery (is it?) back in the vehicle and see if it resolves the problem. Trickle charging which you did earlier is insufficient.

 

Toshiba adjustment?

 

Getting a new top post- the one that was in it is apparently 10 years old even though I bought it like 2 years ago...but yea new battery.

 

My Motorola phone loves Toshiba when it comes to trying to type tps apparently

 

I was wondereing. Click on the link in my signature and go to Post #8.

 

I found it this morning lol but tps was already adjusted as it should be

 

Good. New battery yet? Toshiba makes batteries. LOL.

 

Pahaha yes laptop battery = jeep battery
But naw I'm getting it tomorrow morning after I pick up my sisters new car in blacksburg