HELP!!!! T.P.I. Barely running.

[HOPPER]

I just got this truck not to long ago and when I got it it ran kinda rough. I parked it and did a 1 ton swap and some other little things. Now Im that Im ready to run it it barely runs. Its idling rough, puffing black smoke, if I try to give it throttle it kinda sputters then revs up. I rev it a couple of times real good and when I let off it dies. Its got a fuel pressure gauge thats bouncing around sparaticlly in between 40 and 60 psi. All plug wires are on. Its almost like its missing.
Any help would be greatly appreciated.

 

[BGKYK5]

Vacuum leak?

 

[dyeager535]

You've done a good tuneup on the thing? Plugs/wires are good? Timing set correctly? Cap/rotor in good shape? All wires in the engine bay in good shape? Check engine light functional?

I've not run a gauge on the fuel rail, bouncing there MIGHT be ok due to the injector cycling, but I'd think not as that messes with fuel delivery.

Always start with the basics, (wires, etc) but if someone can corroborate that the fuel pressure should be more consistent, you can troubleshoot that problem. WAG, pressure regulator or vacuum hose to it.

 

[Thunder]

By your description it looks like the regulator may be bad. Your fuel pressure should not fluctuate at all at idle. pressure should only increase under hard acceleration. If you are getting 60 PSI to a injector designed for 40 psi you are getting too much fuel.
IIRC PSI for TPI should be set at 38-48 PSI with vaccum line disconnected.
Is the vaccum line hooked up to the regulator?

 

[HOPPER]

Im waiting on a tune up kit from jegs. Ill check the vaccum line on the regulator as soon as I find the regulator.

 

[Thunder]

The FPR is a round can with a vaccum line. It is a part of the fuel rail. The fuel rail is the lines that feed the injectors.
To change it and get at the fuel rail, you have to pull the plentum and intake runners.
It is located on the fuel rail the back of the engine by the distributor.

 

[odin]

By your description it looks like the regulator may be bad. Your fuel pressure should not fluctuate at all at idle. pressure should only increase under hard acceleration. If you are getting 60 PSI to a injector designed for 40 psi you are getting too much fuel.
IIRC PSI for TPI should be set at 38-48 PSI with vaccum line disconnected.
Is the vaccum line hooked up to the regulator?

X2 fuel pressure at idle should be a steady 35-40 psi.

 

[BobK]

Check the OHM's of each injector.
Normal for the GM/Multec injector is 12-16ohm's.

I just checked mine...had 4 of the 8 not within spec.
One was 3.8ohm,one at 7.8ohm two at 10.1ohm,last four were within spec...two at 12.1ohm and two at 16.8ohm.
Truck started but barely ran,black smoke,no power,etc.

Haven't got new injectors yet so no results to post.

The GM injectors are not serviceable except for O-rings,filter screens and pintle.Basically,the out of spec one's are junk.

Anyway...just something else to check.

 

[dyeager535]

FYI, even though the price has gone way up, the old Ford SVO injectors from Summit were still a great deal last I checked.

Not sure what they are calling them now, but if you check thirdgen.orgs forums for the SVO injectors, you'll find info that cross-references them.

All 8 I believe were $300 a year or two ago.