96 Tahoe.....stalling and no power

[Nightflyer]

Hey Guys,

Every year a new problem with my 96 Tahoe (350tbi). Last year i've changed the injectors (cpfi to mpfi) and everything worked fine..

Now i've another problem: my chevy runs rough at idle, stalling at acceleration and loss power. last year i've changed a lot or parts. With this new problem i've changed:

- Distributor with cap and rotor (timing is correct. checked with scanxl pro)
- spark plugs and cables
- ignition coil and icm
- fuel filter
- air filter
- coolant temperature sensor
- fuel pump

the symptoms are most of the time when the chevy is warm/hot. have no trouble codes or vacuum leaks.
But there's a strange thing with the fuel pressure (that's why i changed the pump):

With ignition on and engine off the pressure is at 58-64psi (and 50 psi at idle). But when i turn the ignition on, the pump works and the fuel pressure gauges reads the 58-64psi the pressure drops to zero after a few seconds (1 or 2 seconds). So it's not a steady pressure...

Could it be the fuel pressure regulator?

I hope someone could help me..

Best regards from germany


Matthias

 

[1BADI5]

Have you ever replaced the distributor?

When I went through the top end of my motor to replace the horrible GM plastic intake manifold gaskets....... the cam gear on the bottom of the distributor was excessively worn. With it being that worn the timing was not right. Also, the screw holes for the cap were cracked, so the cap was not sitting true on the distributor. Overall it fixed numerous issues I was having.

I went with the billet distributor from Summit Racing, was under $200 shipped, it also came with a new cap and rotor.

I might be worth looking into. As far as your fueling issues, how old is the fuel pump? Has is ever been replaced? I ended up replacing mine shortly after I got my timing issue resolved. Once I had both of those done..........ran like a brand new truck but with 200,000 miles on it. Finally, have you replaced the fuel filter in the last few years? I do mine annually, as cheap insurance......a $10 part, 10 minutes of time goes a long a ways.

Hope this helps

 

[Big Mama]

Fuel pressure regulator or voltage to pump is what comes to mind.

 

[Nightflyer]

I've changed:

- the distributor (complete assembly with sensor, cap and rotor)
- a new fuel pump with filter

First i got the code P1345 (ckp and cam sensor not correlation...or so) so i set the timing to something between zero and -2 degrees (not so easy with this programm) and the code was deleted..

I've measured the voltage to the pump: it's very good.

i think there's something wrong with my fuel pressure....son't know. But the fpr is only one year old (comes with the mpfi kit from ACdelco)...

 

[Big Mama]

the culprit seems to be electrical if you have fuel relay and fuses does their voltage drop at start up too?

 

[Nightflyer]

No...the voltage is really good all the time...

It's weird...i've checked the fuel pressure again: with ignition on and engine off the pressure goes to 60psi and falls immediatly down to zero.

 

[SunlitComet]

if pressure builds up full on key on prime then drops to zero when relay go off before actual starter engages then regulator is faulty, injectors are leaking or check valve in pump assy is leaking.

 

[Nightflyer]

I think the injectors are okay because all the spark plugs are dry and there's no gas in the oil. I've tested two fuel pump assys...it's the same: it's not holding the pressure. A new reguulator is ordered...I will fix it on saturday.

 

[drakon543]

when you replaced the injectors did you fully clean and reseal the whole tbi unit or just do the bare minimum and swap the injectors? there is 2 orings that are supposed to seal the injectors in the fuel bowl and 2 or 3 other seals that should be replaced at the same time. outside of that id lean towards the fp regulator which if you buy the tb rebuild kit it comes with a new regulator and all the orings to make sure your injectors are sealed correctly. i think its about 50 bucks or so. ive seen where the spring breaks for the regulator or the diaphragm will crack in the regulator.

 

[Wolfbraid]

Check your oil pressure sensor... I chased a funky fuel issue on my 95, truck would just die, sometimes I would switch the relay(with the A/C or Starter) and it would work... Turned out to be my oil pressure sensor