96 4x4 I-6

Here is what she is doing: Drive it for 20-30 miles cut it off and try to restart it after sitting 10 minutes it shudders, and shakes and idles real rough and cuts off. when you turn the key I can hear the fuel pump cycle everytime. Wait 30 minutes and it starts fine.

So far fuel pressure check by a shop said fuel pressure was ok (but they did not drive the truck 20 miles only warmed it up in the parking lot. They said it held pressure good too. they also checked the fuel pressure regulator and said that was OK. Only code was lean code.

I myself have changed the plugs, cap, rotor, pcv, wires, coolant temp sensor, cleaned the idle air control valve, cleaned the Mass air flow, and replaced a few vaccum lines etc.

when cold the trucks always starts like new, and always cranks fine hot or cold. Runs great, no misses.

This is what I think may be happening, could the fuel pump be getting hot and not working right after driving for 30 miles. I can hear it cycle though always.

Tell me what you think ?

 

Could be the fuel pump. Even though the pump still runs, it might not be pumping enough pressure to keep the engine running, especially since you have the lean code in there. Didn't do the shop much good to be testing it when the truck wasn't acting up. You might want to get a fuel pressure tester of your own, that way you can actually test it when it's acting up.

 

Yeah the dang place charged me an 1 1/2 hours labor which aint cheap.

 

It's trivially easy to hook up a FP tester and rig it so you can see it while you drive. Best is to attach it to the antenna and have a passenger who can log it. You may even be able to borrow or rent one from one of the chain stores. They're not expensive to buy either, that 1 1/2hr labor would buy a very nice one...

What about a TFI module on it's way out?

 

That's the symptom you get when either the TFI module
also called the Ignition Control Module or the PIP sensor
goes bad. No spark.

The PIP sensor is located inside the distributor and produces
pulses when the engine is cranked or running. It passes
the pulses to the TFI module which grounds the coil
which produces the high voltage for the spark plugs.

If the PIP sensor is bad it's easier to purchase a rebuilt
distributor because you need to press off the distributor
drive shaft/gear to change the sensor.

The TFI module on your truck is located on a heat sink
on the driver side fenderwell.

Here's a site that describes how the circuit works and
how to test it with a LED.

http://easyautodiagnostics.com/Ignit...rd/Models.html

 

XLT,

I am getting spark, so I don't think its the ICM or PIP.
That link you provided was a good one for future reference though
Thanks

 

What is the best way do you think to get to the fuel pump, pull the bed or drop the tank. Those last two bolts in the bed near the tailgate look impossible to get any leverage on them ?

 

Have you pulled the codes? That will tell you if you have an EFI, electrical, or fuel related problem.

 

He did say in the OP that it had a "lean" code.

 

Lean code,

New plugs, wires, cap, rotor, fuel filter, cleaned the MAF, cleaned the IAC, upper o2's replaced, checked all the vaccum lines, replaced the PCV and hose, new air filter, new anti-freeze, replaced the coolant temp sensor, changed the oil/filter, new radius arm bushings, and ground wire and ground straps.

Just bought the truck about 3 weeks ago it has 195,000 miles

drive it 20+ miles let it sit 15 mins and try to restart and it shudders and shakes and cuts off. let it sit 30 mins and it restarts fine.

all cold starts are great. can hear fuel pump cycle every time cold or hot and it cranks fine cold or hot.

shop said the fuel pressure was ok (only warmed the engine a few minutes) when they checked the fuel pressure did not drive it 20+ miles like I asked them to do. No gas in the fuel pressure regulator vaccum line, so that should be ok too.

I am thinking the fuel pump may be getting hot after 20 miles of driving and not working right, I can hear it cycle though.

 

When it warms up it begins to suck air somewhere (sounds like). I'd check all the vac lines which are at the crumbling/cracking point in their age. Look around the EGR (side of intake manifold), Idle air control valve/motor (side of throttle body) & where they feed all the air injection control solenoids.

 

OK, i went and got a fuel pressure gauge and hooked it up drove the truck hard 20 miles, cut the engine off let it sit 15 minutes, went out and looked at the guage and it was sitting still at 52lbs, turned the key to the on position (did not start it yet) heard the fuel pump cycle, looked at the guage and it stayed at 52, used the selinoid on the fender to start it so i could watch the guage, when cranking the guage dropped down to about 22 lbs and she started the shaking and rough idle thing it does then she straigtened out and the pressure guage went up to 38 lbs and held there while the engine was running.

What does that mean? dropping to 22 lbs fuel pressure while cranking. Bad fuel pump ? I dont think the injectors are leaking down cause it held 52lbs while sitting.

 

Fuel Pump or pressure regulator ? what do you think ?

 

Finally got time to put the new fuel pump in today, PROBLEM SOLVED !

 

Thanks for the feedback. Nice to know when something works.