95 Tdime issue..

[Confedneck]

i already pmed a guy here about this, but...
bought a 95 t dime 4door for 800 bucks, runs pretty good at an idle

148k, auto

changed the plugs, wires, cap, rotor was in good shape, as were the wires, but what the heck... and the fuel filter, it's had 2 fuel pumps put in by the PO trying to fix the issue at hand

when i got it, the cat had been replaced by a piece of pipe and the muffler was blown in half... so i replaced the muffler with a 40 series flow and a turndown i got cheap... quited it down... still smelled of fuel.. and had a bad stumble/hesitation when you accelerate, any gear, any throttle position.. then it clears up and screams...

so i cleaned the egr, the map sensor, checked the tp sensor for proper operation, cleaned the pcv but it works fine and cleaned the IAC...
while i had the egr out, i filled the intake with seafoam and carb cleaner and let it soak, fired it up, it smoked a little and same issue, added 5 gallons of 93 octane with b12 chemtool to the tank and no change...

im thinking i may have a fuel injector issue, but this has that spider cage abortion under the intake, i read here about a tsb to change to mfi but i cannot find the tsb or parts listings... does this sound like a viable culprit?

thanks in advance
josh
95tdime

[MT-2500]

Welcome to AF
What engine?
Flat top dist or old style?
Does the fuel pressure have a fast leak down?
What is the fuel pressure reading?
Any codes or check engine lights?

[Confedneck]

W code 4.3
horizontal distributor

fuel pressure is good, 57psi KOEO
60 when cranking
53 at idle

WOT is 60psi
and pressure holds steady at 60psi, even when i make the engine stumble by holding it to the rpm range...
if i make it stumble in gear, 1st or reverse 55 psi

when i turn the key off, it drops to 49-50psi

only code was for map sensor no input, but it had been unplugged..

when i was testing fuel pressure, i pushed the bleed button on my gauge to check for solid volume, the truck died and won't restart... seems to still have good fuel pressure, but now the check gauges lights is on and no codes...

getting a spark tester tomorrow, but when i pulled a plug wire and held it near the manifold, number 1 cyl, it seemed to have spark, but not strong...

[MT-2500]

Ac Delco plugs and Dist cap?
Check it over good.
Look for a missing cylinder.
Also a goo scanner data reading and code check may show something.
{Corrected for bad key board and spelling mistakes.}
Also a good scanner data reading and code check may show something.
Good Luck and let us know how it goes.
MT

[old_master]

Fuel pressure is not monitored by the OBD system. Therefore it can not set any codes. The fuel pressure readings you have are too low.

Fuel pump operation:
The fuel pump circuits are designed to energize the fuel pump continuously any time the key is in the START position. When the key is in the RUN position the fuel pump will operate provided the engine is running. If the engine stalls, or is not running for any reason, the PCM will shut off the fuel pump after approximately 2 to 3 seconds.

Fuel pressure test:
Install the fuel pressure gauge to the test port near the distributor. Turn the key to the RUN position but do not start the engine. While the fuel pump is running, fuel pressure must be 60-66psi. After approximately 2 to 3 seconds, the fuel pump will shut off. Fuel pressure must remain between 55-60psi for several minutes. A drop in pressure below 55psi indicates a leak. The most likely place is the fuel pressure regulator, or the lines under the upper intake manifold.

[Confedneck]

i cant start the engine, it wont run anymore... still gets fuel pressure to the gauge KOEO, but wont run, cranks and cranks...

was idling fine until i wanted to check volume through the gauge and it shut off now wont start...

another question is, is the fuel pump the same or at least compatible from 95-99? i have one from a 99 sblazer that worked great, but had erratic gauge readings (would wander 1/8 tank either way from actual)... can i replace the aftermarket one that someone installed with this gm unit?

also, has autolite plugs and wires, next best thing when you cant get delco stuff anywhere in a reasonable amount of time, and a duralast gold cap...

[old_master]

Prime pressure of 57psi is too low. The drop to 50psi is too low also but may be due to the pumps inability to build sufficient fuel pressure. Check with a parts store about interchangability of pumps. You might be able to change just the pump and not the entire module.

[Blue Bowtie]

Originally Posted by MT-2500

Also a goo scanner data reading and code check may show something.

That must be the new scanner - Model "GOO". I can't afford anything that fancy, so I guess I'll have to stick with the old, slow brick:



Does this mean you'll be changing your name soon?

(You now have license to pick on my next keyboarding/fat-finger episode.)

[Confedneck]

what should i watch for when i scan this thing, being it wont start anymore..?

[old_master]

A scan tool will not diagnose low fuel pressure, you have already determined fuel pressure is low. Repair it and go from there.

[Confedneck]

ok so today i finally got it to fire up, should have a scanner tomorrow to use on it... but anyways, i had to use carb cleaner to make it fire up and run, and it seemed the FP picked up after that... and idled for 2 minutes, so i wanted to go for a sprint around the neighborhood... it died 3 times, took carb cleaner to fire it every time, but my question is, why would the fuel pump pick up and run after the truck runs on carb cleaner? possible no CKP signal? where do these pick up the ckp signal? front of the crank or at the rear?


also, on a seperate note, there is a vacuum hose hanging loose and i think it has to do with the 4wd, is there anywhere, other than a service manual where i can find that vacuum diagram? i should have a service manual from the P.O. next week, but dont know what kind it is ie chiltons, haynes, factory, etc...

thank you for all your help

[old_master]

When the engine starts with carb spray it's a CLASSIC example of low fuel pressure. The engine requires more fuel pressure and volume to start and accelerate, than it does just to idle. Skip the scanner, figure out why fuel pressure is low. Insufficient voltage and/or ground at the fuel pump or a faulty fuel pump are the likely causes.

[Confedneck]

well being the fuel pump has been replaced twice, and with cheap aftermarkets, im sourcing a factory one, and while the tank is down, ill replace the ground and ohm the wires to ensure proper full performance...

thanks for all the help gents!

[old_master]

If the pump has been replaced twice, look closely for a poor connection. High resistance will cause premature pump failure, guaranteed. As long as you're there, replace the fuel pump connector pigtail. Solder the connections and use heat shrink tubing or you'll end up with another pump failure.