truck suddenly won't start

[ajpolitz]

Ok, Was getting ready to drop the beast off at the body shop and ...

 

A week prior, filled the tank up with the good stuff.

 

Started the truck up in the garage, started very quick.

Backed her out into the driveway. Let her idle and warm up for 5 mins.

Turn her off for and got side tracked for 1/2 hour. It was time to go, fired her backup again.

 

Backed up out of the driveway, put her in drive and proceeded down the road.

Got 100ft, stalled. Won't start. Push truck back to front of house.

 

Sprayed some gum-out down the throttle body, fires right up, then dies.

 

I figured no fuel, brought new fuel filter, installed, same response.

 

When you attempt to start, it sort feels like she will start but never fully starts.

Sometime she will run for 10-15secs.

 

Disconnected fuel line from filter, and looks like fuel pump is working.

 

Any idea's - This sucks!

 

Anthony

[1999MJ]

do you hear the fuel pump come on at all when you turn the key to the on position? You should here a huming fron the tank for a couple seconds. If you don't it's a fuel issue. Maybe check the resister under the hood. U can bypass it just to see if anything changes

[Pete M]

moved it to Tech for ya. :thumbsup:

[deziped]

My 89 4.0 just did the same thing 15 minutes ago. Just fired it up and went to store 3 blocks away. Wouldn't start when I came out of store but it cranked and stumbled like it wanted to start. Unplugged CPS & replugged it. Still no start. Got p----- and slammed the hood shut. It started right off like normal. Go figure. Maybe I better dig out the old CPS I saved & carry it with me just in case.

[ajpolitz]

I am going to check the resistor when I get home today.

Sometime I do hear the pump and other times I do not.

 

I disconnected the fuel filter and cranked the key to see if fuel was coming out and sure enough, the pump worked.

 

Do you know how many OHM the ballist is? 1.6 or .8.

Ignitions most of the time use .8

 

Anthony

[JeepcoMJ]

also could be the CPS wire melted to the manifold which is now causing inconsistent voltage going through the wires.

[ajpolitz]

Not CPS. The wire is clean and was just replaced.

 

Engine was running 110% prior to the fill up.

But the gas I got out looks good, so I am ruling out bad fuel.

 

Gumout can keep the truck running if spraying it down its throat.

 

Anthony

[Eagle]

Not CPS. The wire is clean and was just replaced.

 

Engine was running 110% prior to the fill up.

But the gas I got out looks good, so I am ruling out bad fuel.

 

Gumout can keep the truck running if spraying it down its throat.

So you obviously have spark and air. The problem is fuel.

 

When you pulled the hose to test the fuel pump, which side of the fuel filter did you pull it from? Are you getting flow through the fuel filter, or did you verify flow to the filter?

 

Have you verified that the injectors are working? Your test with carb cleaner confirms spark, but you're bypassing the injectors with that, so there could be fuel pressure to the rail but no squirt.

[ajpolitz]

Test for fuel into the filter and out, replaced the filter already.

 

Sometime the truck fires up and runs smooth for 10-15secs. No misses.

Majority of the time, she sound like she wants to start but never makes it over the hill.

 

Anthony

[JeepcoMJ]

just humor me a little and check that the CPS wire isn't contacting the exhaust manifold...

 

I put a new one in mine, a week later it was melted to the manifold, and had I ruled it out immediately before I figured it out...

 

-Pat

[ajpolitz]

Well CPS is good.

 

I bypassed the balist resistor and gave it a whirl.

 

Turning the key to the on position made the ppump prime.

Turning the key to start did the same as before.

 

After trying to start it seveeral times, it started to run. So I kept it running for about 1.5 Mins before it stalled again.

 

Same run-on (almost starting) from then on with shprt bust of it running for 10secs.

 

Anymore idea's?

 

Anthony

[Wildman]

Check your grounds.

 

Make sure the body to engine strap is in good shape, any bright green color at all, replace it.

 

Check the battery to engine block ground, that is also where the ECU is grounded with a 14ga wire, and double check that the ECU mounting plate is grounded.

 

I know this does not sound like a fuel problem solution, but......the ECU controls the injector pulse, and of course spark, timing.

 

When you were spraying the gumout down the TB, was the key turned to run the starter?? Or did you turn the key back to the "on" position, and it still ran???

 

I'm thinking there just might be a problem with the ignition switch :hmm: if the grounds check out.

[HOrnbrod]

Sure sounds like a fuel starvation problem. First do a pressure test w. a gauge on the rail test port. If okay, do a fuel flow test. If bad, the problem is prolly in the gas tank, filter sock or internal tank hose problem. Maybe.............

[Oizarod115]

if the fuel pump tests are inconclusive, or your results show good pressure and flow;

 

get a push-in style tag light bulb, (small one 5w or so), take the metal prongs and fold them out straight, then unplug a fuel injector and plug this in its place... then have a buddy run the starter and you shuold be able to watch the light flicker if the injector is being triggered by the ECU. if not check yuor connections and the bulb to be sure its good, then you've got an ECU problem at that point.

[ajpolitz]

I will check all the ground straps tonight.

 

This is very strange for this to all of a sudden happen without any warning.

 

I am pretty sure the injectors are all operating. I have gotten the truck to run for a minute or two on several occations and it did run smooth, but abruptly dies again.

 

Where is this ground wire by the tail lamp?

 

I have not fully been under the truck to check the fuel pump its self. How hard is it to get to?

I have a full 18 gals of gas in there too. Can I remove the pump with the tank full?

 

Anthony

[maddzz1]

Is it possible the timing has skipped? Do you have a 2.5 or a 4.0?

[freakjeep93]

you can takwe the pump out with gas in it just do it crefully and make no sparks or your in for a very un fun BBQ

[ajpolitz]

It so strange this happen, I think I am going to swap out the CPS I replaced when I was originally started swapping out old parts for new.

 

All ground is in it's place and when cold, I can get it to run keeping the RPM above 2k for a minute. When it warms up, I can't get it to start at all. She almost feels like she is going to turn over but never completely does.

 

Anthony

[ajpolitz]

Is it possible the timing has skipped? Do you have a 2.5 or a 4.0?

 

I have a 4.0, Jeep Eliminator.

[XXLMJ]

I had a very similar problem with my 89. I unplugged the ignition switch under the dash on the steering column. It started so i plugged it back in and it has been fine ever since. I had spark, and fuel just like you.

[maddzz1]

Maybe your cat is clogged.

[deziped]

Is that short vaccumn line hooked up from the throttle body to MAP on firewall? Mine wouldn't run when that was disconnected. Sometimes it would start but soon die. It was sending a weird signal to ECU I guess.

[ajpolitz]

I am really think it is something in the fuel after that nice fill up with the "good stuff".

 

For kicks, I swapped out the CPS with the original one in 1hr (Getting good at this) and still the same results.

 

All vacuum lines are good, replaced the full harness not to long ago.

[Oizarod115]

the line is easy enough to disconnect at the fuel rail, try pulling it off and getting a cup, running the pump on the starter to see what kind of fuel sample you can get.

 

after a few cases of bad flooding in our area we have seen cars that won't start due to water in the fuel.

[ajpolitz]

How can I run the pump manually?

 

Can I apply 12volts to one side of the resistor directly?

I'd like to use it to drain the tank since it is FULL and replace the pump.

 

Gas looks good. Stinks like crap. I remember when gas smelled good!

 

Anthony