Dealing with a 94 S10 Blazer 4x4 auto Vin W 4.3 V (CPI)

It was running rough and then would stall out after abourt 20 min or so of run time. So I figured it would be the ECM doing this. But a friend who is workin on this also started to replace parts. Here is what is done so far:

New:

Cap & Rotor (was way over due)
Plugs
Fuel Pump (after this and the filter it would not start at all)
FPR
Filter
replaced CPI

Checked all fuel lines
Checked all vac lines
Checked Injector Pulse

Everything seems to check out, when given Starting fluid it will run till that expires. So I have figured its not getting fuel into the engine for some reason. The pulse for the injector was checked seems like it is sending signal. Fuel does get into the CPI but its not making it threw the injector. FPR is new (thought was bad so took it in for another, same thing,so tried it on a 95 and worked wonderfully). Old one was leaking.

What has me stumped is that it will run if you spray threw the TB to feed the engine but once you stop it will stop. Getting solid strong spark (after cap and rotor), no obstructions with the air intake, no gaps in the lower intake, no fluid mixing any where, good compression, when did have it running for a short strong vacuum. Fuel PSI is within range and does not leak down (sense we changed out the FPR). All fuses are good that we checked (under lower dash).

TPS seems to have (its a 3 prong) signal first 1/4th of the throtle travel, then dead spot til the last 1/4. But seeing as when you feed the engine via the TB it runs, I don't see how this would make it so the Injector would not function.

We have come to a stumped point and can not figure what else would cause it.

 

I have seen the internal electrical wires for the CPI injector go bad before. Check these to make sure that they are getting the signal to the injector.

 

have u had the plenum open? u could check the fuel lines inside of the plenum to see if they leak inside there. (kyle where is that thread that had the pix of the plenum apart i cant find it) also what did the spark plugs look like when u took them out?

 

I think this is what you are thinking of:

4.3 CPI "W", pictures of replacement process for injector

 

yes that was the one i was thinkin of kyle. so ya FreeBird if u read thru that thread that might help as well.

 

The fuel lines don't show any signs of leaking at all. That was one of the first things I checked in the plenum, second thing was the FPR. That was leaking. But even with a new one, it did the same. So replaced the whole CPI unit. Still same results. There is pulse at the injector,used a volt meter and shows its getting pulse. So again, still left with no clue.

Will run like a charm if you feed it threw the TB, but if you let it try by itself, nothing. For some reason its still not getting fuel.

 

sorry i'm not too familar with all the technical termonology so forgive me if u already checked/replaced this but have u checked to see if the injectors r clogged? it seems u have a leak or something that is preventing the proper amt of fuel from getting in the cylinders. could also be o2 sensor or something like that that monitors ur fuel ratio.

 

I would check the fuel pressure and make sure your pressure isnt droping at all.

 

Blue, he replaced the whole CPI spider which didn't help the condition. I would think that new poppet nozzles and a new main injector would atleast fix the condition temporarily if contamination was the problem.

I would definitely recommend a fuel pressure check, especially monitoring it while you crank the engine.